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Zhao X, Zhang Y, Wang P, Guan J, Zhang D. Construction of multileveled and oriented micro/nano channels in Mg doped hydroxyapitite bioceramics and their effect on mimicking mechanical property of cortical bone and biological performance of cancellous bone. BIOMATERIALS ADVANCES 2024; 161:213871. [PMID: 38692181 DOI: 10.1016/j.bioadv.2024.213871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2023] [Revised: 04/13/2024] [Accepted: 04/24/2024] [Indexed: 05/03/2024]
Abstract
Drawing on the structure and components of natural bone, this study developed Mg-doped hydroxyapatite (Mg-HA) bioceramics, characterized by multileveled and oriented micro/nano channels. These channels play a critical role in ensuring both mechanical and biological properties, making bioceramics suitable for various bone defects, particularly those bearing loads. Bioceramics feature uniformly distributed nanogrooves along the microchannels. The compressive strength or fracture toughness of the Mg-HA bioceramics with micro/nano channels formed by single carbon nanotube/carbon fiber (CNT/CF) (Mg-HA(05-CNT/CF)) are comparable to those of cortical bone, attributed to a combination of strengthened compact walls and microchannels, along with a toughening mechanism involving crack pinning and deflection at nanogroove intersections. The introduction of uniform nanogrooves also enhanced the porosity by 35.4 %, while maintaining high permeability owing to the capillary action in the oriented channels. This leads to superior degradation properties, protein adsorption, and in vivo osteogenesis compared with bioceramics with only microchannels. Mg-HA(05-CNT/CF) exhibited not only high strength and toughness comparable to cortical bone, but also permeability similar to cancellous bone, enhanced cell activity, and excellent osteogenic properties. This study presents a novel approach to address the global challenge of applying HA-based bioceramics to load-bearing bone defects, potentially revolutionizing their application in tissue engineering.
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Affiliation(s)
- Xueni Zhao
- College of Mechanical and Electrical Engineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi 710021, PR China.
| | - Yu Zhang
- College of Mechanical and Electrical Engineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi 710021, PR China
| | - Pengfei Wang
- College of Mechanical and Electrical Engineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi 710021, PR China
| | - Jinxin Guan
- College of Mechanical and Electrical Engineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi 710021, PR China
| | - Dexin Zhang
- Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710004, PR China.
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Ibrahim A, Jiang Z, Shirvani K, Dalili A, Abdel Hamid Z. A Novel Viscoelastic Deformation Mechanism Uncovered during Vickers Hardness Study of Bone. J Funct Biomater 2024; 15:87. [PMID: 38667544 PMCID: PMC11051036 DOI: 10.3390/jfb15040087] [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: 03/05/2024] [Revised: 03/26/2024] [Accepted: 03/29/2024] [Indexed: 04/28/2024] Open
Abstract
This study investigates the viscoelastic deformation mechanisms of bone as a response to Vickers hardness indentation. We utilized advanced high-resolution scanning electron microscopy (SEM) to investigate a distinct deformation pattern that originates from the indentation site within the bone matrix. The focus of our research was to analyze a unique deformation mechanism observed in bone tissue, which has been colloquially termed as "screw-like" due to its resemblance to a screw thread when viewed under an optical microscope. The primary goals of this research are to investigate the distinctive characteristics of the "screw-like" deformation pattern and to determine how the microstructure of bone influences the initiation and control of this mechanism. These patterns, emerging during the dwell period of indentation, underscore the viscoelastic nature of bone, indicating its propensity for energy dissipation and microstructural reconfiguration under load. This study uncovered a direct correlation between the length of the "screw-like" deformation and the duration of the indentation dwell time, providing quantifiable evidence of the bone's viscoelastic behavior. This finding is pivotal in understanding the mechanical properties of bone, including its fracture toughness, as it relates to the complex interplay of factors such as energy dissipation, microstructural reinforcement, and stress distribution. Furthermore, this study discusses the implications of viscoelastic properties on the bone's ability to resist mechanical challenges, underscoring the significance of viscoelasticity in bone research.
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Affiliation(s)
- Ahmed Ibrahim
- Mechanical Engineering Department, Farmingdale State College, Farmingdale, NY 11735, USA; (K.S.); (A.D.)
| | - Zhenting Jiang
- The Department of Earth & Planetary Sciences, Yale University, New Haven, CT 06511, USA;
| | - Khosro Shirvani
- Mechanical Engineering Department, Farmingdale State College, Farmingdale, NY 11735, USA; (K.S.); (A.D.)
| | - Alireza Dalili
- Mechanical Engineering Department, Farmingdale State College, Farmingdale, NY 11735, USA; (K.S.); (A.D.)
| | - Z. Abdel Hamid
- Central Metallurgical Research and Development Institute, Helwan 11421, Egypt;
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Agres AN, Alves SA, Höntzsch D, El Attal R, Pohlemann T, Schaser KD, Joeris A, Hess D, Duda GN. Improved weight bearing during gait at 6 weeks post-surgery with an angle stable locking system after distal tibial fracture. Gait Posture 2024; 107:169-176. [PMID: 37845132 DOI: 10.1016/j.gaitpost.2023.09.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Revised: 07/12/2023] [Accepted: 09/25/2023] [Indexed: 10/18/2023]
Abstract
BACKGROUND Functional recovery after intramedullary nailing of distal tibial fractures can be monitored using ipsilateral vertical ground reaction forces (vGRF), giving insight into recovery of patients' gait symmetry. Previous work compared patient cohorts to healthy controls, but it remains unclear if these metrics can identify treatment-based differences in return to function post-surgery. RESEARCH QUESTION Is treatment of a distal tibial fracture with intramedullary nailing with an angle stable locking system (ASLS) associated with higher ipsilateral vGRF and improved symmetry compared to conventional intramedullary nailing at an early time point? METHODS Thirty-nine patients treated with ASLS intramedullary nailing were retrospectively compared to thirty-nine patients with conventional locking. vGRFs were collected at 1, 6, 12, 26, and 52 weeks post-surgery during standing and gait. Discrete metrics of ipsilateral vGRF (maximal force, impulse) and asymmetry were compared between treatments at each time point. Time-scale comparisons of ipsilateral vGRF and lower limb asymmetry were additionally performed for gait trials. Mann-Whitney Test or a two-way analysis of variance tested discrete comparisons; statistical non-parametric mapping tested time-scale data between treatment groups. RESULTS During gait, ASLS-treated patients applied more load on the operated limb (17-38% stance, p = 0.015) and consequently loaded limbs more symmetrically (8-37% stance, p = 0.008) during the loading response at 6 weeks post-surgery compared to conventional IM treatment. Discrete measures of symmetry at the same time point identified treatment-based differences in maximal force (p = 0.039) and impulse (p = 0.012), with ASLS-treated patients exhibiting more symmetry. No differences were identified in gait trials at later time points nor from all standing trials. SIGNIFICANCE During the initial loading response of gait, increased ipsilateral vGRF and improved weightbearing symmetry were identified in ASLS patients at 6 weeks post-surgery compared to conventional IM nailing. Early and objective metrics of dynamic movement are suggested to identify treatment-based differences in functional recovery.
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Affiliation(s)
- Alison N Agres
- Julius Wolff Institute, Berlin Institute of Health at Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Sónia A Alves
- Julius Wolff Institute, Berlin Institute of Health at Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Dankward Höntzsch
- BG Unfallklinik and University Hospital Tübingen, Schnarrenbergstraße 95, 72076 Tübingen, Germany
| | - René El Attal
- Orthopaedics, Traumatology and Sport Traumatology, Akademisches Lehrkrankenhaus, Carinagasse 47, 6800 Feldkirch, Austria
| | - Tim Pohlemann
- Department for Trauma, Hand and Reconstructive Surgery, Saarland University Medical Center, Kirrbergerstr. 1, 66421 Homburg, Germany
| | - Klaus-Dieter Schaser
- University Center of Orthopaedic, Trauma and Plastic Surgery, University Hospital Carl Gustav Carus, Fetscherstraße 74, 01307 Dresden, Germany
| | - Alexander Joeris
- AO Innovation Translation Center, AO Foundation, Stettbachstrasse 6, 8600 Dübendorf, Switzerland
| | - Denise Hess
- AO Education Institute, AO Foundation, Stettbachstrasse 6, 8600 Dübendorf, Switzerland
| | - Georg N Duda
- Julius Wolff Institute, Berlin Institute of Health at Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
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Bevers MSAM, Heyer FL, Wyers CE, van Rietbergen B, Geusens PPMM, Janzing HMJ, Lambers Heerspink O, Poeze M, van den Bergh JP. The contribution of lower-mineralized tissue to the healing of distal radius fractures assessed using HR-pQCT. Bone 2023; 175:116859. [PMID: 37507063 DOI: 10.1016/j.bone.2023.116859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 07/03/2023] [Accepted: 07/25/2023] [Indexed: 07/30/2023]
Abstract
High-resolution peripheral quantitative CT (HR-pQCT) enables quantitative assessment of distal radius fracture healing. In previous studies, lower-mineralized tissue formation was observed on HR-pQCT scans, starting early during healing, but the contribution of this tissue to the stiffness of distal radius fractures is unknown. Therefore, the aim of this study was to investigate the contribution of lower-mineralized tissue to the stiffness of fractured distal radii during the first twelve weeks of healing. We did so by combining the results from two series of micro-finite element (μFE-) models obtained using different density thresholds for bone segmentation. Forty-five postmenopausal women with a conservatively-treated distal radius fracture had HR-pQCT scans of their fractured radius at baseline (BL; 1-2 weeks post-fracture), 3-4 weeks, 6-8 weeks, and 12 weeks post-fracture. Compression stiffness (S) was computed using two series of μFE-models from the scans: one series (Msingle) included only higher-mineralized tissue (>320 mg HA/cm3), and one series (Mdual) differentiated between lower-mineralized tissue (200-320 mg HA/cm3) and higher-mineralized tissue. μFE-elements were assigned a Young's Modulus of 10 GPa (higher-mineralized tissue) or 5 GPa (lower-mineralized tissue), and an axial compression test to 1 % strain was simulated. The contribution of the lower-mineralized tissue to S was quantified as the ratio Sdual/Ssingle. Changes during healing were quantified using linear mixed effects models and expressed as estimated marginal means (EMMs) with 95 %-confidence intervals (95 %-CI). Median time to cast removal was 5.0 (IQR: 1.1) weeks. Sdual and Ssingle gradually increased during healing to a significantly higher value than BL at 12 weeks post-fracture (both p < 0.0001). In contrast, Sdual/Ssingle was significantly higher than BL at 3-4 weeks post-fracture (p = 0.0010), remained significantly higher at 6-8 weeks post-fracture (p < 0.0001), and then decreased to BL-values at the 12-week visit. EMMs ranged between 1.05 (95 %-CI: 1.04-1.06) and 1.08 (95 %-CI: 1.07-1.10). To conclude, combining stiffness results from two series of μFE-models obtained using single- and dual-threshold segmentation enables quantification of the contribution of lower-mineralized tissue to the stiffness of distal radius fractures during healing. This contribution is minor but changes significantly around the time of cast removal. Its course and timing during healing may be clinically relevant. Quantification of the contribution of lower-mineralized tissue to stiffness gives a more complete impression of strength recovery post-fracture than the evaluation of stiffness using a single series of μFE-models.
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Affiliation(s)
- Melissa S A M Bevers
- Department of Internal Medicine, VieCuri Medical Center, Venlo, the Netherlands; NUTRIM School for Nutrition and Translational Research In Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands; Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands
| | - Frans L Heyer
- NUTRIM School for Nutrition and Translational Research In Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands; Department of Surgery, VieCuri Medical Center, Venlo, the Netherlands
| | - Caroline E Wyers
- Department of Internal Medicine, VieCuri Medical Center, Venlo, the Netherlands; NUTRIM School for Nutrition and Translational Research In Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands; Department of Internal Medicine, Subdivision of Rheumatology, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Bert van Rietbergen
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands; Department of Orthopedic Surgery, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Piet P M M Geusens
- Department of Internal Medicine, Subdivision of Rheumatology, Maastricht University Medical Center, Maastricht, the Netherlands; Department of Medicine and Life Sciences, Hasselt University, Belgium
| | | | | | - Martijn Poeze
- NUTRIM School for Nutrition and Translational Research In Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands; Department of Surgery and Trauma Surgery, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Joop P van den Bergh
- Department of Internal Medicine, VieCuri Medical Center, Venlo, the Netherlands; NUTRIM School for Nutrition and Translational Research In Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands; Department of Internal Medicine, Subdivision of Rheumatology, Maastricht University Medical Center, Maastricht, the Netherlands.
