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Chakraborty LS, Le Maitre CL, Chahine NO, Fields AJ, Gawri R, Giers MB, Smith LJ, Tang SY, Zehra U, Haglund L, Samartzis D, Martin JT. Impact of the COVID-19 pandemic on the productivity and career prospects of musculoskeletal researchers. J Orthop Res 2024. [PMID: 38678396 DOI: 10.1002/jor.25866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 03/27/2024] [Accepted: 04/15/2024] [Indexed: 04/30/2024]
Abstract
Academic researchers faced a multitude of challenges posed by the COVID-19 pandemic, including widespread shelter-in-place orders, workplace closures, and cessation of in-person meetings and laboratory activities. The extent to which these challenges impacted musculoskeletal researchers, specifically, is unknown. We developed an anonymous web-based survey to determine the pandemic's impact on research productivity and career prospects among musculoskeletal research trainees and faculty. There were 116 musculoskeletal (MSK) researchers with varying demographic backgrounds who completed the survey. Of respondents, 48.3% (n = 56) believed that musculoskeletal funding opportunities decreased because of COVID-19, with faculty members more likely to hold this belief compared to nonfaculty researchers (p = 0.008). Amongst MSK researchers, 88.8% (n = 103) reported research activity was limited by COVID-19, and 92.2% (n = 107) of researchers reported their research was not able to be refocused on COVID-19-related topics, with basic science researchers less likely to be able to refocus their research compared to clinical researchers (p = 0.030). Additionally, 47.4% (n = 55) reported a decrease in manuscript submissions since the onset of the pandemic. Amongst 51 trainee researchers, 62.8% (n = 32) reported a decrease in job satisfaction directly attributable to the COVID-19 pandemic. In summary, study findings indicated that MSK researchers struggled to overcome challenges imposed by the pandemic, reporting declines in funding opportunities, research productivity, and manuscript submission. Trainee researchers experienced significant disruptions to critical research activities and worsening job satisfaction. Our findings motivate future efforts to support trainees in developing their careers and target the recovery of MSK research from the pandemic stall.
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Affiliation(s)
- Lauren S Chakraborty
- Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, USA
| | - Christine L Le Maitre
- Division of Clinical Medicine, School of Medicine and Population Health, University of Sheffield, Sheffield, UK
| | - Nadeen O Chahine
- Department of Orthopedic Surgery, Columbia University, New York, New York, USA
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California in San Francisco, San Francisco, California, USA
| | - Rahul Gawri
- Division of Orthopaedic Surgery, Department of Surgery, McGill University, Montréal, Quebec, Canada
| | - Morgan B Giers
- School of Chemical, Biological & Environmental Engineering, Oregon State University, Corvallis, Oregon, USA
| | - Lachlan J Smith
- Departments of Orthopaedic Surgery and Neurosurgery, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Simon Y Tang
- Department of Orthopaedic Surgery, Washington University, St. Louis, Missouri, USA
| | - Uruj Zehra
- Department of Anatomy, University of Health Sciences, Lahore, Pakistan
| | - Lisbet Haglund
- Division of Orthopaedic Surgery, Department of Surgery, McGill University, Montréal, Quebec, Canada
| | - Dino Samartzis
- Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, USA
| | - John T Martin
- Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, USA
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Hue TF, Lotz JC, Zheng P, Black DM, Bailey J, Ewing SK, Fields AJ, Mehling W, Scheffler A, Strigo I, Petterson T, Wu LA, O'Neill C. Design of the COMEBACK and BACKHOME Studies, Longitudinal Cohorts for Comprehensive Deep Phenotyping of Adults with Chronic Low-Back Pain (cLBP): a part of the BACPAC Research Program. medRxiv 2024:2024.04.09.24305574. [PMID: 38645207 PMCID: PMC11030474 DOI: 10.1101/2024.04.09.24305574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
Objective The University of California, San Francisco (UCSF) Core Center for Patient-centric, Mechanistic Phenotyping in Chronic Low Back Pain (REACH) is one of the three NIH Back Pain Consortium (BACPAC) Research Programs Mechanistic Research Centers (MRCs). The goal of UCSF REACH is to define cLBP phenotypes and pain mechanisms that can lead to effective, personalized treatments for patients across the population. The primary objective of this research project is to address the critical need for new diagnostic and prognostic markers, and associated patient classification protocols for chronic low back pain (cLBP) treatment. Design To meet this objective, REACH is conducting two large investigator-initiated translational research cohort studies called: The Longitudinal Clinical Cohort for Comprehensive Deep Phenotyping of Chronic Low-Back Pain (cLBP) Adults Study (comeBACK) and the Chronic Low-Back Pain (cLBP) in Adults Study (BACKHOME). Setting comeBACK is a longitudinal multicenter in-person observational study of 450 adults with chronic low back pain designed to perform comprehensive deep phenotyping. While, the BACKHOME study is a site-less longitudinal observational e-cohort of approximately 3000 U.S. adults with cLBP. To our knowledge, BACKHOME is the largest prospective remote registry of nationwide adults with cLBP. Methods Both the comeBACK and BACKHOME studies are collecting a robust and comprehensive set of risk factors, outcomes, and covariates in order to perform deep phenotyping of cLBP patients based on combined biopsychosocial variables to: define cLBP subtypes, establish phenotyping tools for routine clinical evaluation, and lead to improved cLBP outcomes in the future. The data from both studies will be used to establish techniques to develop a patient-centric definition of treatment success and to analyze cLBP patient traits to define clinically useful cLBP phenotypes, using a combination of traditional data analyses and deep learning methods. Conclusions These 2 pivotal studies, in conjunction with the ancillary studies being performed in both comeBACK and BACKHOME, and the other BACPAC-consortium research projects, we will be able to address a number of diagnostic and therapeutic issues in this complex and diverse patient population with cLBP. These studies will help clarify biopsychosocial mechanisms of cLBP with the aim to provide a foundation to improve the evaluation of treatment effectiveness and to spur new avenues of therapeutic research, including personalized outcome measures that constitute a clinically meaningful treatment effect for individual cLBP patients.
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Jung J, Habib M, Morrissette LJ, Timmons SC, Maerz T, Fields AJ. Non-enzymatic glycation reduces glucose transport in the human cartilage endplate independently of matrix porosity or proteoglycan content. JOR Spine 2024; 7:e1297. [PMID: 38222801 PMCID: PMC10782066 DOI: 10.1002/jsp2.1297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 08/30/2023] [Accepted: 09/11/2023] [Indexed: 01/16/2024] Open
Abstract
Background Intervertebral disc degeneration is associated with low back pain, which is a leading cause of disability. While the precise causes of disc degeneration are unknown, inadequate nutrient and metabolite transport through the cartilage endplate (CEP) may be one important factor. Prior work shows that CEP transport properties depend on the porosity of the CEP matrix, but little is known about the role of CEP characteristics that could influence transport properties independently from porosity. Here, we show that CEP transport properties depend on the extent of non-enzymatic glycation of the CEP matrix. Methods and Results Using in vitro ribosylation to induce non-enzymatic glycation and promote the formation of advanced glycation end products, we found that ribosylation reduced glucose partition coefficients in human cadaveric lumbar CEP tissues by 10.7%, on average, compared with donor- and site-matched CEP tissues that did not undergo ribosylation (p = 0.04). These reductions in glucose uptake were observed in the absence of differences in CEP porosity (p = 0.89) or in the amounts of sulfated glycosaminoglycans (sGAGs, p = 0.47) or collagen (p = 0.61). To investigate whether ribosylation altered electrostatic interactions between fixed charges on the sGAG molecules and the mobile free ions, we measured the charge density in the CEP matrix using equilibrium partitioning of a cationic contrast agent using micro-computed tomography. After contrast enhancement, mean X-ray attenuation was 11.9% lower in the CEP tissues that had undergone ribosylation (p = 0.02), implying the CEP matrix was less negatively charged. Conclusions Taken together, these findings indicate that non-enzymatic glycation negatively impacts glucose transport in the CEP independent of matrix porosity or sGAG content and that the effects may be mediated by alterations to matrix charge density.
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Affiliation(s)
- Jae‐Young Jung
- Department of Orthopaedic SurgeryUniversity of California San FranciscoSan FranciscoCaliforniaUSA
| | - Mohamed Habib
- Department of Orthopaedic SurgeryUniversity of California San FranciscoSan FranciscoCaliforniaUSA
| | - Luke J. Morrissette
- Department of Natural SciencesLawrence Technological UniversitySouthfieldMichiganUSA
| | - Shannon C. Timmons
- Department of Natural SciencesLawrence Technological UniversitySouthfieldMichiganUSA
| | - Tristan Maerz
- Departments of Orthopaedic Surgery and Biomedical EngineeringUniversity of MichiganAnn ArborMichiganUSA
| | - Aaron J. Fields
- Department of Orthopaedic SurgeryUniversity of California San FranciscoSan FranciscoCaliforniaUSA
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Mauck MC, Aylward AF, Barton CE, Birckhead B, Carey T, Dalton DM, Fields AJ, Fritz J, Hassett AL, Hoffmeyer A, Jones SB, McLean SA, Mehling WE, O'Neill CW, Schneider MJ, Williams DA, Zheng P, Wasan AD. [Evidence-based interventions to treat chronic low back pain: treatment selection for a personalized medicine approach : German version]. Schmerz 2024:10.1007/s00482-024-00798-x. [PMID: 38381187 DOI: 10.1007/s00482-024-00798-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/29/2024] [Indexed: 02/22/2024]
Abstract
INTRODUCTION Chronic low back pain (cLBP) is highly prevalent in the United States and globally, resulting in functional impairment and lowered quality of life. While many treatments are available for cLBP, clinicians have little information about which specific treatment(s) will work best for individual patients or subgroups of patients. The Back Pain Research Consortium, part of the National Institutes of Health Helping to End Addiction Long-termSM (HEAL) Initiative, will conduct a collaborative clinical trial, which seeks to develop a personalized medicine algorithm to optimize patient and provider treatment selection for patients with cLBP. OBJECTIVE The primary objective of this article is to provide an update on evidence-based cLBP interventions and describe the process of reviewing and selecting interventions for inclusion in the clinical trial. METHODS A working group of cLBP experts reviewed and selected interventions for inclusion in the clinical trial. The primary evaluation measures were strength of evidence and magnitude of treatment effect. When available in the literature, duration of effect, onset time, carryover effect, multimodal efficacy, responder subgroups, and evidence for the mechanism of treatment effect or biomarkers were considered. CONCLUSION The working group selected 4 leading, evidence-based treatments for cLBP to be tested in the clinical trial and for use in routine clinical treatment. These treatments include (1) duloxetine, (2) acceptance and commitment therapy, (3) a classification-based exercise and manual therapy intervention, and (4) a self-management approach. These interventions each had a moderate to high level of evidence to support a therapeutic effect and were from different therapeutic classes.
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Affiliation(s)
- Matthew C Mauck
- Department of Anesthesiology, University of North Carolina at Chapel Hill, CB#7011, 27599-7010, Chapel Hill, NC, USA.
| | - Aileen F Aylward
- Department of Emergency Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Chloe E Barton
- Department of Anesthesiology, University of North Carolina at Chapel Hill, CB#7011, 27599-7010, Chapel Hill, NC, USA
| | - Brandon Birckhead
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Timothy Carey
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Diane M Dalton
- Department of Physical Therapy, Boston University, College of Health and Rehabilitation Sciences, Sargent, Boston, MA, USA
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, Kalifornien, USA
| | - Julie Fritz
- Department of Physical Therapy and Athletic Training, University of Utah, Salt Lake City, UT, USA
| | - Afton L Hassett
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI, USA
| | - Anna Hoffmeyer
- University of North Carolina at Chapel Hill, Collaborative Studies Coordinating Center, Chapel Hill, NC, USA
| | - Sara B Jones
- Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Samuel A McLean
- Department of Anesthesiology, University of North Carolina at Chapel Hill, CB#7011, 27599-7010, Chapel Hill, NC, USA
| | - Wolf E Mehling
- Department of Family and Community Medicine, University of California San Francisco, San Francisco, Kalifornien, USA
| | - Conor W O'Neill
- Section of Physical Medicine and Rehabilitation, Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, Kalifornien, USA
| | - Michael J Schneider
- Department of Physical Therapy and Clinical and Translational Science Institute, University of Pittsburgh, Pittsburgh, PA, USA
| | - David A Williams
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI, USA
| | - Patricia Zheng
- Section of Physical Medicine and Rehabilitation, Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, Kalifornien, USA
| | - Ajay D Wasan
- Departments of Anesthesiology and Perioperative Medicine and Psychiatry, University of Pittsburgh Medical Center, Pittsburgh, PA, USA
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Rosenberg JL, Schaible E, Bostrom A, Lazar AA, Graham JL, Stanhope KL, Ritchie RO, Alliston TN, Lotz JC, Havel PJ, Acevedo C, Fields AJ. Type 2 diabetes impairs annulus fibrosus fiber deformation and rotation under disc compression in the University of California Davis type 2 diabetes mellitus (UCD-T2DM) rat model. PNAS Nexus 2023; 2:pgad363. [PMID: 38094616 PMCID: PMC10718642 DOI: 10.1093/pnasnexus/pgad363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 10/17/2023] [Indexed: 12/17/2023]
Abstract
Understanding the biomechanical behavior of the intervertebral disc is crucial for studying disease mechanisms and developing tissue engineering strategies for managing disc degeneration. We used synchrotron small-angle X-ray scattering to investigate how changes to collagen behavior contribute to alterations in the disc's ability to resist compression. Coccygeal motion segments from 6-month-old lean Sprague-Dawley rats ( n = 7 ) and diabetic obese University of California Davis type 2 diabetes mellitus (UCD-T2DM) rats ( n = 6 , diabetic for 68 ± 7 days) were compressed during simultaneous synchrotron scanning to measure collagen strain at the nanoscale (beamline 7.3.3 of the Advanced Light Source). After compression, the annulus fibrosus was assayed for nonenzymatic cross-links. In discs from lean rats, resistance to compression involved two main energy-dissipation mechanisms at the nanoscale: (1) rotation of the two groups of collagen fibrils forming the annulus fibrosus and (2) straightening (uncrimping) and stretching of the collagen fibrils. In discs from diabetic rats, both mechanisms were significantly impaired. Specifically, diabetes reduced fibril rotation by 31% and reduced collagen fibril strain by 30% (compared to lean discs). The stiffening of collagen fibrils in the discs from diabetic rats was consistent with a 31% higher concentration of nonenzymatic cross-links and with evidence of earlier onset plastic deformations such as fibril sliding and fibril-matrix delamination. These findings suggest that fibril reorientation, stretching, and straightening are key deformation mechanisms that facilitate whole-disc compression, and that type 2 diabetes impairs these efficient and low-energy elastic deformation mechanisms, thereby altering whole-disc behavior and inducing the earlier onset of plastic deformation.
