A model of tissue differentiation and bone remodelling in fractured vertebrae treated with minimally invasive percutaneous fixation (original) (raw)
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A mechano-regulation model of fracture repair in vertebral bodies
Journal of Orthopaedic Research, 2011
In this study a multi-scale mechano-regulation model was developed in order to investigate the mechanobiology of trabecular fracture healing in vertebral bodies. A macro-scale finite element model of the spinal segment L3-L4-L5, including a mild wedge fracture in the body of the L4 vertebra, was used to determine the boundary conditions acting on a micro-scale finite element model simulating a portion of fractured trabecular bone. The micro-scale model, in turn, was utilized to predict the local patterns of tissue differentiation within the fracture gap and then how the equivalent mechanical properties of the macro-scale model change with time. The patterns of tissue differentiation predicted by the model appeared consistent with those observed in vivo. Bone formation occurred primarily through endochondral ossification. New woven bone was predicted to occupy the majority of the space within the fracture site approximately 7-8 weeks after the fracture event. Remodeling of cancellous bone architecture was then predicted, with complete new trabeculae forming due to bridging of the microcallus between the remnant trabeculae.
World Journal of Orthopedics, 2017
Author contributions: Hosseini Faradonbeh SA and Jamshidi N substantially contributed to the conception and design of the study, acquisition, analysis and interpretation of data; all authors drafted the article and made critical revisions related to the intellectual content of the manuscript, and approved the final version of the article to be published. Institutional review board statement: The study was approved by the head of animal care center at Department of Biomedical Engineering at the University of Isfahan. Institutional animal care and use committee statement: The fresh ovine vertebrae were harvested from the dead sheep Carcasses without meaning any harm or pain to the living animals; approved by the University of Isfahan's Animal Care Committee at the time of adoption.
2009
Spine fractures are the most frequent complication of osteoporosis, a disease characterized by low bone mass and structural deterioration of bone tissue. In case of the spine, the trabecular network plays the main role in load carrying and distribution. A correct description of mechanical properties of this bone structure helps to differentiate between strong and weak bones and can be useful for fracture prediction and treatment monitoring. By means of the finite element method (FEM), applied to μCT images, we modelled biomechanical processes in probes during loading and correlated the estimated failure load with the maximum compressive strength (MCS), obtained in real biomechanical tests. We studied a sample of 151 specimens taken from the trabecular part of human vertebrae in vitro, visualised using μCT imaging at an isotropic resolution of 26μm and tested by uniaxial compression. Besides the standard way of estimating failure load, which takes into account only strong micro-fractures, we also included small micro-fractures, what improved the correlation with MCS (Pearson's correlation coefficient r=0.78 vs. r=0.58). This correlation coefficient was larger than that for both the standard morphometric parameters (r=0.73 for bone volume fraction) and for texture measures defined by the local (an-) isotropic scaling indices method (r=0.55) and Minkowski Functionals (r=0.61). However, the performance of the FEM was different for subsamples selected according to the MCS value. The correlation increased for strong specimens (r=0.88), slightly decreased for weak specimens (r=0.68) and markedly dropped for specimens with medium MCS, e.g. between 60<MCS<120, r=0.26.
Spinal Fracture Treatment: Finite Element Analysis Of Different Fixation Techniques
2020
The spondylolysis is usually associated with the fracture occurring in the pars interarticularis of the neural arch of the vertebra. It is considered to be caused by the hyperextension or excessive rotation movement due to sports injuries and it is suspected to cause back pain to 50 % of the young athletes. If not treated, the fracture could worsen and develop into spondylolisthesis in 51-80% of all cases. When non-surgical conservative treatments are not successful, clinical intervention may be the solution. Our work aims to compare, through a finite element analysis, the surgical techniques representing the state of the art, such as Buck technique and the evolution of the Morscher technique, with a new design combining both methods to reduce the fracture as proposed by new developments in the Biomechanics Research Laboratory.