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Ishimoto T, Kobayashi Y, Takahata M, Ito M, Matsugaki A, Takahashi H, Watanabe R, Inoue T, Matsuzaka T, Ozasa R, Hanawa T, Yokota K, Nakashima Y, Nakano T. Outstanding in vivo mechanical integrity of additively manufactured spinal cages with a novel "honeycomb tree structure" design via guiding bone matrix orientation. Spine J 2022; 22:1742-1757. [PMID: 35675865 DOI: 10.1016/j.spinee.2022.05.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 05/31/2022] [Accepted: 05/31/2022] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Therapeutic devices for spinal disorders, such as spinal fusion cages, must be able to facilitate the maintenance and rapid recovery of spinal function. Therefore, it would be advantageous that future spinal fusion cages facilitate rapid recovery of spinal function without secondary surgery to harvest autologous bone. PURPOSE This study investigated a novel spinal cage configuration that achieves in vivo mechanical integrity as a devise/bone complex by inducing bone that mimicked the sound trabecular bone, hierarchically and anisotropically structured trabeculae strengthened with a preferentially oriented extracellular matrix. STUDY DESIGN/SETTINGS In vivo animal study. METHODS A cage possessing an anisotropic through-pore with a grooved substrate, that we termed "honeycomb tree structure," was designed for guiding bone matrix orientation; it was manufactured using a laser beam powder bed fusion method through an additive manufacturing processes. The newly designed cages were implanted into sheep vertebral bodies for 8 and 16 weeks. An autologous bone was not installed in the newly designed cage. A pull-out test was performed to evaluate the mechanical integrity of the cage/bone interface. Additionally, the preferential orientation of bone matrix consisting of collagen and apatite was determined. RESULTS The cage/host bone interface strength assessed by the maximum pull-out load for the novel cage without an autologous bone graft (3360±411 N) was significantly higher than that for the conventional cage using autologous bone (903±188 N) after only 8 weeks post-implantation. CONCLUSIONS These results highlight the potential of this novel cage to achieve functional fusion between the cage and host bone. Our study provides insight into the design of highly functional spinal devices based on the anisotropic nature of bone. CLINICAL SIGNIFICANCE The sheep spine is similar to the human spine in its stress condition and trabecular bone architecture and is widely recognized as a useful model for the human spine. The present design may be useful as a new spinal device for humans.
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Affiliation(s)
- Takuya Ishimoto
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka, 565-0871, Japan; Anisotropic Design and Additive Manufacturing Research Center, Osaka University, 2-1 Yamada-Oka, Suita, Osaka, 565-0871, Japan
| | - Yoshiya Kobayashi
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka, 565-0871, Japan
| | - Masahiko Takahata
- Department of Orthopedic Surgery, Graduate School of Medicine, Hokkaido University, North-15, West-7, Kita-ku, Sapporo, Hokkaido, 060-8638, Japan
| | - Manabu Ito
- Department of Spine and Spinal Cord Disorders, National Hospital Organization, Hokkaido Medical Center, 5-7-1-1, Yamanote, Nishi-ku, Sapporo, Hokkaido, 063-0005, Japan
| | - Aira Matsugaki
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka, 565-0871, Japan; Anisotropic Design and Additive Manufacturing Research Center, Osaka University, 2-1 Yamada-Oka, Suita, Osaka, 565-0871, Japan
| | - Hiroyuki Takahashi
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka, 565-0871, Japan; Teijin Nakashima Medical Co., Ltd., 688-1 Joto-Kitagata, Higashi-ku, Okayama, 709-0625, Japan
| | - Ryota Watanabe
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka, 565-0871, Japan; Teijin Nakashima Medical Co., Ltd., 688-1 Joto-Kitagata, Higashi-ku, Okayama, 709-0625, Japan
| | - Takayuki Inoue
- Teijin Nakashima Medical Co., Ltd., 688-1 Joto-Kitagata, Higashi-ku, Okayama, 709-0625, Japan
| | - Tadaaki Matsuzaka
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka, 565-0871, Japan
| | - Ryosuke Ozasa
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka, 565-0871, Japan; Anisotropic Design and Additive Manufacturing Research Center, Osaka University, 2-1 Yamada-Oka, Suita, Osaka, 565-0871, Japan
| | - Takao Hanawa
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka, 565-0871, Japan; Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-0062, Japan
| | - Katsuhiko Yokota
- Teijin Nakashima Medical Co., Ltd., 688-1 Joto-Kitagata, Higashi-ku, Okayama, 709-0625, Japan
| | - Yoshio Nakashima
- Teijin Nakashima Medical Co., Ltd., 688-1 Joto-Kitagata, Higashi-ku, Okayama, 709-0625, Japan
| | - Takayoshi Nakano
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka, 565-0871, Japan; Anisotropic Design and Additive Manufacturing Research Center, Osaka University, 2-1 Yamada-Oka, Suita, Osaka, 565-0871, Japan.
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Roseren F, Roffino S, Pithioux M. Mechanical Characterization at the Microscale of Mineralized Bone Callus after Bone Lengthening. MATERIALS (BASEL, SWITZERLAND) 2022; 15:6207. [PMID: 36143518 PMCID: PMC9501547 DOI: 10.3390/ma15186207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 08/31/2022] [Accepted: 09/02/2022] [Indexed: 06/16/2023]
Abstract
Distraction osteogenesis (DO) involves several processes to form an organized distracted callus. While bone regeneration during DO has been widely described, no study has yet focused on the evolution profile of mechanical properties of mineralized tissues in the distracted callus. The aim of this study was therefore to measure the elastic modulus and hardness of calcified cartilage and trabecular and cortical bone within the distracted callus during the consolidation phase. We used a microindentation assay to measure the mechanical properties of periosteal and endosteal calluses; each was subdivided into two regions. Histological sections were used to localize the tissues. The results revealed that the mechanical properties of calcified cartilage did not evolve over time. However, trabecular bone showed temporal variation. For elastic modulus, in three out of four regions, a similar evolution profile was observed with an increase and decrease over time. Concerning hardness, this evolves differently depending on the location in the distracted callus. We also observed spatial changes in between regions. A first duality was apparent between regions close to the native cortices and the central area, while latter differences were seen between periosteal and endosteal calluses. Data showed a heterogeneity of mechanical properties in the distracted callus with a specific mineralization profile.
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Affiliation(s)
- Flavy Roseren
- Aix Marseille Univ, CNRS, ISM, 13009 Marseille, France
- Aix Marseille Univ, APHM, CNRS, ISM, Sainte-Marguerite Hospital, Institute for Locomotion, Department of Orthopaedics and Traumatology, 13009 Marseille, France
- Aix Marseille Univ, APHM, CNRS, ISM, Mecabio Platform, Anatomy Laboratory, 13009 Marseille, France
| | - Sandrine Roffino
- Aix Marseille Univ, CNRS, ISM, 13009 Marseille, France
- Aix Marseille Univ, APHM, CNRS, ISM, Sainte-Marguerite Hospital, Institute for Locomotion, Department of Orthopaedics and Traumatology, 13009 Marseille, France
- Aix Marseille Univ, APHM, CNRS, ISM, Mecabio Platform, Anatomy Laboratory, 13009 Marseille, France
| | - Martine Pithioux
- Aix Marseille Univ, CNRS, ISM, 13009 Marseille, France
- Aix Marseille Univ, APHM, CNRS, ISM, Sainte-Marguerite Hospital, Institute for Locomotion, Department of Orthopaedics and Traumatology, 13009 Marseille, France
- Aix Marseille Univ, APHM, CNRS, ISM, Mecabio Platform, Anatomy Laboratory, 13009 Marseille, France
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Peña Fernández M, Sasso SJ, McPhee S, Black C, Kanczler J, Tozzi G, Wolfram U. Nonlinear micro finite element models based on digital volume correlation measurements predict early microdamage in newly formed bone. J Mech Behav Biomed Mater 2022; 132:105303. [PMID: 35671669 DOI: 10.1016/j.jmbbm.2022.105303] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 04/27/2022] [Accepted: 05/27/2022] [Indexed: 12/21/2022]
Abstract
Bone regeneration in critical-sized defects is a clinical challenge, with biomaterials under constant development aiming at enhancing the natural bone healing process. The delivery of bone morphogenetic proteins (BMPs) in appropriate carriers represents a promising strategy for bone defect treatment but optimisation of the spatial-temporal release is still needed for the regeneration of bone with biological, structural, and mechanical properties comparable to the native tissue. Nonlinear micro finite element (μFE) models can address some of these challenges by providing a tool able to predict the biomechanical strength and microdamage onset in newly formed bone when subjected to physiological or supraphysiological loads. Yet, these models need to be validated against experimental data. In this study, experimental local displacements in newly formed bone induced by osteoinductive biomaterials subjected to in situ X-ray computed tomography compression in the apparent elastic regime and measured using digital volume correlation (DVC) were used to validate μFE models. Displacement predictions from homogeneous linear μFE models were highly correlated to DVC-measured local displacements, while tissue heterogeneity capturing mineralisation differences showed negligible effects. Nonlinear μFE models improved the correlation and showed that tissue microdamage occurs at low apparent strains. Microdamage seemed to occur next to large cavities or in biomaterial-induced thin trabeculae, independent of the mineralisation. While localisation of plastic strain accumulation was similar, the amount of damage accumulated in these locations was slightly higher when including material heterogeneity. These results demonstrate the ability of the nonlinear μFE model to capture local microdamage in newly formed bone tissue and can be exploited to improve the current understanding of healing bone and mechanical competence. This will ultimately aid the development of BMPs delivery systems for bone defect treatment able to regenerate bone with optimal biological, mechanical, and structural properties.
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Affiliation(s)
- Marta Peña Fernández
- School of Engineering and Physical Sciences, Institute of Mechanical, Process and Energy Engineering, Heriot-Watt University, EH14 4AS, UK.
| | - Sebastian J Sasso
- School of Engineering and Physical Sciences, Institute of Mechanical, Process and Energy Engineering, Heriot-Watt University, EH14 4AS, UK
| | - Samuel McPhee
- School of Engineering and Physical Sciences, Institute of Mechanical, Process and Energy Engineering, Heriot-Watt University, EH14 4AS, UK
| | - Cameron Black
- Bone & Joint Research Group, Centre for Human Development, Stem Cells and Regeneration, Human Development & Health, Institute of Development Sciences, University of Southampton, SO16 6YD, UK
| | - Janos Kanczler
- Bone & Joint Research Group, Centre for Human Development, Stem Cells and Regeneration, Human Development & Health, Institute of Development Sciences, University of Southampton, SO16 6YD, UK
| | - Gianluca Tozzi
- Zeiss Global Centre, School of Mechanical and Design Engineering, University of Portsmouth, PO1 3DJ, UK
| | - Uwe Wolfram
- School of Engineering and Physical Sciences, Institute of Mechanical, Process and Energy Engineering, Heriot-Watt University, EH14 4AS, UK.
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8
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Bachmeier AT, Euler E, Bader R, Böcker W, Thaller PH. Novel approach to estimate distraction forces in distraction osteogenesis and application in the human lower leg. J Mech Behav Biomed Mater 2022; 128:105133. [PMID: 35217291 DOI: 10.1016/j.jmbbm.2022.105133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 01/18/2022] [Accepted: 02/11/2022] [Indexed: 11/19/2022]
Abstract
PURPOSE In distraction osteogenesis (DO) of long bones, new bone tissue is distracted to lengthen limbs or reconstruct bone defects. However, mechanical boundary conditions in human application such as arising forces are mainly based on limited empirical data. Our aim was the numerical determination of the callus distraction force (CDF) and the total distraction force (TDF) during DO in the tibia of adults to advance the understanding of callus tissue behavior and optimize DO procedures. METHOD We implemented a mathematical model based on an animal experiment to enable the calculation of forces arising while distracting callus tissue, excluding the influence of surrounding soft tissue (muscles, skin etc.). The CDF progression for the distraction period was calculated using the implemented model and varying distraction parameters (initial gap, area, step size, time interval, length). Further, we estimated the CDF based on reported forces in humans and compared the results to our model predictions. In addition, we calculated the TDF based on our CDF predictions in combination with reported resisting forces due to soft tissue presence in human cadavers. Finally, we compared the progressions to in vivo TDF measurements for validation. RESULTS Due to relaxation, a peak and resting CDF is observable for each distraction step. Our biomechanical results show a non-linear degressive increase of the resting and peak CDF at the beginning and a steady non-linear increase thereafter. The calculated resting and peak CDF in the tibial metaphysis ranged from 0.00075 to 0.0089 N and 0.22-2.6 N at the beginning as well as 20-25 N and 70-75 N at the end of distraction. The comparison to in vivo data showed the plausibility of our predictions and resulted in a 10-33% and 10-23% share of resting CDF in the total resting force for bone transport and elongation, respectively. Further, the percentage of peak CDF in total peak force was found to be 29-58% and 27-55% for bone transport and elongation, respectively. Moreover, our TDF predictions were valid based on the comparison to in vivo forces and resulted in a degressive increase from 6 to 125 N for the peak TDF and from 5 to 76 N for the resting TDF. CONCLUSION Our approach enables the estimation of forces arising due to the distraction of callus tissue in humans and results in plausible force progressions as well as absolute force values for the callus distraction force during DO. In combination with measurements of resisting forces due to the presence of soft tissue, the total distraction force in DO may also be evaluated. We thus propose the application of this method to approximate the behavior of mechanical callus properties during DO in humans as an alternative to in vivo measurements.
