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American Football On-Field Head Impact Kinematics: Influence of Acceleration Signal Characteristics on Peak Maximal Principal Strain. Ann Biomed Eng 2024:10.1007/s10439-024-03514-z. [PMID: 38758459 DOI: 10.1007/s10439-024-03514-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 03/28/2024] [Indexed: 05/18/2024]
Abstract
Recorded head kinematics from head-impact measurement devices (HIMd) are pivotal for evaluating brain stress and strain through head finite element models (hFEM). The variability in kinematic recording windows across HIMd presents challenges as they yield inconsistent hFEM responses. Despite establishing an ideal recording window for maximum principal strain (MPS) in brain tissue, uncertainties persist about the impact characteristics influencing vulnerability when this window is shortened. This study aimed to scrutinize factors within impact kinematics affecting the reliability of different recording windows on whole-brain peak MPS using a validated hFEM. Utilizing 53 on-field head impacts recorded via an instrumented mouthguard during a Canadian varsity football game, 10 recording windows were investigated with varying pre- and post-impact-trigger durations. Tukey pair-wise comparisons revealed no statistically significant differences in MPS responses for the different recording windows. However, specific impacts showed marked variability up to 40%. It was found, through correlation analyses, that impacts with lower peak linear acceleration exhibited greater response variability across different pre-trigger durations. Signal shape, analyzed through spectral analysis, influenced the time required for MPS development, resulting in specific impacts requiring a prolonged post-trigger duration. This study adds to the existing consensus on standardizing HIMd acquisition time windows and sheds light on impact characteristics leading to peak MPS variation across different head impact kinematic recording windows. Considering impact characteristics in research assessments is crucial, as certain impacts, affected by recording duration, may lead to significant errors in peak MPS responses during cumulative longitudinal exposure assessments.
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Contribution of impactor misalignment to the neurofunctional variability in porcine spinal cord contusion models. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-4. [PMID: 38082881 DOI: 10.1109/embc40787.2023.10340195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Traumatic spinal cord lesions studies are often carried out with animal models or numerical simulations. Unfortunately, animal models usually present a high variability in severity and type of neurofunctional impairments following impact surgery. We postulate that the variability of outcomes is strongly dependent on the positioning and alignment of the impactor during the contusion. A finite elements model of the spinal cord, predicting the action potential (AP) conduction alteration, was proposed and used to perform nine numerical simulations of a 50 g weight dropped from 200 mm on the exposed spinal cord in its spinal canal. Simulations followed a 32 factorial design with impactor eccentricity and spinal cord tilt angle as factors on two outcomes: injured spinal cord area (AP < 10 % of its baseline, 1h post-injury), and asymmetry of injury (ratio of right/left injured area of both half spinal cord). Eccentricity contributed highly and significantly on both outcomes, but not tilt angle. Damaged axons were found in conscious motor, sensory, and unconscious proprioception tracts. Variability in impactor alignment beyond ±6.2 % of the spinal canal width affects neurofunctional outcomes, and careful assessment of the impactor course is therefore key when producing spinal cord injury by contusion.Clinical Relevance- A precision value is proposed to mitigate the contribution of impactor misalignment to neurofunctional variability in animal models, allowing the reduction of animal used in research. The proposed method of action potential conduction assessment could easily be implanted in human numerical models for the cross-study of patient's cases.
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Automatic detection of spinal injuries under dynamic compressive loading using high-speed cine-radiography. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-4. [PMID: 38082790 DOI: 10.1109/embc40787.2023.10339973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Every year, new cases of individuals suffering from traumatic spinal injuries are detected. Advances in numerical models have allowed for the understanding of the damage caused by trauma and its impact on the patient's life. However, the kinematics and dynamics of vertebral fracture formation from its point of origin to the speed of propulsion of the fragments remain unknown. This is mainly due to the lack of data that essentially includes high-speed videos, load and displacement measurements during experimental tests reproducing spinal traumatic loading conditions. This lack of data can be addressed by the analysis of X-Ray images of animal specimens acquired during the traumatic spinal injury formation process. Thus, the purpose of this study was to develop an approach to automatically detect and track in vitro vertebral fractures using high-speed cine-radiography imaging. Four segments of porcine thoracolumbar vertebrae were dynamically compressed using a servo-hydraulic test bench. The compression process was filmed with a custom high-speed cine-radiography device, and the imaging parameters were optimized based on the physical properties of vertebrae. This paper demonstrates the feasibility of using high-speed cine-radiography imaging in this way, combined with an image processing pipeline to allow automatic documentation of the fracture's appearance and its evolution in the vertebra over time.Clinical Relevance- The proposed method will provide helpful information for proper handling of traumatic spinal injuries.
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In vitro assessment of the role of the nucleus pulposus in the mechanism of vertebral body fracture under dynamic compressive loading using high-speed cineradiography. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2020:4717-4720. [PMID: 33019045 DOI: 10.1109/embc44109.2020.9176150] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Traumatic Spinal Cord Injuries (TSCI) have a disastrous effect on the physical and mental health of both the patients and their relatives. Around 15 % of these injuries are caused by burst fractures, a sub-type of compressive fractures of the vertebral body. The transient dynamics of these fracture have been studied through in vitro experiments coupled with numerical simulations, but no direct observation have ever been made of their genesis and evolution and the behaviour of the nucleus pulposus under compressive loading has only been hypothesized. The purpose of this study was to evaluate the interactions between the vertebral body and the nucleus pulposus under dynamic compressive loading using high-speed cineradiography. A radiopaque agent was injected into the nuclei pulposi of 4 young porcine thoraco-lumbar and lumbar cadaveric segments, and a dynamic compressive load was applied to them using a servo-hydraulic bench-test. The compression process was filmed with a custom high-speed fluoroscope. The nucleus pulposus loaded the vertebral endplate up to 14,142 ± 486 N, before fracturing it and diffusing into the vertebral body. Then, internal pressure seemingly built up until an outward projection of the nucleus pulposus, at an antero-posterior velocity up to 2.9 m.s-1, or until retroprojection of bony fragments into the spinal canal. These results directly corroborate the hypotheses previously made by other studies and stress the unprecedented advantages of using high-speed cineradiography for the study of complex fractures genesis and evolution.Clinical Relevance- Methodology and results from this study would provide an unprecedented insight on the genesis and transient evolution of complex spinal fractures.