Determinants of the mechanical behavior of human lumbar vertebrae after simulated mild fracture
Journal of Bone and Mineral Research, 2011
The ability of a vertebra to carry load after an initial deformation and the determinants of this postfracture load-bearing capacity are critical but poorly understood. This study aimed to determine the mechanical behavior of vertebrae after simulated mild fracture and to identify the determinants of this postfracture behavior. Twenty-one human L 3 vertebrae were analyzed for bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) and for microarchitecture by micro-computed tomography (mCT). Mechanical testing was performed in two phases: initial compression of vertebra to 25% deformity, followed, after 30 minutes of relaxation, by a similar test to failure to determine postfracture behavior. We assessed (1) initial and postfracture mechanical parameters, (2) changes in mechanical parameters, (3) postfracture elastic behavior by recovery of vertebral height after relaxation, and (4) postfracture plastic behavior by residual strength and stiffness. Postfracture failure load and stiffness were 11% AE 19% and 53% AE 18% lower than initial values ( p ¼ .021 and p < .0001, respectively), with 29% to 69% of the variation in the postfracture mechanical behavior explained by the initial values. Both initial and postfracture mechanical behaviors were significantly correlated with bone mass and microarchitecture. Vertebral deformation recovery averaged 31% AE 7% and was associated with trabecular and cortical thickness (r ¼ 0.47 and r ¼ 0.64; p ¼ .03 and p ¼ .002, respectively). Residual strength and stiffness were independent of bone mass and initial mechanical behavior but were related to trabecular and cortical microarchitecture (jrj ¼ 0.50 to 0.58; p ¼ .02 to .006). In summary, we found marked variation in the postfracture load-bearing capacity following simulated mild vertebral fractures. Bone microarchitecture, but not bone mass, was associated with postfracture mechanical behavior of vertebrae. ß Note: D ¼ difference between postfracture and initial parameters in % [mean AE SD (range)]. The comparisons between initial and postfracture mechanical parameters were performed using Wilcoxon signed-rank tests ( Ã p < .05).
PloS one, 2016
Vertebral fragility fractures are often treated by injecting bone cement into the collapsed vertebral bodies (vertebroplasty). The mechanisms by which vertebroplasty induces pain relief are not completely understood yet and recent debates cast doubt over the outcome of the procedure. The controversy is intensified by inconsistent results of randomized clinical trials and biomechanical studies that have investigated the effectiveness or the change in biomechanical response due to the reinforcement. The purpose of this study was to evaluate the effectiveness of vertebroplasty, by varying the relevant treatment parameters and (a) computationally predicting the improvement of the fracture risk depending on the chosen treatment strategy, and (b) identifying the determinants of a successful treatment. A Finite Element model with a patient-specific failure criterion and direct simulation of PMMA infiltration in four lumbar vertebrae was used to assess the condition of the bone under compre...
International Journal for Numerical Methods in Biomedical Engineering, 2019
This study aims to enhance the understanding of the relationship between Ilizarov fixator configuration and its effects on bone fracture healing. Using Taylor spatial frame (TSF) as an example, the roles of critical parameters (ie, TSF ring diameter, wire pre‐tension, fracture gap size, and axial load) that govern fracture healing during the early stages were investigated by using computational modelling in conjunction with mechanical testing involving an advanced 3D optical measurement system. The computational model was first validated using the mechanical test results and then used to simulate mesenchymal stem cell (MSC) differentiations within different regions of the fracture site under various combinations of TSF ring diameter, wire pre‐tension, fracture gap size, and axial load values. Predicted spatially dependent MSC differentiation patterns and the influence of each parameter on differentiations were compared with in vivo results, and good agreement was seen between the tw...
The initial phase of fracture healing is specifically sensitive to mechanical conditions
Journal of Orthopaedic Research, 2003
Interfragmentary movements affect the quality and quantity of callus formation. The mounting plane of monolateral external fixators may give direction to those movements. Therefore, the aim of this study was to determine the influence of the fixator mounting plane on the process of fracture healing. Identically configured fixators were mounted either medially or anteromedially on the tibiae of sheep. Interfragmentary movements and ground reaction forces were evaluated in vivo during a nine week period. Histomorphological and biomechanical parameters described the bone healing processes. Changing only the mounting plane led to a modification of interfragmentary movements in the initial healing phase. The difference in interfragmentary movements between the groups was only significant during the first post-operative period. However, these initial differences in mechanical conditions influenced callus tissue formation significantly. The group with the anteromedially mounted fixator, initially showing significantly more interfragmentary movements, ended up with a significantly smaller callus diameter and a significantly higher callus stiffness as a result of advanced fracture healing. This demonstrates that the initial phase of healing is sensitive to mechanical conditions and influences the course of healing. Therefore, initial mechanical stability of an osteosynthesis should be considered an important factor in clinical fracture treatment.