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Affiliation(s)
- A T Bachmeier
- 3D-Surgery, Department of General, Trauma and Reconstructive Surgery, University Hospital LMU Munich, Munich, Germany; Biomechanics and Implant Technology Research Laboratory, University Medicine Rostock, Rostock, Germany.
| | - E Euler
- Department of General, Trauma and Reconstructive Surgery, University Hospital LMU Munich, Munich, Germany
| | - R Bader
- Biomechanics and Implant Technology Research Laboratory, University Medicine Rostock, Rostock, Germany
| | - W Böcker
- Department of General, Trauma and Reconstructive Surgery, University Hospital LMU Munich, Munich, Germany
| | - P H Thaller
- 3D-Surgery, Department of General, Trauma and Reconstructive Surgery, University Hospital LMU Munich, Munich, Germany
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9
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Inglis B, Schwarzenberg P, Klein K, von Rechenberg B, Darwiche S, Dailey HL. Biomechanical duality of fracture healing captured using virtual mechanical testing and validated in ovine bones. Sci Rep 2022; 12:2492. [PMID: 35169187 PMCID: PMC8847550 DOI: 10.1038/s41598-022-06267-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 01/17/2022] [Indexed: 01/08/2023] Open
Abstract
Bone fractures commonly repair by forming a bridging structure called callus, which begins as soft tissue and gradually ossifies to restore rigidity to the bone. Virtual mechanical testing is a promising technique for image-based assessment of structural bone healing in both preclinical and clinical settings, but its accuracy depends on the validity of the material model used to assign tissue mechanical properties. The goal of this study was to develop a constitutive model for callus that captures the heterogeneity and biomechanical duality of the callus, which contains both soft tissue and woven bone. To achieve this, a large-scale optimization analysis was performed on 2363 variations of 3D finite element models derived from computed tomography (CT) scans of 33 osteotomized sheep under normal and delayed healing conditions. A piecewise material model was identified that produced high absolute agreement between virtual and physical tests by differentiating between soft and hard callus based on radiodensity. The results showed that the structural integrity of a healing long bone is conferred by an internal architecture of mineralized hard callus that is supported by interstitial soft tissue. These findings suggest that with appropriate material modeling, virtual mechanical testing is a reliable surrogate for physical biomechanical testing.
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Affiliation(s)
- Brendan Inglis
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA, 18015, USA.
| | - Peter Schwarzenberg
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA, 18015, USA
| | - Karina Klein
- Musculoskeletal Research Unit (MSRU), Vetsuisse Faculty, University of Zurich, 8057, Zurich, Switzerland
| | - Brigitte von Rechenberg
- Musculoskeletal Research Unit (MSRU), Vetsuisse Faculty, University of Zurich, 8057, Zurich, Switzerland.,Center for Applied Biotechnology and Molecular Medicine (CABMM), University of Zurich, 8057, Zurich, Switzerland
| | - Salim Darwiche
- Musculoskeletal Research Unit (MSRU), Vetsuisse Faculty, University of Zurich, 8057, Zurich, Switzerland.,Center for Applied Biotechnology and Molecular Medicine (CABMM), University of Zurich, 8057, Zurich, Switzerland
| | - Hannah L Dailey
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA, 18015, USA.
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10
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Image-based radiodensity profilometry measures early remodeling at the bone-callus interface in sheep. Biomech Model Mechanobiol 2022; 21:615-626. [PMID: 34997398 DOI: 10.1007/s10237-021-01553-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 12/21/2021] [Indexed: 11/02/2022]
Abstract
Bone healing has been traditionally described as a four-phase process: inflammatory response, soft callus formation, hard callus development, and remodeling. The remodeling phase has been largely neglected in most numerical mechanoregulation models of fracture repair in favor of capturing early healing using a pre-defined callus domain. However, in vivo evidence suggests that remodeling occurs concurrently with repair and causes changes in cortical bone adjacent to callus that are typically neglected in numerical models of bone healing. The objective of this study was to use image processing techniques to quantify this early-stage remodeling in ovine osteotomies. To accomplish this, we developed a numerical method for radiodensity profilometry with optimization-based curve fitting to mathematically model the bone density gradients in the radial direction across the cortical wall and callus. After assessing data from 26 sheep, we defined a dimensionless density fitting function that revealed significant remodeling occurring in the cortical wall adjacent to callus during early healing, a 23% average reduction in density compared to intact. This fitting function is robust for modeling radial density gradients in both intact bone and fracture repair scenarios and can capture a wide variety of the healing responses. The fitting function can also be scaled easily for comparison to numerical model predictions and may be useful for validating future mechanoregulatory models of coupled fracture repair and remodeling.
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11
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Alccayhuaman KAA, Tangl S, Blouin S, Hartmann MA, Heimel P, Kuchler U, Lee JS, Gruber R. Osteoconductive Properties of a Volume-Stable Collagen Matrix in Rat Calvaria Defects: A Pilot Study. Biomedicines 2021; 9:biomedicines9070732. [PMID: 34202317 PMCID: PMC8301482 DOI: 10.3390/biomedicines9070732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 06/16/2021] [Accepted: 06/16/2021] [Indexed: 11/17/2022] Open
Abstract
Volume-stable collagen matrices (VSCM) are conductive for the connective tissue upon soft tissue augmentation. Considering that collagen has osteoconductive properties, we have investigated the possibility that the VSCM also consolidates with the newly formed bone. To this end, we covered nine rat calvaria circular defects with a VSCM. After four weeks, histology, histomorphometry, quantitative backscattered electron imaging, and microcomputed tomography were performed. We report that the overall pattern of mineralization inside the VSCM was heterogeneous. Histology revealed, apart from the characteristic woven bone formation, areas of round-shaped hypertrophic chondrocyte-like cells surrounded by a mineralized extracellular matrix. Quantitative backscattered electron imaging confirmed the heterogenous mineralization occurring within the VSCM. Histomorphometry found new bone to be 0.7 mm2 (0.01 min; 2.4 max), similar to the chondrogenic mineralized extracellular matrix with 0.7 mm2 (0.0 min; 4.2 max). Microcomputed tomography showed the overall mineralized tissue in the defect to be 1.6 mm3 (min 0.0; max 13.3). These findings suggest that in a rat cranial defect, VSCM has a limited and heterogeneous capacity to support intramembranous bone formation but may allow the formation of bone via the endochondral route.
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Affiliation(s)
- Karol Alí Apaza Alccayhuaman
- Department of Oral Biology, Dental School, Medical University of Vienna, Sensengasse 2a, 1090 Vienna, Austria; (K.A.A.A.); (J.-S.L.)
- Karl Donath Laboratory for Hard Tissue and Biomaterial Research, Division of Oral Surgery, School of Dentistry, Medical University of Vienna, 1090 Vienna, Austria; (S.T.); (P.H.)
| | - Stefan Tangl
- Karl Donath Laboratory for Hard Tissue and Biomaterial Research, Division of Oral Surgery, School of Dentistry, Medical University of Vienna, 1090 Vienna, Austria; (S.T.); (P.H.)
- Austrian Cluster for Tissue Regeneration, Medical University of Vienna, 1200 Vienna, Austria
| | - Stéphane Blouin
- 1st Medical Department, Ludwig Boltzmann Institute of Osteology at the Hanusch Hospital of OEGK and AUVA Trauma Centre Meidling, Hanusch Hospital, 1140 Vienna, Austria; (S.B.); (M.A.H.)
| | - Markus A. Hartmann
- 1st Medical Department, Ludwig Boltzmann Institute of Osteology at the Hanusch Hospital of OEGK and AUVA Trauma Centre Meidling, Hanusch Hospital, 1140 Vienna, Austria; (S.B.); (M.A.H.)
| | - Patrick Heimel
- Karl Donath Laboratory for Hard Tissue and Biomaterial Research, Division of Oral Surgery, School of Dentistry, Medical University of Vienna, 1090 Vienna, Austria; (S.T.); (P.H.)
- Austrian Cluster for Tissue Regeneration, Medical University of Vienna, 1200 Vienna, Austria
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, 1200 Vienna, Austria
| | - Ulrike Kuchler
- Department of Oral Surgery, Medical University of Vienna, 1090 Vienna, Austria;
| | - Jung-Seok Lee
- Department of Oral Biology, Dental School, Medical University of Vienna, Sensengasse 2a, 1090 Vienna, Austria; (K.A.A.A.); (J.-S.L.)
- Department of Periodontology, Research Institute for Periodontal Regeneration, College of Dentistry, Yonsei University, Seoul 03722, Korea
| | - Reinhard Gruber
- Department of Oral Biology, Dental School, Medical University of Vienna, Sensengasse 2a, 1090 Vienna, Austria; (K.A.A.A.); (J.-S.L.)
- Austrian Cluster for Tissue Regeneration, Medical University of Vienna, 1200 Vienna, Austria
- Department of Periodontology, School of Dental Medicine, University of Bern, 3010 Bern, Switzerland
- Correspondence: ; Tel.: +43-1-40070-2660
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12
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Arkin V, Narendrakumar U, Madhyastha H, Manjubala I. Characterization and In Vitro Evaluations of Injectable Calcium Phosphate Cement Doped with Magnesium and Strontium. ACS OMEGA 2021; 6:2477-2486. [PMID: 33553866 PMCID: PMC7859950 DOI: 10.1021/acsomega.0c03927] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 01/04/2021] [Indexed: 05/17/2023]
Abstract
Injectable calcium phosphate cement is a promising biomaterial for hard tissue repair due to its osteoinductivity, biocompatibility properties, and its use to correct defect areas involving narrow cavities with limited accessibility by the minimally invasive technique. Microwave-synthesized hydroxyapatite (HA) was used for the preparation of cement. In recent years, both magnesium and strontium calcium phosphate cements have exhibited rapid setting, improved mechanical strength, and a good resorption rate. A big step still remains to develop injectable magnesium and strontium phosphate cements with ideal self-setting properties, adequate mechanical strength, and good biocompatibility for clinical applications. In this study, both magnesium and strontium were doped with synthesized semiamorphous and crystalline hydroxyapatite (HA). The powder mixture was mixed with Na2HPO4, NaH2PO4, and a carboxymethyl cellulose (CMC) solution to develop the novel magnesium and strontium calcium phosphate cement. The setting time, physiochemical properties of hardened cement, microstructure, mechanical strength, and injectability of the prepared cement were studied. The toxicity evaluation and cell adhesion, which are necessary to identify the suitability of the material for different applications, were quantified and investigated using fibroblast cells. The setting time of cement was reduced substantially for magnesium- or strontium-doped cement by 2 min. The phase composition of the hardened cement expresses the semiamorphous or crystalline phase of HA with additives. Smooth and complete injection of cement paste was observed in semiamorphous HA-based cement. The intercellular reactive oxygen stress (ROS) of the Sr2+-doped cement sample showed varied degrees of toxicity to cells in terms of different concentrations. The Mg2+-doped cement showed significant attachment of cells after treatment at varying incubation times.
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Affiliation(s)
- Vetharaj
HephzibahRajam Arkin
- Department
of Biosciences, School of Bio Sciences and Technology, Vellore Institute of Technology, Vellore 632014, India
| | - Uttamchand Narendrakumar
- Department
of Manufacturing Engineering, School of Mechanical Engineering, Vellore Institute of Technology, Vellore 632014, India
| | - Harishkumar Madhyastha
- Department
of Applied Physiology, Faculty of Medicine, University of Miyazaki, Miyazaki 8891692, Japan
| | - Inderchand Manjubala
- Department
of Biosciences, School of Bio Sciences and Technology, Vellore Institute of Technology, Vellore 632014, India
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13
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Morgan EF, Giacomo AD, Gerstenfeld LC. Overview of Skeletal Repair (Fracture Healing and Its Assessment). Methods Mol Biol 2021; 2230:17-37. [PMID: 33197006 DOI: 10.1007/978-1-0716-1028-2_2] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The study of postnatal skeletal repair is of immense clinical interest. Optimal repair of skeletal tissue is necessary in all varieties of elective and reparative orthopedic surgical treatments. However, the repair of fractures is unique in this context in that fractures are one of the most common traumas that humans experience and are the end-point manifestation of osteoporosis, the most common chronic disease of aging. In the first part of this introduction the basic biology of fracture healing is presented. The second part discusses the primary methodological approaches that are used to examine repair of skeletal hard tissue and specific considerations for choosing among and implementing these approaches.
