Computational model-based probabilistic analysis of in vivo material properties for ligament stiffness using the laxity test and computed tomography

Influence of the Initial Guess on the Estimation of Knee Ligament Parameters via Optimization Procedures

Optimization procedures provide ligament parameters by minimizing the difference between experimental measurements and computational simulations. Literature values are used as initial guesses of ligament parameters for these optimization procedures. However, it remains unknown how these values affect the estimation of ligament parameters. This study evaluates the effects of the initial guess on estimations of ligament parameters. A synthetic data set was generated using a subject-specific knee computational model, reference ligament parameters and simulated laxity tests. Subsequently, ligament parameters were estimated using an optimization routine and four different initial guesses. The distance of these initial guesses from their true values ranged from 0 to 3.5 kN and from 0 to 3.6% for the stiffness and reference strains, respectively. The optimized ligament parameters had an average absolute mean error ranging from 0.15 (0.09) kN and 0.08 (0.04)% to 3.67 (2.46) kN and 1.25 (0.76)%, while the kinematic error remained below 1 mm and 1.2° for all conditions. Our results showed that the estimations of the ligament parameters worsened as the initial guesses moved farther away from their true values. Moreover, the optimization procedure resulted in suboptimal ligament parameters that provided similar behavior to the true laxity behavior, which is an alarming finding that should be further investigated.

The effect of trapeziometacarpal joint passive stiffness on mechanical loadings of cartilages

Hypermobility of the trapeziometacarpal joint is commonly considered to be a potential risk factor for osteoarthritis. Nevertheless, the results remain controversial due to a lack of quantitative validation. The objective of this study was to evaluate the effect of joint laxity on the mechanical loadings of cartilage. A patient-specific finite element model of trapeziometacarpal joint passive stiffness was developed. The joint passive stiffness was modeled by creating linear springs all around the joint. The linear spring stiffness was determined by using an optimization process to fit force-displacement data measured during laxity tests performed on eight healthy volunteers. The estimated passive stiffness parameters were then included in a full thumb finite element simulation of a pinch grip task driven by muscle forces to evaluate the effect on trapeziometacarpal loading. The correlation between stiffness and the loading of cartilage in terms of joint contact pressure and maximum shear strain was analyzed. A significant negative correlation was found between the trapeziometacarpal joint passive stiffness and the contact pressure on trapezium cartilage during the simulated pinch grip task. These results therefore suggest that the hypermobility of the trapeziometacarpal joint could affect the contact pressure on trapezium cartilage and support the existence of an increased risk associated with hypermobility.

Knee instability caused by altered graft mechanical properties after anterior cruciate ligament reconstruction: the early onset of osteoarthritis?

Anterior cruciate ligament (ACL) rupture is a very common knee joint injury. Torn ACLs are currently reconstructed using tendon autografts. However, half of the patients develop osteoarthritis (OA) within 10 to 14 years postoperatively. Proposedly, this is caused by altered knee kine(ma)tics originating from changes in graft mechanical properties during the in vivo remodeling response. Therefore, the main aim was to use subject-specific finite element knee models and investigate the influence of decreasing graft stiffness and/or increasing graft laxity on knee kine(ma)tics and cartilage loading. In this research, 4 subject-specific knee geometries were used, and the material properties of the ACL were altered to either match currently used grafts or mimic in vivo graft remodeling, i.e., decreasing graft stiffness and/or increasing graft laxity. The results confirm that the in vivo graft remodeling process increases the knee range of motion, up to >300 percent, and relocates the cartilage contact pressures, up to 4.3 mm. The effect of remodeling-induced graft mechanical properties on knee stability exceeded that of graft mechanical properties at the time of surgery. This indicates that altered mechanical properties of ACL grafts, caused by in vivo remodeling, can initiate the early onset of osteoarthritis, as observed in many patients clinically.

