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BACKGROUND: Anatomic referencing in total knee arthroplasty places the femoral component flush to the anterior cortex while maintaining posterior condylar offset (PCO). The intent of this study was to evaluate how component position influences the femoral component size. METHODS: Digital surface models were created using 446 femora from an established computed tomography database. Virtual bone resections, component sizing, and component placement were performed assuming neutral (0°) flexion and neutral (3°) rotation relative to the posterior condyles. The appropriately sized femoral component, which had 2 mm of incremental size, was placed flush with the anterior cortex for optimal restoration of the PCO. Sizing and placement were repeated using 3 and 6° flexion and 0, 5, and 7° external rotation (ER). RESULTS: At 0° flexion, decreasing ER from 3 to 0° resulted in an average decreased anterior-posterior height (APH) of 1.9 mm, corresponding to a component size decrease of 1 for 88% of patients. At 7° ER, component size increased by an average of 2.5 mm, corresponding to a size increase for 80% of patients. Flexing the femoral component to 3° with ER at 3° resulted in a decrease in APH of 2.2 mm (1 size decrease in 93% of patients). At 3° flexion and 3° ER, 86% had the same component size as at 0° flexion and 0° ER. Increasing ER at 3° flexion increased APH by 1.2 mm at 5° and 3.1 mm at 7° on average, relative to 3° ER. Increasing flexion from 3 to 6° extended this effect. CONCLUSIONS: Flexion decreases the APH when the ER is held constant. The ER of the femoral component increases the APH across all tested flexion angles, causing an increase in the ideal femoral component size to maintain PCO. With anatomic referencing, alterations in femoral component positioning and subsequent changes in component size can be accounted for.
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Artroplastia do Joelho , Fêmur , Articulação do Joelho , Prótese do Joelho , Tomografia Computadorizada por Raios X , Humanos , Artroplastia do Joelho/métodos , Fêmur/anatomia & histologia , Fêmur/cirurgia , Fêmur/diagnóstico por imagem , Articulação do Joelho/anatomia & histologia , Articulação do Joelho/cirurgia , Articulação do Joelho/diagnóstico por imagem , Articulação do Joelho/fisiologia , Amplitude de Movimento Articular , Feminino , Masculino , Idoso , Rotação , Pessoa de Meia-IdadeRESUMO
PURPOSE: Wear of polyethylene bearings represents a limiting factor in the long-term success of total elbow prostheses. Bearing stress is 1 factor contributing to accelerated wear. Physiological loading of total elbow prostheses and implant design influence upon bearing stresses have not been well described. This study evaluates bearing stresses in 3 commercially available implant designs under loads associated with daily living. METHODS: Motion tracking from a healthy volunteer helped establish a musculoskeletal model to simulate flexor and extensor muscle activation at 0°, 45°, and 90° of shoulder abduction with a 2.3-kg weight in hand-forces and moments were measured at the elbow. Resulting physiological joint reaction forces and moments were applied to finite element models of 3 total elbow bearing designs (Coonrad/Morrey, Nexel, and Discovery) to evaluate contact area and polyethylene stresses. RESULTS: Increasing shoulder abduction resulted in minimal changes to the elbow joint reaction force but greater joint moments. All implants showed greater peak stresses with increasing shoulder abduction-elbow varus. Discovery and Nexel achieved greater contact area (23% vs > 100%) and demonstrated up to 39% lower peak polyethylene stresses compared with the Coonrad/Morrey design. CONCLUSIONS: Shoulder abduction results in a varus moment at the elbow. Newer bearing designs (Nexel and Discovery) provide a combination of higher contact area, improved load sharing, reduced edge loading, and lower stresses through elbow range of motion when compared with a cylindrical hinge-bearing design (Coonrad/Morrey). CLINICAL RELEVANCE: Although the Coonrad/Morrey is a clinically successful prosthesis, our physiological loading model shows that Discovery and Nexel provide greater contact area, better load sharing and lower peak stresses. This may lead to a decrease in polyethylene wear rates and the eventual risks of osteolysis and aseptic loosening. Further studies are needed to determine how these findings translate clinically.