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Gait analysis of a post induced traumatic spinal cord injury porcine model. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2020:3803-3806. [PMID: 33018829 DOI: 10.1109/embc44109.2020.9175280] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Porcine model constitutes a potential translational model to study traumatic spinal cord injuries (TSCI) considering its recent use in numerous studies. Recovery of the animal is currently monitored through a qualitative evaluation of the gait. Adding a quantitative evaluation might help to better assess the functional recovery of the animal. In this study, a new controlled method involving the use of an electro-magnetic actuator was used on a pig to induce a TSCI. Chronic monitoring was done using a quantitative analysis of the gait. Results show both, the injury of the pig and its functional recovery. This large animal model will help to provide a better understanding of injury and recovery mechanisms and thus could constitute a strong preclinical model for future therapeutic studies.Clinical Relevance- Methodology and results from this study would provide a better insight on the functional recovery after traumatic spinal cord injuries.
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A novel spinal cord surrogate for the study of compressive traumatic spinal cord injuries .. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2019:5678-5680. [PMID: 31947141 DOI: 10.1109/embc.2019.8857641] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Although in vitro studies are frequent for the study of traumatic spine and spinal cord injuries, few include the spinal cord due to its prompt post-mortem decay. Several materials have been proposed to mimic the spinal cord behaviour, but none matched its mechanical properties under transverse compression, which is vital for the study of burst fractures and other injury mechanisms leading to spinal cord compression. In this study, a new material named Soma Foama 15 (Reynolds Advanced Material, USA) was used to manufacture three spinal cord surrogates at 3 mixing ratios of elastomer to catalyst (1:1, 2:1 and 3:1) and tested at three different strain rates (0.5, 5 and 50 .s-1). The mixing ratio 3:1 presents a mechanical behaviour comparable to that of the porcine spinal cord at each of these strain rates, making the surrogate a valid substitute up to 75 % of transverse compression.
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Comparison of Two Intervertebral Disc Failure Models in a Numerical C4-C5 Trauma Model .. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2019:5415-5418. [PMID: 31947080 DOI: 10.1109/embc.2019.8857095] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The intervertebral disc (IVD) is essential for the mobility and stability of the spine. During flexion-distraction injuries, which are frequent at the cervical spine level, the IVD is often disrupted. Finite element studies have been done to investigate injury mechanisms and patterns at the cervical spine. However, they rarely include IVD failure model. The aim of this paper was to implement and compare two types of IVD failure models and their impact on hyperflexion and hyperflexion-compression injuries simulations. The failure models were tested on a detailed C4-C5 finite elements model. The first failure model consisted in a maximal strain model applied to the elements of the annulus and nucleus. The second failure model consisted in the implementation of a rupture plane in the middle of the IVD with a tied interface created between the two sections. This interface is defined by threshold stress values of detachment in traction and shearing. The two failure models were tested in flexion only and in flexion-compression. The model without inclusion of an IVD failure model was also tested. Loads at failure and injury patterns were reported. Both failure models produce failure loads that were consistent with experimental data. Injury patterns observed were in agreement with experimental and numerical studies. However, in flexion-compression, the rupture plane model simulation reached important energy error due to high deformations in the IVD elements. Also, without inclusion of an IVD failure model, energy error forced the end of the simulation in flexion-compression. Therefore, inclusion of IVD failure model is important since it leads to realistic results, but the maximal strain failure model is recommended.
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Ultrashort laser induced spatial redistribution of silver species and nano-patterning of etching selectivity in silver-containing glasses. OPTICS EXPRESS 2019; 27:13675-13680. [PMID: 31163827 DOI: 10.1364/oe.27.013675] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 04/03/2019] [Indexed: 06/09/2023]
Abstract
Femtosecond laser-induced spatial redistribution of silver species (ions, clusters, and hole centers) in a silver-containing phosphate glass is investigated by correlative means of near-field scanning optical microscopy (NSOM) images, numerical simulations, chemical micro-probe analysis, and nanoscale spatial profiles after soft etching. In particular, we found that the chemical etching selectivity for nanoscale patterning is strongly dependent upon the irradiation of femtosecond laser due to the spatial redistribution of silver species within the affected area. These results strongly indicate that controlling the distribution of silver species by femtosecond laser irradiation may open new routes for surface nanoscale chemical and/or spatial patterning for the fabrication of 2D surface photonic crystals.
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Limb Sparing in Dogs using Individualized 3D-Printed Endoprostheses and Cutting Guides for Distal Radial Osteosarcoma: A Pilot Study. Vet Comp Orthop Traumatol 2019. [DOI: 10.1055/s-0039-1692225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Laser writing of nonlinear optical properties in silver-doped phosphate glass. OPTICS LETTERS 2017; 42:1688-1691. [PMID: 28454136 DOI: 10.1364/ol.42.001688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The formation of both local second- and third-harmonic generations (SHG and THG) induced by a train of femtosecond laser pulses in silver-doped phosphate glasses is addressed. Based on modeling calculations, including various diffusion and kinetic processes, THG is shown to result from the formation of silver clusters. The latter organize into a ring-shape structure, leading to the emergence of a static electric field. By breaking the glass centro-symmetry, this field gives rise to a local effective second-order susceptibility, inducing SHG. Both theoretically predicted SHG and THG evolutions with respect to the number of pulses in the train are in good agreement with experimental observations. In particular, the observed reaching of a maximum in the nonlinear optical responses after a few thousands of pulses is explained by the competition of various physical processes. A cooling of the glass is shown to improve the process efficiency of the laser writing of second-order nonlinearity.