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Affiliation(s)
- James L Rosenberg
- Departments of Mechanical and Biomedical Engineering, University of Utah, Salt Lake City, UT 84112, USA
| | - Eric Schaible
- Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, CA 94720, USA
| | - Alan Bostrom
- Department of Epidemiology and Biostatistics, University of California, San Francisco, CA 94143, USA
| | - Ann A Lazar
- Department of Epidemiology and Biostatistics, University of California, San Francisco, CA 94143, USA
| | - James L Graham
- Department of Molecular Biosciences, University of California, Davis, CA 95616, USA
- Department of Nutrition, University of California, Davis, CA 95616, USA
| | - Kimber L Stanhope
- Department of Molecular Biosciences, University of California, Davis, CA 95616, USA
- Department of Nutrition, University of California, Davis, CA 95616, USA
| | - Robert O Ritchie
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA
| | - Tamara N Alliston
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143, USA
| | - Jeffrey C Lotz
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143, USA
| | - Peter J Havel
- Department of Molecular Biosciences, University of California, Davis, CA 95616, USA
- Department of Nutrition, University of California, Davis, CA 95616, USA
| | - Claire Acevedo
- Departments of Mechanical and Biomedical Engineering, University of Utah, Salt Lake City, UT 84112, USA
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093, USA
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143, USA
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Mauck MC, Lotz J, Psioda MA, Carey TS, Clauw DJ, Majumdar S, Marras WS, Vo N, Aylward A, Hoffmeyer A, Zheng P, Ivanova A, McCumber M, Carson C, Anstrom KJ, Bowden AE, Dalton D, Derr L, Dufour J, Fields AJ, Fritz J, Hassett AL, Harte SE, Hue TF, Krug R, Loggia ML, Mageswaran P, McLean SA, Mitchell UH, O’Neill C, Pedoia V, Quirk DA, Rhon DI, Rieke V, Shah L, Sowa G, Spiegel B, Wasan AD, Wey HY(M, LaVange L. The Back Pain Consortium (BACPAC) Research Program: Structure, Research Priorities, and Methods. Pain Med 2023; 24:S3-S12. [PMID: 36622041 PMCID: PMC10403298 DOI: 10.1093/pm/pnac202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 11/29/2022] [Accepted: 12/01/2022] [Indexed: 01/10/2023]
Abstract
In 2019, the National Health Interview survey found that nearly 59% of adults reported pain some, most, or every day in the past 3 months, with 39% reporting back pain, making back pain the most prevalent source of pain, and a significant issue among adults. Often, identifying a direct, treatable cause for back pain is challenging, especially as it is often attributed to complex, multifaceted issues involving biological, psychological, and social components. Due to the difficulty in treating the true cause of chronic low back pain (cLBP), an over-reliance on opioid pain medications among cLBP patients has developed, which is associated with increased prevalence of opioid use disorder and increased risk of death. To combat the rise of opioid-related deaths, the National Institutes of Health (NIH) initiated the Helping to End Addiction Long-TermSM (HEAL) initiative, whose goal is to address the causes and treatment of opioid use disorder while also seeking to better understand, diagnose, and treat chronic pain. The NIH Back Pain Consortium (BACPAC) Research Program, a network of 14 funded entities, was launched as a part of the HEAL initiative to help address limitations surrounding the diagnosis and treatment of cLBP. This paper provides an overview of the BACPAC research program's goals and overall structure, and describes the harmonization efforts across the consortium, define its research agenda, and develop a collaborative project which utilizes the strengths of the network. The purpose of this paper is to serve as a blueprint for other consortia tasked with the advancement of pain related science.
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Affiliation(s)
- Matthew C Mauck
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Jeffrey Lotz
- University of California San Francisco (UCSF), San Fransisco, CA, United States
| | - Matthew A Psioda
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Timothy S Carey
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Daniel J Clauw
- University of Michigan (U Mich), Ann Arbor, MI, United States
| | - Sharmila Majumdar
- University of California San Francisco (UCSF), San Fransisco, CA, United States
| | | | - Nam Vo
- University of Pittsburgh (U Pitt), Pittsburgh, PA, United States
| | - Ayleen Aylward
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Anna Hoffmeyer
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Patricia Zheng
- University of California San Francisco (UCSF), San Fransisco, CA, United States
| | - Anastasia Ivanova
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Micah McCumber
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Christiane Carson
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Kevin J Anstrom
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Anton E Bowden
- Brigham Young University (BYU), Proto, UT, United States
| | | | - Leslie Derr
- National Institutes of Health (NIH), Bethesda, MA, United States
| | | | - Aaron J Fields
- University of California San Francisco (UCSF), San Fransisco, CA, United States
| | - Julie Fritz
- University of Utah, Salt Lake City, UT, United States
| | - Afton L Hassett
- University of Michigan (U Mich), Ann Arbor, MI, United States
| | - Steven E Harte
- University of Michigan (U Mich), Ann Arbor, MI, United States
| | - Trisha F Hue
- University of California San Francisco (UCSF), San Fransisco, CA, United States
| | - Roland Krug
- University of California San Francisco (UCSF), San Fransisco, CA, United States
| | - Marco L Loggia
- Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
| | | | - Samuel A McLean
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | | | - Conor O’Neill
- University of California San Francisco (UCSF), San Fransisco, CA, United States
| | - Valentina Pedoia
- University of California San Francisco (UCSF), San Fransisco, CA, United States
| | | | - Daniel I Rhon
- Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Viola Rieke
- University of Utah, Salt Lake City, UT, United States
| | - Lubdha Shah
- University of Utah, Salt Lake City, UT, United States
| | - Gwendolyn Sowa
- University of Pittsburgh (U Pitt), Pittsburgh, PA, United States
| | - Brennan Spiegel
- Cedars-Sinai Comprehensive Transplant Center (CTC), Los Angeles, CA, United States
| | - Ajay D Wasan
- University of Pittsburgh (U Pitt), Pittsburgh, PA, United States
| | | | - Lisa LaVange
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
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Martin JT, Asimakopoulos D, Hornung AL, Toro SJ, Le Maitre CL, Chahine NO, Fields AJ, Gawri R, Giers MB, Smith LJ, Tang SY, Zehra U, Haglund L, Samartzis D. Bullying, harassment, and discrimination of musculoskeletal researchers and the impact of the COVID-19 pandemic: an international study. Eur Spine J 2023; 32:1861-1875. [PMID: 37014436 PMCID: PMC10071222 DOI: 10.1007/s00586-023-07684-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 03/11/2023] [Accepted: 03/23/2023] [Indexed: 04/05/2023]
Abstract
PURPOSE Bullying, harassment, and discrimination (BHD) are prevalent in academic, scientific, and clinical departments, particularly orthopedic surgery, and can have lasting effects on victims. As it is unclear how BHD affects musculoskeletal (MSK) researchers, the following study assessed BHD in the MSK research community and whether the COVID-19 pandemic, which caused hardships in other industries, had an impact. METHODS A web-based anonymous survey was developed in English by ORS Spine Section members to assess the impact of COVID-19 on MSK researchers in North America, Europe, and Asia, which included questions to evaluate the personal experience of researchers regarding BHD. RESULTS 116 MSK researchers completed the survey. Of respondents, 34.5% (n = 40) focused on spine, 30.2% (n = 35) had multiple areas of interest, and 35.3% (n = 41) represented other areas of MSK research. BHD was observed by 26.7% (n = 31) of respondents and personally experienced by 11.2% (n = 13), with mid-career faculty both observing and experiencing the most BHD. Most who experienced BHD (53.8%, n = 7) experienced multiple forms. 32.8% (n = 38) of respondents were not able to speak out about BHD without fear of repercussions, with 13.8% (n = 16) being unsure about this. Of those who observed BHD, 54.8% (n = 17) noted that the COVID-19 pandemic had no impact on their observations. CONCLUSIONS To our knowledge, this is the first study to address the prevalence and determinants of BHD among MSK researchers. MSK researchers experienced and observed BHD, while many were not comfortable reporting and discussing violations to their institution. The COVID-19 pandemic had mixed-effects on BHD. Awareness and proactive policy changes may be warranted to reduce/eliminate the occurrence of BHD in this community.
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Affiliation(s)
- John T Martin
- Department of Orthopedic Surgery, Orthopedic Building, Rush University Medical Center, 1611 W. Harrison Street, Chicago, IL, 60612, USA
- International Spine Research and Innovation Initiative, Rush University Medical Center, Chicago, USA
| | | | - Alexander L Hornung
- Department of Orthopedic Surgery, Orthopedic Building, Rush University Medical Center, 1611 W. Harrison Street, Chicago, IL, 60612, USA
- International Spine Research and Innovation Initiative, Rush University Medical Center, Chicago, USA
| | - Sheila J Toro
- Department of Orthopedic Surgery, Orthopedic Building, Rush University Medical Center, 1611 W. Harrison Street, Chicago, IL, 60612, USA
- International Spine Research and Innovation Initiative, Rush University Medical Center, Chicago, USA
| | | | - Nadeen O Chahine
- Department of Orthopedic Surgery, Columbia University, New York, USA
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California in San Francisco, San Francisco, USA
| | - Rahul Gawri
- Department of Surgery, The Orthopaedic Research Laboratory Montreal General Hospital, McGill University, 1650 Cedar Avenue, Room C10.148.2, Montreal, QC, H3G 1A4, Canada
| | - Morgan B Giers
- School of Chemical, Biological & Environmental Engineering, Oregon State University, Corvallis, USA
| | - Lachlan J Smith
- Departments of Orthopaedic Surgery and Neurosurgery, University of Pennsylvania, Philadelphia, USA
| | - Simon Y Tang
- Department of Orthopaedic Surgery, Washington University, St. Louis, USA
| | - Uruj Zehra
- Department of Anatomy, University of Health Sciences, Lahore, Pakistan
| | - Lisbet Haglund
- Department of Surgery, The Orthopaedic Research Laboratory Montreal General Hospital, McGill University, 1650 Cedar Avenue, Room C10.148.2, Montreal, QC, H3G 1A4, Canada.
| | - Dino Samartzis
- Department of Orthopedic Surgery, Orthopedic Building, Rush University Medical Center, 1611 W. Harrison Street, Chicago, IL, 60612, USA.
- International Spine Research and Innovation Initiative, Rush University Medical Center, Chicago, USA.
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Bonnheim NB, Lazar AA, Kumar A, Akkaya Z, Zhou J, Guo X, O'Neill C, Link TM, Lotz JC, Krug R, Fields AJ. ISSLS Prize in Bioengineering Science 2023: Age- and sex-related differences in lumbar intervertebral disc degeneration between patients with chronic low back pain and asymptomatic controls. Eur Spine J 2023; 32:1517-1524. [PMID: 36805320 PMCID: PMC10205694 DOI: 10.1007/s00586-023-07542-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Revised: 10/18/2022] [Accepted: 01/13/2023] [Indexed: 02/20/2023]
Abstract
PURPOSE Clinical management of disc degeneration in patients with chronic low back pain (cLBP) is hampered by the challenge of distinguishing pathologic changes relating to pain from physiologic changes related to aging. The goal of this study was to use imaging biomarkers of disc biochemical composition to distinguish degenerative changes associated with cLBP from normal aging. METHODS T1ρ MRI data were acquired from 133 prospectively enrolled subjects for this observational study (80 cLBP, 53 controls; mean ± SD age = 43.9 ± 13.4 years; 61 females, 72 males). The mean T1ρ relaxation time in the nucleus pulposus (NP-T1ρ; n = 650 discs) was used as a quantitative biomarker of disc biochemical composition. Linear regression was used to assess associations between NP-T1ρ and age, sex, spinal level, and study group, and their interactions. RESULTS NP-T1ρ values were lower in cLBP patients than controls (70.8 ± 22.8 vs. 76.4 ± 22.2 ms, p = 0.009). Group differences were largest at L5-S1 (ΔT1ρcLBP-control = -11.3 ms, p < 0.0001), representing biochemical deterioration typically observed over a 9-12 year period (NP-T1ρ declined by 0.8-1.1 ms per year [95% CI]). Group differences were large in younger patients and diminished with age. Finally, the age-dependence of disc degeneration was stronger in controls than cLBP patients. CONCLUSION Aging effects on the biochemical composition of the L5-S1 disc may involve a relatively uniform set of factors from which many cLBP patients deviate. NP-T1ρ values at L5-S1 may be highly relevant to clinical phenotyping, particularly in younger individuals.
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Affiliation(s)
- Noah B Bonnheim
- Department of Orthopaedic Surgery, University of California, San Francisco, USA
| | - Ann A Lazar
- Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA
| | - Anika Kumar
- Department of Orthopaedic Surgery, University of California, San Francisco, USA
| | - Zehra Akkaya
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Jiamin Zhou
- Department of Orthopaedic Surgery, University of California, San Francisco, USA
| | - Xiaojie Guo
- Department of Orthopaedic Surgery, University of California, San Francisco, USA
| | - Conor O'Neill
- Department of Orthopaedic Surgery, University of California, San Francisco, USA
| | - Thomas M Link
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Jeffrey C Lotz
- Department of Orthopaedic Surgery, University of California, San Francisco, USA
| | - Roland Krug
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California, San Francisco, USA.
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9
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Bonnheim NB, Wang L, Lazar AA, Chachad R, Zhou J, Guo X, O’Neill C, Castellanos J, Du J, Jang H, Krug R, Fields AJ. Deep-learning-based biomarker of spinal cartilage endplate health using ultra-short echo time magnetic resonance imaging. Quant Imaging Med Surg 2023; 13:2807-2821. [PMID: 37179932 PMCID: PMC10167428 DOI: 10.21037/qims-22-729] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Accepted: 02/07/2023] [Indexed: 03/13/2023]
Abstract
Background T2* relaxation times in the spinal cartilage endplate (CEP) measured using ultra-short echo time magnetic resonance imaging (UTE MRI) reflect aspects of biochemical composition that influence the CEP's permeability to nutrients. Deficits in CEP composition measured using T2* biomarkers from UTE MRI are associated with more severe intervertebral disc degeneration in patients with chronic low back pain (cLBP). The goal of this study was to develop an objective, accurate, and efficient deep-learning-based method for calculating biomarkers of CEP health using UTE images. Methods Multi-echo UTE MRI of the lumbar spine was acquired from a prospectively enrolled cross-sectional and consecutive cohort of 83 subjects spanning a wide range of ages and cLBP-related conditions. CEPs from the L4-S1 levels were manually segmented on 6,972 UTE images and used to train neural networks utilizing the u-net architecture. CEP segmentations and mean CEP T2* values derived from manually- and model-generated segmentations were compared using Dice scores, sensitivity, specificity, Bland-Altman, and receiver-operator characteristic (ROC) analysis. Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were calculated and related to model performance. Results Compared with manual CEP segmentations, model-generated segmentations achieved sensitives of 0.80-0.91, specificities of 0.99, Dice scores of 0.77-0.85, area under the receiver-operating characteristic curve values of 0.99, and precision-recall (PR) AUC values of 0.56-0.77, depending on spinal level and sagittal image position. Mean CEP T2* values and principal CEP angles derived from the model-predicted segmentations had low bias in an unseen test dataset (T2* bias =0.33±2.37 ms, angle bias =0.36±2.65°). To simulate a hypothetical clinical scenario, the predicted segmentations were used to stratify CEPs into high, medium, and low T2* groups. Group predictions had diagnostic sensitivities of 0.77-0.86 and specificities of 0.86-0.95. Model performance was positively associated with image SNR and CNR. Conclusions The trained deep learning models enable accurate, automated CEP segmentations and T2* biomarker computations that are statistically similar to those from manual segmentations. These models address limitations with inefficiency and subjectivity associated with manual methods. Such techniques could be used to elucidate the role of CEP composition in disc degeneration etiology and guide emerging therapies for cLBP.