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Affiliation(s)
- Elise F Morgan
- Boston University School of Medicine, Boston, MA, USA
- Department of Mechanical Engineering, College of Engineering, Boston University, Boston, MA, USA
| | - Anthony De Giacomo
- Department of Orthopedic Surgery, Woodland Hills Medical Center, Woodland Hills, CA, USA
- Boston University School of Medicine, Boston, MA, USA
| | - Louis C Gerstenfeld
- Department of Orthopaedic Surgery, Orthopaedic Research Laboratory, Boston University School of Medicine, Boston, MA, USA.
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14
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Schemenz V, Gjardy A, Chamasemani FF, Roschger A, Roschger P, Zaslansky P, Helfen L, Burghammer M, Fratzl P, Weinkamer R, Brunner R, Willie BM, Wagermaier W. Heterogeneity of the osteocyte lacuno-canalicular network architecture and material characteristics across different tissue types in healing bone. J Struct Biol 2020; 212:107616. [PMID: 32920138 DOI: 10.1016/j.jsb.2020.107616] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 09/01/2020] [Accepted: 09/04/2020] [Indexed: 02/08/2023]
Abstract
Various tissue types, including fibrous connective tissue, bone marrow, cartilage, woven and lamellar bone, coexist in healing bone. Similar to most bone tissue type, healing bone contains a lacuno-canalicular network (LCN) housing osteocytes. These cells are known to orchestrate bone remodeling in healthy bone by sensing mechanical strains and translating them into biochemical signals. The structure of the LCN is hypothesized to influence mineralization processes. Hence, the aim of the present study was to visualize and match spatial variations in the LCN topology with mineral characteristics, within and at the interfaces of the different tissue types that comprise healing bone. We applied a correlative multi-method approach to visualize the LCN architecture and quantify mineral particle size and orientation within healing femoral bone in a mouse osteotomy model (26 weeks old C57BL/6 mice). This approach revealed structural differences across several length scales during endochondral ossification within the following regions: calcified cartilage, bony callus, cortical bone and a transition zone between the cortical and callus region analyzed 21 days after the osteotomy. In this transition zone, we observed a continuous convergence of mineral characteristics and osteocyte lacunae shape as well as discontinuities in the lacunae volume and LCN connectivity. The bony callus exhibits a 34% higher lacunae number density and 40% larger lacunar volume compared to cortical bone. The presented correlations between LCN architecture and mineral characteristics improves our understanding of how bone develops during healing and may indicate a contribution of osteocytes to bone (re)modeling.
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Affiliation(s)
- Victoria Schemenz
- Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - André Gjardy
- Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Am Mühlenberg 1, 14476 Potsdam, Germany
| | | | - Andreas Roschger
- Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Am Mühlenberg 1, 14476 Potsdam, Germany; Paris-Lodron-University of Salzburg, Department of Chemistry and Physics of Materials, Salzburg, Austria
| | - Paul Roschger
- Ludwig Boltzmann Institute of Osteology at Hanusch Hospital of ÖGK and AUVA Trauma Centre Meidling, 1st Medical Department, Hanusch Hospital, Vienna, Austria
| | - Paul Zaslansky
- Department for Restorative and Preventive Dentistry, Charité-Universitaetsmedizin Berlin, Berlin 14197, Germany
| | - Lukas Helfen
- Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany; Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France
| | | | - Peter Fratzl
- Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Richard Weinkamer
- Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Roland Brunner
- Materials Center Leoben Forschung GmbH, 8700 Leoben, Austria
| | - Bettina M Willie
- Research Centre, Shriners Hospitals for Children-Canada, Department of Pediatric Surgery, McGill University, 1003 Decarie Blvd, Montreal, Quebec H4A 0A9, Canada
| | - Wolfgang Wagermaier
- Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Am Mühlenberg 1, 14476 Potsdam, Germany.
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15
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Blázquez-Carmona P, Mora-Macías J, Morgaz J, Fernández-Sarmiento JA, Domínguez J, Reina-Romo E. Mechanobiology of Bone Consolidation During Distraction Osteogenesis: Bone Lengthening Vs. Bone Transport. Ann Biomed Eng 2020; 49:1209-1221. [PMID: 33111968 DOI: 10.1007/s10439-020-02665-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 10/16/2020] [Indexed: 01/29/2023]
Abstract
Bone lengthening and bone transport are regeneration processes that commonly rely on distraction osteogenesis, a widely accepted surgical procedure to deal with numerous bony pathologies. Despite the extensive study in the literature of the influence of biomechanical factors, a lack of knowledge about their mechanobiological differences prevents a clinical particularization. Bone lengthening treatments were performed on sheep metatarsus by reproducing the surgical and biomechanical protocol of previous bone transport experiments. Several in vivo monitoring techniques were employed to build an exhaustive comparison: gait analysis, radiographic and CT assessment, force measures through the fixation, or mechanical characterization of the new tissue. A significant initial loss of the bearing capacity, quantified by the ground reaction forces and the limb contact time with the ground, is suffered by the bone lengthening specimens. The potential effects of this anomaly on the musculoskeletal force distribution and the evolution of the bone callus elastic modulus over time are also analyzed. Imaging techniques also seem to reveal lower bone volume in the bone lengthening callus than in the bone transport one, but an equivalent mineralization rate. The simultaneous quantification of biological and mechanical parameters provides valuable information for the daily clinical routine and numerical tools development.
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Affiliation(s)
- Pablo Blázquez-Carmona
- Escuela Técnica Superior de Ingeniería, Universidad de Sevilla, Avenida Camino de los Descubrimientos s/n, 41092, Seville, Spain.
| | - Juan Mora-Macías
- Escuela Técnica Superior de Ingeniería, Universidad de Huelva, 21007, Huelva, Spain
| | - Juan Morgaz
- Departamento Medicina y Cirugía Animal, Ctra. Nacional IV-A, Campus Universitario de Rabanales, Km 396, 14014, Córdoba, Spain
| | - José Andrés Fernández-Sarmiento
- Departamento Medicina y Cirugía Animal, Ctra. Nacional IV-A, Campus Universitario de Rabanales, Km 396, 14014, Córdoba, Spain
| | - Jaime Domínguez
- Escuela Técnica Superior de Ingeniería, Universidad de Sevilla, Avenida Camino de los Descubrimientos s/n, 41092, Seville, Spain
| | - Esther Reina-Romo
- Escuela Técnica Superior de Ingeniería, Universidad de Sevilla, Avenida Camino de los Descubrimientos s/n, 41092, Seville, Spain
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16
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Terzini M, Aldieri A, Nurisso S, De Nisco G, Bignardi C. Finite Element Modeling Application in Forensic Practice: A Periprosthetic Femoral Fracture Case Study. Front Bioeng Biotechnol 2020; 8:619. [PMID: 32656199 PMCID: PMC7324477 DOI: 10.3389/fbioe.2020.00619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 05/20/2020] [Indexed: 11/13/2022] Open
Abstract
The incidence of periprosthetic fractures has rapidly increased in the last two decades and has been the cause of a large number of revision surgeries and permanent physical disability for many patients, as well as a significant socioeconomic burden for many nations. This research deals with a periprosthetic femur fracture real event, occurred following a total hip arthroplasty and treated with one of the most widespread internal fixation methods: the implant of a periprosthetic femur plate system. A Finite Element analysis was performed to investigate the implanted femur plate break after a short follow-up and to understand the plate break causes. Such events are currently object of forensic debate as more and more often hospitals, surgeons, and medical device manufacturers are denounced by patients to whom similar events occur. In this work, different load situations acting on the femur during daily and incidental activities were simulated, in order to validate the correct behavior of the plate, according to the intended use recommended by the manufacturer. The analysis demonstrates that the plate failure can occur in situations of unconventional loading such as that caused by stumbling and in presence of incomplete bone healing.
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Affiliation(s)
- Mara Terzini
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy.,PolitoBIOMed Lab, Politecnico di Torino, Turin, Italy
| | - Alessandra Aldieri
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy.,PolitoBIOMed Lab, Politecnico di Torino, Turin, Italy
| | - Stefania Nurisso
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy.,PolitoBIOMed Lab, Politecnico di Torino, Turin, Italy
| | - Giuseppe De Nisco
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy.,PolitoBIOMed Lab, Politecnico di Torino, Turin, Italy
| | - Cristina Bignardi
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy.,PolitoBIOMed Lab, Politecnico di Torino, Turin, Italy
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17
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Karali A, Kao AP, Meeson R, Roldo M, Blunn GW, Tozzi G. Full-field strain of regenerated bone tissue in a femoral fracture model. J Microsc 2020; 285:156-166. [PMID: 32530049 DOI: 10.1111/jmi.12937] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 05/29/2020] [Accepted: 06/10/2020] [Indexed: 02/06/2023]
Abstract
The mechanical behaviour of regenerated bone tissue during fracture healing is key in determining its ability to withstand physiological loads. However, the strain distribution in the newly formed tissue and how this influences the way a fracture heals it is still unclear. X-ray Computed Tomography (XCT) has been extensively used to assess the progress of mineralised tissues in regeneration and when combined with in situ mechanics and digital volume correlation (DVC) has been proven a powerful tool to understand the mechanical behaviour and full-field three-dimensional (3D) strain distribution in bone. The purpose of this study is therefore to use in situ XCT mechanics and DVC to investigate the strain distribution and load-bearing capacity in a regenerating fracture in the diaphyseal bone, using a rodent femoral fracture model stabilised by external fixation. Rat femurs with 1 mm and 2 mm osteotomy gaps were tested under in situ XCT step-wise compression in the apparent elastic region. High strain was present in the newly formed bone (εp1 and εp3 reaching 29 000 µε and -43 000 µε, respectively), with a wide variation and inhomogeneity of the 3D strain distribution in the regenerating tissues of the fracture gap, which is directly related to the presence of unmineralised tissue observed in histological images. The outcomes of this study will contribute in understanding natural regenerative ability of bone and its mechanical behaviour under loading.
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Affiliation(s)
- A Karali
- Zeiss Global Centre, School of Mechanical and Design Engineering, University of Portsmouth, Portsmouth, UK
| | - A P Kao
- Zeiss Global Centre, School of Mechanical and Design Engineering, University of Portsmouth, Portsmouth, UK
| | - R Meeson
- Royal Veterinary College, Hatfield, Hertfordshire, UK
| | - M Roldo
- School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK
| | - G W Blunn
- School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK
| | - G Tozzi
- Zeiss Global Centre, School of Mechanical and Design Engineering, University of Portsmouth, Portsmouth, UK
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18
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Mechanoregulation modeling of bone healing in realistic fracture geometries. Biomech Model Mechanobiol 2020; 19:2307-2322. [DOI: 10.1007/s10237-020-01340-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 05/12/2020] [Indexed: 01/08/2023]
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19
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Elastic Modulus of Woven Bone: Correlation with Evolution of Porosity and X-ray Greyscale. Ann Biomed Eng 2020; 49:180-190. [PMID: 32388799 DOI: 10.1007/s10439-020-02529-6] [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: 12/05/2019] [Accepted: 05/02/2020] [Indexed: 10/24/2022]
Abstract
The woven bone created during the healing of bone regeneration processes is characterized as being extremely inhomogeneous and having a variable stiffness that increases with time. Therefore, it is important to study how the mechanical properties of woven bone are dependent on its microarchitecture and especially on its porosity and mineral content. The porosity and the x-ray greyscale of specimens taken from bone transport studies in sheep were assessed by means of ex vivo imaging. Our study demonstrates that the porosity of the woven bone in the distraction area diminishes during the healing process from 73.3% 35 days after surgery to 31.9% 525 days after surgery. In addition, the woven bone's porosity is negatively correlated with its Young's modulus. The x-ray greyscale, was measured as an indicator of the level of mineralization of the woven bone. Greyscale index has been demonstrated to be inversely proportional to porosity and to increase to up to 60-80% of the level in cortical bone. The results of this study may contribute to the development of micromechanical models of woven bone and improvements in in silico modelling.