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Articulação do Cotovelo/fisiologia , Prótese de Cotovelo , Desenho de Prótese , Estresse Mecânico , Suporte de Carga/fisiologia , Artroplastia de Substituição do Cotovelo/instrumentação , Simulação por Computador , Análise de Elementos Finitos , Voluntários Saudáveis , Humanos , Masculino , Polietileno , Amplitude de Movimento Articular/fisiologia , Articulação do Ombro/fisiologiaRESUMO
Detailed knowledge of the loading conditions within the human body is essential for the development and optimization of treatments for disorders and injuries of the musculoskeletal system. While loads in the major joints of the lower limb have been the subject of extensive study, relatively little is known about the forces applied to the individual bones of the foot. The objective of this study was to use a detailed musculoskeletal model to compute the loads applied to the metatarsal bones during gait across several healthy subjects. Motion-captured gait trials and computed tomography (CT) foot scans from four healthy subjects were used as the inputs to inverse dynamic simulations that allowed the computation of loads at the metatarsal joints. Low loads in the metatarsophalangeal (MTP) joint were predicted before terminal stance, however, increased to an average peak of 1.9 times body weight (BW) before toe-off in the first metatarsal. At the first tarsometatarsal (TMT) joint, loads of up to 1.0 times BW were seen during the early part of stance, reflecting tension in the ligaments and muscles. These loads subsequently increased to an average peak of 3.0 times BW. Loads in the first ray were higher compared to rays 2-5. The joints were primarily loaded in the longitudinal direction of the bone.
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Marcha/fisiologia , Ossos do Metatarso/fisiologia , Músculos/fisiologia , Adulto , Fenômenos Biomecânicos , Humanos , Articulações/fisiologia , Masculino , Pessoa de Meia-Idade , Modelagem Computacional Específica para o Paciente , Suporte de CargaRESUMO
Effectively addressing population-level variability within orthopedic analyses requires robust data sets that span the target population and can be greatly facilitated by statistical methods for incorporating such data into functional biomechanical models. Data sets continue to be disseminated that include not just anatomical information but also key mechanical data including tissue or joint stiffness, gait patterns, and other inputs relevant to analysis of joint function across a range of anatomies and physiologies. Statistical modeling can be used to establish correlations between a variety of structural and functional biometrics rooted in these data and to quantify how these correlations change from health to disease and, finally, to joint reconstruction or other clinical intervention. Principal component analysis provides a basis for effectively and efficiently integrating variability in anatomy, tissue properties, joint kinetics, and kinematics into mechanistic models of joint function. With such models, bioengineers are able to study the effects of variability on biomechanical performance, not just on a patient-specific basis but in a way that may be predictive of a larger patient population. The goal of this paper is to demonstrate the broad use of statistical modeling within orthopedics and to discuss ways to continue to leverage these techniques to improve biomechanical understanding of orthopedic systems across populations.
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Articulações/fisiologia , Articulações/cirurgia , Modelos Biológicos , Modelos Estatísticos , Procedimentos Ortopédicos , Próteses e Implantes , Animais , Simulação por Computador , Humanos , Dinâmica Populacional , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
PURPOSE: Contemporary total knee arthroplasty femoral component designs offer various degrees of fit amongst the global population. The purpose of this study was to assess component fit of contemporary femoral component design families against multiple ethnicities. METHODS: Using a multi-ethnic dataset including Caucasian, Indian, and Korean subjects, this study investigated component fit in six contemporary femoral component design families (A: Persona™, B: NexGen (®), C: Sigma (®), D: GENESIS™ II, E: Triathlon (®), F: Vanguard (®)). Component overhang/underhang was measured between the resected distal femur and its corresponding component size and compared across design families and ethnicities. The severity of overhang/underhang and propensity of downsizing due to clinically significant overhang were quantified for the overall dataset and each ethnicity. RESULTS: In all the overhang cases, Designs A and B had significantly lower component overhang than the other designs (p < 0.02). In all the underhang cases, Designs C and E had significantly greater underhang than the other designs (p < 0.01). Component design influenced the occurrence (% bones) of component downsizing due to clinically significant overhang (>3 mm), with the highest incidence observed in Designs D (20.5%) and F (17.7%), and the lowest incidence observed in Designs A (0%) and B (0.4%). Variation in component fit was significantly impacted by designs (p < 0.01) but not ethnicities (n.s.). CONCLUSIONS: The inclusion of multiple ML/AP shape offerings and the increased number of available sizes in Design A, as compared to other contemporary femoral component design families studied, result in improved femoral component fit across various ethnicities.