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Biomechanical evaluation of pedicle screw loosening mechanism using synthetic bone surrogate of various densities. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:4346-9. [PMID: 25570954 DOI: 10.1109/embc.2014.6944586] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Pedicle screw fixation is a well-established procedure for various spinal disorders. However, pedicle screws failures are still reported. Therefore, there is a need for a greater understanding of the pedicle screw failure mechanism. This experimental study investigates the biomechanical stability of pedicle screws using a synthetic bone surrogate with a special focus on the screw loosening mechanism. Pedicle screws have been inserted in thirty six polyurethane foam blocks of three different densities. In half of the specimens from each density group, pedicle screws were submitted to cyclic bending (toggling) before pullout. The rest of specimens were solely loaded in axial pullout. The peak pullout force and stiffness were determined from load-displacement curve of each specimen. Statistical analyses were performed to investigate on the effect of toggling and bone surrogate density on the pedicle screw's pullout force. The results suggest that the pullout force and stiffness were significantly affected by toggling and density. Higher pullout forces resulted from higher grades of density. The proposed method allowed investigating the pedicle screw loosening mechanism. However, conducing further experimental tests on animal or cadaveric vertebrae are needed to confirm these findings.
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Estimation of pedicle screw fixation strength from probe indentation force and screw insertion torque: a biomechanical study on bone surrogates of various densities. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:4350-3. [PMID: 25570955 DOI: 10.1109/embc.2014.6944587] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Posterior pedicle screw fixation is commonly used for patients with spinal disorders. However, failure of fixation is reported in many cases and surgeons have only little information. The objective of this study was to assess the correlation between the probe indentation force, screw insertion torque and the pullout force using bone surrogates of different densities. The indentation force and insertion torque were measured using a custom made test bench during screw insertion into polyurethane foam blocks. The two variables were significantly correlated to pullout force and to density. A high correlation was also found between indentation force and the peak insertion torque. The proposed methods for measuring indentation force and screw insertion torque were reproducible. This study suggests that the peak screw insertion torque and the indentation force can predict the screw fixation strength in synthetic bone models. Additional tests should be performed on animal and human specimens to confirm and to translate these findings to clinical applications.
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Combined Spine Conference of the Canadian Spine Society New Zealand Orthopaedic Spine Society, Spine Society of Australia: Fairmont Château Lake Louise, Lake, Louise, Alberta, Tuesday, Feb. 25 to Saturday, Mar. 1, 20141.1.01 The use of suspension radiographs to predict LIV tilt.1.1.02 Surgical correction of adolescent idiopathic scoliosis without fusion: an animal model.1.1.03 Are full torso surface topography postural measurements more sensitive to change than back only parameters in adolescents with idiopathic scoliosis and a main thoracic curve?1.2.04 Restoration of thoracic kyphosis in adolescent idiopathic kyphosis: comparative radiographic analysis of round versus rail rods.1.2.05 Scoliosis surgery in spastic quadriplegic cerebral palsy: Is fusion to the pelvis always necessary? A 4–18-year follow-up study.1.2.06 Identification and validation of pain-related biomarkers surrounding spinal surgery in adolescents.1.3.07 Cervical sagittal deformity develops after PJK in adult throacolumbar deformity correction: radiographic analysis using a novel global sagittal angular parameter, the CTPA.1.3.08 Impact of obesity on complications and patient-reported outcomes in adult spinal deformity surgery.1.3.09 The T1 pelvic angle, a novel radiographic measure of sagittal deformity, accounts for both pelvic retroversion and truncal inclination and correlates strongly with HRQOL.1.4.10 Determining cervical sagittal deformity when it is concurrent with thoracolumbar deformity.1.4.11 The influence of sagittal balance and pelvic parameters on the outcome of surgically treated patients with degenerative spondylolisthesis.1.4.12 Predictors of degenerative spondylolisthesis and loading translation in surgical lumbar spinal stenosis patients.2.1.13 Mechanical allodynia following disc herniation requires intraneural macrophage infiltration and can be blocked by systemic selenium delivery or attenuation of BDNF activity.2.1.14 The effect of alanyl-glutamine on epidural fibrosis in a rat laminectomy model.2.1.15 Anterior lumbar interbody fusion using recombinant human bone morphogenetic protein-2: a prospective study of complications.2.2.16 2-year results of a Canadian, multicentre, blinded, pilot study of a novel peptide in promoting lumbar spine fusion.2.2.17 Comparative outcomes and cost-utility following surgical treatment of focal lumbar spinal stenosis compared with osteoarthritis of the hip or knee: long-term change in health-related quality of life.2.2.18 Changes in objectively measured walking performance, function, and pain following surgery for spondylolisthesis and lumbar spinal stenosis.2.3.19 A prospective multicentre observational data-monitored study of minimally invasive fusion to treat degenerative lumbar disorders: complications and outcomes at 1-year follow-up.2.3.20 Assessment and classification of subsidence in lateral interbody fusion using serial computed tomography.2.3.21 Predictors of willingness to undergo spinal and orthopaedic surgery after surgical consultation.2.4.22 Indirect foraminal decompression is independent of facet arthropathy in extreme lateral interbody fusion.2.4.23 Cervical artificial disc replacement with ProDisc-C: clinical and radiographic outcomes with long-term follow-up.2.4.24 Tantalum trabecular metal implants in anterior cervical corpectomy and fusion.3.1.25 Hemangiomas of the spine: results of surgical management and prognostic variables for local recurrence and mortality in a multicentre study.3.1.26 Chondrosarcomas of the spine: prognostic variables for local recurrence and mortality in a multicentre study.3.1.27 Risk factors for recurrence of surgically treated spine schwannomas: analysis of 169 patients from a multicentre international database.3.2.28 Survival pattern and the effect of surgery on health related quality of life and functional outcome in patients with metastatic epidural spinal cord compression from lung cancer — the AOSpine North America prospective multicentre study.3.2.29 A biomechanical assessment of kyphoplasty as a stand-alone treatment in a human cadaveric burst fracture model.3.2.30 What is