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20
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Wang W, Lynch JP. Quantitative assessment of compress-type osseointegrated prosthetic implants in human bone using electromechanical impedance spectroscopic methods. Biomed Eng Lett 2020; 10:129-147. [PMID: 32175134 PMCID: PMC7046876 DOI: 10.1007/s13534-019-00139-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 10/06/2019] [Accepted: 10/10/2019] [Indexed: 01/05/2023] Open
Abstract
Osseointegrated (OI) prostheses are a promising alternative to traditional socket prostheses. They can enhance the quality of life of amputees by avoiding fit and comfort issues commonly associated with sockets. The main structural element of the OI prosthesis is a biocompatible metallic implant that is surgically implanted into the bone of the residual limb. The implant is designed to provide a conducive surface for the host bone to osseointegrate with. The osseointegration process of the implant is difficult to clinically evaluate, leading to conservative postoperative rehabilitation approaches. Elastic stress waves generated in an OI prosthesis have been previously proposed to interrogate the implant-bone interface for quantitative assessment of the osseointegration process. This paper provides a detailed overview of the various elastic stress wave methods previously explored for in situ characterization of OI implants. Specifically, the paper explores the use of electromechanical impedance spectroscopy (EIS) to assess the OI process in compress-type OI prostheses. The EIS approach measures the electrical impedance spectrum of lead zirconate titanate elements bonded to the free end of the implant. The research utilizes both numerical simulation and experimental verification to establish that the electromechanical impedance spectrum is sensitive (between 400 and 460 kHz) to both the degree and location of osseointegration. A baseline-free OI index is proposed to quantify the degree of osseointegration at the implant-bone interface and to assess the stability of the OI implant for clinical decision making.
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Affiliation(s)
- Wentao Wang
- Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI 48109 USA
| | - Jerome P. Lynch
- Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI 48109 USA
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21
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Stefanowski J, Lang A, Rauch A, Aulich L, Köhler M, Fiedler AF, Buttgereit F, Schmidt-Bleek K, Duda GN, Gaber T, Niesner RA, Hauser AE. Spatial Distribution of Macrophages During Callus Formation and Maturation Reveals Close Crosstalk Between Macrophages and Newly Forming Vessels. Front Immunol 2019; 10:2588. [PMID: 31956322 PMCID: PMC6953593 DOI: 10.3389/fimmu.2019.02588] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 10/18/2019] [Indexed: 01/15/2023] Open
Abstract
Macrophages are essential players in the process of fracture healing, acting by remodeling of the extracellular matrix and enabling vascularization. Whilst activated macrophages of M1-like phenotype are present in the initial pro-inflammatory phase of hours to days of fracture healing, an anti-inflammatory M2-like macrophage phenotype is supposed to be crucial for the induction of downstream cascades of healing, especially the initiation of vascularization. In a mouse-osteotomy model, we provide a comprehensive characterization of vessel (CD31+, Emcn+) and macrophage phenotypes (F4/80, CD206, CD80, Mac-2) during the process of fracture healing. To this end, we phenotype the phases of vascular regeneration-the expansion phase (d1-d7 after injury) and the remodeling phase of the endothelial network, until tissue integrity is restored (d14-d21 after injury). Vessels which appear during the bone formation process resemble type H endothelium (CD31hiEmcnhi), and are closely connected to osteoprogenitors (Runx2+, Osx+) and F4/80+ macrophages. M1-like macrophages are present in the initial phase of vascularization until day 3 post osteotomy, but they are rare during later regeneration phases. M2-like macrophages localize mainly extramedullary, and CD206+ macrophages are found to express Mac-2+ during the expansion phase. VEGFA expression is initiated by CD80+ cells, including F4/80+ macrophages, until day 3, while subsequently osteoblasts and chondrocytes are main contributors to VEGFA production at the fracture site. Using Longitudinal Intravital Microendoscopy of the Bone (LIMB) we observe changes in the motility and organization of CX3CR1+ cells, which infiltrate the injury site after an osteotomy. A transient accumulation, resulting in spatial polarization of both, endothelial cells and macrophages, in regions distal to the fracture site, is evident. Immunofluorescence histology followed by histocytometric analysis reveals that F4/80+CX3CR1+ myeloid cells precede vascularization.
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Affiliation(s)
- Jonathan Stefanowski
- Department of Rheumatology and Clinical Immunology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.,German Rheumatism Research Centre (DRFZ) Berlin, a Leibniz Institute, Berlin, Germany
| | - Annemarie Lang
- Department of Rheumatology and Clinical Immunology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.,German Rheumatism Research Centre (DRFZ) Berlin, a Leibniz Institute, Berlin, Germany.,Berlin-Brandenburg Center for Regenerative Therapies, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Ariana Rauch
- German Rheumatism Research Centre (DRFZ) Berlin, a Leibniz Institute, Berlin, Germany
| | - Linus Aulich
- German Rheumatism Research Centre (DRFZ) Berlin, a Leibniz Institute, Berlin, Germany
| | - Markus Köhler
- German Rheumatism Research Centre (DRFZ) Berlin, a Leibniz Institute, Berlin, Germany
| | - Alexander F Fiedler
- German Rheumatism Research Centre (DRFZ) Berlin, a Leibniz Institute, Berlin, Germany
| | - Frank Buttgereit
- Department of Rheumatology and Clinical Immunology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.,German Rheumatism Research Centre (DRFZ) Berlin, a Leibniz Institute, Berlin, Germany.,Berlin-Brandenburg Center for Regenerative Therapies, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Katharina Schmidt-Bleek
- Berlin-Brandenburg Center for Regenerative Therapies, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.,Julius Wolff Institute for Biomechanics and Musculoskeletal Regeneration, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Georg N Duda
- Berlin-Brandenburg Center for Regenerative Therapies, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.,Julius Wolff Institute for Biomechanics and Musculoskeletal Regeneration, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Timo Gaber
- Department of Rheumatology and Clinical Immunology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.,German Rheumatism Research Centre (DRFZ) Berlin, a Leibniz Institute, Berlin, Germany.,Berlin-Brandenburg Center for Regenerative Therapies, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Raluca A Niesner
- German Rheumatism Research Centre (DRFZ) Berlin, a Leibniz Institute, Berlin, Germany.,Dynamic and Functional in vivo Imaging, Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
| | - Anja E Hauser
- Department of Rheumatology and Clinical Immunology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.,German Rheumatism Research Centre (DRFZ) Berlin, a Leibniz Institute, Berlin, Germany
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22
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Ghiasi MS, Chen JE, Rodriguez EK, Vaziri A, Nazarian A. Computational modeling of human bone fracture healing affected by different conditions of initial healing stage. BMC Musculoskelet Disord 2019; 20:562. [PMID: 31767007 PMCID: PMC6878676 DOI: 10.1186/s12891-019-2854-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 09/26/2019] [Indexed: 01/07/2023] Open
Abstract
Background Bone healing process includes four phases: inflammatory response, soft callus formation, hard callus development, and remodeling. Mechanobiological models have been used to investigate the role of various mechanical and biological factors on bone healing. However, the effects of initial healing phase, which includes the inflammatory stage, the granulation tissue formation, and the initial callus formation during the first few days post-fracture, are generally neglected in such studies. Methods In this study, we developed a finite-element-based model to simulate different levels of diffusion coefficient for mesenchymal stem cell (MSC) migration, Young’s modulus of granulation tissue, callus thickness and interfragmentary gap size to understand the modulatory effects of these initial phase parameters on bone healing. Results The results quantified how faster MSC migration, stiffer granulation tissue, thicker callus, and smaller interfragmentary gap enhanced healing to some extent. However, after a certain threshold, a state of saturation was reached for MSC migration rate, granulation tissue stiffness, and callus thickness. Therefore, a parametric study was performed to verify that the callus formed at the initial phase, in agreement with experimental observations, has an ideal range of geometry and material properties to have the most efficient healing time. Conclusions Findings from this paper quantified the effects of the initial healing phase on healing outcome to better understand the biological and mechanobiological mechanisms and their utilization in the design and optimization of treatment strategies. It is also demonstrated through a simulation that for fractures, where bone segments are in close proximity, callus development is not required. This finding is consistent with the concepts of primary and secondary bone healing.
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Affiliation(s)
- Mohammad S Ghiasi
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Avenue, RN115, Boston, MA, 02215, USA.,Department of Mechanical and Industrial Engineering, Northeastern University, 360 Huntington Avenue, 334 Snell Engineering Center, Boston, MA, 02115, USA
| | - Jason E Chen
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Avenue, RN115, Boston, MA, 02215, USA
| | - Edward K Rodriguez
- Carl J. Shapiro Department of Orthopaedic Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Ashkan Vaziri
- Department of Mechanical and Industrial Engineering, Northeastern University, 360 Huntington Avenue, 334 Snell Engineering Center, Boston, MA, 02115, USA.
| | - Ara Nazarian
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Avenue, RN115, Boston, MA, 02215, USA. .,Carl J. Shapiro Department of Orthopaedic Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA. .,Department of Orthopaedic Surgery, Yerevan State Medical University, Yerevan, Armenia.
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23
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Grover K, Hu M, Lin L, Muir J, Qin YX. Functional disuse initiates medullary endosteal micro-architectural impairment in cortical bone characterized by nanoindentation. J Bone Miner Metab 2019; 37:1048-1057. [PMID: 31292723 DOI: 10.1007/s00774-019-01011-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 05/16/2019] [Indexed: 01/22/2023]
Abstract
In this study, we evaluated the effect of functional disuse-induced bone remodeling on its mechanical properties, individually at periosteum and medullary endosteum regions of the cortical bone. Left middle tibiae were obtained from 5-month-old female Sprague-Dawley rats for the baseline control as well as hindlimb suspended (disuse) groups. Micro-nano-mechanical elastic moduli (at lateral region) was evaluated along axial (Z), circumferential (C) and radial (R) orientations using nanoindentation. Results indicated an anisotropic microstructure with axial orientation having the highest and radial orientation with the lowest moduli at periosteum and medullary endosteum for both baseline control as well as disuse groups. Between the groups: at periosteum, an insignificant difference was evaluated for each of the orientations (p > 0.05) and at endosteum, a significant decrease of elastic moduli in the radial (p < 0.0001), circumferential (p < 0.001) and statistically insignificant difference in axial (p > 0.05) orientation. For the moduli ratios between groups: at periosteum, only significant difference in the Z/R (p < 0.05) anisotropy ratio, whereas at endosteum, a statistically significant difference in Z/C (p < 0.001), and Z/R (p < 0.001), as well as C/R (p < 0.05) anisotropy ratios, was evaluated. The results suggested initial bone remodeling impaired bone micro-architecture predominantly at the medullary endosteum with possible alterations in the geometric orientations of collagen and mineral phases inside the bone. The findings could be significant for studying the mechanotransduction pathways involved in maintaining the bone micro-architecture and possibly have high clinical significance for drug use against impairment from functional disuse.
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Affiliation(s)
- Kartikey Grover
- Department of Biomedical Engineering, SUNY Stony Brook University, 215 Bioengineering Building, Stony Brook, New York, 11794, USA
| | - Minyi Hu
- Department of Biomedical Engineering, SUNY Stony Brook University, 215 Bioengineering Building, Stony Brook, New York, 11794, USA
| | - Liangjun Lin
- Department of Biomedical Engineering, SUNY Stony Brook University, 215 Bioengineering Building, Stony Brook, New York, 11794, USA
| | - Jesse Muir
- Department of Biomedical Engineering, SUNY Stony Brook University, 215 Bioengineering Building, Stony Brook, New York, 11794, USA
| | - Yi-Xian Qin
- Department of Biomedical Engineering, SUNY Stony Brook University, 215 Bioengineering Building, Stony Brook, New York, 11794, USA.
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24
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Mora-Macías J, Giráldez-Sánchez MÁ, López M, Domínguez J, Reina-Romo ME. Comparison of methods for assigning the material properties of the distraction callus in computational models. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2019; 35:e3227. [PMID: 31197959 DOI: 10.1002/cnm.3227] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 05/20/2019] [Accepted: 05/28/2019] [Indexed: 06/09/2023]
Abstract
In silico models of distraction osteogenesis and fracture healing usually assume constant mechanical properties for the new bone tissue generated. In addition, these models do not always account for the porosity of the woven bone and its evolution. In this study, finite element analyses based on computed tomography (CT) are used to predict the stiffness of the callus until 69 weeks after surgery using 15 CT images obtained at different stages of an experiment on bone transport, technique in which distraction osteogenesis is used to correct bone defects. Three different approaches were used to assign the mechanical properties to the new bone tissue. First, constant mechanical properties of the hard callus tissue and no porosity were assumed. Nevertheless, this approach did not show good correlations. Second, random variations in the elastic modulus and porosity of the woven bone were taken from previous experimental studies. Finally, the elastic properties of each element were assigned depending on gray scale in CT images. The numerically predicted callus stiffness was compared with previous in vivo measurements. It was concluded firstly that assignment depending on gray scale is the method that provides the best results and secondly that the method that considers a random distribution of porosity and elastic modulus of the callus is also suitable to predict the callus stiffness from 15 weeks after surgery. This finding provides a method for assigning the material properties of the distraction callus, which does not require CT images and may contribute to improve current in silico models.