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Artroplastia do Joelho/instrumentação , Fêmur/cirurgia , Articulação do Joelho/cirurgia , Prótese do Joelho , Desenho de Prótese , Adulto , Idoso , Povo Asiático , Pesos e Medidas Corporais , Bases de Dados Factuais , Feminino , Fêmur/anatomia & histologia , Humanos , Articulação do Joelho/anatomia & histologia , Masculino , Pessoa de Meia-Idade , População BrancaRESUMO
PURPOSE: The aim of this study was to comprehensively evaluate contemporary tibial component designs against global tibial anatomy. We hypothesized that anatomically designed tibial components offer increased morphological fit to the resected proximal tibia with increased alignment accuracy compared to symmetric and asymmetric designs. METHODS: Using a multi-ethnic bone dataset, six contemporary tibial component designs were investigated, including anatomic, asymmetric, and symmetric design types. Investigations included (1) measurement of component conformity to the resected tibia using a comprehensive set of size and shape metrics; (2) assessment of component coverage on the resected tibia while ensuring clinically acceptable levels of rotation and overhang; and (3) evaluation of the incidence and severity of component downsizing due to adherence to rotational alignment and overhang requirements, and the associated compromise in tibial coverage. Differences in coverage were statistically compared across designs and ethnicities, as well as between placements with or without enforcement of proper rotational alignment. RESULTS: Compared to non-anatomic designs investigated, the anatomic design exhibited better conformity to resected tibial morphology in size and shape, higher tibial coverage (92% compared to 85-87%), more cortical support (posteromedial region), lower incidence of downsizing (3% compared to 39-60%), and less compromise of tibial coverage (0.5% compared to 4-6%) when enforcing proper rotational alignment. CONCLUSIONS: The anatomic design demonstrated meaningful increase in tibial coverage with accurate rotational alignment compared to symmetric and asymmetric designs, suggesting its potential for less intra-operative compromises and improved performance. LEVEL OF EVIDENCE: III.
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Artroplastia do Joelho/instrumentação , Mau Alinhamento Ósseo/prevenção & controle , Prótese do Joelho , Desenho de Prótese , Tíbia/cirurgia , Adulto , Idoso , Idoso de 80 Anos ou mais , Mau Alinhamento Ósseo/cirurgia , Pré-Escolar , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Rotação , Tíbia/anatomia & histologiaRESUMO
BACKGROUND AND OBJECTIVE: The use of in silico clinical trials (ISCTs) to generate clinically-relevant data on new medical devices is an emerging area of regulatory research. Interest in ISCTs stems from recognized challenges in acquiring sufficient clinical data and the continued maturation of in silico technologies. There is currently no guidance in place for evaluating the credibility of ISCT applications. The objective of this work was to adapt an existing risk-based credibility framework specifically for ISCT applications, and demonstrate its utility on a contemporary case study. METHODS: Expanding on guidance currently in place for assessing the risk of traditional modeling applications of medical devices and demonstrating model credibility through benchtop validation activities, a framework is proposed to (1) evaluate the model risk for ISCT applications based on the independent factors of scope, coverage, and severity, and (2) assess the credibility of clinical validation activities based on consideration of the clinical comparator, the validation model, the agreement between the two, and the applicability of the clinical validation activities to the ISCT application. RESULTS: The resulting framework spans across the range of ISCT applications that may be envisioned, as well as the variety of clinical datasets that can be used to demonstrate model credibility. Credibility factors reflect the expected clinical variability in the validation comparator and validation model, the statistical power of the comparator, the rigor of agreement between the comparator and model in terms of both inputs and outputs, and the overall similarity of the device in the validation activities to the device within the intended ISCT. When applied to a high-risk case study, the framework reveals that planned clinical validation activities require additional rigor in order to achieve the credibility targets, enabling an assessment of the validation effort relative to the potential benefit prior to investing in the validation studies. DISCUSSION: An objective and risk-based framework for establishing credibility requirements for ISCT applications is a critical step in advancing ISCT from theory to practice. The proposed framework enforces that appropriate validation of ISCT applications requires evidence that the intended clinical environment is accurately represented. The framework will contribute to reducing uncertainty amongst technical, clinical, and regulatory constituents on ISCT applications, and promote rational adoption.