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Affiliation(s)
- Noah B. Bonnheim
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Linshanshan Wang
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Ann A. Lazar
- Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA
| | - Ravi Chachad
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Jiamin Zhou
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Xiaojie Guo
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Conor O’Neill
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Joel Castellanos
- Department of Anesthesiology, University of California, San Diego, CA, USA
| | - Jiang Du
- Department of Radiology, University of California, San Diego, CA, USA
| | - Hyungseok Jang
- Department of Radiology, University of California, San Diego, CA, USA
| | - Roland Krug
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Aaron J. Fields
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
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10
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Batorsky A, Bowden AE, Darwin J, Fields AJ, Greco CM, Harris RE, Hue TF, Kakyomya J, Mehling W, O'Neill C, Patterson CG, Piva SR, Sollmann N, Toups V, Wasan AD, Wasserman R, Williams DA, Vo NV, Psioda MA, McCumber M. The BACPAC Research Program Data Harmonization: Rationale for Data Elements and Standards. Pain Med 2023:7017526. [PMID: 36721327 DOI: 10.1093/pm/pnad008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 01/19/2023] [Accepted: 01/19/2023] [Indexed: 02/02/2023]
Abstract
OBJECTIVE One aim of the Back Pain Consortium (BACPAC) Research Program is to develop an integrated model of chronic low back pain that is informed by combined data from translational research and clinical trials. We describe efforts to maximize data harmonization and accessibility to facilitate Consortium-wide analyses. METHODS Consortium-wide working groups established harmonized data elements to be collected in all studies and developed standards for tabular and non-tabular data (e.g., imaging and omics). The BACPAC Data Portal was developed to facilitate research collaboration across the Consortium. RESULTS Clinical experts developed the BACPAC Minimum Dataset with required domains and outcome measures to be collected using questionnaires across projects. Other non-required domain-specific measures are collected by multiple studies. To optimize cross-study analyses, a modified data standard was developed based on the Clinical Data Interchange Standards Consortium Study Data Tabulation Model to harmonize data structures and facilitate integration of baseline characteristics, participant-reported outcomes, chronic low back pain treatments, clinical exam, functional performance, psychosocial characteristics, quantitative sensory testing, imaging and biomechanical data. Standards to accommodate the unique features of chronic low back pain data were adopted. Research units submit standardized study data to the BACPAC Data Portal, developed as a secure cloud-based central data repository and computing infrastructure for researchers to access and conduct analyses on data collected by or acquired for BACPAC. CONCLUSIONS BACPAC harmonization efforts and data standards serve as an innovative model for data integration that could be used as a framework for other consortia with multiple, decentralized research programs.
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Affiliation(s)
- Anna Batorsky
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Anton E Bowden
- Department of Mechanical Engineering, Brigham Young University, Provo, UT, USA
| | - Jessa Darwin
- Department of Physical Medicine and Rehabilitation, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Carol M Greco
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Department of Physical Therapy, School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Richard E Harris
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI, USA
| | - Trisha F Hue
- Department of Epidemiology & Biostatistics, University of California San Francisco, San Francisco, CA, USA
| | - Joseph Kakyomya
- School of Health and Rehabilitation Sciences Data Center, University of Pittsburgh, Pittsburgh, PA, USA
| | - Wolf Mehling
- Department of Family and Community Medicine, University of California San Francisco, San Francisco, CA, USA
| | - Conor O'Neill
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Charity G Patterson
- Department of Physical Therapy, School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, PA, USA.,School of Health and Rehabilitation Sciences Data Center, University of Pittsburgh, Pittsburgh, PA, USA
| | - Sara R Piva
- Department of Physical Therapy, School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Nico Sollmann
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA.,Department of Diagnostic and Interventional Radiology, University Hospital Ulm, Ulm, Germany.,Department of Diagnostic and Interventional Neuroradiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany.,TUM-Neuroimaging Center, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Vincent Toups
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Ajay D Wasan
- Department of Anesthesiology and Perioperative Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ronald Wasserman
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI, USA.,Back and Pain Center, University of Michigan, Ann Arbor, MI, USA
| | - David A Williams
- Chronic Pain and Fatigue Research Center, Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, MI, USA.,Department of Psychiatry, University of Michigan Medical School, Ann Arbor, MI, USA.,Department of Internal Medicine-Rheumatology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Nam V Vo
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Ferguson Laboratory for Orthopaedic and Spine Research, University of Pittsburgh, Pittsburgh, PA, USA
| | - Matthew A Psioda
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Micah McCumber
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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11
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Habib M, Hussien S, Jeon O, Lotz JC, Wu PIK, Alsberg E, Fields AJ. Intradiscal treatment of the cartilage endplate for improving solute transport and disc nutrition. Front Bioeng Biotechnol 2023; 11:1111356. [PMID: 36923455 PMCID: PMC10008947 DOI: 10.3389/fbioe.2023.1111356] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 02/09/2023] [Indexed: 03/03/2023] Open
Abstract
Poor nutrient transport through the cartilage endplate (CEP) is a key factor in the etiology of intervertebral disc degeneration and may hinder the efficacy of biologic strategies for disc regeneration. Yet, there are currently no treatments for improving nutrient transport through the CEP. In this study we tested whether intradiscal delivery of a matrix-modifying enzyme to the CEP improves solute transport into whole human and bovine discs. Ten human lumbar motion segments harvested from five fresh cadaveric spines (38-66 years old) and nine bovine coccygeal motion segments harvested from three adult steers were treated intradiscally either with collagenase enzyme or control buffer that was loaded in alginate carrier. Motion segments were then incubated for 18 h at 37 °C, the bony endplates removed, and the isolated discs were compressed under static (0.2 MPa) and cyclic (0.4-0.8 MPa, 0.2 Hz) loads while submerged in fluorescein tracer solution (376 Da; 0.1 mg/ml). Fluorescein concentrations from site-matched nucleus pulposus (NP) samples were compared between discs. CEP samples from each disc were digested and assayed for sulfated glycosaminoglycan (sGAG) and collagen contents. Results showed that enzymatic treatment of the CEP dramatically enhanced small solute transport into the disc. Discs with enzyme-treated CEPs had up to 10.8-fold (human) and 14.0-fold (bovine) higher fluorescein concentration in the NP compared to site-matched locations in discs with buffer-treated CEPs (p < 0.0001). Increases in solute transport were consistent with the effects of enzymatic treatment on CEP composition, which included reductions in sGAG content of 33.5% (human) and 40% (bovine). Whole disc biomechanical behavior-namely, creep strain and disc modulus-was similar between discs with enzyme- and buffer-treated CEPs. Taken together, these findings demonstrate the potential for matrix modification of the CEP to improve the transport of small solutes into whole intact discs.
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Affiliation(s)
- Mohamed Habib
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, United States.,Department of Mechanical Engineering, Al Azhar University, Cairo, Egypt
| | - Shayan Hussien
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, United States
| | - Oju Jeon
- Department of Biomedical Engineering, University of Illinois, Chicago, IL, United States
| | - Jeffrey C Lotz
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, United States
| | - Peter I-Kung Wu
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, United States
| | - Eben Alsberg
- Department of Biomedical Engineering, University of Illinois, Chicago, IL, United States
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, United States
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12
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Fields AJ, Dudli S, Schrepf A, Kim A, Pham B, Gallego E, Mendoza S, Meropol SB, Darwin J, Sowa G, Vo NV. Protocol for Biospecimen Collection and Analysis within the BACPAC Research Program. Pain Med 2022:6917076. [PMID: 36525387 PMCID: PMC10403310 DOI: 10.1093/pm/pnac197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 11/17/2022] [Accepted: 12/12/2022] [Indexed: 12/23/2022]
Abstract
The Biospecimen Collection and Processing Working Group of the NIH HEAL Initiative BACPAC Research Program was charged with identifying molecular biomarkers of interest to chronic low back pain (cLBP). Having identified biomarkers of interest, the Working Group worked with the New York University Grossman School of Medicine, Center for Biospecimen Research and Development-funded by the Early Phase Pain Investigation Clinical Network Data Coordinating Center-to harmonize consortium-wide and site-specific efforts for biospecimen collection and analysis. Biospecimen collected are saliva, blood (whole, plasma, serum), urine, stool, and spine tissue (paraspinal muscle, ligamentum flavum, vertebral bone, facet cartilage, disc endplate, annulus fibrosus, or nucleus pulposus). The omics data acquisition and analyses derived from the biospecimen include genomics and epigenetics from DNA, proteomics from protein, transcriptomics from RNA, and microbiomics from 16S rRNA. These analyses contribute to the overarching goal of BACPAC to phenotype cLBP and will guide future efforts for precision medicine treatment.
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Affiliation(s)
- Aaron J Fields
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Stefan Dudli
- Center of Experimental Rheumatology, University Hospital Zurich and Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Andrew Schrepf
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI, USA
| | - Angie Kim
- The New York University Langone Health, Center for Biospecimen Research and Development, Office of Science and Research, NYU Grossman School of Medicine, New York, NY, USA
| | - Bernice Pham
- The New York University Langone Health, Center for Biospecimen Research and Development, Office of Science and Research, NYU Grossman School of Medicine, New York, NY, USA
| | - Estefania Gallego
- The New York University Langone Health, Center for Biospecimen Research and Development, Office of Science and Research, NYU Grossman School of Medicine, New York, NY, USA
| | - Sandra Mendoza
- The New York University Langone Health, Center for Biospecimen Research and Development, Office of Science and Research, NYU Grossman School of Medicine, New York, NY, USA
| | - Sharon B Meropol
- NYU Grossman School of Medicine, Department of Population Health, New York, NY, USA
| | - Jessa Darwin
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Gwendolyn Sowa
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Ferguson Laboratory for Orthopaedic and Spine Research, University of Pittsburgh, Pittsburgh, PA, USA
| | - Nam V Vo
- Ferguson Laboratory for Orthopaedic and Spine Research, University of Pittsburgh, Pittsburgh, PA, USA.,Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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13
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Sollmann N, Bonnheim NB, Joseph GB, Chachad R, Zhou J, Akkaya Z, Pirmoazen AM, Bailey JF, Guo X, Lazar AA, Link TM, Fields AJ, Krug R. Paraspinal Muscle in Chronic Low Back Pain: Comparison Between Standard Parameters and Chemical Shift Encoding-Based Water-Fat MRI. J Magn Reson Imaging 2022; 56:1600-1608. [PMID: 35285561 PMCID: PMC9470775 DOI: 10.1002/jmri.28145] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 02/23/2022] [Accepted: 02/25/2022] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Paraspinal musculature (PSM) is increasingly recognized as a contributor to low back pain (LBP), but with conventional MRI sequences, assessment is limited. Chemical shift encoding-based water-fat MRI (CSE-MRI) enables the measurement of PSM fat fraction (FF), which may assist investigations of chronic LBP. PURPOSE To investigate associations between PSM parameters from conventional MRI and CSE-MRI and between PSM parameters and pain. STUDY TYPE Prospective, cross-sectional. POPULATION Eighty-four adults with chronic LBP (44.6 ± 13.4 years; 48 males). FIELD STRENGTH/SEQUENCE 3-T, T1-weighted fast spin-echo and iterative decomposition of water and fat with echo asymmetry and least squares estimation sequences. ASSESSMENT T1-weighted images for Goutallier classification (GC), muscle volume, lumbar indentation value, and muscle-fat index, CSE-MRI for FF extraction (L1/2-L5/S1). Pain was self-reported using a visual analogue scale (VAS). Intra- and/or interreader agreement was assessed for MRI-derived parameters. STATISTICAL TESTS Mixed-effects and linear regression models to 1) assess relationships between PSM parameters (entire cohort and subgroup with GC grades 0 and 1; statistical significance α = 0.0025) and 2) evaluate associations of PSM parameters with pain (α = 0.05). Intraclass correlation coefficients (ICCs) for intra- and/or interreader agreement. RESULTS The FF showed excellent intra- and interreader agreement (ICC range: 0.97-0.99) and was significantly associated with GC at all spinal levels. Subgroup analysis suggested that early/subtle changes in PSM are detectable with FF but not with GC, given the absence of significant associations between FF and GC (P-value range: 0.036 at L5/S1 to 0.784 at L2/L3). Averaged over all spinal levels, FF and GC were significantly associated with VAS scores. DATA CONCLUSION In the absence of FF, GC may be the best surrogate for PSM quality. Given the ability of CSE-MRI to detect muscle alterations at early stages of PSM degeneration, this technique may have potential for further investigations of the role of PSM in chronic LBP. LEVEL OF EVIDENCE 2 TECHNICAL EFFICACY STAGE: 2.
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Affiliation(s)
- Nico Sollmann
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA
- Department of Diagnostic and Interventional Radiology, University Hospital Ulm, Ulm, Germany
- Department of Diagnostic and Interventional Neuroradiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
- TUM-Neuroimaging Center, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Noah B. Bonnheim
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, California, USA
| | - Gabby B. Joseph
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA
| | - Ravi Chachad
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA
| | - Jiamin Zhou
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA
| | - Zehra Akkaya
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA
| | - Amir M. Pirmoazen
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA
| | - Jeannie F. Bailey
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, California, USA
| | - Xiaojie Guo
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, California, USA
| | - Ann A. Lazar
- Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, California, USA
| | - Thomas M. Link
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA
| | - Aaron J. Fields
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, California, USA
| | - Roland Krug
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA
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14
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Sollmann N, Fields AJ, O'Neill C, Nardo L, Majumdar S, Chin CT, Tosun D, Han M, Vu AT, Ozhinsky E, Shah LM, Harris RE, Lobo R, Anderst W, Herzog R, Psioda MA, Standaert CJ, Price RT, Lotz JC, Link TM, Krug R. Magnetic resonance imaging of the lumbar spine-recommendations for acquisition and image evaluation from the BACPAC Spine Imaging Working Group. Pain Med 2022:6687139. [PMID: 36069660 PMCID: PMC10403314 DOI: 10.1093/pm/pnac130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Management of patients suffering from low back pain (LBP) is challenging and requires development of diagnostic techniques to identify specific patient subgroups and phenotypes in order to customize treatment and predict clinical outcome. The Back Pain Consortium (BACPAC) Spine Imaging Working Group has developed standard operating procedures (SOPs) for spinal imaging protocols to be used in all BACPAC studies. These SOPs include procedures to conduct spinal imaging assessments with guidelines for standardizing the collection, reading/grading (using structured reporting with semi-quantitative evaluation using ordinal rating scales), and storage of images. This article presents the approach to image acquisition and evaluation recommended by the BACPAC Spine Imaging Working Group. While the approach is specific to BACPAC studies, it is general enough to be applied at other centers performing MRI acquisitions in patients with LBP. The herein presented SOPs are meant to improve understanding of pain mechanisms and facilitate patient phenotyping by codifying MRI-based methods that provide standardized, non-invasive assessments of spinal pathologies. Finally, these recommended procedures may facilitate the integration of better harmonized MRI data of the lumbar spine across studies and sites within and outside of BACPAC studies.