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Affiliation(s)
- Juan Mora-Macías
- Department of Mining, Mechanical, Energy and Construction Engineering, University of Huelva, Huelva, Spain
| | - Miguel Ángel Giráldez-Sánchez
- Clinical Orthopaedics, Trauma Surgery and Rheumatology Management Unit, Virgen del Rocío Universitary Hospital, Seville, Spain
| | | | - Jaime Domínguez
- Department of Mechanical Engineering and Manufacturing, University of Seville, Seville, Spain
| | - María Esther Reina-Romo
- Department of Mechanical Engineering and Manufacturing, University of Seville, Seville, Spain
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25
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Zimmermann EA, Riedel C, Schmidt FN, Stockhausen KE, Chushkin Y, Schaible E, Gludovatz B, Vettorazzi E, Zontone F, Püschel K, Amling M, Ritchie RO, Busse B. Mechanical Competence and Bone Quality Develop During Skeletal Growth. J Bone Miner Res 2019; 34:1461-1472. [PMID: 30913317 DOI: 10.1002/jbmr.3730] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 02/25/2019] [Accepted: 03/05/2019] [Indexed: 02/01/2023]
Abstract
Bone fracture risk is influenced by bone quality, which encompasses bone's composition as well as its multiscale organization and architecture. Aging and disease deteriorate bone quality, leading to reduced mechanical properties and higher fracture incidence. Largely unexplored is how bone quality and mechanical competence progress during longitudinal bone growth. Human femoral cortical bone was acquired from fetal (n = 1), infantile (n = 3), and 2- to 14-year-old cases (n = 4) at the mid-diaphysis. Bone quality was assessed in terms of bone structure, osteocyte characteristics, mineralization, and collagen orientation. The mechanical properties were investigated by measuring tensile deformation at multiple length scales via synchrotron X-ray diffraction. We find dramatic differences in mechanical resistance with age. Specifically, cortical bone in 2- to 14-year-old cases exhibits a 160% greater stiffness and 83% higher strength than fetal/infantile cases. The higher mechanical resistance of the 2- to 14-year-old cases is associated with advantageous bone quality, specifically higher bone volume fraction, better micronscale organization (woven versus lamellar), and higher mean mineralization compared with fetal/infantile cases. Our study reveals that bone quality is superior after remodeling/modeling processes convert the primary woven bone structure to lamellar bone. In this cohort of female children, the microstructural differences at the femoral diaphysis were apparent between the 1- to 2-year-old cases. Indeed, the lamellar bone in 2- to 14-year-old cases had a superior structural organization (collagen and osteocyte characteristics) and composition for resisting deformation and fracture than fetal/infantile bone. Mechanistically, the changes in bone quality during longitudinal bone growth lead to higher fracture resistance because collagen fibrils are better aligned to resist tensile forces, while elevated mean mineralization reinforces the collagen scaffold. Thus, our results reveal inherent weaknesses of the fetal/infantile skeleton signifying its inferior bone quality. These results have implications for pediatric fracture risk, as bone produced at ossification centers during children's longitudinal bone growth could display similarly weak points. © 2019 American Society for Bone and Mineral Research.
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Affiliation(s)
| | - Christoph Riedel
- Department of Osteology and Biomechanics, University Medical Center, Hamburg, Germany
| | - Felix N Schmidt
- Department of Osteology and Biomechanics, University Medical Center, Hamburg, Germany
| | - Kilian E Stockhausen
- Department of Osteology and Biomechanics, University Medical Center, Hamburg, Germany
| | - Yuriy Chushkin
- Beamline ID 10, European Synchrotron Radiation Facility, Grenoble, France
| | - Eric Schaible
- Experimental Systems Group, Advanced Light Source, Berkeley, CA, USA
| | - Bernd Gludovatz
- School of Mechanical and Manufacturing Engineering, UNSW Sydney, NSW, Australia
| | - Eik Vettorazzi
- Department of Medical Biometry and Epidemiology, University Medical Center, Hamburg, Germany
| | - Federico Zontone
- Beamline ID 10, European Synchrotron Radiation Facility, Grenoble, France
| | - Klaus Püschel
- Department of Forensic Medicine, University Medical Center, Hamburg, Germany
| | - Michael Amling
- Department of Osteology and Biomechanics, University Medical Center, Hamburg, Germany
| | - Robert O Ritchie
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA.,Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Björn Busse
- Department of Osteology and Biomechanics, University Medical Center, Hamburg, Germany
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26
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Martínez-Reina J, García-Rodríguez J, Mora-Macías J, Domínguez J, Reina-Romo E. Comparison of the volumetric composition of lamellar bone and the woven bone of calluses. Proc Inst Mech Eng H 2018; 232:682-689. [PMID: 29962326 DOI: 10.1177/0954411918784085] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Woven tissue is mainly present in the bone callus, formed very rapidly either after a fracture or in distraction processes. This high formation speed is probably responsible for its disorganized microstructure and this, in turn, for its low stiffness. Nonetheless, the singular volumetric composition of this tissue may also play a key role in its mechanical properties. The volumetric composition of woven tissue extracted from the bone transport callus of sheep was investigated and compared with that of the lamellar tissue extracted from the cortical shell of the same bone. Significant differences were found in the mineral and water contents, but they can be due to the different ages of both tissues, which affects the mineral/water ratio. However, the content in organic phase remains more or less constant throughout the mineralization process and has proven to be a good variable to measure the different composition of both tissues, being that content significantly higher in woven tissue. This may be linked to the abnormally high concentration of osteocytes in this tissue, which is likely a consequence of the more abundant presence of osteoblasts secreting osteoid and burying other osteoblasts, which then differentiate into osteocytes. This would explain the high formation rate of woven tissue, useful to recover the short-term stability of the bone. Nonetheless, the more abundant presence of organic phase prevents the woven tissue from reaching a stiffness similar to that of lamellar tissue in the long term, when it is fully mineralized.
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Affiliation(s)
- Javier Martínez-Reina
- 1 Departamento de Ingeniería Mecánica y Fabricación, Escuela Técnica Superior de Ingeniería, Universidad de Sevilla, Seville, Spain
| | - Javier García-Rodríguez
- 1 Departamento de Ingeniería Mecánica y Fabricación, Escuela Técnica Superior de Ingeniería, Universidad de Sevilla, Seville, Spain
| | - Juan Mora-Macías
- 2 Departamento de Ingeniería Minera, Mecánica, Energética y de la Construcción, Universidad de Huelva, Huelva, Spain
| | - Jaime Domínguez
- 1 Departamento de Ingeniería Mecánica y Fabricación, Escuela Técnica Superior de Ingeniería, Universidad de Sevilla, Seville, Spain
| | - Esther Reina-Romo
- 1 Departamento de Ingeniería Mecánica y Fabricación, Escuela Técnica Superior de Ingeniería, Universidad de Sevilla, Seville, Spain
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Li J, Zhao X, Hu X, Tao C, Ji R. A finite element analysis for monitoring the healing progression of fixator-bone system under three loading conditions. Biomed Mater Eng 2018; 29:473-483. [PMID: 30282344 DOI: 10.3233/bme-181003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Unilateral external fixators are widely used in orthopedics to stabilize fractured bones and in the treatment of limb deformities. The main value for evaluation of mechanical stability of the external fixator is fixator stiffness. The fixator stiffness is an important factor as it will influence the biomechanical environment to which fixator and regenerating tissues are exposed. OBJECTIVE The main objective of this work was to monitor the transmission of stress and the change of displacement generated in fixator-bone system under three loading conditions during healing process. METHODS In this study, a finite element model with changing Young's modulus of the callus is established, finite element analysis was used to investigating stress and deformation of fixator-bone system caused by axial load, torsional load and bending load during three healing stages. RESULTS The results reveal that at different healing stages, stress distribution between the fixator and fractured bone is different, the position of displacement is mainly concentrated in the fracture site and proximal bone and with the increase of healing time, the deformation decreased. CONCLUSIONS This work helps orthopedic doctors to monitor the progression of fracture healing and determine the appropriate time for removal of a fixation device and provide useful information.
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Affiliation(s)
- Jianfeng Li
- Beijing University of Technology, Beijing, China
| | - Xia Zhao
- Beijing University of Technology, Beijing, China
| | - XiaoJie Hu
- Beijing University of Technology, Beijing, China
| | - Chunjing Tao
- National Research Center for Rehabilitation Technical Aids, Beijing, China
| | - Run Ji
- National Research Center for Rehabilitation Technical Aids, Beijing, China
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28
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Manjubala I, Basu P, Narendrakumar U. In situ synthesis of hydroxyapatite/carboxymethyl cellulose composites for bone regeneration applications. Colloid Polym Sci 2018. [DOI: 10.1007/s00396-018-4393-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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29
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Schlundt C, Bucher CH, Tsitsilonis S, Schell H, Duda GN, Schmidt-Bleek K. Clinical and Research Approaches to Treat Non-union Fracture. Curr Osteoporos Rep 2018. [PMID: 29536393 DOI: 10.1007/s11914-018-0432-1] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE OF REVIEW Impaired healing outcomes or even non-unions after bone injury are still a highly relevant problem in the daily clinical life. Especially within an aging population, the occurrence of bone fractures increases and thus novel treatment approaches to overcome compromised bone regeneration are needed. RECENT FINDINGS The gold standard to treat delayed or non-healing bone injuries is still the use of autologous bone grafts to foster regeneration. Besides its successful treatment outcome, it also has disadvantages: a second surgery is needed in order to harvest the bone material and the material is highly limited. Looking into the recent literature, a multitude of different research approaches were already conducted to identify new possible strategies to treat impaired bone regeneration: application of mesenchymal stromal cells, platelet lysates, growth factors, interference in the immune system, or bone formation stimulation by ultrasound. This review gives an overview of the treatment approaches actually performed in the clinic as well as at the bench in the context of compromised bone healing. It clearly highlights the complexity of the nature of non-healing bone fractures as well as patient-dependent factors influencing the healing process.
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Affiliation(s)
- Claudia Schlundt
- Julius Wolff Institut and Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany
- Berlin-Brandenburg Center for Regenerative Therapies, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Christian H Bucher
- Julius Wolff Institut and Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany
- Berlin-Brandenburg Center for Regenerative Therapies, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Serafeim Tsitsilonis
- Julius Wolff Institut and Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany
- Berlin-Brandenburg Center for Regenerative Therapies, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Hanna Schell
- Julius Wolff Institut and Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany
| | - Georg N Duda
- Julius Wolff Institut and Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
- Berlin-Brandenburg Center for Regenerative Therapies, Charité-Universitätsmedizin Berlin, Berlin, Germany.
| | - Katharina Schmidt-Bleek
- Julius Wolff Institut and Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany
- Berlin-Brandenburg Center for Regenerative Therapies, Charité-Universitätsmedizin Berlin, Berlin, Germany
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30
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Li J, Zhao X, Hu X, Tao C, Ji R. A theoretical analysis and finite element simulation of fixator-bone system stiffness on healing progression. J Appl Biomater Funct Mater 2018; 16:115-125. [PMID: 29582693 DOI: 10.1177/2280800017750357] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
INTRODUCTION The unilateral external fixator has become a quick and easy application for fracture stabilization of the extremities; the main value for evaluation of mechanical stability of the external fixator is stiffness. The stiffness property of the external fixator affects the local biomechanical environment of fractured bone. METHODS In this study, a theoretical model with changing Young's modulus of the callus is established by using the Castigliano's theory, investigating compression stiffness, torsional stiffness and bending stiffness of the fixator-bone system during the healing process. The effects of pin deviation angle on three stiffness methods are also investigated. In addition, finite element simulation is discussed regarding the stress distribution between the fixator and bone. RESULTS The results reveal the three stiffness evaluation methods are similar for the fixator-bone system. Finite element simulation shows that with increased healing time, the transmission of the load between the fixator and bone are different. In addition, the finite element analyses verify the conclusions obtained from the theoretical model. CONCLUSIONS This work helps orthopedic doctors to monitor the progression of fracture healing and determine the appropriate time for removal of a fixation device and provide important theoretical methodology.