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Stakeholders in the modeling and simulation (M&S) community organized a workshop at the 2019 Annual Meeting of the Orthopaedic Research Society (ORS) entitled "Reproducibility in Modeling and Simulation of the Knee: Academic, Industry, and Regulatory Perspectives." The goal was to discuss efforts among these stakeholders to address irreproducibility in M&S focusing on the knee joint. An academic representative from a leading orthopedic hospital in the United States described a multi-institutional, open effort funded by the National Institutes of Health to assess model reproducibility in computational knee biomechanics. A regulatory representative from the United States Food and Drug Administration indicated the necessity of standards for reproducibility to increase utility of M&S in the regulatory setting. An industry representative from a major orthopedic implant company emphasized improving reproducibility by addressing indeterminacy in personalized modeling through sensitivity analyses, thereby enhancing preclinical evaluation of joint replacement technology. Thought leaders in the M&S community stressed the importance of data sharing to minimize duplication of efforts. A survey comprised 103 attendees revealed strong support for the workshop and for increasing emphasis on computational modeling at future ORS meetings. Nearly all survey respondents (97%) considered reproducibility to be an important issue. Almost half of respondents (45%) tried and failed to reproduce the work of others. Two-thirds of respondents (67%) declared that individual laboratories are most responsible for ensuring reproducible research whereas 44% thought that journals are most responsible. Thought leaders and survey respondents emphasized that computational models must be reproducible and credible to advance knee M&S.
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Articulação do Joelho , Estados Unidos , Reprodutibilidade dos Testes , Simulação por Computador , Fenômenos BiomecânicosRESUMO
Total hip arthroplasty (THA) failure and the need for revision surgery can result from fretting-corrosion damage of the head-neck modular taper junctions. Prior work has shown that implant geometry, such as microgrooves, influences damage on retrieved implants. Microgroove deformation within the modular taper junction occurs when the female head taper meets the male stem taper during THA surgical procedure. The objective of this work was to validate microgroove deformation after head-neck THA assembly as calculated by finite element analysis (FEA). Four 28 mm CoCrMo head tapers and four Ti6Al4V stem tapers were scanned via white light interferometry. Heads were assembled onto stem tapers until 6kN reaction force was achieved, followed by head removal using a cut-off machine. The stem tapers were then rescanned and analyzed. Simultaneously, a 2D axisymmetric FEA model was developed and assembled per implant geometries and experimental data. For experiments and FEA, the mean change in microgroove height was 1.23 µm and 1.40 µm, respectively. The largest microgroove height change occurred on the proximal stem taper due to the conical angles of the head and stem tapers. FEA showed that the head-stem assembly induced high stresses and microgroove peaks flattening. 76-89% and 91-100% of the microgrooves in the experiments and FEA, respectively, showed height changes along the contact length of the stem taper. A validated FEA model of THA head-neck modular junction contact mechanics is essential to identifying implant geometries and surface topographies that can potentially minimize the risk of fretting and fretting-corrosion at modular junctions.
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Artroplastia de Quadril , Prótese de Quadril , Corrosão , Feminino , Humanos , Masculino , Desenho de Prótese , Falha de PróteseRESUMO
The orthopedic device industry relies heavily on clinical evaluation to confirm the safety, performance, and clinical benefits of its implants. Limited sample size often prevents these studies from capturing the full spectrum of patient variability and real-life implant use. The device industry is accustomed to simulating benchtop tests with numerical methods and recent developments now enable virtual "in silico clinical trials" (ISCT). In this article, we describe how the advancement of computer modeling has naturally led to ISCT; outline the potential benefits of ISCT to patients, healthcare systems, manufacturers, and regulators; and identify how hurdles associated with ISCT may be overcome. In particular, we highlight a process for defining the relevant patient risks to address with ISCT, the utility of a versatile software pipeline, the necessity to ensure model credibility, and the goal of limiting regulatory uncertainty. By complementing-not replacing-traditional clinical trials with computational evidence, ISCT provides a viable technical and regulatory strategy for characterizing the full spectrum of patients, clinical conditions, and configurations that are embodied in contemporary orthopedic implant systems.
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Simulação por Computador , Análise de Falha de Equipamento , Equipamentos Ortopédicos/normas , Europa (Continente) , Humanos , Indústrias , SoftwareRESUMO
A series of pressurization and tensile loading experiments on mouse carotid arteries is performed with deformation measurements acquired during each experiment using three-dimensional digital image correlation. Using a combination of finite element analysis and a microstructure-based constitutive model to describe the response of biological tissue, the measured surface strains during pressurization, and the average axial strains during tensile loading, an inverse procedure is used to identify the optimal constitutive parameters for the mouse carotid artery. The results demonstrate that surface strain measurements can be combined with computational methods to identify material properties in a vascular tissue. Additional computational studies using the optimal material parameters for the mouse carotid artery are discussed with emphasis on the significance of the qualitative trends observed.