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Affiliation(s)
- Nico Sollmann
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.,Department of Diagnostic and Interventional Radiology, University Hospital Ulm, Ulm, Germany.,Department of Diagnostic and Interventional Neuroradiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany.,TUM-Neuroimaging Center, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Conor O'Neill
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Lorenzo Nardo
- Department of Radiology, University of California, Davis, Sacramento, CA, USA
| | - Sharmila Majumdar
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.,Center for Digital Health Innovation, University of California, San Francisco, San Francisco, CA, USA
| | - Cynthia T Chin
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Duygu Tosun
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Misung Han
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - An T Vu
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.,VA Advanced Imaging Research Center, San Francisco VA Health Care System, San Francisco, CA, USA
| | - Eugene Ozhinsky
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.,VA Advanced Imaging Research Center, San Francisco VA Health Care System, San Francisco, CA, USA
| | - Lubdha M Shah
- Department of Radiology, University of Utah, Salt Lake City, UT, USA
| | - Richard E Harris
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI, USA
| | - Remy Lobo
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - William Anderst
- Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA
| | - Richard Herzog
- Department of Radiology and Imaging, Hospital for Special Surgery, New York, NY, USA
| | - Matthew A Psioda
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Christopher J Standaert
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - River T Price
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Jeffrey C Lotz
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Thomas M Link
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Roland Krug
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
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15
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Ballatori AM, Shahrestani S, Nyayapati P, Agarwal V, Krug R, Han M, Fields AJ, O'Neill C, Demir‐Deviren S, Lotz JC, Bailey JF. Influence of patient-specific factors when comparing multifidus fat infiltration between chronic low back pain patients and asymptomatic controls. JOR Spine 2022; 5:e1217. [PMID: 36601370 PMCID: PMC9799081 DOI: 10.1002/jsp2.1217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Revised: 06/17/2022] [Accepted: 06/26/2022] [Indexed: 01/07/2023] Open
Abstract
Introduction Many studies have attempted to link multifidus (MF) fat infiltration with muscle quality and chronic low back pain (cLBP), but there is no consensus on these relationships. Methods In this cross-sectional cohort study, 39 cLBP patients and 18 asymptomatic controls were included. The MF muscle was manually segmented at each lumbar disc level and fat fraction (FF) measurements were taken from the corresponding advanced imaging water-fat images. We assessed the distribution patterns of MF fat from L1L2 to L5S1 and compared these patterns between groups. The sample was stratified by age, sex, body mass index (BMI), subject-reported pain intensity (VAS), and subject-reported low back pain disability (oswestry disability index, ODI). Results Older patients had significantly different MF FF distribution patterns compared to older controls (p < 0.0001). Male patients had 34.8% higher mean lumbar spine MF FF compared to male controls (p = 0.0006), significantly different MF FF distribution patterns (p = 0.028), 53.7% higher mean MF FF measurements at L2L3 (p = 0.037), and 50.6% higher mean MF FF measurements at L3L4 (p = 0.041). Low BMI patients had 29.7% higher mean lumbar spine MF FF compared to low BMI controls (p = 0.0077). High BMI patients only had 4% higher mean lumbar spine MF FF compared to high BMI controls (p = 0.7933). However, high BMI patients had significantly different MF FF distribution patterns compared to high BMI controls (p = 0.0324). Low VAS patients did not significantly differ from the control cohort for any of our outcomes of interest; however, high VAS patients had 24.3% higher mean lumbar spine MF FF values (p = 0.0011), significantly different MF FF distribution patterns (p < 0.0001), 34.7% higher mean MF FF at L2L3 (p = 0.040), and 34.6% higher mean MF FF at L3L4 (p = 0.040) compared to the control cohort. Similar trends were observed for ODI. Conclusions This study suggests that when the presence of paraspinal muscle fat infiltration is not characteristic of an individual's age, sex, and BMI, it may be associated with lower back pain.
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Affiliation(s)
- Alexander M. Ballatori
- Keck School of Medicine of USCLos AngelesCaliforniaUSA
- Department of Orthopaedic SurgeryUniversity of CaliforniaSan FranciscoCaliforniaUSA
| | - Shane Shahrestani
- Keck School of Medicine of USCLos AngelesCaliforniaUSA
- Department of Medical EngineeringCalifornia Institute of TechnologyPasadenaCaliforniaUSA
| | - Priya Nyayapati
- Department of Orthopaedic SurgeryUniversity of CaliforniaSan FranciscoCaliforniaUSA
- Albany Medical CollegeAlbanyNew YorkUSA
| | - Vibhu Agarwal
- Department of Quantitative SciencesStanford UniversityStanfordCaliforniaUSA
| | - Roland Krug
- Department of RadiologyUniversity of CaliforniaSan FranciscoCaliforniaUSA
| | - Misung Han
- Department of RadiologyUniversity of CaliforniaSan FranciscoCaliforniaUSA
| | - Aaron J. Fields
- Department of Orthopaedic SurgeryUniversity of CaliforniaSan FranciscoCaliforniaUSA
| | - Conor O'Neill
- Department of Orthopaedic SurgeryUniversity of CaliforniaSan FranciscoCaliforniaUSA
| | - Sibel Demir‐Deviren
- Department of Orthopaedic SurgeryUniversity of CaliforniaSan FranciscoCaliforniaUSA
| | - Jeffrey C. Lotz
- Department of Orthopaedic SurgeryUniversity of CaliforniaSan FranciscoCaliforniaUSA
| | - Jeannie F. Bailey
- Department of Orthopaedic SurgeryUniversity of CaliforniaSan FranciscoCaliforniaUSA
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16
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Bonnheim NB, Wang L, Lazar AA, Zhou J, Chachad R, Sollmann N, Guo X, Iriondo C, O'Neill C, Lotz JC, Link TM, Krug R, Fields AJ. The contributions of cartilage endplate composition and vertebral bone marrow fat to intervertebral disc degeneration in patients with chronic low back pain. Eur Spine J 2022; 31:1866-1872. [PMID: 35441890 PMCID: PMC9252939 DOI: 10.1007/s00586-022-07206-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Revised: 03/07/2022] [Accepted: 03/31/2022] [Indexed: 01/22/2023]
Abstract
Purpose The composition of the subchondral bone marrow and cartilage endplate (CEP) could affect intervertebral disc health by influencing vertebral perfusion and nutrient diffusion. However, the relative contributions of these factors to disc degeneration in patients with chronic low back pain (cLBP) have not been quantified. The goal of this study was to use compositional biomarkers derived from quantitative MRI to establish how CEP composition (surrogate for permeability) and vertebral bone marrow fat fraction (BMFF, surrogate for perfusion) relate to disc degeneration. Methods MRI data from 60 patients with cLBP were included in this prospective observational study (28 female, 32 male; age = 40.0 ± 11.9 years, 19–65 [mean ± SD, min–max]). Ultra-short echo-time MRI was used to calculate CEP T2* relaxation times (reflecting biochemical composition), water-fat MRI was used to calculate vertebral BMFF, and T1ρ MRI was used to calculate T1ρ relaxation times in the nucleus pulposus (NP T1ρ, reflecting proteoglycan content and degenerative grade). Univariate linear regression was used to assess the independent effects of CEP T2* and vertebral BMFF on NP T1ρ. Mixed effects multivariable linear regression accounting for age, sex, and BMI was used to assess the combined relationship between variables. Results CEP T2* and vertebral BMFF were independently associated with NP T1ρ (p = 0.003 and 0.0001, respectively). After adjusting for age, sex, and BMI, NP T1ρ remained significantly associated with CEP T2* (p = 0.0001) but not vertebral BMFF (p = 0.43). Conclusion Poor CEP composition plays a significant role in disc degeneration severity and can affect disc health both with and without deficits in vertebral perfusion.
Supplementary Information The online version contains supplementary material available at 10.1007/s00586-022-07206-x.
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Affiliation(s)
- Noah B Bonnheim
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Linshanshan Wang
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Ann A Lazar
- Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA
| | - Jiamin Zhou
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Ravi Chachad
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Nico Sollmann
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.,Department of Diagnostic and Interventional Radiology, University Hospital Ulm, Ulm, Germany.,Department of Diagnostic and Interventional Neuroradiology, School of Medicine, Klinikum Rechts Der Isar, Technical University of Munich, Munich, Germany.,TUM-Neuroimaging Center, Klinikum Rechts Der Isar, Technical University of Munich, Munich, Germany
| | - Xiaojie Guo
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Claudia Iriondo
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Conor O'Neill
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Jeffrey C Lotz
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Thomas M Link
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Roland Krug
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA.
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17
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Werbner B, Lee M, Lee A, Yang L, Habib M, Fields AJ, O'Connell GD. Non-enzymatic glycation of annulus fibrosus alters tissue-level failure mechanics in tension. J Mech Behav Biomed Mater 2022; 126:104992. [PMID: 34864399 DOI: 10.1016/j.jmbbm.2021.104992] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Revised: 11/18/2021] [Accepted: 11/18/2021] [Indexed: 10/19/2022]
Abstract
Advanced-glycation end products (AGEs) are known to accumulate in biological tissues with age and at an accelerated rate in patients with diabetes and chronic kidney disease. Clinically, diabetes has been linked to increased frequency and severity of back pain, accelerated disc degeneration, and an increased risk of disc herniation. Despite significant clinical evidence suggesting that diabetes-induced AGEs may play a role in intervertebral disc failure and substantial previous work investigating the effects of AGEs on bone, cartilage, and tendon mechanics, the effects of AGEs on annulus fibrosus (AF) failure mechanics have not yet been reported. Thus, the aim of this study was to determine the relationship between physiological levels of AGEs and AF tensile mechanics at two distinct loading rates. In vitro glycation treatments with methylglyoxal were applied to minimize changes in tissue hydration and induce two distinct levels of AGEs based on values measured from human AF tissues. In vitro glycation increased modulus by 48-99% and failure stress by 45-104% versus control and decreased post-failure energy absorption capacity by 15-32% versus control (ANOVA p < 0.0001 on means; range given across two loading rates and glycation levels). AGE content correlated strongly with modulus (R = 0.74, p < 0.0001) and failure stress (R = 0.70, p < 0.0001) and moderately with post-failure energy absorption capacity (R = 0.62, p < 0.0001). Failure strain was reduced by 10-17% at the high-glycation level (ANOVA p = 0.01). Tissue water content remained near or just above fresh-tissue levels for all groups. The alterations in mechanics with glycation reported here are consistent with trends from other connective tissues but do not fully explain the clinical predisposition of diabetics to disc herniation. The results from this study may be used in the development of advanced computational models that aim to study disc disease progression and to provide a deeper understanding of altered structure-function relationships that may lead to tissue dysfunction and failure with aging and disease.
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Affiliation(s)
- Benjamin Werbner
- Department of Mechanical Engineering University of California, Berkeley, USA
| | - Matthew Lee
- Department of Mechanical Engineering University of California, Berkeley, USA
| | - Allan Lee
- Department of Bioengineering University of California, Berkeley, USA
| | - Linda Yang
- Department of Bioengineering University of California, Berkeley, USA
| | - Mohamed Habib
- Department of Orthopaedic Surgery University of California, San Francisco, USA; Mechanical Engineering Department Al Azhar University, Cairo, Egypt
| | - Aaron J Fields
- Department of Orthopaedic Surgery University of California, San Francisco, USA
| | - Grace D O'Connell
- Department of Mechanical Engineering University of California, Berkeley, USA; Department of Orthopaedic Surgery University of California, San Francisco, USA.
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18
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Wang L, Han M, Wong J, Zheng P, Lazar AA, Krug R, Fields AJ. Evaluation of human cartilage endplate composition using MRI: Spatial variation, association with adjacent disc degeneration, and in vivo repeatability. J Orthop Res 2021; 39:1470-1478. [PMID: 32592504 PMCID: PMC7765737 DOI: 10.1002/jor.24787] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 06/02/2020] [Accepted: 06/24/2020] [Indexed: 02/04/2023]
Abstract
Cartilage endplate (CEP) biochemical composition may influence disc degeneration and regeneration. However, evaluating CEP composition in patients remains a challenge. We used T2* mapping from ultrashort echo-time (UTE) magnetic resonance imaging (MRI), which is sensitive to CEP hydration, to investigate spatial variations in CEP T2* values and to determine how CEP T2* values correlate with adjacent disc degeneration. Thirteen human cadavers (56.4 ± 12.7 years) and seven volunteers (36.9 ± 10.9 years) underwent 3T MRI, including UTE and T1ρ mapping sequences. Spatial mappings of T2* values in L4-S1 CEPs were generated from UTE images and compared between subregions. In the abutting discs, mean T1ρ values in the nucleus pulposus were compared between CEPs with high vs low T2* values. To assess in vivo repeatability, precision errors in mean T2* values, and intraclass correlation coefficients (ICC) were measured from repeat scans. Results showed that CEP T2* values were highest centrally and lowest posteriorly. In the youngest individuals (<50 years), who had mild-to-moderately degenerated Pfirrmann grade II-III discs, low CEP T2* values associated with severer disc degeneration: T1ρ values were 26.7% lower in subjects with low CEP T2* values (P = .025). In older individuals, CEP T2* values did not associate with disc degeneration (P = .39-.62). Precision errors in T2* ranged from 1.7 to 2.6 ms, and reliability was good-to-excellent (ICC = 0.89-0.94). These findings suggest that deficits in CEP composition, as indicated by low T2* values, associate with severer disc degeneration during the mild-to-moderate stages. Measuring CEP T2* values with UTE MRI may clarify the role of CEP composition in patients with mild-to-moderate disc degeneration.
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Affiliation(s)
- Linshanshan Wang
- Department of Orthopaedic SurgeryUniversity of CaliforniaSan FranciscoCalifornia
| | - Misung Han
- Department of Radiology & Biomedical ImagingUniversity of CaliforniaSan FranciscoCalifornia
| | - Jason Wong
- Department of Orthopaedic SurgeryUniversity of CaliforniaSan FranciscoCalifornia
| | - Patricia Zheng
- Department of Orthopaedic SurgeryUniversity of CaliforniaSan FranciscoCalifornia
| | - Ann A. Lazar
- Department of Epidemiology and BiostatisticsUniversity of CaliforniaSan FranciscoCalifornia,Department of Preventive and Restorative Dental SciencesUniversity of CaliforniaSan FranciscoCalifornia
| | - Roland Krug
- Department of Radiology & Biomedical ImagingUniversity of CaliforniaSan FranciscoCalifornia
| | - Aaron J. Fields
- Department of Orthopaedic SurgeryUniversity of CaliforniaSan FranciscoCalifornia
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19
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Zhou J, Damasceno PF, Chachad R, Cheung JR, Ballatori A, Lotz JC, Lazar AA, Link TM, Fields AJ, Krug R. Automatic Vertebral Body Segmentation Based on Deep Learning of Dixon Images for Bone Marrow Fat Fraction Quantification. Front Endocrinol (Lausanne) 2020; 11:612. [PMID: 32982989 PMCID: PMC7492292 DOI: 10.3389/fendo.2020.00612] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 07/27/2020] [Indexed: 12/16/2022] Open
Abstract
Background: Bone marrow fat (BMF) fraction quantification in vertebral bodies is used as a novel imaging biomarker to assess and characterize chronic lower back pain. However, manual segmentation of vertebral bodies is time consuming and laborious. Purpose: (1) Develop a deep learning pipeline for segmentation of vertebral bodies using quantitative water-fat MRI. (2) Compare BMF measurements between manual and automatic segmentation methods to assess performance. Materials and Methods: In this retrospective study, MR images using a 3D spoiled gradient-recalled echo (SPGR) sequence with Iterative Decomposition of water and fat with Echo Asymmetry and Least-squares estimation (IDEAL) reconstruction algorithm were obtained in 57 subjects (28 women, 29 men, mean age, 47.2 ± 12.6 years). An artificial network was trained for 100 epochs on a total of 165 lumbar vertebrae manually segmented from 31 subjects. Performance was assessed by analyzing the receiver operating characteristic curve, precision-recall, F1 scores, specificity, sensitivity, and similarity metrics. Bland-Altman analysis was used to assess performance of BMF fraction quantification using the predicted segmentations. Results: The deep learning segmentation method achieved an AUC of 0.92 (CI 95%: 0.9186, 0.9195) on a testing dataset (n = 24 subjects) on classification of pixels as vertebrae. A sensitivity of 0.99 and specificity of 0.80 were achieved for a testing dataset, and a mean Dice similarity coefficient of 0.849 ± 0.091. Comparing manual and automatic segmentations on fat fraction maps of lumbar vertebrae (n = 124 vertebral bodies) using Bland-Altman analysis resulted in a bias of only -0.605% (CI 95% = -0.847 to -0.363%) and agreement limits of -3.275% and +2.065%. Automatic segmentation was also feasible in 16 ± 1 s. Conclusion: Our results have demonstrated the feasibility of automated segmentation of vertebral bodies using deep learning models on water-fat MR (Dixon) images to define vertebral regions of interest with high specificity. These regions of interest can then be used to quantify BMF with comparable results as manual segmentation, providing a framework for completely automated investigation of vertebral changes in CLBP.