Evaluation of anterior cruciate ligament surgical reconstruction through finite element analysis

Anterior cruciate ligament (ACL) tear is one of the most common knee injuries. The ACL reconstruction surgery aims to restore healthy knee function by replacing the injured ligament with a graft. Proper selection of the optimal surgery parameters is a complex task. To this end, we developed an automated modeling framework that accepts subject-specific geometries and produces finite element knee models incorporating different surgical techniques. Initially, we developed a reference model of the intact knee, validated with data provided by the Open Knee(s) project. This helped us evaluate the effectiveness of estimating ligament stiffness directly from MRI. Next, we performed a plethora of “what-if” simulations, comparing responses with the reference model. We found that (a) increasing graft pretension and radius reduces relative knee displacement, (b) the correlation of graft radius and tension should not be neglected, (c) graft fixation angle of 20\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{\circ }$$\end{document}∘ can reduce knee laxity, and (d) single-versus double-bundle techniques demonstrate comparable performance in restraining knee translation. In most cases, these findings confirm reported values from comparative clinical studies. The numerical models are made publicly available, allowing for experimental reuse and lowering the barriers for meta-studies. The modeling approach proposed here can complement orthopedic surgeons in their decision-making.

Finite element analysis of femoral component sagittal alignment in mobile-bearing total knee arthroplasty

BACKGROUND: Recently, there has been an increasing interest in mobile-bearing total knee arthroplasty (TKA). However, changes in biomechanics for femoral component alignment in mobile-bearing TKA have not been explored in depth. OBJECTIVE: This study aims to evaluate the biomechanical effect of sagittal alignment of the femoral component in mobile-bearing TKA. METHODS: We developed femoral sagittal alignment models with −3°, 0°, 3°, 5°, and 7° flexion. We also examine the kinematics of the tibiofemoral (TF) joint, contact point on the TF joint, contact stress on the patellofemoral (PF) joint, collateral ligament force, and quadriceps force using a validated computational model under a deep-knee-bend condition. RESULTS: Posterior kinematics of the TF joint increases as the femoral component flexes. The contact stress on the PF joint, collateral ligament force, and the quadriceps force decreases as the femoral component flexes. CONCLUSIONS: Our results show that a slight, approximately 0°∼3°, flexion of the implantation could be an effective substitute technique. However, excessive flexion should be avoided because of the potential loosening of the TF joint.

Developing a Technique for the Imaging-Based Measurement of ACL Elongation: A Proof of Principle

Towards the goal of obtaining non-invasive biomarkers reflecting the anterior cruciate ligament’s (ACL) loading capacity, this project aimed to develop a magnetic resonance imaging (MRI)-based method facilitating the measurement of ACL elongations during the execution of knee stress tests. An MRI-compatible, computer-controlled, and pneumatically driven knee loading device was designed to perform Lachman-like tests and induce ACL strain. A human cadaveric leg was used for test purposes. During the execution of the stress tests, a triggered real-time cine MRI sequence with a temporal resolution of 10 Hz was acquired in a parasagittal plane to capture the resultant ACL elongations. To test the accuracy of these measurements, the results were compared to in situ data of ACL elongation that were acquired by measuring the length changes of a surgical wire directly sutured to the ACL’s anteromedial bundle. The MRI-based ACL elongations ranged between 0.7 and 1.7 mm and agreed very well with in situ data (root mean square errors, RMSEs ≤ 0.25 mm), although peak elongation rates were underestimated by the MRI (RMSEs 0.19–0.36 mm/s). The high accuracy of elongation measurements underlines the potential of the technique to yield an imaging-based biomarker of the ACL’s loading capacity.