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Artérias Carótidas/fisiologia , Animais , Fenômenos Biomecânicos , Engenharia Biomédica/instrumentação , Artérias Carótidas/anatomia & histologia , Simulação por Computador , Análise de Elementos Finitos , Imageamento Tridimensional , Técnicas In Vitro , Camundongos , Modelos Cardiovasculares , Pressão , Estresse Mecânico , Resistência à TraçãoRESUMO
Revision rates in total ankle arthroplasty (TAA) are nearly double compared with hip or knee arthroplasty procedures. Contact mechanics for metal-polyethylene articulation in TAA is critical due to the reduced size of the implant and higher expected load, compared with a hip or knee joint. This study was focused on developing a validated computational model to predict contact area in a polyethylene tibial bearing articulating with a metallic talar component in a bicondylar TAA design. Contact area was evaluated at five different flexion angles in an experimental test and in a computational model, per ASTM F2665. The overall contact area values predicted in the computational model matched closely (within 8%) with that measured in the comparator; well within the range reported in the literature. The credibility of the model to sufficiently predict the outputs relative to the experimental data was discussed using the guidelines provided by the recently published ASME V&V 40-2018 standard. Various sensitivities associated with both the model and the comparator, were explored. It was concluded that the validated modeling approach presented in this study demonstrated sufficient accuracy to support the use of modeling for evaluation of contact area of TAA designs. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:1063-1069, 2020.
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Articulação do Tornozelo/fisiologia , Artroplastia de Substituição do Tornozelo , Modelos Biológicos , HumanosRESUMO
Determination of material parameters for soft tissue frequently involves regression of material parameters for nonlinear, anisotropic constitutive models against experimental data from heterogeneous tests. Here, parameter estimation based on membrane inflation is considered. A four parameter nonlinear, anisotropic hyperelastic strain energy function was used to model the material, in which the parameters are cast in terms of key response features. The experiment was simulated using finite element (FE) analysis in order to predict the experimental measurements of pressure versus profile strain. Material parameter regression was automated using inverse FE analysis; parameter values were updated by use of both local and global techniques, and the ability of these techniques to efficiently converge to a best case was examined. This approach provides a framework in which additional experimental data, including surface strain measurements or local structural information, may be incorporated in order to quantify heterogeneous nonlinear material properties.
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Simulação por Computador , Elasticidade , Análise de Elementos Finitos , Membranas , Modelos Biológicos , Dinâmica não Linear , Anisotropia , Módulo de ElasticidadeRESUMO
BACKGROUND: Highly crosslinked polyethylene (HXLPE) was developed for its superior wear properties in comparison to conventional polyethylene (CPE). Concern over fatigue resistance has prevented widespread adoption of HXLPE for use in total ankle arthroplasty (TAA). The aim of this study was to determine whether HXLPE has sufficient fatigue strength for total ankle arthroplasty under simulated physiologically relevant motion profiles and loading in the ankle. METHODS: Physiologic load and motion profiles representative of walking gait were incorporated into a computational model of a semiconstrained, fixed-bearing TAA to determine the loading state with highest stresses in the HXLPE bearing. Subsequent fatigue testing to 10 million cycles (Mc) at 5600 N was performed to assess bearing strength. RESULTS: Peak stresses in the bearing were predicted at peak axial load and peak dorsiflexion during gait, occurring near heel off. All samples withstood 10 Mc of fatigue loading at that orientation without polyethylene bearing fracture. CONCLUSION: HXLPE had sufficient fatigue strength to withstand 10 Mc of loading at more than 5 times body weight at the point of peak stresses during simulated gait in total ankle arthroplasty. CLINICAL RELEVANCE: HXLPE may be mechanically strong enough to withstand the in vivo demands of the ankle. Improvements in wear afforded by HXLPE can be obtained without compromising sufficient polyethylene strength properties in total ankle arthroplasty.