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Affiliation(s)
- Jianfeng Li
- 1 College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing, China
| | - Xia Zhao
- 1 College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing, China
| | - Xiaojie Hu
- 1 College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing, China
| | - Chunjing Tao
- 2 National Research Center for Rehabilitation Technical Aids, Beijing, China
| | - Run Ji
- 2 National Research Center for Rehabilitation Technical Aids, Beijing, China
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31
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Open questions on the 3D structures of collagen containing vertebrate mineralized tissues: A perspective. J Struct Biol 2018; 201:187-198. [DOI: 10.1016/j.jsb.2017.11.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 11/19/2017] [Accepted: 11/20/2017] [Indexed: 12/29/2022]
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32
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Correlations between nanostructure and micromechanical properties of healing bone. J Mech Behav Biomed Mater 2018; 77:258-266. [DOI: 10.1016/j.jmbbm.2017.08.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 07/27/2017] [Accepted: 08/17/2017] [Indexed: 12/15/2022]
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Sakka S, Gafni RI, Davies JH, Clarke B, Tebben P, Samuels M, Saraff V, Klaushofer K, Fratzl-Zelman N, Roschger P, Rauch F, Högler W. Bone Structural Characteristics and Response to Bisphosphonate Treatment in Children With Hajdu-Cheney Syndrome. J Clin Endocrinol Metab 2017; 102:4163-4172. [PMID: 28938420 PMCID: PMC5673271 DOI: 10.1210/jc.2017-01102] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Accepted: 09/05/2017] [Indexed: 02/07/2023]
Abstract
CONTEXT Hajdu-Cheney syndrome (HJCYS) is a rare, multisystem bone disease caused by heterozygous mutations in the NOTCH2 gene. Histomorphometric and bone ultrastructural analyses in children have not been reported and sparse evidence exists on response to bisphosphonate (BP) therapy. OBJECTIVE To investigate clinical and bone histomorphometric characteristics, bone matrix mineralization, and the response of bone geometry and density to BP therapy. PATIENTS Five children with HJCYS (three males) between 6.7 and 15.3 years of age. INTERVENTIONS Various BP regimens (pamidronate, zoledronic acid, and alendronate) were used for between 1 and 10 years. MAIN OUTCOME MEASURES Pretreatment transiliac bone biopsy specimens and peripheral quantitative computed tomography results were available in four and three subjects, respectively. Bone histomorphometry and quantitative backscattered electron imaging were performed in two patients. The response to BP was monitored using dual-energy X-ray absorptiometry and peripheral quantitative computed tomography. RESULTS Three patients had previously unreported NOTCH2 mutations. Histomorphometry demonstrated increased bone resorption and osteoclast numbers, increased heterogeneity of mineralization, and immature, woven bone. Trabecular bone formation was normal or elevated. Radius cortical thickness and density and lumbar spine bone mineral density were reduced at baseline and increased in response to BP therapy, which was not sustained after therapy discontinuation. CONCLUSIONS Increased bone resorption and low cortical thickness are consistent with the effect of activating NOTCH2 mutations, which stimulate osteoclastogenesis. The increase in lumbar spine bone density and radial cortical thickness and density by BP therapy provides evidence of beneficial treatment effects in children with HJCYS.
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Affiliation(s)
- Sophia Sakka
- Department of Endocrinology and Diabetes, Birmingham Children's Hospital, Birmingham B4 6NH, United Kingdom
| | - Rachel I. Gafni
- Section on Skeletal Disorders and Mineral Homeostasis, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
| | - Justin H. Davies
- Department of Endocrinology, Southampton Children's Hospital, Southampton SO16 6YD, United Kingdom
| | - Bart Clarke
- Department of Internal Medicine, Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Peter Tebben
- Department of Internal Medicine, Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Mark Samuels
- Centre de Recherché du Centre Hospitalier Universitaire Ste‐Justine, Université de Montréal, Montreal H3T 1C5, Canada
- Department of Medicine, Université de Montréal, Montreal H3C 3J7, Canada
| | - Vrinda Saraff
- Department of Endocrinology and Diabetes, Birmingham Children's Hospital, Birmingham B4 6NH, United Kingdom
| | - Klaus Klaushofer
- Ludwig Boltzmann Institute of Osteology at Hanusch Hospital of WGKK, 1140 Vienna, Austria
- AUVA Trauma Centre Meidling, 1st Medical Department, Hanusch Hospital, 1120 Vienna, Austria
| | - Nadja Fratzl-Zelman
- Ludwig Boltzmann Institute of Osteology at Hanusch Hospital of WGKK, 1140 Vienna, Austria
- AUVA Trauma Centre Meidling, 1st Medical Department, Hanusch Hospital, 1120 Vienna, Austria
| | - Paul Roschger
- Ludwig Boltzmann Institute of Osteology at Hanusch Hospital of WGKK, 1140 Vienna, Austria
- AUVA Trauma Centre Meidling, 1st Medical Department, Hanusch Hospital, 1120 Vienna, Austria
| | - Frank Rauch
- Shriners Hospital for Children and McGill University, Montreal, Quebec H4A 0A9, Canada
| | - Wolfgang Högler
- Department of Endocrinology and Diabetes, Birmingham Children's Hospital, Birmingham B4 6NH, United Kingdom
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham B15 2TT, United Kingdom
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Mechanical characterization via nanoindentation of the woven bone developed during bone transport. J Mech Behav Biomed Mater 2017. [DOI: 10.1016/j.jmbbm.2017.05.031] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Systemic administration of mesenchymal stem cells combined with parathyroid hormone therapy synergistically regenerates multiple rib fractures. Stem Cell Res Ther 2017; 8:51. [PMID: 28279202 PMCID: PMC5345153 DOI: 10.1186/s13287-017-0502-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 01/18/2017] [Accepted: 02/09/2017] [Indexed: 01/08/2023] Open
Abstract
Background A devastating condition that leads to trauma-related morbidity, multiple rib fractures, remain a serious unmet clinical need. Systemic administration of mesenchymal stem cells (MSCs) has been shown to regenerate various tissues. We hypothesized that parathyroid hormone (PTH) therapy would enhance MSC homing and differentiation, ultimately leading to bone formation that would bridge rib fractures. Methods The combination of human MSCs (hMSCs) and a clinically relevant PTH dose was studied using immunosuppressed rats. Segmental defects were created in animals’ fifth and sixth ribs. The rats were divided into four groups: a negative control group, in which animals received vehicle alone; the PTH-only group, in which animals received daily subcutaneous injections of 4 μg/kg teriparatide, a pharmaceutical derivative of PTH; the hMSC-only group, in which each animal received five injections of 2 × 106 hMSCs; and the hMSC + PTH group, in which animals received both treatments. Longitudinal in vivo monitoring of bone formation was performed biweekly using micro-computed tomography (μCT), followed by histological analysis. Results Fluorescently-dyed hMSCs were counted using confocal microscopy imaging of histological samples harvested 8 weeks after surgery. PTH significantly augmented the number of hMSCs that homed to the fracture site. Immunofluorescence of osteogenic markers, osteocalcin and bone sialoprotein, showed that PTH induced cell differentiation in both exogenously administered cells and resident cells. μCT scans revealed a significant increase in bone volume only in the hMSC + PTH group, beginning by the 4th week after surgery. Eight weeks after surgery, 35% of ribs in the hMSC + PTH group had complete bone bridging, whereas there was complete bridging in only 6.25% of ribs (one rib) in the PTH-only group and in none of the ribs in the other groups. Based on the μCT scans, biomechanical analysis using the micro-finite element method demonstrated that the healed ribs were stiffer than intact ribs in torsion, compression, and bending simulations, as expected when examining bone callus composed of woven bone. Conclusions Administration of both hMSCs and PTH worked synergistically in rib fracture healing, suggesting this approach may pave the way to treat multiple rib fractures as well as additional fractures in various anatomical sites. Electronic supplementary material The online version of this article (doi:10.1186/s13287-017-0502-9) contains supplementary material, which is available to authorized users.
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Grover K, Lin L, Hu M, Muir J, Qin YX. Spatial distribution and remodeling of elastic modulus of bone in micro-regime as prediction of early stage osteoporosis. J Biomech 2016; 49:161-6. [PMID: 26705110 PMCID: PMC4761497 DOI: 10.1016/j.jbiomech.2015.11.052] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 11/17/2015] [Accepted: 11/21/2015] [Indexed: 11/24/2022]
Abstract
We assessed the local distribution of bone mechanical properties on a micro-nano-scale and its correlation to strain distribution. Left tibia samples were obtained from 5-month old female Sprague Dawley rats, including baseline control (n=9) and hindlimb suspended (n=9) groups. Elastic modulus was measured by nanoindentation at the dedicated locations. Three additional tibias from control rats were loaded axially to measure bone strain, with 6-10N at 1Hz on a Bose machine for strain measurements. In the control group, the difference of the elastic modulus between periosteum and endosteum was much higher at the anterior and posterior regions (2.6GPa), where higher strain differences were observed (45μɛ). Minimal elastic modulus difference between periosteum and endosteum was observed at the medial region (0.2GPa), where neutral axis of the strain distribution was oriented with lower strain difference (5μɛ). In the disuse group, however, the elastic modulus differences in the anterior posterior regions reduced to 1.2GPa from 2.6GPa in the control group, and increased in the medial region to 2.7GPa from 0.2GPa. It is suggested that the remodeling rate in a region of bone is possibly influenced by the strain gradient from periosteum to endosteum. Such pattern of moduli gradients was compromised in disuse osteopenia, suggesting that the remodeling in distribution of micro-nano-elastic moduli among different regions may serve as a predictor for early stage of osteoporosis.
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Affiliation(s)
- Kartikey Grover
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
| | - Liangjun Lin
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
| | - Minyi Hu
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
| | - Jesse Muir
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
| | - Yi-Xian Qin
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA.
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Gao J, Gong H, Huang X, Zhang R, Ma R, Zhu D. Multi-Level Assessment of Fracture Calluses in Rats Subjected to Low-Magnitude High-Frequency Vibration with Different Rest Periods. Ann Biomed Eng 2016; 44:2489-2504. [DOI: 10.1007/s10439-015-1532-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 12/02/2015] [Indexed: 12/15/2022]
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Abstract
Osteoporosis is a chronic systemic bone disease of growing relevance due to the on-going demographic change. Since the underlying regulatory mechanisms of this critical illness are still not fully understood and treatment options are not satisfactorily resolved, there is still a great need for osteoporosis research in general and animal models in particular. Ovariectomized rodents are standard animal models for postmenopausal osteoporosis and highly attractive due to the possibility to specifically modify their genetic background. However, some aspects can only be addressed in large animal models; such as metaphyseal fracture healing and advancement of orthopedic implants. Among other large animal models sheep in particular have been proven invaluable for osteoporosis research in this context. In conclusion, today we are able to influence the bone metabolism in animals causing a more or less pronounced systemic bone loss and structural deterioration comparable to the situation found in patients suffering from osteoporosis. However, there is no perfect model for osteoporosis, but a variety of models appropriate for answering specific questions. Though, the appropriateness of an animal model is not only defined in regard to the similarity to human physiology and the disease itself, but also in regard to acquisition, housing requirements, handling, costs, and particularly ethical concerns and animal welfare.
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Affiliation(s)
- Ralf Oheim
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany.
| | - Thorsten Schinke
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
| | - Michael Amling
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
| | - Pia Pogoda
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
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Mora-Macías J, Reina-Romo E, Domínguez J. Distraction osteogenesis device to estimate the axial stiffness of the callus in Vivo. Med Eng Phys 2015; 37:969-78. [DOI: 10.1016/j.medengphy.2015.07.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Revised: 07/01/2015] [Accepted: 07/21/2015] [Indexed: 10/23/2022]
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Cipitria A, Wagermaier W, Zaslansky P, Schell H, Reichert J, Fratzl P, Hutmacher D, Duda G. BMP delivery complements the guiding effect of scaffold architecture without altering bone microstructure in critical-sized long bone defects: A multiscale analysis. Acta Biomater 2015; 23:282-294. [PMID: 26004222 DOI: 10.1016/j.actbio.2015.05.015] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 05/10/2015] [Accepted: 05/15/2015] [Indexed: 10/23/2022]
Abstract
Scaffold architecture guides bone formation. However, in critical-sized long bone defects additional BMP-mediated osteogenic stimulation is needed to form clinically relevant volumes of new bone. The hierarchical structure of bone determines its mechanical properties. Yet, the micro- and nanostructure of BMP-mediated fast-forming bone has not been compared with slower regenerating bone without BMP. We investigated the combined effects of scaffold architecture (physical cue) and BMP stimulation (biological cue) on bone regeneration. It was hypothesized that a structured scaffold directs tissue organization through structural guidance and load transfer, while BMP stimulation accelerates bone formation without altering the microstructure at different length scales. BMP-loaded medical grade polycaprolactone-tricalcium phosphate scaffolds were implanted in 30mm tibial defects in sheep. BMP-mediated bone formation after 3 and 12 months was compared with slower bone formation with a scaffold alone after 12 months. A multiscale analysis based on microcomputed tomography, histology, polarized light microscopy, backscattered electron microscopy, small angle X-ray scattering and nanoindentation was used to characterize bone volume, collagen fiber orientation, mineral particle thickness and orientation, and local mechanical properties. Despite different observed kinetics in bone formation, similar structural properties on a microscopic and sub-micron level seem to emerge in both BMP-treated and scaffold only groups. The guiding effect of the scaffold architecture is illustrated through structural differences in bone across different regions. In the vicinity of the scaffold increased tissue organization is observed at 3 months. Loading along the long bone axis transferred through the scaffold defines bone micro- and nanostructure after 12 months.