safer in incompetent vertebrae with posterior wall defects, kyphoplasty or vertebroplasty: a study in vertebral analogs.3.3.31 Feasibility of recruiting subjects for acute spinal cord injury (SCI) clinical trials in Canada.3.3.32 Prospective analysis of adverse events in elderly patients with traumatic spinal cord injury.3.3.33 Does traction before surgery influence time to neural decompression in patients with spinal cord injury?3.4.34 Current treatment of individuals with traumatic spinal cord injury: Do we need age-specific guidelines?3.4.35 Current surgical practice for traumatic spinal cord injury in Canada.3.4.36 The importance of “time to surgery” for traumatic spinal cord injured patients: results from an ambispective Canadian cohort of 949 patients.3.5.37 Assessment of a novel coil-shaped radiofrequency probe in the porcine spine.3.5.38 The effect of norepinephrine and dopamine on cerebrospinal fluid pressure after acute spinal cord injury.3.5.39 The learning curve of pedicle screw placement: How many screws are enough?4.1.40 Preliminary report from the Ontario Inter-professional Spine Assessment and Education Clinics (ISAEC).4.1.41 A surrogate model of the spinal cord complex for simulating bony impingement.4.1.42 Clinical and surgical predictors of specific complications following surgery for the treatment of degenerative cervical myelopathy: results from the multicentre, prospective AOSpine international study on 479 patients.4.2.43 Outcomes of surgical management of cervical spondylotic myelopathy: results of the prospective, multicentre, AOSpine international study in 479 patients.4.2.44 A clinical prediction rule for clinical outcomes in patients undergoing surgery for degenerative cervical myelopathy: analysis of an international AOSpine prospective multicentre data set of 757 subjects.4.2.45 The prevalence and impact of low back and leg pain among aging Canadians: a cross-sectional survey.4.3.46 Adjacent segment pathology: Progressive disease course or a product of iatrogenic fusion?4.3.47 Natural history of degenerative lumbar spondylolisthesis in patients with spinal stenosis.4.3.48 Changes in self-reported clinical status and health care utilization during wait time for surgical spine consultation: a prospective observational study.4.3.49 The Canadian surgical wait list for lumbar degenerative spinal stenosis has a detrimental effect on patient outcomes.4.3.50 Segmental lordosis is independent of interbody cage position in XLIF.4.3.51 Elevated patient BMI does not negatively affect self-reported outcomes of thoracolumbar surgery.1.5.52 The Spinal Stenosis Pedometer and Nutrition Lifestyle Intervention (SSPANLI): development and pilot.1.5.53 Study evaluating the variability of surgical strategy planning for patients with adult spinal deformity.1.5.54 Atlantoaxial instability in acute odontoid fractures is associated with nonunion and mortality.1.5.55 Peripheral hypersensitivity to subthreshold stimuli persists after resolution of acute experimental disc-herniation neuropathy.1.5.56 Radiation induced lumbar spinal osteonecrosis: case report and literature review.1.5.57 Comparative outcomes and cost-utility following surgical treatment of focal lumbar spinal stenosis compared with osteoarthritis of the hip or knee: Part 2 — estimated lifetime incremental cost-utility ratios.1.5.58 A predictive model of progression for adolescent idiopathic scoliosis based on 3D spine parameters at first visit.1.5.59 Development of a clinical prediction model for surgical decision making in patients with degenerative lumbar spine disease.2.5.60 Canadian spine surgery fellowship education: evaluating opportunity in developing a nationally based training curriculum.2.5.61 Pedicle subtraction osteotomy for severe proximal thoracic junctional kyphosis.2.5.62 A comparison of spine surgery referrals triaged through a multidisciplinary care pathway versus conventional referrals.2.5.63 Results and complications of posterior-based 3 column osteotomies in patients with previously fused spinal deformities.2.5.64 Orthopaedic Surgical AdVerse Event Severity (Ortho-SAVES) system: identifying opportunities for improved patient safety and resource utilization.2.5.65 Spontaneous spinal extra-axial haematomas — surgical experience in Otago and Southland 2011–2013.2.5.66 Obesity and spinal epidural lipomatosis in cauda equina syndrome.2.5.67 Factors affecting restoration of lumbar lordosis in adult degenerative scoliosis patients treated with lateral trans-psoas interbody fusion.3.6.68 Systematic review of complications in spinal surgery: a comparison of retrospective and prospective study design.3.6.69 Postsurgical rehabilitation patients have similar fear avoidance behaviour levels as those in nonoperative care.3.6.70 Outcomes of surgical treatment of adolescent spondyloptosis: a case series.3.6.71 Surgical success in primary versus revision thoracolumbar spine surgery.3.6.72 The effect of smoking on subjective patient outcomes in thoracolumbar surgery.3.6.73 Modelling patient recovery to predict outcomes following elective thoracolumbar surgery for degenerative pathologies.3.6.74 Outcomes from trans-psoas versus open approaches in the treatment of adult degenerative scoliosis.3.6.75 Lumbar spinal stenosis and presurgical assessment: the impact of walking induced strain on a performance-based outcome measure. Can J Surg 2014. [DOI: 10.1503/cjs.005614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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Prediction of bone anisotropic mechanical properties in osteoporotic human vertebral body from microstructural parameters. Comput Methods Biomech Biomed Engin 2013; 16 Suppl 1:326-7. [PMID: 23923960 DOI: 10.1080/10255842.2013.815944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Two-photon excited fluorescence in the LYB:Eu monoclinic crystal: towards a new scheme of single-beam dual-voxel direct laser writing in crystals. OPTICS EXPRESS 2013; 21:822-833. [PMID: 23388975 DOI: 10.1364/oe.21.000822] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report on two-photon excited fluorescence in the oriented Eu(3+)doped LYB monoclinic crystal under femtosecond laser tight focusing. Due to spatial walk-off, the two polarization modes of the incident femtosecond beam simultaneously provide the independent excitation of two distinct focuses, leading to a single-beam dual-voxel nonlinear excitation of fluorescence below material modification threshold. These observations emphasize on the anisotropy of both two-photon absorption as well as fluorescence emission. They demonstrate the localized control of the nonlinear energy deposit, thanks to the adjustment of both the input power and polarization, by properly balancing the injected energy in each voxel. Such approach should be considered for future direct laser writing of waveguides in propagation directions out of the dielectric axes, so as to optimally cope with the highly probable anisotropy of laser-induced material modification thresholds in these crystals. These results open new ways for further potential developments in direct laser writing as the simultaneous inscription of double-line structures for original waveguides processes.