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Affiliation(s)
- Jiamin Zhou
- Department of Radiology and Biomedical Imaging, School of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Pablo F. Damasceno
- Department of Radiology and Biomedical Imaging, School of Medicine, University of California, San Francisco, San Francisco, CA, United States
- Bakar Computational Health Sciences Institute, University of California, San Francisco, San Francisco, CA, United States
- Center for Intelligent Imaging, University of California, San Francisco, San Francisco, CA, United States
| | - Ravi Chachad
- Department of Radiology and Biomedical Imaging, School of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Justin R. Cheung
- Department of Radiology and Biomedical Imaging, School of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Alexander Ballatori
- Department of Orthopaedic Surgery, School of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Jeffrey C. Lotz
- Department of Orthopaedic Surgery, School of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Ann A. Lazar
- Department of Preventive and Restorative Dental Sciences, School of Dentistry, University of California, San Francisco, San Francisco, CA, United States
- Department of Epidemiology and Biostatistics, School of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Thomas M. Link
- Department of Radiology and Biomedical Imaging, School of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Aaron J. Fields
- Department of Orthopaedic Surgery, School of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Roland Krug
- Department of Radiology and Biomedical Imaging, School of Medicine, University of California, San Francisco, San Francisco, CA, United States
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20
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Mazur CM, Woo JJ, Yee CS, Fields AJ, Acevedo C, Bailey KN, Kaya S, Fowler TW, Lotz JC, Dang A, Kuo AC, Vail TP, Alliston T. Osteocyte dysfunction promotes osteoarthritis through MMP13-dependent suppression of subchondral bone homeostasis. Bone Res 2019; 7:34. [PMID: 31700695 PMCID: PMC6828661 DOI: 10.1038/s41413-019-0070-y] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 07/25/2019] [Accepted: 07/29/2019] [Indexed: 12/28/2022] Open
Abstract
Osteoarthritis (OA), long considered a primary disorder of articular cartilage, is commonly associated with subchondral bone sclerosis. However, the cellular mechanisms responsible for changes to subchondral bone in OA, and the extent to which these changes are drivers of or a secondary reaction to cartilage degeneration, remain unclear. In knee joints from human patients with end-stage OA, we found evidence of profound defects in osteocyte function. Suppression of osteocyte perilacunar/canalicular remodeling (PLR) was most severe in the medial compartment of OA subchondral bone, with lower protease expression, diminished canalicular networks, and disorganized and hypermineralized extracellular matrix. As a step toward evaluating the causality of PLR suppression in OA, we ablated the PLR enzyme MMP13 in osteocytes while leaving chondrocytic MMP13 intact, using Cre recombinase driven by the 9.6-kb DMP1 promoter. Not only did osteocytic MMP13 deficiency suppress PLR in cortical and subchondral bone, but it also compromised cartilage. Even in the absence of injury, osteocytic MMP13 deficiency was sufficient to reduce cartilage proteoglycan content, change chondrocyte production of collagen II, aggrecan, and MMP13, and increase the incidence of cartilage lesions, consistent with early OA. Thus, in humans and mice, defects in PLR coincide with cartilage defects. Osteocyte-derived MMP13 emerges as a critical regulator of cartilage homeostasis, likely via its effects on PLR. Together, these findings implicate osteocytes in bone-cartilage crosstalk in the joint and suggest a causal role for suppressed perilacunar/canalicular remodeling in osteoarthritis.
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Affiliation(s)
- Courtney M. Mazur
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143 USA
- UC Berkeley-UCSF Graduate Program in Bioengineering, San Francisco, CA 94143 USA
| | - Jonathon J. Woo
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143 USA
| | - Cristal S. Yee
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143 USA
| | - Aaron J. Fields
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143 USA
| | - Claire Acevedo
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143 USA
- Department of Mechanical Engineering, University of Utah, Salt Lake City, UT 84112 USA
| | - Karsyn N. Bailey
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143 USA
- UC Berkeley-UCSF Graduate Program in Bioengineering, San Francisco, CA 94143 USA
| | - Serra Kaya
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143 USA
| | - Tristan W. Fowler
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143 USA
| | - Jeffrey C. Lotz
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143 USA
- UC Berkeley-UCSF Graduate Program in Bioengineering, San Francisco, CA 94143 USA
| | - Alexis Dang
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143 USA
- San Francisco Veterans Affairs Medical Center, San Francisco, CA 94121 USA
| | - Alfred C. Kuo
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143 USA
- San Francisco Veterans Affairs Medical Center, San Francisco, CA 94121 USA
| | - Thomas P. Vail
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143 USA
| | - Tamara Alliston
- Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143 USA
- UC Berkeley-UCSF Graduate Program in Bioengineering, San Francisco, CA 94143 USA
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21
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Fields AJ, Battié MC, Herzog RJ, Jarvik JG, Krug R, Link TM, Lotz JC, O'Neill CW, Sharma A. Measuring and reporting of vertebral endplate bone marrow lesions as seen on MRI (Modic changes): recommendations from the ISSLS Degenerative Spinal Phenotypes Group. Eur Spine J 2019; 28:2266-2274. [PMID: 31446492 DOI: 10.1007/s00586-019-06119-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 08/09/2019] [Accepted: 08/17/2019] [Indexed: 01/26/2023]
Abstract
PURPOSE The positive association between low back pain and MRI evidence of vertebral endplate bone marrow lesions, often called Modic changes (MC), offers the exciting prospect of diagnosing a specific phenotype of chronic low back pain (LBP). However, imprecision in the reporting of MC has introduced substantial challenges, as variations in both imaging equipment and scanning parameters can impact conspicuity of MC. This review discusses key methodological factors that impact MC classification and recommends guidelines for more consistent MC reporting that will allow for better integration of research into this LBP phenotype. METHODS Non-systematic literature review. RESULTS The high diagnostic specificity of MC classification for a painful level contributes to the significant association observed between MC and LBP, whereas low and variable sensitivity underlies the between- and within-study variability in observed associations. Poor sensitivity may be owing to the presence of other pain generators, to the limited MRI resolution, and to the imperfect reliability of MC classification, which lowers diagnostic sensitivity and thus influences the association between MC and LBP. Importantly, magnetic field strength and pulse sequence parameters also impact detection of MC. Advances in pulse sequences may improve reliability and prove valuable for quantifying lesion severity. CONCLUSIONS Comparison of MC data between studies can be problematic. Various methodological factors impact detection and classification of MC, and the lack of reporting guidelines hinders interpretation and comparison of findings. Thus, it is critical to adopt imaging and reporting standards that codify acceptable methodological criteria. These slides can be retrieved under Electronic Supplementary Material.
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Affiliation(s)
- Aaron J Fields
- Department of Orthopaedic Surgery, University of California, 513 Parnassus Avenue, S-1161, Box 0514, San Francisco, CA, 94143-0514, USA.
| | - Michele C Battié
- Faculty of Health Sciences and Western's Bone and Joint Institute, University of Western Ontario, London, ON, Canada
| | - Richard J Herzog
- Department of Radiology, Hospital for Special Surgery, New York, NY, USA
| | - Jeffrey G Jarvik
- Departments of Radiology, Neurosurgery and Health Services, and the Comparative Effectiveness, Cost and Outcomes Research Center, University of Washington, Seattle, WA, USA
| | - Roland Krug
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Thomas M Link
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Jeffrey C Lotz
- Department of Orthopaedic Surgery, University of California, 513 Parnassus Avenue, S-1161, Box 0514, San Francisco, CA, 94143-0514, USA
| | - Conor W O'Neill
- Department of Orthopaedic Surgery, University of California, 513 Parnassus Avenue, S-1161, Box 0514, San Francisco, CA, 94143-0514, USA
| | - Aseem Sharma
- Mallinckrodt Institute of Radiology, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
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22
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Dolor A, Sampson SL, Lazar AA, Lotz JC, Szoka FC, Fields AJ. Matrix modification for enhancing the transport properties of the human cartilage endplate to improve disc nutrition. PLoS One 2019; 14:e0215218. [PMID: 30970007 PMCID: PMC6457523 DOI: 10.1371/journal.pone.0215218] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 03/28/2019] [Indexed: 02/07/2023] Open
Abstract
Poor solute transport through the cartilage endplate (CEP) impairs disc nutrition and could be a key factor that limits the success of intradiscal biologic therapies. Here we demonstrate that treating the CEP with matrix metalloproteinase-8 (MMP-8) reduces the matrix constituents that impede solute uptake and thereby improves nutrient diffusion. Human CEP tissues harvested from four fresh cadaveric lumbar spines (age range: 38-66 years old) were treated with MMP-8. Treatment caused a dose-dependent reduction in sGAG, localized reductions to the amount of collagen, and alterations to collagen structure. These matrix modifications corresponded with 16-24% increases in the uptake of a small solute (376 Da). Interestingly, the effects of MMP-8 treatment depended on the extent of non-enzymatic glycation: treated CEPs with high concentrations of advanced glycation end products (AGEs) exhibited the lowest uptake compared to treated CEPs with low concentrations of AGEs. Moreover, AGE concentrations were donor-specific, and the donor tissues with the highest AGE concentrations appeared to have lower uptake than would be expected based on the initial amounts of collagen and sGAG. Finally, increasing solute uptake in the CEP improved cell viability inside diffusion chambers, which supports the nutritional relevance of enhancing the transport properties of the CEP. Taken together, our results provide new insights and in vitro proof-of-concept for a treatment approach that could improve disc nutrition for biologic therapy: specifically, matrix reduction by MMP-8 can enhance solute uptake and nutrient diffusion through the CEP, and AGE concentration appears to be an important, patient-specific factor that influences the efficacy of this approach.
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Affiliation(s)
- Aaron Dolor
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, United States of America
| | - Sara L. Sampson
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, United States of America
| | - Ann A. Lazar
- Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, CA, United States of America
- Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, United States of America
| | - Jeffrey C. Lotz
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, United States of America
| | - Francis C. Szoka
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, United States of America
| | - Aaron J. Fields
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, United States of America
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23
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Sampson SL, Sylvia M, Fields AJ. Effects of dynamic loading on solute transport through the human cartilage endplate. J Biomech 2018; 83:273-279. [PMID: 30554819 DOI: 10.1016/j.jbiomech.2018.12.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2018] [Revised: 11/07/2018] [Accepted: 12/03/2018] [Indexed: 12/29/2022]
Abstract
Nutrient and metabolite transport through the cartilage endplate (CEP) is important for maintaining proper disc nutrition, but the mechanisms of solute transport remain unclear. One unresolved issue is the role of dynamic loading. In comparison to static loading, dynamic loading is thought to enhance transport by increasing convection. However, the CEP has a high resistance to fluid flow, which could limit solute convection. Here we measure solute transport through site-matched cadaveric human lumbar CEP tissues under static vs. dynamic loading, and we determine how the degree of transport enhancement from dynamic loading depends on CEP porosity and solute size. We found that dynamic loading significantly increased small and large solute transport through the CEP: on average, dynamic loading increased the transport of sodium fluorescein (376 Da) by a factor of 1.85 ± 0.64 and the transport of a large dextran (4000 Da) by a factor of 4.97 ± 3.05. Importantly, CEP porosity (0.65 ± 0.07; range: 0.47-0.76) strongly influenced the degree of transport enhancement. Specifically, for both solutes, transport enhancement was greater for CEPs with low porosity than for CEPs with high porosity. This is because the CEPs with low porosity were susceptible to larger improvements in fluid flow under dynamic loading. The CEP becomes less porous and less hydrated with aging and as disc degeneration progresses. Together, these findings suggest that as those changes occur, dynamic loading has a greater effect on solute transport through the CEP compared to static loading, and thus may play a larger role in disc nutrition.
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Affiliation(s)
- Sara L Sampson
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Meghan Sylvia
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA.
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24
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Woronowicz KC, Gline SE, Herfat ST, Fields AJ, Schneider RA. FGF and TGFβ signaling link form and function during jaw development and evolution. Dev Biol 2018; 444 Suppl 1:S219-S236. [PMID: 29753626 PMCID: PMC6239991 DOI: 10.1016/j.ydbio.2018.05.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 04/20/2018] [Accepted: 05/06/2018] [Indexed: 12/14/2022]
Abstract
How does form arise during development and change during evolution? How does form relate to function, and what enables embryonic structures to presage their later use in adults? To address these questions, we leverage the distinct functional morphology of the jaw in duck, chick, and quail. In connection with their specialized mode of feeding, duck develop a secondary cartilage at the tendon insertion of their jaw adductor muscle on the mandible. An equivalent cartilage is absent in chick and quail. We hypothesize that species-specific jaw architecture and mechanical forces promote secondary cartilage in duck through the differential regulation of FGF and TGFβ signaling. First, we perform transplants between chick and duck embryos and demonstrate that the ability of neural crest mesenchyme (NCM) to direct the species-specific insertion of muscle and the formation of secondary cartilage depends upon the amount and spatial distribution of NCM-derived connective tissues. Second, we quantify motility and build finite element models of the jaw complex in duck and quail, which reveals a link between species-specific jaw architecture and the predicted mechanical force environment. Third, we investigate the extent to which mechanical load mediates FGF and TGFβ signaling in the duck jaw adductor insertion, and discover that both pathways are mechano-responsive and required for secondary cartilage formation. Additionally, we find that FGF and TGFβ signaling can also induce secondary cartilage in the absence of mechanical force or in the adductor insertion of quail embryos. Thus, our results provide novel insights on molecular, cellular, and biomechanical mechanisms that couple musculoskeletal form and function during development and evolution.
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Affiliation(s)
- Katherine C Woronowicz
- Department of Orthopaedic Surgery, University of California, San Francisco, 513 Parnassus Avenue, S-1161, San Francisco, CA 94143-0514, USA
| | - Stephanie E Gline
- Department of Orthopaedic Surgery, University of California, San Francisco, 513 Parnassus Avenue, S-1161, San Francisco, CA 94143-0514, USA
| | - Safa T Herfat
- Department of Orthopaedic Surgery, University of California, San Francisco, 513 Parnassus Avenue, S-1161, San Francisco, CA 94143-0514, USA
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California, San Francisco, 513 Parnassus Avenue, S-1161, San Francisco, CA 94143-0514, USA
| | - Richard A Schneider
- Department of Orthopaedic Surgery, University of California, San Francisco, 513 Parnassus Avenue, S-1161, San Francisco, CA 94143-0514, USA.