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Artroplastia de Substituição do Tornozelo/instrumentação , Prótese Articular , Teste de Materiais , Polietilenos , Estresse Mecânico , Humanos , Desenho de PróteseRESUMO
Reverse total shoulder arthroplasty (rTSA) is commonly used in the shoulder replacement surgeries for the relief of pain and to restore function, in patients with grossly deficient rotator cuff. Primary instability due to glenoid loosening is one of the critical complications of rTSA; the implants are designed and implanted such that the motion between the glenoid baseplate and underlying bone is minimized to facilitate adequate primary fixation. Finite element analysis (FEA) is commonly used to simulate the test setup per ASTM F2028-14 for comparing micromotion between designs or configurations to study the pre-clinical indications for stability. The FEA results can be influenced by the underlying modeling assumptions. It is a common practice to simplify the screw shafts by modeling them as cylinders and modeling the screw-bone interface using bonded contact, to evaluate micromotion in rTSA components. The goal of this study was to evaluate the effect of three different assumptions for modeling the screw-bone interface on micromotion predictions. The credibility of these modeling assumptions was examined by comparing the micromotion rank order predicted among three different modular configurations with similar information from the literature. Eight configurations were modeled using different number of screws, glenosphere offset, and baseplate sizes. An axial compression and shear load was applied through the glenosphere and micromotion at the baseplate-bone interface was measured. Three modeling assumptions pertaining to modeling of the screw-bone interface were used and micromotion results were compared to study the effect of number of peripheral screws, eccentricities, and baseplate diameter. The relative comparison of micromotion between configurations using two versus four peripheral screws remained unchanged irrespective of the three modeling assumptions. However, the relative comparison between two inferior offsets and baseplate sizes changed depending on the modeling assumptions used for the screw-bone interface. The finding from this study challenges the generally believed hypothesis that FEA models can be used to make relative comparison of micromotion in rTSA designs as long as the same modeling assumptions are used across all models. The comparisons with previously published work matched the finding from this study in some cases, whereas the comparison was contradicting in other cases. It is essential to validate the computer modeling approach with an experiment using similar designs and methods to increase the confidence in the predictions to make design decisions.
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It has been observed in load controlled laboratory tests of myocardium and skin that the tissues can exhibit a decrease in nonlinear stiffness with an increase in loading rate: the faster a test is performed, the more compliant is the preconditioned material behavior. This response seems to conflict with what is generally expected of soft tissues based on stretch or strain controlled tests, in which an increased rate of deformation results in a stiffer material response. It is hypothesized that this anomalous behavior has not been observed previously due to the small number of cyclic load controlled mechanical characterization tests that are geared specifically towards viscoelastic tissue response. The goal of this paper is to examine the preconditioned response of soft tissue to load controlled deformation using nonlinear viscoelastic material models including quasi-linear viscoelasticity, and to determine under what conditions this anomalous behavior becomes apparent. Results from this study suggest that this behavior is a true phenomenon unique to load controlled deformations that results from the interplay of nonlinear effects and creep behavior. These results call for increased attention to experimental parameters when testing and modeling nonlinear viscoelastic material behavior.
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Modelos Biológicos , Miocárdio , Dinâmica não Linear , Pele , Animais , Fenômenos Biomecânicos , Simulação por Computador , Elasticidade , Estresse Mecânico , Suínos , ViscosidadeRESUMO
BACKGROUND: Aseptic component loosening is a leading cause of revision for total ankle replacement. Different operative approaches for resecting the tibia and talus impact the bony support for the prostheses due to variations in both bone density and resection area, and may therefore impact loosening performance. METHODS: Computed tomography data from 116 subjects were obtained, and solid models of the talus and tibia were generated. Bone density, resection area, and bony support were measured on a series of flat resections for each subject, at multiple resection depths. Similar measurements were performed using a series of subject-specific, anatomic radius-based resections ("round resections") at multiple depths. Results were compared to assess the impact of both resection type (flat vs round) and resection depth (6-16 mm for the tibia, 2-6 mm for the talus) on bony support. RESULTS: Statistically significant decreases in bony support for both the talus and the tibia were obtained for flat resections as compared to round resections. A decrease of 8% to 19% for the tibia was seen for all resection depths; a decrease of 8% to 46% for the talus was seen, with greater decreases seen for shallower flat-cut resections. CONCLUSION: Bony support in total ankle arthroplasty may be decreased using flat resections compared to round resections at comparable resection depths. Estimated differences are resection-level dependent and different for the distal tibia vs the proximal talus. CLINICAL RELEVANCE: Biomechanical characteristics of total ankle replacement impacted by bony support of the prostheses, including implant stability and resistance to subsidence, may be improved with round resections as compared to flat-cut resections.