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Laser Filament Induced Water Condensation. EPJ WEB OF CONFERENCES 2013. [DOI: 10.1051/epjconf/20134112008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Higher-order Kerr improve quantitative modeling of laser filamentation. OPTICS LETTERS 2012; 37:4347-4349. [PMID: 23073458 DOI: 10.1364/ol.37.004347] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We test numerical filamentation models against experimental data about the peak intensity and electron density in laser filaments. We show that the consideration of the higher-order Kerr effect improves the quantitative agreement without the need of adjustable parameters.
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Strength evaluation of a variable diameter acetabular trial implant under realistic loading conditions. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2011; 2011:7433-7436. [PMID: 22256057 DOI: 10.1109/iembs.2011.6091731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A variable diameter acetabular trial implant (VDATI) was designed to reduce the costs related to cleaning, sterilisation and storage of surgical instruments used for total hip arthroplasty. The purpose of this study was to evaluate the mechanical strength of a functional prototype of the VDATI. Experimental testing was performed to identify if the VDATI can resist loading conditions similar to the ones occurring during the surgical procedure and to validate a finite element model (FEM) of the VDATI. The results highlighted the potential of the current concept of the VDATI and demonstrated the relevance to continue its development.
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Abstract
We derive the spectral dependence of the non-linear susceptibility of any order, generalizing the common form of Sellmeier equations. This dependence is fully defined by the knowledge of the linear dispersion of the medium. This finding generalizes the Miller formula to any order of non-linearity. In the frequency-degenerate case, it yields the spectral dependence of non-linear refractive indices of arbitrary order.
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Finite element analysis of an acetabular trial implant. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2010; 2010:3930-3933. [PMID: 21097086 DOI: 10.1109/iembs.2010.5627680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A variable diameter trial liner (VDTL) was designed to reduce the costs related to cleaning, sterilisation and storage of surgical instruments used for total hip arthroplasty. The purpose of this study was to develop a finite element model to evaluate the mechanical behavior of the VDTL before manufacturing of a functional prototype. The finite element analysis consists to identify the maximum stresses applied on the VDTL and compare these values to the yield strength of stainless steel 17-4 (540 MPa) to asses if the VDTL will resist to loading conditions similar to the ones occurring during the surgical procedure. The results demonstrated the need to improve the mechanical strength of the current concept of the VDTL. These results will serve as indications for upcoming design refinements.
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Finite element model of a greater trochanteric reattachment system. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2010; 2010:3926-3929. [PMID: 21097085 DOI: 10.1109/iembs.2010.5627683] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Detachment of greater trochanter (GT) is generally associated with hip arthroplasty complications and needs for repositioning and fixation. A new GT reattachment system (Y3) was proposed to reduce GT displacements in anterior-posterior direction to decrease non-union issues. The goal of this study is to develop and validate a FEM of the Y3 GTR system. FEM validation suggests a good concordance between numerical and experimental GT displacements. Sensitivity study show that the transition between proximal and distal branches of Y3 design is the most influent part on all GT displacements. The anterior branch affects more anterior-posterior displacements and rotation while the posterior branch affects more proximal displacements and rotation. This study provides an improved understanding of the influence of Y3 geometry on GT displacements.
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Abstract
We demonstrate that filaments generated by ultrashort laser pulses can induce a remarkably large birefringence in Argon over its whole length, resulting in an ultrafast "half-wave plate" for a copropagating probe beam. This birefringence originates from the difference between the nonlinear refractive indices induced by the filament on the axes parallel and orthogonal to its polarization. An angle of 45 degrees between the filament and the probe polarizations allows the realization of ultrafast Kerr-gates, with a switching time ultimately limited by the duration of the filamenting pulse.
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Biomechanical modelling of segmental instrumentation for surgical correction of 3D spinal deformities using Euler-Bernoulli thin-beam elastic deformation equations. Med Biol Eng Comput 2004; 42:216-21. [PMID: 15125152 DOI: 10.1007/bf02344634] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
A simplified computer-modelling technique intended to analyse 3D spinal deformity correction with segmental instrumentation is presented. The spine was modelled as a thin beam-composed structure linked by implants to two deformable rods. The Landau vector representation of Euler-Bernoulli beam elastic deformation equations was used to formulate the simulation approach. All types of essential deformation (bending, torsion, tension, compression) were considered. An iterative numerical method was proposed to obtain an appropriate load, able to deform the spine axial curve to the desired post-operative shape. A simulation based on the spine of a real scoliotic patient (thoracic and lumbar Cobb angles: 39 degrees and 8 degrees), corrected using surgical instrumentation intervention, is presented. Force loads within the range of 20-350 N were able to deform the pre-operational spine axial curve to the post-operational one with a root mean square approximation error of 3.7 mm. Similarly good corrections were obtained using different force patterns. This highlights the uncertainty of which corresponding surgical instrumentation to use. Such uncertainty is related to the 'ill-posed problems' property of mechanical systems.