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25
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Abstract
STUDY DESIGN Descriptive histologic and magnetic resonance imaging study of human cadaveric spines. OBJECTIVE To identify and characterize common endplate pathologies to form a histologic foundation for an etiology-based classification system. SUMMARY OF BACKGROUND DATA Irregularities at the spinal disc-vertebra interface are associated with back pain and intervertebral disc herniation injuries. However, there is currently a lack of consensus regarding terminology for classification. This limits the potential for advancing understanding of back pain mechanisms, and prohibits meaningful comparisons for identifying priorities for prevention and treatment. Prior classification systems largely rely on observations from clinical imaging, which may miss subtle pathologic features. METHODS Fifteen cadaveric spines with moderate to severe disc degeneration were obtained and scanned with MRI in the sagittal plane using two-dimensional T1-weighted and T2-weighted fast spin-echo sequences. Eighty-nine lumbar and lower thoracic bone-disc-bone motion segments were extracted, fixed, sectioned, and stained for histologic evaluation. Focal endplate irregularities were identified and categorized based on features that inferred causation. The presence, type, and anatomic location were recorded. A classification system with three major categories of focal endplate irregularities was created. RESULTS Disc-vertebra avulsion and vertebral rim degeneration were more common than subchondral nodes: 50% of irregularities were classified as rim degeneration (75/150), 35% were classified as avulsions (52/150), and 15% were classified as nodes (23/150). Ninety percent of avulsions were subclassified as "tidemark avulsions," a highly prevalent form of endplate irregularity in which the outer annulus separates from the vertebra at the tidemark. These tidemark avulsions have not been previously described, yet are visible on T2-weighted MRI as high-intensity regions. CONCLUSION This study provides histologic basis for a system to classify focal endplate irregularities. Included is a previously unidentified but prevalent finding of tidemark avulsions, which are visible with both histology and magnetic resonance imaging. These observations will help clinicians better organize patients into meaningful groups to facilitate diagnosis, treatment, and clinical research. LEVEL OF EVIDENCE 3.
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26
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Acevedo C, Sylvia M, Schaible E, Graham JL, Stanhope KL, Metz LN, Gludovatz B, Schwartz AV, Ritchie RO, Alliston TN, Havel PJ, Fields AJ. Contributions of Material Properties and Structure to Increased Bone Fragility for a Given Bone Mass in the UCD-T2DM Rat Model of Type 2 Diabetes. J Bone Miner Res 2018; 33:1066-1075. [PMID: 29342321 PMCID: PMC6011658 DOI: 10.1002/jbmr.3393] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2017] [Revised: 12/30/2017] [Accepted: 01/10/2018] [Indexed: 12/18/2022]
Abstract
Adults with type 2 diabetes (T2D) have a higher fracture risk for a given bone quantity, but the mechanisms remain unclear. Using a rat model of polygenic obese T2D, we demonstrate that diabetes significantly reduces whole-bone strength for a given bone mass (μCT-derived BMC), and we quantify the roles of T2D-induced deficits in material properties versus bone structure; ie, geometry and microarchitecture. Lumbar vertebrae and ulnae were harvested from 6-month-old lean Sprague-Dawley rats, obese Sprague-Dawley rats, and diabetic obese UCD-T2DM rats (diabetic for 69 ± 7 days; blood glucose >200 mg/dL). Both obese rats and those with diabetes had reduced whole-bone strength for a given BMC. In obese rats, this was attributable to structural deficits, whereas in UCD-T2DM rats, this was attributable to structural deficits and to deficits in tissue material properties. For the vertebra, deficits in bone structure included thinner and more rod-like trabeculae; for the ulnae, these deficits included inefficient distribution of bone mass to resist bending. Deficits in ulnar material properties in UCD-T2DM rats were associated with increased non-enzymatic crosslinking and impaired collagen fibril deformation. Specifically, small-angle X-ray scattering revealed that diabetes reduced collagen fibril ultimate strain by 40%, and those changes coincided with significant reductions in the elastic, yield, and ultimate tensile properties of the bone tissue. Importantly, the biomechanical effects of these material property deficits were substantial. Prescribing diabetes-specific tissue yield strains in high-resolution finite element models reduced whole-bone strength by a similar amount (and in some cases a 3.4-fold greater amount) as the structural deficits. These findings provide insight into factors that increase bone fragility for a given bone mass in T2D; not only does diabetes associate with less biomechanically efficient bone structure, but diabetes also reduces tissue ductility by limiting collagen fibril deformation, and in doing so, reduces the maximum load capacity of the bone. © 2018 American Society for Bone and Mineral Research.
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Affiliation(s)
- Claire Acevedo
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA.,Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Department of Mechanical Engineering, University of Utah, Salt Lake City, UT, USA
| | - Meghan Sylvia
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Eric Schaible
- Experimental Systems Group, Advanced Light Source, Berkeley, CA, USA
| | - James L Graham
- Department of Molecular Biosciences, University of California, Davis, Davis, CA, USA.,Department of Nutrition, University of California, Davis, Davis, CA, USA
| | - Kimber L Stanhope
- Department of Molecular Biosciences, University of California, Davis, Davis, CA, USA.,Department of Nutrition, University of California, Davis, Davis, CA, USA
| | - Lionel N Metz
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Bernd Gludovatz
- School of Mechanical and Manufacturing Engineering, UNSW Sydney, NSW, Australia
| | - Ann V Schwartz
- Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA, USA
| | - Robert O Ritchie
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA, USA
| | - Tamara N Alliston
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Peter J Havel
- Department of Molecular Biosciences, University of California, Davis, Davis, CA, USA.,Department of Nutrition, University of California, Davis, Davis, CA, USA
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
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27
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Martin JT, Gullbrand SE, Fields AJ, Purmessur D, Diwan AD, Oxland TR, Chiba K, Guilak F, Hoyland JA, Iatridis JC. Publication trends in spine research from 2007 to 2016: Comparison of the Orthopaedic Research Society Spine Section and the International Society for the Study of the Lumbar Spine. JOR Spine 2018; 1:e1006. [PMID: 29770804 PMCID: PMC5944392 DOI: 10.1002/jsp2.1006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 02/14/2018] [Accepted: 02/17/2018] [Indexed: 11/06/2022] Open
Abstract
This study investigated current trends in spine publications of the membership of Orthopaedic Research Society Spine Section (ORS3) and the more global and clinically focused International Society for the Study of the Lumbar Spine (ISSLS). The PubMed database was probed to quantify trends in the overall number of articles published, the number of journals these articles were published in, and the number of active scientists producing new manuscripts. We also evaluated trends in flagship spine journals (Spine, European Spine Journal, and The Spine Journal) and in the Journal of Orthopaedic Research. The total number of active ORS3 and ISSLS authors and articles published have increased over the last 10 years. These articles are being published in hundreds of distinct journals; the number of journals is also increasing. Members of both societies published their work in Spine more than any other journal. Yet, publications in Spine decreased over the last 5 years for both ORS3 and ISSLS members, while those in European Spine Journal, and The Spine Journal remained unchanged. Furthermore, members of both societies have published in Journal of Orthopaedic Research at a consistent level. The increasing number of manuscripts and journals reflects a characteristic intrinsic to science as a whole—the global scientific workforce and output are growing and new journals are being created to accommodate the demand. These data suggest that existing spine journals do not fully serve the diverse publication needs of ORS3 and ISSLS members and highlight an unmet need for consolidating the premiere basic and translational spine research in an open access spine‐specific journal. This analysis was an important part of a decision process by the ORS to introduce JOR Spine.
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Affiliation(s)
- John T Martin
- Department of Orthopaedic Surgery Duke University Durham North Carolina USA
| | - Sarah E Gullbrand
- Department of Orthopaedic Surgery University of Pennsylvania Philadelphia Pennsylvania USA
| | - Aaron J Fields
- Department of Orthopaedic Surgery University of California San Francisco California USA
| | - Devina Purmessur
- Department of Biomedical Engineering The Ohio State University Columbus Ohio USA
| | - Ashish D Diwan
- Spine Service, St. George and Sutherland Clinical School The University of New South Wales Kogarah Australia
| | - Thomas R Oxland
- Departments of Orthopaedics and Mechanical Engineering The University of British Columbia Vancouver Canada.,International Collaboration on Repair Discoveries (ICORD) The University of British Columbia Vancouver Canada
| | - Kazuhiro Chiba
- Department of Orthopaedic Surgery National Defense Medical College Saitama Japan
| | - Farshid Guilak
- Department of Orthopaedic Surgery Washington University in St. Louis and Shriners Hospitals for Children St. Louis Missouri USA
| | - Judith A Hoyland
- Faculty of Biology, Medicine and Health, Division of Cell Matrix Biology and Regenerative Medicine The University of Manchester Manchester UK
| | - James C Iatridis
- Leni and Peter W. May Department of Orthopaedics Icahn School of Medicine at Mount Sinai New York New York USA
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28
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Berg‐Johansen B, Fields AJ, Liebenberg EC, Li A, Lotz JC. Structure-function relationships at the human spinal disc-vertebra interface. J Orthop Res 2018; 36:192-201. [PMID: 28590060 PMCID: PMC5720932 DOI: 10.1002/jor.23627] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 05/28/2017] [Indexed: 02/04/2023]
Abstract
Damage at the intervertebral disc-vertebra interface associates with back pain and disc herniation. However, the structural and biomechanical properties of the disc-vertebra interface remain underexplored. We sought to measure mechanical properties and failure mechanisms, quantify architectural features, and assess structure-function relationships at this vulnerable location. Vertebra-disc-vertebra specimens from human cadaver thoracic spines were scanned with micro-computed tomography (μCT), surface speckle-coated, and loaded to failure in uniaxial tension. Digital image correlation (DIC) was used to calculate local surface strains. Failure surfaces were scanned using scanning electron microscopy (SEM), and adjacent sagittal slices were analyzed with histology and SEM. Seventy-one percent of specimens failed initially at the cartilage endplate-bone interface of the inner annulus region. Histology and SEM both indicated a lack of structural integration between the cartilage endplate (CEP) and bone. The interface failure strength was increased in samples with higher trabecular bone volume fraction in the vertebral endplates. Furthermore, failure strength decreased with degeneration, and in discs with thicker CEPs. Our findings indicate that poor structural connectivity between the CEP and vertebra may explain the structural weakness at this region, and provide insight into structural features that may contribute to risk for disc-vertebra interface injury. The disc-vertebra interface is the site of failure in the majority of herniation injuries. Here we show new structure-function relationships at this interface that may motivate the development of diagnostics, prevention strategies, and treatments to improve the prognosis for many low back pain patients with disc-vertebra interface injuries. © 2017 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 36:192-201, 2018.
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Affiliation(s)
- Britta Berg‐Johansen
- University of California513 Parnassus Avenue, S‐1157San FranciscoCalifornia94143‐0514
| | - Aaron J. Fields
- University of California513 Parnassus Avenue, S‐1157San FranciscoCalifornia94143‐0514
| | - Ellen C. Liebenberg
- University of California513 Parnassus Avenue, S‐1157San FranciscoCalifornia94143‐0514
| | - Alfred Li
- University of California513 Parnassus Avenue, S‐1157San FranciscoCalifornia94143‐0514
| | - Jeffrey C. Lotz
- University of California513 Parnassus Avenue, S‐1157San FranciscoCalifornia94143‐0514
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29
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Millard SM, Wang L, Wattanachanya L, O'Carroll D, Fields AJ, Pang J, Kazakia G, Lotz JC, Nissenson RA. Role of Osteoblast Gi Signaling in Age-Related Bone Loss in Female Mice. Endocrinology 2017; 158:1715-1726. [PMID: 28407060 PMCID: PMC5460929 DOI: 10.1210/en.2016-1365] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 04/06/2017] [Indexed: 11/19/2022]
Abstract
Age-related bone loss is an important risk factor for fractures in the elderly; it results from an imbalance in bone remodeling mainly due to decreased bone formation. We have previously demonstrated that endogenous G protein-coupled receptor (GPCR)-driven Gi signaling in osteoblasts (Obs) restrains bone formation in mice during growth. Here, we launched a longitudinal study to test the hypothesis that Gi signaling in Obs restrains bone formation in aging mice, thereby promoting bone loss. Our approach was to block Gi signaling in maturing Obs by the induced expression of the catalytic subunit of pertussis toxin (PTX) after the achievement of peak bone mass. In contrast to the progressive cancellous bone loss seen in aging sex-matched littermate control mice, aging female Col1(2.3)+/PTX+ mice showed an age-related increase in bone volume. Increased bone volume was associated with increased bone formation at both trabecular and endocortical surfaces as well as increased bending strength of the femoral middiaphyses. In contrast, male Col1(2.3)+/PTX+ mice were not protected from age-related bone loss. Our results indicate that Gi signaling markedly restrains bone formation at cancellous and endosteal bone surfaces in female mice during aging. Blockade of the relevant Gi-coupled GPCRs represents an approach for the development of osteoporosis therapies-at least in the long bones of aging women.
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Affiliation(s)
- Susan M Millard
- Endocrine Research Unit, VA Medical Center, San Francisco, California 94158
| | - Liping Wang
- Endocrine Research Unit, VA Medical Center, San Francisco, California 94158
- Department of Medicine and Physiology, University of California, San Francisco, California 94158
| | | | - Dylan O'Carroll
- Endocrine Research Unit, VA Medical Center, San Francisco, California 94158
| | - Aaron J Fields
- Department of Orthopedic Surgery, University of California, San Francisco, California 94158
| | - Joyce Pang
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California 94143
| | - Galateia Kazakia
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California 94143
| | - Jeffrey C Lotz
- Department of Orthopedic Surgery, University of California, San Francisco, California 94158
| | - Robert A Nissenson
- Endocrine Research Unit, VA Medical Center, San Francisco, California 94158
- Department of Medicine and Physiology, University of California, San Francisco, California 94158
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30
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Fowler TW, Acevedo C, Mazur CM, Hall-Glenn F, Fields AJ, Bale HA, Ritchie RO, Lotz JC, Vail TP, Alliston T. Glucocorticoid suppression of osteocyte perilacunar remodeling is associated with subchondral bone degeneration in osteonecrosis. Sci Rep 2017; 7:44618. [PMID: 28327602 PMCID: PMC5361115 DOI: 10.1038/srep44618] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 02/10/2017] [Indexed: 11/09/2022] Open
Abstract
Through a process called perilacunar remodeling, bone-embedded osteocytes dynamically resorb and replace the surrounding perilacunar bone matrix to maintain mineral homeostasis. The vital canalicular networks required for osteocyte nourishment and communication, as well as the exquisitely organized bone extracellular matrix, also depend upon perilacunar remodeling. Nonetheless, many questions remain about the regulation of perilacunar remodeling and its role in skeletal disease. Here, we find that suppression of osteocyte-driven perilacunar remodeling, a fundamental cellular mechanism, plays a critical role in the glucocorticoid-induced osteonecrosis. In glucocorticoid-treated mice, we find that glucocorticoids coordinately suppress expression of several proteases required for perilacunar remodeling while causing degeneration of the osteocyte lacunocanalicular network, collagen disorganization, and matrix hypermineralization; all of which are apparent in human osteonecrotic lesions. Thus, osteocyte-mediated perilacunar remodeling maintains bone homeostasis, is dysregulated in skeletal disease, and may represent an attractive therapeutic target for the treatment of osteonecrosis.