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Articulação do Tornozelo/cirurgia , Artroplastia de Substituição do Tornozelo , Tálus/cirurgia , Tíbia/cirurgia , Tomografia Computadorizada por Raios X/métodos , Artroplastia de Substituição do Tornozelo/métodos , Humanos , Tomografia Computadorizada por Raios X/mortalidadeRESUMO
BACKGROUND: Wear debris of polyethylene within joint replacement systems can result in clinical complications including osteolysis and component loosening. Highly crosslinked polyethylene (HXPE) was introduced to improve these outcomes, and has been shown to result in improved wear performance in several joint replacement systems. However, bearing couples within total ankle replacement (TAR) systems have historically used conventional polyethylene (CPE) articulating on metal. The extent to which HXPE would result in a reduction of polyethylene wear compared to CPE in the ankle has not been studied. The hypothesis motivating this study was that use of HXPE within TAR will result in significantly lower wear rate than CPE. METHODS: HXPE and CPE inserts within a semiconstrained, bicondylar TAR system were manufactured for this study. Samples were subjected to 5.0 million cycles of wear on an in vitro wear simulator. Testing was performed within a physiological environment, using kinematic and kinetic loading profiles characteristic of walking gait. Samples were weighed at regular intervals to determine gravimetric mass loss, and the morphology of wear particles was analyzed. RESULTS: The wear rates for CPE and HXPE samples were 7.4 ± 1.3 and 1.9 ± 0.3 mg/Mc (mean ± SD), respectively. HXPE samples exhibited a significant (P < .01) wear rate reduction of 74% when compared with the CPE. Debris morphology trends between HXPE and CPE were consistent with what has been observed in other joint systems. CONCLUSION: Use of HXPE significantly reduces wear of TAR as compared to CPE, based on in vitro wear testing. CLINICAL RELEVANCE: Highly crosslinked polyethylene may reduce clinical complications of total ankle replacement that are linked to polyethylene wear.
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Artroplastia de Substituição do Tornozelo/instrumentação , Prótese Articular , Teste de Materiais/métodos , Polietilenos , Desenho de Prótese/métodos , Artroplastia de Substituição do Tornozelo/efeitos adversos , Artroplastia de Substituição do Tornozelo/métodos , Análise de Falha de Equipamento/métodos , Humanos , Falha de Prótese , Medição de Risco , Sensibilidade e Especificidade , Estresse Mecânico , Suporte de CargaRESUMO
The mechanical behavior of soft tissue demonstrates a number of complex features including nonlinearity, anisotropy, viscoelasticity, and growth. Characteristic features of the time-dependent and anisotropic behavior are related to the properties of various components of the tissue such as fibrous collagen and elastin networks, large proteins and sugars attached to these networks, and interstitial fluid. Attempts to model the elastic behavior of these tissues based on assumptions about the behavior of the underlying constituents have been reasonably successful, but the essential addition of viscoelasticity to these models has been met with varying success. Here, a new rheological network model is proposed using, as its basis, an orthotropic hyperelastic constitutive model for fibrous tissue and a viscoelastic reptation model for soft materials. The resulting model has been incorporated into numerical and computational models, and is shown to capture the mechanical behavior of soft tissue in various modes of deformation including uniaxial and biaxial tension and simple shear.
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Tecido Conjuntivo/fisiologia , Modelos Biológicos , Reologia , Animais , Anisotropia , Elasticidade , Análise de Elementos Finitos , Coelhos , Estresse Mecânico , ViscosidadeRESUMO
Better understanding of proximal tibia morphology can lead to improvements in total knee arthroplasty (TKA) through development of tibial tray families that adequately reflect the diversity of global anatomy using an appropriate number of components. We quantified variations in proximal tibial morphology at the TKA level and characterized differences attributable to gender and ethnicity. Virtual TKA was performed on digital models of 347 tibiae, spanning both genders and multiple ethnicities. The geometry of the resection profile was quantified using both a comprehensive set of morphological measurements (reflecting size and shape) and principal component analysis (PCA). The dominant statistical modes of variation were associated primarily with size (plateau dimensions, radii, and area), with lesser contributions associated with asymmetry and aspect ratios. Medial and lateral AP dimensions were strongly correlated with plateau ML width, with minimal differences in correlations due to gender or ethnicity. In conclusion, clinically relevant differences in proximal tibia morphology at the level of TKA resections across genders and multiple ethnicities can be attributed largely to variations in overall proximal tibial size, not gender- or ethnic-specific shape variations.