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Personalized biomechanical simulations of orthotic treatment in idiopathic scoliosis. Clin Biomech (Bristol, Avon) 2004; 19:190-5. [PMID: 14967583 DOI: 10.1016/j.clinbiomech.2003.11.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2003] [Accepted: 11/14/2003] [Indexed: 02/07/2023]
Abstract
OBJECTIVES To analyse patient-specific bracing biomechanics in the treatment of scoliosis. DESIGN Two complementary computer tools have been developed to quantify the brace action on scoliotic spine from pressure measurements, and to simulate its effect on patient-adapted finite element model. BACKGROUND Brace pad forces and brace effect on spine deformities have been reported. However, the brace mechanisms still need to be better understood to obtain more effective treatments. METHODS The 3D geometry of the spine and rib cage of three scoliotic adolescents treated by the Boston brace was obtained using a multiview radiographic reconstruction technique. A personalized biomechanical model was constructed for each patient. Pressures generated by the brace on the thorax were measured using pressure sensors. For each zone with a threshold pressure higher than 30 mmHg, a total equivalent force was calculated and applied to the corresponding model nodes. RESULTS The pressure were generally scattered on the overall torso, with the highest pressures measured on five distinct regions: right thoracic, left lumbar, abdominal, right and left sides of the pelvis. The equivalent forces were of 18-73 N. Differences between simulated deformed shapes and real in-brace geometry of the patients were less than 6 and 9.8 mm for the vertebral positions in the coronal and sagittal planes, and 7.7 degrees for the Cobb angles. CONCLUSION The results supported the feasibility of such approach to analyse patient-specific bracing biomechanics, which may be useful in the design of more effective braces.
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Patient-specific mechanical properties of a flexible multi-body model of the scoliotic spine. Med Biol Eng Comput 2004; 42:55-60. [PMID: 14977223 DOI: 10.1007/bf02351011] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The flexibility of the scoliotic spine is an important biomechanical parameter to take into account in the planning of surgical instrumentation. The objective of the paper was to develop a method to characterise in vivo the mechanical properties of the scoliotic spine using a flexible multi-body model. Vertebrae were represented as rigid bodies, and intervertebral elements were defined at every level using a spherical joint and three torsion springs. The initial mechanical properties of motion segments were defined from in vitro experimental data reported in the literature. They were adjusted using an optimisation algorithm to reduce the discrepancy between the simulated and the measured Ferguson angles in lateral bending of three spine segments (major or compensatory left thoracic, right thoracic and left lumbar scoliosis curves). The flexural rigidity of the spine segments was defined in three categories (flexible, nominal, rigid) according to the estimated mechanical factors (alpha). This approach was applied with ten scoliotic patients undergoing spinal correction. Personalisation of the model resulted in an increase of the initial flexural rigidity for seven of the ten lumbar segments (1.38 < or = alpha < or = 10.0) and four of the ten right thoracic segments (1.74 < or = alpha < or = 5.18). The adjustment of the mechanical parameters based on the lateral bending tests improved the model's ability to predict the spine shape change described by the Ferguson angles by up to 50%. The largest differences after personalisation were for the left lumbar segments in left bending (4 degrees +/- 3 degrees). The in vivo identification of the mechanical properties of the scoliotic spine will improve the ability of biomechanical models adequately to predict the surgical correction, which should help clinicians in the planning of surgical instrumentation manoeuvres.
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Assessment of the 3-d reconstruction and high-resolution geometrical modeling of the human skeletal trunk from 2-D radiographic images. IEEE Trans Biomed Eng 2003; 50:989-98. [PMID: 12892326 DOI: 10.1109/tbme.2003.814525] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This paper presents an in vivo validation of a method for the three-dimensional (3-D) high-resolution modeling of the human spine, rib cage, and pelvis for the study of spinal deformities. The method uses an adaptation of a standard close-range photogrammetry method called direct linear transformation to reconstruct the 3-D coordinates of anatomical landmarks from three radiographic images of the subject's trunk. It then deforms in 3-D 1-mm-resolution anatomical primitives (reference bones) obtained by serial computed tomography-scan reconstruction of a dry specimen. The free-form deformation is calculated using dual kriging equations. In vivo validation of this method on 40 scoliotic vertebrae gives an overall accuracy of 3.3 +/- 3.8 mm, making it an adequate tool for clinical studies and mechanical analysis purposes.
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Abstract
Scoliosis is a three-dimensional deformation of the spine that can be treated by vertebral fusion using surgical instrumentation. However, the optimal configuration of instrumentation remains controversial. Simulating the surgical maneuvers with personalized biomechanical models may provide an analytical tool to determine instrumentation configuration during the pre-operative planning. Finite element models used in surgical simulations display convergence difficulties as a result of discontinuities and stiffness differences between elements. A kinetic model using flexible mechanisms has been developed to address this problem, and this study presents its use in the simulation of Cotrel-Dubousset Horizon surgical maneuvers. The model of the spine is composed of rigid bodies corresponding to the thoracic and lumbar vertebrae, and flexible elements representing the intervertebral structures. The model was personalized to the geometry of three scoliotic patients (with a thoracic Cobb angle of 45 degrees, 49 degrees and 39 degrees ). Binary joints and kinematic constraints were used to represent the rod-implant-vertebra joints. The correction procedure was simulated using three steps: (1) Translation of hooks and screws on the first rod; (2) 90 degrees rod rotation; (3) Hooks and screws look-up on the rod. After the simulation, slight differences of 0-6 degrees were found for the thoracic spine scoliosis and the kyphosis, and of 1-8 degrees for the axial rotation of the apical vertebra and for the orientation of the plane of maximum deformity, compared to the real post-operative shape of the patient. Reaction loads at the vertebra-implant link were mostly below 1000 N, while reaction loads at the boundary conditions (representing the overall action of the surgeon) were in the range 7-470 N and maximum torque applied to the rod was 1.8 Nm. This kinetic modeling approach using flexible mechanisms provided a realistic representation of the surgical maneuvers. It may offer a tool to predict spinal geometry correction and assist in the pre-operative planning of surgical instrumentation of the scoliotic spine.