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Affiliation(s)
- Tristan W Fowler
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Claire Acevedo
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, USA.,Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Courtney M Mazur
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, USA.,UC Berkeley-UCSF Graduate Program in Bioengineering, University of California Berkeley, Berkeley, CA, USA
| | - Faith Hall-Glenn
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Hrishikesh A Bale
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Robert O Ritchie
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Department of Materials Science and Engineering, University of California Berkeley, Berkeley, CA, USA
| | - Jeffrey C Lotz
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, USA.,UC Berkeley-UCSF Graduate Program in Bioengineering, University of California Berkeley, Berkeley, CA, USA
| | - Thomas P Vail
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Tamara Alliston
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, USA.,UC Berkeley-UCSF Graduate Program in Bioengineering, University of California Berkeley, Berkeley, CA, USA
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31
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Fields AJ, Berg-Johansen B, Metz LN, Miller S, La B, Liebenberg EC, Coughlin DG, Graham JL, Stanhope KL, Havel PJ, Lotz JC. Alterations in intervertebral disc composition, matrix homeostasis and biomechanical behavior in the UCD-T2DM rat model of type 2 diabetes. J Orthop Res 2015; 33:738-46. [PMID: 25641259 PMCID: PMC4408867 DOI: 10.1002/jor.22807] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 11/20/2014] [Accepted: 12/13/2014] [Indexed: 02/04/2023]
Abstract
Type 2 diabetes (T2D) adversely affects many tissues, and the greater incidence of discogenic low back pain among diabetic patients suggests that the intervertebral disc is affected too. Using a rat model of polygenic obese T2D, we demonstrate that diabetes compromises several aspects of disc composition, matrix homeostasis, and biomechanical behavior. Coccygeal motion segments were harvested from 6-month-old lean Sprague-Dawley rats, obese Sprague-Dawley rats, and diabetic obese UCD-T2DM rats (diabetic for 69 ± 7 days). Findings indicated that diabetes but not obesity reduced disc glycosaminoglycan and water contents, and these degenerative changes correlated with increased vertebral endplate thickness and decreased endplate porosity, and with higher levels of the advanced glycation end-product (AGE) pentosidine. Consistent with their diminished glycosaminoglycan and water contents and their higher AGE levels, discs from diabetic rats were stiffer and exhibited less creep when compressed. At the matrix level, elevated expression of hypoxia-inducible genes and catabolic markers in the discs from diabetic rats coincided with increased oxidative stress and greater interactions between AGEs and one of their receptors (RAGE). Taken together, these findings indicate that endplate sclerosis, increased oxidative stress, and AGE/RAGE-mediated interactions could be important factors for explaining the greater incidence of disc pathology in T2D.
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Affiliation(s)
- Aaron J. Fields
- Orthopaedic Bioengineering Laboratory, Department of Orthopaedic Surgery, University of California, San Francisco, CA, United States
| | - Britta Berg-Johansen
- Orthopaedic Bioengineering Laboratory, Department of Orthopaedic Surgery, University of California, San Francisco, CA, United States
| | - Lionel N. Metz
- Orthopaedic Bioengineering Laboratory, Department of Orthopaedic Surgery, University of California, San Francisco, CA, United States
| | - Stephanie Miller
- Orthopaedic Bioengineering Laboratory, Department of Orthopaedic Surgery, University of California, San Francisco, CA, United States
| | - Brandan La
- Orthopaedic Bioengineering Laboratory, Department of Orthopaedic Surgery, University of California, San Francisco, CA, United States
| | - Ellen C. Liebenberg
- Orthopaedic Bioengineering Laboratory, Department of Orthopaedic Surgery, University of California, San Francisco, CA, United States
| | - Dezba G. Coughlin
- Orthopaedic Bioengineering Laboratory, Department of Orthopaedic Surgery, University of California, San Francisco, CA, United States
| | - James L. Graham
- Department of Molecular Biosciences, University of California, Davis, CA, United States,Department of Nutrition, University of California, Davis, CA, United States
| | - Kimber L. Stanhope
- Department of Molecular Biosciences, University of California, Davis, CA, United States,Department of Nutrition, University of California, Davis, CA, United States
| | - Peter J. Havel
- Department of Molecular Biosciences, University of California, Davis, CA, United States,Department of Nutrition, University of California, Davis, CA, United States
| | - Jeffrey C. Lotz
- Orthopaedic Bioengineering Laboratory, Department of Orthopaedic Surgery, University of California, San Francisco, CA, United States
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32
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Wang J, Zhou B, Liu XS, Fields AJ, Sanyal A, Shi X, Adams M, Keaveny TM, Guo XE. Trabecular plates and rods determine elastic modulus and yield strength of human trabecular bone. Bone 2015; 72:71-80. [PMID: 25460571 PMCID: PMC4282941 DOI: 10.1016/j.bone.2014.11.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 11/10/2014] [Accepted: 11/12/2014] [Indexed: 10/24/2022]
Abstract
The microstructure of trabecular bone is usually perceived as a collection of plate-like and rod-like trabeculae, which can be determined from the emerging high-resolution skeletal imaging modalities such as micro-computed tomography (μCT) or clinical high-resolution peripheral quantitative CT (HR-pQCT) using the individual trabecula segmentation (ITS) technique. It has been shown that the ITS-based plate and rod parameters are highly correlated with elastic modulus and yield strength of human trabecular bone. In the current study, plate-rod (PR) finite element (FE) models were constructed completely based on ITS-identified individual trabecular plates and rods. We hypothesized that PR FE can accurately and efficiently predict elastic modulus and yield strength of human trabecular bone. Human trabecular bone cores from proximal tibia (PT), femoral neck (FN) and greater trochanter (GT) were scanned by μCT. Specimen-specific ITS-based PR FE models were generated for each μCT image and corresponding voxel-based FE models were also generated in comparison. Both types of specimen-specific models were subjected to nonlinear FE analysis to predict the apparent elastic modulus and yield strength using the same trabecular bone tissue properties. Then, mechanical tests were performed to experimentally measure the apparent modulus and yield strength. Strong linear correlations for both elastic modulus (r(2) = 0.97) and yield strength (r(2) = 0.96) were found between the PR FE model predictions and experimental measures, suggesting that trabecular plate and rod morphology adequately captures three-dimensional (3D) microarchitecture of human trabecular bone. In addition, the PR FE model predictions in both elastic modulus and yield strength were highly correlated with the voxel-based FE models (r(2) = 0.99, r(2) = 0.98, respectively), resulted from the original 3D images without the PR segmentation. In conclusion, the ITS-based PR models predicted accurately both elastic modulus and yield strength determined experimentally across three distinct anatomic sites. Trabecular plates and rods accurately determine elastic modulus and yield strength of human trabecular bone.
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Affiliation(s)
- Ji Wang
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY, USA.
| | - Bin Zhou
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY, USA.
| | - X Sherry Liu
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY, USA; McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA.
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, USA; Department of Mechanical Engineering, University of California Berkeley, Berkeley, CA, USA.
| | - Arnav Sanyal
- Department of Mechanical Engineering, University of California Berkeley, Berkeley, CA, USA.
| | - Xiutao Shi
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY, USA.
| | - Mark Adams
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA.
| | - Tony M Keaveny
- Department of Mechanical Engineering, University of California Berkeley, Berkeley, CA, USA.
| | - X Edward Guo
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY, USA.
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Fields AJ, Han M, Krug R, Lotz JC. Cartilaginous end plates: Quantitative MR imaging with very short echo times-orientation dependence and correlation with biochemical composition. Radiology 2014; 274:482-9. [PMID: 25302832 DOI: 10.1148/radiol.14141082] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To measure the T2* of the human cartilaginous end plate by using magnetic resonance (MR) imaging with very short echo times and to determine the effect of the orientation of the end plate on T2* and on relationships between T2* and biochemical composition. MATERIALS AND METHODS This study was exempt from institutional review board approval, and informed consent was not required. Thirty-four samples of three cadaveric lumbar spines (from subjects who died at ages 51, 57, and 66 years) containing cartilaginous end plates and subchondral bone were prepared. Samples were imaged with a 3-T imager for T2* quantification by using a three-dimensional very short echo time sequence (repetition time msec/echo times msec, 30/0.075, 2, 5, 12, 18). Samples were imaged with the end plate at three orientations with respect to the constant magnetic induction field: 0°, 54.7°, and 90°. After imaging, the cartilage was assayed for its water, glycosaminoglycan, and collagen content. Pearson correlations were used to investigate the effect of orientation on the relationships between T2* and biochemical composition. RESULTS T2* was significantly longer when measured at an orientation of 54.7° (21.8 msec ± 2.8 [± standard error of the mean]) than at 0° (10.0 msec ± 0.7, P < .001) or 90° (9.9 msec ± 0.4, P < .001). At 54.7°, T2* was highly correlated with glycosaminoglycan content (r = 0.85, P < .001), the collagen-to-glycosaminoglycan ratio (r = -0.79, P < .001), and water content (r = 0.62, P = .02); at 0° and 90°, there were no significant differences in these relationships, with a minimum P value of .19. CONCLUSION T2* evaluation can allow noninvasive estimation of the degeneration of the cartilaginous end plate; however, the accuracy of T2*-based estimates of biochemical composition depends on the orientation of the end plate.
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Affiliation(s)
- Aaron J Fields
- From the Department of Orthopaedic Surgery (A.J.F., R.K., J.C.L.) and Department of Radiology and Biomedical Imaging (M.H., R.K.), University of California-San Francisco, 513 Parnassus Ave, Room S-1161, San Francisco, CA 94143-0514
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Bailey JF, Fields AJ, Liebenberg E, Mattison JA, Lotz JC, Kramer PA. Comparison of vertebral and intervertebral disc lesions in aging humans and rhesus monkeys. Osteoarthritis Cartilage 2014; 22:980-5. [PMID: 24821664 PMCID: PMC4105267 DOI: 10.1016/j.joca.2014.04.027] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 03/28/2014] [Accepted: 04/23/2014] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To compare gross and histologic patterns of age-related degeneration within the intervertebral disc and adjacent vertebra between rhesus monkeys and humans. MATERIALS AND METHODS We examined age-related patterns of disc degeneration from mid-sagittal sections of the intervertebral disc and adjacent vertebral bodies (VB) among six rhesus monkey thoracolumbar and seven human lumbar spines. Gross morphology and histopathology were assessed via the Thompson grading scheme and other degenerative features of the disc and adjacent bone. RESULTS Thompson grades ranged from 3 through 5 for rhesus monkey discs (T9-L1) and 2 through 5 for the human discs (T12-S1). In both rhesus monkey and human discs, presence of distinct lesions was positively associated with Thompson grade of the overall segment. Degenerative patterns differed for radial tears, which were more prevalent with advanced disc degeneration in humans only. Additionally, compared to the more uniform anteroposterior disc degeneration patterns of humans, rhesus monkeys showed more severe osteophytosis and degeneration on the anterior border of the vertebral column. CONCLUSIONS Rhesus monkey spines evaluated in the present study appear to develop age-related patterns of disc degeneration similar to humans. One exception is the absence of an association between radial tears and disc degeneration, which could reflect species-specific differences in posture and spinal curvature. Considering rhesus monkeys demonstrate similar patterns of disc degeneration, and age at a faster rate than humans, these findings suggest longitudinal studies of rhesus monkeys may be a valuable model for better understanding the progression of human age-related spinal osteoarthritis (OA) and disc degeneration.
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Affiliation(s)
- J F Bailey
- Depts. of Anthropology and Orthopaedics & Sports Medicine, University of Washington, Seattle, WA, USA.
| | - A J Fields
- Dept. of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - E Liebenberg
- Dept. of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - J A Mattison
- Translational Gerontology Branch, National Institute on Aging, Intramural Research Program, Poolesville, MD, USA
| | - J C Lotz
- Dept. of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - P A Kramer
- Depts. of Anthropology and Orthopaedics & Sports Medicine, University of Washington, Seattle, WA, USA
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Fields AJ, Liebenberg EC, Lotz JC. Innervation of pathologies in the lumbar vertebral end plate and intervertebral disc. Spine J 2014; 14:513-21. [PMID: 24139753 PMCID: PMC3945018 DOI: 10.1016/j.spinee.2013.06.075] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2012] [Revised: 05/21/2013] [Accepted: 06/24/2013] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Magnetic resonance imaging (MRI) has limited diagnostic value for chronic low back pain because of the unclear relationship between any anatomic abnormalities on MRI and pain reported by the patient. Assessing the innervation of end plate and disc pathologies-and determining the relationship between these pathologies and any abnormalities seen on MRI-could clarify the sources of back pain and help identify abnormalities with enhanced diagnostic value. PURPOSE To quantify innervation in the vertebral end plate and intervertebral disc and to relate variation in innervation to the presence of pathologic features observed by histology and conventional MRI. STUDY DESIGN/SETTING A cross-sectional histology and imaging study of vertebral end plates and intervertebral discs harvested from human cadaver spines. METHODS We collected 92 end plates and 46 intervertebral discs from seven cadaver spines (ages 51-67 years). Before dissection, the spines were scanned with MRI to grade for Modic changes and high-intensity zones (HIZ). Standard immunohistochemical techniques were used to localize the general nerve marker protein gene product 9.5. We quantified innervation in the following pathologies: fibrovascular end-plate marrow, fatty end-plate marrow, end-plate defects, and annular tears. RESULTS Nerves were present in the majority of end plates with fibrovascular marrow, fatty marrow, and defects. Nerve density was significantly higher in fibrovascular end-plate marrow than in normal end-plate marrow (p<.001). Of the end plates with fibrovascular and fatty marrow, less than 40% were Modic on MRI. Innervated marrow pathologies collocated with more than 75% of the end plate defects; hence, innervation was significantly higher in end plate defects than in normal end plates (p<.0001). In the disc, nerves were observed in only 35% of the annular tears; in particular, innervation in radial tears tended to be higher than in normal discs (p=.07). Of the discs with radial tears, less than 13% had HIZ on T2 MRI. Innervation was significantly less in radial tears than in fibrovascular end-plate marrow (p=.05) and end-plate defects (p=.02). CONCLUSIONS These findings indicate that vertebral end-plate pathologies are more innervated than intervertebral disc pathologies and that many innervated end-plate pathologies are not detectable on MRI. Taken together, these findings suggest that improved visualization of end-plate pathologies could enhance the diagnostic value of MRI for chronic low back pain.