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Doyle H, Lohfeld S, McHugh P. Evaluating the effect of increasing ceramic content on the mechanical properties, material microstructure and degradation of selective laser sintered polycaprolactone/β-tricalcium phosphate materials. Med Eng Phys 2015; 37:767-76. [DOI: 10.1016/j.medengphy.2015.05.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 03/26/2015] [Accepted: 05/09/2015] [Indexed: 10/23/2022]
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In Vivo Mechanical Characterization of the Distraction Callus During Bone Consolidation. Ann Biomed Eng 2015; 43:2663-74. [DOI: 10.1007/s10439-015-1330-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 04/27/2015] [Indexed: 10/23/2022]
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The connection between cellular mechanoregulation and tissue patterns during bone healing. Med Biol Eng Comput 2015; 53:829-42. [DOI: 10.1007/s11517-015-1285-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 03/23/2015] [Indexed: 02/05/2023]
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Hoerth RM, Baum D, Knötel D, Prohaska S, Willie BM, Duda GN, Hege HC, Fratzl P, Wagermaier W. Registering 2D and 3D imaging data of bone during healing. Connect Tissue Res 2015; 56:133-43. [PMID: 25825970 DOI: 10.3109/03008207.2015.1005210] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
UNLABELLED PURPOSE/AIMS OF THE STUDY: Bone's hierarchical structure can be visualized using a variety of methods. Many techniques, such as light and electron microscopy generate two-dimensional (2D) images, while micro-computed tomography (µCT) allows a direct representation of the three-dimensional (3D) structure. In addition, different methods provide complementary structural information, such as the arrangement of organic or inorganic compounds. The overall aim of the present study is to answer bone research questions by linking information of different 2D and 3D imaging techniques. A great challenge in combining different methods arises from the fact that they usually reflect different characteristics of the real structure. MATERIALS AND METHODS We investigated bone during healing by means of µCT and a couple of 2D methods. Backscattered electron images were used to qualitatively evaluate the tissue's calcium content and served as a position map for other experimental data. Nanoindentation and X-ray scattering experiments were performed to visualize mechanical and structural properties. RESULTS We present an approach for the registration of 2D data in a 3D µCT reference frame, where scanning electron microscopies serve as a methodic link. Backscattered electron images are perfectly suited for registration into µCT reference frames, since both show structures based on the same physical principles. We introduce specific registration tools that have been developed to perform the registration process in a semi-automatic way. CONCLUSIONS By applying this routine, we were able to exactly locate structural information (e.g. mineral particle properties) in the 3D bone volume. In bone healing studies this will help to better understand basic formation, remodeling and mineralization processes.
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Affiliation(s)
- Rebecca M Hoerth
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces , Potsdam , Germany
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Computational modelling of ovine critical-sized tibial defects with implanted scaffolds and prediction of the safety of fixator removal. J Mech Behav Biomed Mater 2015; 44:133-46. [DOI: 10.1016/j.jmbbm.2015.01.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 01/05/2015] [Accepted: 01/07/2015] [Indexed: 11/23/2022]
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Aido M, Kerschnitzki M, Hoerth R, Checa S, Spevak L, Boskey AL, Fratzl P, Duda GN, Wagermaier W, Willie BM. Effect of in vivo loading on bone composition varies with animal age. Exp Gerontol 2015; 63:48-58. [PMID: 25639943 PMCID: PMC4352172 DOI: 10.1016/j.exger.2015.01.048] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Revised: 12/23/2014] [Accepted: 01/28/2015] [Indexed: 01/07/2023]
Abstract
Loading can increase bone mass and size and this response is reduced
with aging. It is unclear, however how loading affects bone mineral and matrix
properties. Fourier Transform Infrared Imaging and high resolution synchrotron
scanning small angle X-ray scattering were used to study how bone’s
microscale and nanoscale compositional properties were altered in the tibial
midshaft of young, adult, and elderly female C57Bl/6J mice after two weeks of
controlled in vivo compressive loading in comparison to
physiological loading. The effect of controlled loading on bone composition
varied with animal age, since it predominantly influenced the bone composition
of elderly mice. Interestingly, controlled loading led to enhanced collagen
maturity in elderly mice. In addition, although the rate of bone formation was
increased by controlled loading based on histomorphometry, the newly formed
tissue had similar material quality to new bone tissue formed during
physiological loading. Similar to previous studies, our data showed that bone
composition was animal and tissue age dependent during physiological loading.
The findings that the new tissue formed in response to controlled loading and
physiological loading had similar bone composition and that controlled loading
enhanced bone composition in elderly mice further supports the use of physical
activity as a noninvasive treatment to enhance bone quality as well as maintain
bone mass in individuals suffering from age-related bone loss.
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Affiliation(s)
- Marta Aido
- Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Germany; Berlin-Brandenburg School for Regenerative Therapies (BSRT), Berlin, Germany
| | - Michael Kerschnitzki
- Berlin-Brandenburg School for Regenerative Therapies (BSRT), Berlin, Germany; Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
| | - Rebecca Hoerth
- Berlin-Brandenburg School for Regenerative Therapies (BSRT), Berlin, Germany; Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
| | - Sara Checa
- Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Germany
| | | | | | - Peter Fratzl
- Berlin-Brandenburg School for Regenerative Therapies (BSRT), Berlin, Germany; Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
| | - Georg N Duda
- Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Germany; Berlin-Brandenburg School for Regenerative Therapies (BSRT), Berlin, Germany; Berlin-Brandenburg Center for Regenerative Therapies (BCRT), Berlin, Germany
| | | | - Bettina M Willie
- Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Germany.
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Bianchi M, Boi M, Sartori M, Giavaresi G, Lopomo N, Fini M, Dediu A, Tampieri A, Marcacci M, Russo A. Nanomechanical mapping of bone tissue regenerated by magnetic scaffolds. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2015; 26:5363. [PMID: 25578711 DOI: 10.1007/s10856-014-5363-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 08/06/2014] [Indexed: 06/04/2023]
Abstract
Nanoindentation can provide new insights on the maturity stage of regenerating bone. The aim of the present study was the evaluation of the nanomechanical properties of newly-formed bone tissue at 4 weeks from the implantation of permanent magnets and magnetic scaffolds in the trabecular bone of rabbit femoral condyles. Three different groups have been investigated: MAG-A (NdFeB magnet + apatite/collagen scaffold with magnetic nanoparticles directly nucleated on the collagen fibers during scaffold synthesis); MAG-B (NdFeB magnet + apatite/collagen scaffold later infiltrated with magnetic nanoparticles) and MAG (NdFeB magnet). The mechanical properties of different-maturity bone tissues, i.e. newly-formed immature, newly-formed mature and native trabecular bone have been evaluated for the three groups. Contingent correlations between elastic modulus and hardness of immature, mature and native bone have been examined and discussed, as well as the efficacy of the adopted regeneration method in terms of "mechanical gap" between newly-formed and native bone tissue. The results showed that MAG-B group provided regenerated bone tissue with mechanical properties closer to that of native bone compared to MAG-A or MAG groups after 4 weeks from implantation. Further, whereas the mechanical properties of newly-formed immature and mature bone were found to be fairly good correlated, no correlation was detected between immature or mature bone and native bone. The reported results evidence the efficacy of nanoindentation tests for the investigation of the maturity of newly-formed bone not accessible through conventional analyses.
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Affiliation(s)
- Michele Bianchi
- Laboratory of Nano-Biotechnologies (NaBi), Rizzoli Orthopaedic Institute, Via Gobetti 1/10, Bologna, 40136, Italy,
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Morgan EF, De Giacomo A, Gerstenfeld LC. Overview of skeletal repair (fracture healing and its assessment). Methods Mol Biol 2014; 1130:13-31. [PMID: 24482162 DOI: 10.1007/978-1-62703-989-5_2] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The study of postnatal skeletal repair is of immense clinical interest. Optimal repair of skeletal tissue is necessary in all varieties of elective and reparative orthopedic surgical treatments. However, the repair of fractures is unique in this context in that fractures are one of the most common traumas that humans experience and are the end-point manifestation of osteoporosis, the most common chronic disease of aging. In the first part of this introduction the basic biology of fracture healing is presented. The second part discusses the primary methodological approaches that are used to examine repair of skeletal hard tissue and specific considerations for choosing among and implementing these approaches.
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Schmidt-Bleek K, Petersen A, Dienelt A, Schwarz C, Duda GN. Initiation and early control of tissue regeneration - bone healing as a model system for tissue regeneration. Expert Opin Biol Ther 2014; 14:247-59. [PMID: 24397854 DOI: 10.1517/14712598.2014.857653] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Tissue regeneration in itself is a fascinating process that promises repeated renewal of tissue and organs. AREAS COVERED This article aims to illustrate the different strategies available to control tissue regeneration at a very early stage, using bone as an exemplary tissue. The aspects of a controlled inflammatory cascade to achieve a balanced immune response, cell therapeutic approaches for improved tissue formation and angiogenesis, guiding the organization of newly formed extracellular matrix by biomaterials, the relevance of mechanical signals for tissue regeneration processes, and the chances and limitations of growth factor treatments are discussed. EXPERT OPINION The currently available knowledge is reviewed and perspectives for potential new targets are given. This is done under the assumption that early identification of risk patients as well as the application of early intervention strategies is possible.
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Affiliation(s)
- Katharina Schmidt-Bleek
- Charité - Universitätsmedizin Berlin, Julius Wolff Institut and Center for Musculoskeletal Surgery , Augustenburger Platz 1, D-13353 Berlin , Germany +49 30 450 536196 ; +49 30 450 559969 ;
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Hoerth RM, Seidt BM, Shah M, Schwarz C, Willie BM, Duda GN, Fratzl P, Wagermaier W. Mechanical and structural properties of bone in non-critical and critical healing in rat. Acta Biomater 2014; 10:4009-19. [PMID: 24929204 DOI: 10.1016/j.actbio.2014.06.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 05/19/2014] [Accepted: 06/03/2014] [Indexed: 02/06/2023]
Abstract
A fracture in bone results in a dramatic change of mechanical loading conditions at the site of injury. Usually, bone injuries heal normally but with increasing fracture gaps, healing is retarded, eventually leading to non-unions. The clinical situation of these two processes with different outcomes is well described. However, the exact relation between the mechanical environment and characteristics of the tissues at all levels of structural hierarchy remains unclear. Here we studied the differences in material formation of non-critical (1mm) and critical (5mm gap) healing. We employed a rat osteotomy model to explore bone material structure depending upon the different mechanical conditions. In both cases, primary bone formation was followed by secondary bone deposition with mineral particle sizes changing from on average short and thick to long and thin particles. Bony bridging occurred at first in the endosteal callus and the nanostructure and microstructure developed towards cortical ordered material organization. In contrast, in critical healing, instead of bridging, a marrow cavity closure was formed endosteal, exhibiting tissue structure oriented along the curvature and a periosteal callus with less mature material structure. The two healing processes separated between 4 and 6 weeks post-osteotomy. The outcome of healing was determined by the varied geometrical conditions in critical and non-critical healing, inducing completely different mechanical situations.
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Affiliation(s)
- Rebecca M Hoerth
- Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Golm, 14424 Potsdam, Germany; Berlin-Brandenburg School for Regenerative Therapies (BSRT), Charité - Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Britta M Seidt
- Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Golm, 14424 Potsdam, Germany
| | - Miheer Shah
- Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Golm, 14424 Potsdam, Germany
| | - Carolin Schwarz
- Berlin-Brandenburg School for Regenerative Therapies (BSRT), Charité - Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany; Julius Wolff Institute & Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Bettina M Willie
- Julius Wolff Institute & Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Georg N Duda
- Julius Wolff Institute & Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Peter Fratzl
- Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Golm, 14424 Potsdam, Germany
| | - Wolfgang Wagermaier
- Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Golm, 14424 Potsdam, Germany.
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