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Biomechanical simulation of Colorado instrumentation of the scoliotic spine: a preliminary study. Stud Health Technol Inform 2002; 88:415-8. [PMID: 15456074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
Few biomechanical models of the scoliotic spine were developed to simulate the Cotrel-Dubousset instrumentation, although none was dedicated to the Colorado system. The objective of this study is to adapt and assess an existing biomechanical model to simulate the effect of the Colorado instrumentation of the scoliotic spine as a function of pre-operative geometry and surgical planning. Fifteen scoliotic patients operated with a Colorado system were analysed using a knowledge extraction technique to simplify surgical procedure and to establish the biomechanical model (boundary conditions, simulation procedures,...). Preliminary results on one patient show that the Colorado surgical technique can be adequately modelled using the preoperative geometric data and limited simulation strategy parameters.
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Relation between patient positioning, trunk flexibility and surgical correction of the scoliotic spine. Stud Health Technol Inform 2002; 88:400-3. [PMID: 15456070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
The purpose of this work is to investigate the relations between the correction of idiopathic scoliosis obtained by surgical instrumentation and the positioning of the patient on the surgical table as well as the curve reduction following the bending test. A retrospective study of preoperative standing, supine and lateral bending films as well as postoperative standing films was made using multiple regressions in order to identify the most significant parameters and define linear statistical models to predict the surgical correction. Postoperative thoracic Cobb angle is significantly associated to left and right bending Cobb angles and the post-op lumbar Cobb is associated to the supine and the left bending Cobb angles. This preliminary study suggests that such parameters should be considered in the pre-operative planning of surgery as well as in biomechanical models to obtain more adequate predictive values of the surgical outcome and to better understand the biomechanics of scoliosis surgical correction.
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[Correlation study between spinal curvatures and vertebral and disk deformities in idiopathic scoliosis]. ANNALES DE CHIRURGIE 1999; 53:798-807. [PMID: 10584392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
Idiopathic scoliosis involves complex tridimensional (3D) deformations of the spine associated with intrinsic alterations (wedging) of vertebral bodies (VB) and intervertebral disks (ID). This study intends to evaluate analytically in vivo 2D and 3D scoliotic descriptors, based on clinical data from 40 thoracic curves of scoliotic adolescents, and to establish relationships between the regional curve deformations and the local VB and ID deformities. A multiplanar radiographic technique provided 3D positioning of vertebral landmarks. Cobb angle in the postero-anterior (PA) view, in the plane of maximum deformity (CobbP.Max) and the angular orientation of the plane of maximum deformity were used as regional descriptors. Vertebral body endplates were modeled as 3D oriented ellipses. Axial rotation, global PA and local frontal wedgings (inclinations of projected ellipses in the global and vertebral frontal planes), 3D maximum wedging (real inclination of adjacent ellipses) as well as the angular orientation of 3D wedging were calculated to characterize local deformations at the thoracic apex. Mean values for CobbPA, CobbP.Max and the angular orientation of the maximum deformity (with respect to the sagittal plane) reached 44 degrees, 48 degrees and 67 degrees respectively. On average, vertebral axial rotation, global PA, local frontal and 3D wedging angles were respectively 15 degrees, 8.3 degrees, 8.2 degrees and 9.7 degrees. Analyses indicated statistical correlation between: a) Cobb angles and vertebral wedging; b) the orientations of the maximum deformity and of 3D vertebral wedging; c) the axial rotation and CobbPA; d) the axial rotation and the angular orientation of 3D vertebral wedging. At the thoracic level, statistical analyses indicated that vertebral wedging and axial rotation increase with curve progression. Scoliosis severity, as measured by Cobb angles, evolves simultaneously to a coronalization of the plane of maximum deformity, revealing an hypokyphotic phenomenon, and to a real vertebral wedging shifting towards the frontal plane of the vertebra. These 3D in vivo analyses allowed interpretation of spatial relationships between regional and local scoliotic deformities. Compared to 2D in vivo or 3D in vitro analyses alone, this 3D in vivo study provides a more complete assessment of spinal curve progression to fully interpret the real 3D curvature and intrinsic deformations as well as their evolution processes.
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Abstract
STUDY DESIGN A mechanical evaluation of brace strap tensions to document their variability in different patient positions and to assess their biomechanical effectiveness. OBJECTIVES To measure the strap tensions at which adolescents with scoliosis are wearing their braces and to determine the variations in strap tension in different patient positions. SUMMARY OF BACKGROUND DATA The biomechanical action of thoracolumbosacral orthoses in still not well understood, and there is no standardized strap tension at which the brace should be fastened to obtain optimal results. METHODS This study was conducted in 34 adolescents with idiopathic scoliosis wearing thoracolumbosacral orthoses. Brace straps were instrumented with load cells and tightened at four tensions (the ones prescribed by their treating physician and three standardized values: 20, 40, and 60 N). In each case, the tension was recorded while the patients assumed nine positions corresponding to normal daily tasks. The variability of strap tension was evaluated by comparing the changes from the original standing position. RESULTS The prescribed tensions measured in thoracic and pelvic straps were markedly variable. The greatest changes in tension occurred when the patients were lying down. Relaxation of strap tension was found when the patients returned to the standing position after having completed the tasks. CONCLUSIONS If strap tension affects the biomechanical actions of the brace, these results indicate that regular brace strap tension adjustments are needed and raise questions about the efficacy of nighttime bracing to correct spinal deformities.