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Fields AJ, Rodriguez D, Gary KN, Liebenberg EC, Lotz JC. Influence of biochemical composition on endplate cartilage tensile properties in the human lumbar spine. J Orthop Res 2014; 32:245-52. [PMID: 24273192 PMCID: PMC4039641 DOI: 10.1002/jor.22516] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2013] [Accepted: 10/14/2013] [Indexed: 02/04/2023]
Abstract
Endplate cartilage integrity is critical to spine health and is presumably impaired by deterioration in biochemical composition. Yet, quantitative relationships between endplate biochemical composition and biomechanical properties are unavailable. Using endplate cartilage harvested from human lumbar spines (six donors, ages 51-67 years) we showed that endplate biochemical composition has a significant influence on its equilibrium tensile properties and that the presence of endplate damage associates with a diminished composition-function relationship. We found that the equilibrium tensile modulus (5.9 ± 5.7 MPa) correlated significantly with collagen content (559 ± 147 µg/mg dry weight, r(2) = 0.35) and with the collagen/GAG ratio (6.0 ± 2.1, r(2) = 0.58). Accounting for the damage status of the adjacent cartilage improved the latter correlation (r(2) = 0.77) and indicated that samples with adjacent damage such as fissures and avulsions had a diminished modulus-collagen/GAG relationship (p = 0.02). Quasi-linear viscoelastic relaxation properties (C, t1 , and t2 ) did not correlate with biochemical composition. We conclude that reduced matrix quantity decreases the equilibrium tensile modulus of human endplate cartilage and that characteristics of biochemical composition that are independent of matrix quantity, that is, characteristics related to matrix quality, may also be important.
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Affiliation(s)
- Aaron J. Fields
- Orthopaedic Bioengineering Laboratory; Department of Orthopaedic Surgery; University of California; 513 Parnassus Avenue S-1157 San Francisco California 94143-0514
| | - David Rodriguez
- Orthopaedic Bioengineering Laboratory; Department of Orthopaedic Surgery; University of California; 513 Parnassus Avenue S-1157 San Francisco California 94143-0514
| | - Kaitlyn N. Gary
- Orthopaedic Bioengineering Laboratory; Department of Orthopaedic Surgery; University of California; 513 Parnassus Avenue S-1157 San Francisco California 94143-0514
| | - Ellen C. Liebenberg
- Orthopaedic Bioengineering Laboratory; Department of Orthopaedic Surgery; University of California; 513 Parnassus Avenue S-1157 San Francisco California 94143-0514
| | - Jeffrey C. Lotz
- Orthopaedic Bioengineering Laboratory; Department of Orthopaedic Surgery; University of California; 513 Parnassus Avenue S-1157 San Francisco California 94143-0514
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Sahli F, Cuellar J, Pérez A, Fields AJ, Campos M, Ramos-Grez J. Structural parameters determining the strength of the porcine vertebral body affected by tumours. Comput Methods Biomech Biomed Engin 2014; 18:890-9. [DOI: 10.1080/10255842.2013.855728] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Zhou B, Liu XS, Wang J, Lu XL, Fields AJ, Guo XE. Dependence of mechanical properties of trabecular bone on plate-rod microstructure determined by individual trabecula segmentation (ITS). J Biomech 2013; 47:702-8. [PMID: 24360196 DOI: 10.1016/j.jbiomech.2013.11.039] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 11/24/2013] [Indexed: 12/01/2022]
Abstract
Individual trabecula segmentation (ITS) technique can decompose the trabecular bone network into individual trabecular plates and rods and is capable of quantifying the plate/rod-related microstructural characteristics of trabecular bone. This novel technique has been shown to be able to provide in-depth insights into micromechanics and failure mechanisms of human trabecular bone, as well as to distinguish the fracture status independent of area bone mineral density in clinical applications. However, the plate/rod microstructural parameters from ITS have never been correlated to experimentally determined mechanical properties of human trabecular bone. In this study, on-axis cylindrical trabecular bone samples from human proximal tibia (n=22), vertebral body (n=10), and proximal femur (n=21) were harvested, prepared, scanned using micro computed-tomography (µCT), analyzed with ITS and mechanically tested. Regression analyses showed that the plate bone volume fraction (pBV/TV) and axial bone volume fraction (aBV/TV) calculated by ITS analysis correlated the best with elastic modulus (R(2)=0.96-0.97) and yield strength (R(2)=0.95-0.96). Trabecular plate-related microstructural parameters correlated highly with elastic modulus and yield strength, while most rod-related parameters were found inversely and only moderately correlated with the mechanical properties. In addition, ITS analysis also identified that trabecular bone at human femoral neck had the highest trabecular plate-related parameters while the other sites were similar with each other in terms of plate-rod microstructure.
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Affiliation(s)
- Bin Zhou
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY, USA
| | - X Sherry Liu
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY, USA; McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA
| | - Ji Wang
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY, USA
| | - X Lucas Lu
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY, USA; Cartilage Bioengineering Laboratory, Department of Mechanical Engineering, University of Delaware, Newark, DE, USA
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA; Orthopaedic Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, CA, USA
| | - X Edward Guo
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY, USA.
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Abstract
The mechanisms of age-related vertebral fragility remain unclear, but may be related to the degree of "structural redundancy" of the vertebra; ie, its ability to safely redistribute stress internally after local trabecular failure from an isolated mechanical overload. To better understand this issue, we performed biomechanical testing and nonlinear micro-CT-based finite element analysis on 12 elderly human thoracic ninth vertebral bodies (age 76.9 ± 10.8 years). After experimentally overloading the vertebrae to measure strength, we used nonlinear finite element analysis to estimate the amount of failed tissue and understand the failure mechanisms. We found that the amount of failed tissue per unit bone mass decreased with decreasing bone volume fraction (r(2) = 0.66, p < 0.01). Thus, for the weak vertebrae with low bone volume fraction, overall failure of the vertebra occurred after failure of just a tiny proportion of the bone tissue (<5%). This small proportion of failed tissue had two sources: the existence of fewer vertically oriented load paths to which load could be redistributed from failed trabeculae; and the vulnerability of the trabeculae in these few load paths to undergo bending-type failure mechanisms, which further weaken the bone. Taken together, these characteristics suggest that diminished structural redundancy may be an important aspect of age-related vertebral fragility: vertebrae with low bone volume fraction are highly susceptible to collapse because so few trabeculae are available for load redistribution if the external loads cause any trabeculae to fail.
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Affiliation(s)
- Aaron J Fields
- Orthopaedic Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, CA, USA
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Yang H, Nawathe S, Fields AJ, Keaveny TM. Micromechanics of the human vertebral body for forward flexion. J Biomech 2012; 45:2142-8. [PMID: 22704826 DOI: 10.1016/j.jbiomech.2012.05.044] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 04/21/2012] [Accepted: 05/19/2012] [Indexed: 11/18/2022]
Abstract
To provide mechanistic insight into the etiology of osteoporotic wedge fractures, we investigated the spatial distribution of tissue at the highest risk of initial failure within the human vertebral body for both forward flexion and uniform compression loading conditions. Micro-CT-based linear elastic finite element analysis was used to virtually load 22 human T9 vertebral bodies in either 5° of forward flexion or uniform compression; we also ran analyses replacing the simulated compliant disc (E=8 MPa) with stiff polymethylmethacrylate (PMMA, E=2500 MPa). As expected, we found that, compared to uniform compression, forward flexion increased the overall endplate axial load on the anterior half of the vertebra and shifted the spatial distribution of high-risk tissue within the vertebra towards the anterior aspect of the vertebral body. However, despite that shift, the high-risk tissue remained primarily within the central regions of the trabecular bone and endplates, and forward flexion only slightly altered the ratio of cortical-to-trabecular load sharing at the mid-vertebral level (mean±SD for n=22: 41.3±7.4% compression; 44.1±8.2% forward flexion). When the compliant disc was replaced with PMMA, the anterior shift of high-risk tissue was much more severe. We conclude that, for a compliant disc, a moderate degree of forward flexion does not appreciably alter the spatial distribution of stress within the vertebral body.
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Affiliation(s)
- Haisheng Yang
- Orthopaedic Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, CA 94720-1740, USA.
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Abstract
Osteoporosis heightens vertebral fragility owing to the biomechanical effects of diminished bone structure and composition. These biomechanical effects are only partially explained by loss in bone mass, so additional factors that are independent of bone mass are also thought to play an important role in vertebral fragility. Recent advances in imaging equipment, imaging-processing methods, and computational capacity allow researchers to quantify trabecular architecture in the vertebra at the level of the individual trabecular elements and to derive biomechanics-based measures of architecture that are independent of bone mass and density. These advances have shed light on the role of architecture in vertebral fragility. In addition to the adverse biomechanical consequences associated with trabecular thinning and loss of connectivity, a reduction in the number of vertical trabecular plates appears to be particularly harmful to vertebral strength. In the clinic, detailed architecture analysis is primarily applied to peripheral sites such as the distal radius and tibia. Analysis of trabecular architecture at these peripheral sites has shown mixed results for discriminating between patients with and without a vertebral fracture independent of bone mass, but has the potential to provide unique insight into the effects of therapeutic treatments. Overall, it does appear that trabecular architecture has an independent role on vertebral strength. Additional research is required to determine how and where architecture should be measured in vivo and whether assessment of trabecular architecture in a clinical setting improves prospective fracture risk assessment for the vertebra.
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Affiliation(s)
- Aaron J Fields
- Department of Orthopaedic Surgery, University of California, 513 Parnassus Avenue, S-1161, San Francisco, CA, 94143-0514, USA.
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Fields AJ, Lee GL, Keaveny TM. Mechanisms of initial endplate failure in the human vertebral body. J Biomech 2011; 43:3126-31. [PMID: 20817162 DOI: 10.1016/j.jbiomech.2010.08.002] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Revised: 07/29/2010] [Accepted: 08/01/2010] [Indexed: 01/16/2023]
Abstract
Endplate failure occurs frequently in osteoporotic vertebral fractures and may be related to the development of high tensile strain. To determine whether the highest tensile strains in the vertebra occur in the endplates, and whether such high tensile strains are associated with the material behavior of the intervertebral disc, we used micro-CT-based finite element analysis to assess tissue-level strains in 22 elderly human vertebrae (81.5 ± 9.6 years) that were compressed through simulated intervertebral discs. In each vertebra, we compared the highest tensile and compressive strains across the different compartments: endplates, cortical shell, and trabecular bone. The influence of Poisson-type expansion of the disc on the results was determined by compressing the vertebrae a second time in which we suppressed the Poisson expansion. We found that the highest tensile strains occurred within the endplates whereas the highest compressive strains occurred within the trabecular bone. The ratio of strain to assumed tissue-level yield strain was the highest for the endplates, indicating that the endplates had the greatest risk of initial failure. Suppressing the Poisson expansion of the disc decreased the amount of highly tensile-strained tissue in the endplates by 79.4 ± 11.3%. These results indicate that the endplates are at the greatest risk of initial failure due to the development of high tensile strains, and that such high tensile strains are associated with the Poisson expansion of the disc. We conclude that initial failure of the vertebra is associated with high tensile strains in the endplates, which in turn are influenced by the material behavior of the disc.
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Affiliation(s)
- Aaron J Fields
- Orthopaedic Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, CA, USA.
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Abstract
Vertebral strength, a key etiologic factor of osteoporotic fracture, may be affected by the relative amount of vertically oriented trabeculae. To better understand this issue, we performed experimental compression testing, high-resolution micro-computed tomography (µCT), and micro-finite-element analysis on 16 elderly human thoracic ninth (T(9)) whole vertebral bodies (ages 77.5 ± 10.1 years). Individual trabeculae segmentation of the µCT images was used to classify the trabeculae by their orientation. We found that the bone volume fraction (BV/TV) of just the vertical trabeculae accounted for substantially more of the observed variation in measured vertebral strength than did the bone volume fraction of all trabeculae (r(2) = 0.83 versus 0.59, p < .005). The bone volume fraction of the oblique or horizontal trabeculae was not associated with vertebral strength. Finite-element analysis indicated that removal of the cortical shell did not appreciably alter these trends; it also revealed that the major load paths occur through parallel columns of vertically oriented bone. Taken together, these findings suggest that variation in vertebral strength across individuals is due primarily to variations in the bone volume fraction of vertical trabeculae. The vertical tissue fraction, a new bone quality parameter that we introduced to reflect these findings, was both a significant predictor of vertebral strength alone (r(2) = 0.81) and after accounting for variations in total bone volume fraction in multiple regression (total R(2) = 0.93). We conclude that the vertical tissue fraction is a potentially powerful microarchitectural determinant of vertebral strength.
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Affiliation(s)
- Aaron J Fields
- Orthopaedic Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, CA 94720-1740, USA.
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Eswaran SK, Fields AJ, Nagarathnam P, Keaveny TM. Multi-scale modeling of the human vertebral body: comparison of micro-CT based high-resolution and continuum-level models. Pac Symp Biocomput 2009:293-303. [PMID: 19209709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The overall goal of this study was to assess the mechanistic fidelity of continuum-level finite element models of the vertebral body, which represent a promising tool for understanding and predicting clinical fracture risk. Two finite element (FE) models were generated from micro-CT scans of each of 13 T9 vertebral bodies--a micro-FE model at 60-micron resolution and a coarsened, continuum-level model at 0.96-mm resolution. Two previously-reported continuum-level modulus-density relationships for human vertebral bone were parametrically varied to investigate their effects on model fidelity using the micro-CT models as a gold standard. We found that the modulus-density relation, particularly that assigned to the peripheral bone, substantially altered the regression coefficients, but not the degree of correlation between continuum and micro-FE predictions of whole-vertebral stiffness. The major load paths through the vertebrae compared well between the continuum-level and micro-FE models (von-Mises distribution), but the distributions of minimum principal strain were notably different. We conclude that continuum-level models provide robust measures of whole-vertebral behavior, describe well the load transfer paths through the vertebra, but provide strain distributions that are markedly different than the volume-averaged micro-scale strains. Appreciation of these multi-scale differences should improve interpretation of results from these sorts of continuum models and may improve their clinical utility.
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Affiliation(s)
- Senthil K Eswaran
- Orthopaedic Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, CA 94720, USA
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Abstract
The alpha 4 beta 1 integrin has been suggested to play important roles in embryogenesis and pathogenesis of many diseases which involve both cell adhesion and cell migration. Previous studies using anti-alpha 4 beta 1 antibodies and fibronectin (Fn) fragments have suggested that alpha 4 beta 1 integrins may be involved in cell motility on Fn and vascular cell adhesion molecule-1 (VCAM-1). However, the cells used in these studies also express other Fn integrin receptors including alpha 5 beta 1 integrin, which is known to function in cell motility on Fn. To test whether alpha 4 beta 1 integrins mediate cell motility on Fn and VCAM-1 in the absence of alpha 5 beta 1 integrin, we expressed human alpha 4 integrin in a Chinese hamster ovary (CHO) cell line that is deficient in alpha 5 beta 1 integrin (CHO B2). The parental alpha 5 deficient CHO B2 cells were unable to adhere, spread or migrate on Fn, nor could they assemble a fibrillar Fn matrix. Expression of alpha 4 beta 1 integrin in the CHO B2 cells enabled the cells to adhere, spread and migrate on Fn and on VCAM-1 but not to assemble a fibrillar Fn matrix. The cellular processes mediated by the interaction of alpha 4 beta 1 with Fn or VCAM-1 were inhibited by the CS1 peptide derived from the major alpha 4 beta 1 binding site on Fn. These findings demonstrate that alpha 4 beta 1 integrins not only function as cell adhesion receptors but also as cell motility receptors for Fn and VCAM-1 independent of alpha 5 beta 1. Moreover, they reveal important functional differences between Fn binding integrins. The alpha 4-positive, alpha 5-negative CHO cells described in this report will be useful tools in studying the mechanism of molecular signalling during integrin mediated cellular processes.
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Affiliation(s)
- C Wu
- Samule C. Johnson Medical Research Center, Mayo Clinic Scottsdale, AZ 85259, USA
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