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[Customized 3D radiographic reconstruction of the human pelvis]. ANNALES DE CHIRURGIE 1998; 52:744-51. [PMID: 9846424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
The pelvis is an essential element in the study of scoliosis since it constitutes the base of the spine and its orientation may affects postural balance. In order to study the role of the pelvis in the evolution and treatment of this disease, a new technique for the 3D personalised reconstruction of the pelvis was developed. It consists in identifying and digitizing 19 pelvic anatomical landmarks on postero-anterior and lateral x-rays and to reconstruct them in 3D with two techniques: the DLT algorithm developed by Marzan (1976) and, for 6 of the 19 landmarks, an adaptation of it called DLT with confidence coefficients. The latter takes into account the confidence given to the identification of the landmarks on each x-rays. Two methods were used to validate the reconstruction of the pelvis. The first one, used for 11 scoliotic patients and 2 dry pelvis specimens, consists in applying the reconstruction algorithm in an inverse way on the 3D coordinates of the reconstructed landmarks to obtain their 2D retroprojection on the x-ray planes, and thus comparing the retroprojected coordinates with the 2D digitized coordinates. The second method consists in measuring a dry pelvis specimen and comparing the 3D measured landmarks with the ones reconstructed with the x-rays of this specimen. For the first validation, results have shown that the lowest retroprojection errors (less than 2.5 +/- 2.6 mm) for the scoliotic patient group are located on the superior base of the sacrum, on the sacral curve and on the acetabula, while the highest (6.4 +/- 7.2 mm) were on the iliac crests. For the dry specimens, the retroprojection errors were below the millimeter. The second validation method showed 3D differences of 2.4 +/- 1.2 mm between measured and reconstructed landmarks of a dry specimen, which is of the same order of magnitude as what is reported in the literature for vertebrae. The reconstruction of the pelvis is thus considered adequate and its graphical wireframe representation allows to visualise and measure clinical indices concerning its orientation in space. Moreover, the reconstructed landmarks will be used to develop a personalised geometrical and mechanical model of the pelvis which, when integrated with the one for the spine and rib cage, will allow to simulate in a more realistic manner the biomechanical behaviour of the scoliotic trunk, particularly for the study of orthopaedic treatments with braces leaning on it.
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Estimation of 3D location and orientation of human vertebral facet joints from standing digital radiographs. Med Biol Eng Comput 1998; 36:389-94. [PMID: 10198519 DOI: 10.1007/bf02523204] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
This study provides a biplanar radiographic reconstruction method of volumes of interest to evaluate the location, dimensions and orientation of human facet joints. Visibility of facet anatomical landmarks and areas of interest was evaluated on digital radiographs of 20 idiopathic scoliotic adolescents. Areas of interest have provided the most reliable evaluation of facet joints on postero-anterior and lateral digital radiographs. Volumes of interest of a thoracic and lumbar spinal segment (T1 to L3) were computed using the proposed biplanar 3D reconstruction method and compared with serial tomographic reconstructed models. Differences of 1.5 +/- 0.7 mm in 3D location and 1.8 +/- 1.2 degrees in sagittal orientation of volumes of interest were observed between both representations. This in vivo geometric information on human vertebral facet joints will help us to understand their role in spinal disorders and will provide important data for personalised biomechanical simulations.
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Boston brace treatment vs simulation of a new orthotic approach for the correction of scoliotic deformities. J Biomech 1998. [DOI: 10.1016/s0021-9290(98)80276-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Effect of strap tension on the pressure generated by the boston brace on idiopathic scoliosispatients: A preliminary study. J Biomech 1998. [DOI: 10.1016/s0021-9290(98)80353-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Three-dimensional measurement of wedged scoliotic vertebrae and intervertebral disks. EUROPEAN SPINE JOURNAL : OFFICIAL PUBLICATION OF THE EUROPEAN SPINE SOCIETY, THE EUROPEAN SPINAL DEFORMITY SOCIETY, AND THE EUROPEAN SECTION OF THE CERVICAL SPINE RESEARCH SOCIETY 1998; 7:59-65. [PMID: 9548361 PMCID: PMC3615358 DOI: 10.1007/s005860050029] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Idiopathic scoliosis involves complex spinal intrinsic deformations such as the wedging of vertebral bodies (VB) and intervertebral disks (ID), and it is obvious that the clinical evaluation obtained by the spinal projections on the two-dimensional (2D) radiographic planes do not give a full and accurate interpretation of scoliotic deformities. This paper presents a method that allows reconstruction in 3D of the vertebral body endplates and measurement of the 3D wedging angles. This approach was also used to verify whether 2D radiographic measurements could lead to a biased evaluation of scoliotic spine wedging. The 3D reconstruction of VB contours was done using calibrated biplanar X-rays and an iterative projection computer procedure that fits 3D oriented ellipses of adequate diameters onto the 3D endplate contours. "3D wedging angles" of the VB and ID (representing the maximum angle between adjacent vertebrae) as well as their angular locations with respect to the vertebral frontal planes were computed by finding the positions of the shortest and longest distances between consecutive endplates along their contour. This method was extensively validated using several approaches: (1) by comparing the 3D reconstructed endplates of a cadaveric functional unit (T8-T9) with precise 3D measurements obtained using a coordinate measuring machine for 11 different combinations of vertebral angular positions; (2) by a sensitivity study on 400 different vertebral segments mathematically generated, with errors randomly introduced on the digitized points (standard deviations of 0.5, 1, 2, and 3 mm); (3) by comparing the clinical wedging measurements (on postero-anterior and lateral radiographs) at the thoracic apical level of 34 scoliotic patients (15 degrees < Cobb < 45 degrees) to the computed values. Mean errors for the 11 vertebral positions were 0.5 +/- 0.4 mm for VB thickness, less than 2.2 degrees for endplate orientation, and about 11 degrees (3 mm) for the location of the maximum 3D wedging angle along the endplate contour. The errors below 2 mm (introduced on the digitized points) slightly affected the 3D wedging angle (< 2 degrees) and its location (< 4 degrees) for the ID. As for the clinical evaluation, average angular errors were less than 0.4 degrees in the radiographic frontal and lateral planes. The mean 3D wedged angles were about 4.9 degrees +/- 1.9 degrees for the VB and 6.0 degrees +/- 1.7 degrees for the ID. Linear relations were found between the 2D and the 3D angles, but the 3D angles were located on diagonal planes statistically different than the radiographic ones (between 100 degrees and 221 degrees). There was no statistical relation between the 2D radiographic angles and the locations of the 3D intervertebral wedging angles. These results clearly indicate that VB and ID endplates are wedged in 3D, and that measurements on plain radiographs allow incomplete evaluation of spinal wedging. Clinicians should be aware of these limitations while using wedging measurements from plain radiographs for diagnosis and/or research on scoliotic deformities.
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