Influence of Variation in Sagittal Placement of the Femoral Component after Cruciate-Retaining Total Knee Arthroplasty

Prosthetic alignment is an important factor for long-term survival in cruciate-retaining (CR) total knee arthroplasty (TKA). The purpose of this study is to investigate the influence of sagittal placement of the femoral component on tibiofemoral (TF) kinematics and kinetics in CR-TKA. Five sagittal placements of femoral component models with -3, 0, 3, 5, and 7 degrees of flexion are developed. The TF joint kinematics, quadriceps force, patellofemoral contact force, and posterior cruciate ligament force are evaluated using the models under deep knee-bend loading. The kinematics of posterior TF translation is found to occur with the increase in femoral-component flexion. The quadriceps force and patellofemoral contact force decrease with the femoral-component flexion increase. In addition, extension of the femoral component increases with the increase in posterior cruciate ligament force. The flexed femoral component in CR-TKA provides a positive biomechanical effect compared with a neutral position. Slight flexion could be an effective alternative technique to enable positive biomechanical effects with TKA prostheses.

Effects of contact stress on patellarfemoral joint and quadriceps force in fixed and mobile-bearing medial unicompartmental knee arthroplasty

Background

Unicompartmental knee arthroplasty (UKA) is an effective treatment for end-stage, symptomatic unicompartmental osteoarthritis of the knee joint. However, patellofemoral joint degeneration is a contraindication to medial UKA. Therefore, the objective of this study was to evaluate the biomechanical effect of medial UKA using fixed-bearing (FB) and mobile-bearing (MB) design prostheses on the patellofemoral joint.

Methods

A three-dimensional finite-element model of a normal knee joint was developed using medical image data. We performed statistical analysis for each model. The differences in contact stress on the patellofemoral joint and the quadriceps force between the FB and MB designs were evaluated under a deep-knee-bend condition.

Results

At an early flexion angle, the results of contact stress showed no significant difference between the FB and MB medial UKA models compared with the intact model. However, at high flexion angles, we observed a significant increase in contact stress with the FB models compared with the intact model. On the contrary, in the case of the MB models, we found no statistically significant increment compared with the intact model. A larger quadriceps force was needed to produce an identical flexion angle for both the FB and MB UKA designs than for the intact model. At high flexion angles, a significant increase quadriceps force whit the FB model compared with the intact model.

Conclusions

Our results indicate that with medial UKA, the contact stress increased and greater quadriceps force was applied to the patellofemoral joint. However, performing UKA on a patellofemoral joint with osteoarthritis should not be difficult, unless anterior knee pain is present, because the increase in contact stress is negligible.

Effects of the material properties of a focal knee articular prosthetic on the human knee joint using computational simulation

BACKGROUND

Localized cartilage defects are related to joint pain and reduced function to the development of osteoarthritis. The mechanical properties of the implant for treatment do influence its longevity. Therefore, we aimed to evaluate the effect of material properties' variations of anatomically shaped focal knee implants in the knee joint using numerical finite element analysis.

METHODS

Computational simulations were performed for different cases including an intact knee, a knee with a focal cartilage defect, and a knee fitted with a focal articular prosthetic having three distinct mechanical properties: cobalt-chromium, pyrolytic carbon, and polyethylene. Femoral cartilage, tibial cartilage, and menisci contact pressures were evaluated under the load. In addition, bone stress was evaluated to investigate the stress shielding effect.

RESULTS

Compared with the intact model, the contact stress of the focal implant model was increased; on the femoral lateral cartilage by 14%, on medial and lateral tibial cartilages by nine percent and 10%, on medial and lateral menisci by 23% and 20%. In contrast, the focal implant model had no effect on the menisci but contact stress on the tibial cartilage increased compared with the intact model. The BioPoly model showed the lowest contact stress on femoral and tibial cartilages. Additionally, the cobalt-chromium model showed the lowest bone stress that improved the load-sharing effect.

CONCLUSIONS

The results suggested that implant material properties are an important parameter in the design of a focal implant. The polyethylene model potentially restored the intact knee contact mechanics and it reduced the risk of physiological damage to the articular cartilage.

Biomechanical effect of tibial slope on the stability of medial unicompartmental knee arthroplasty in posterior cruciate ligament-deficient knees

Aims

Unicompartmental knee arthroplasty (UKA) has become a popular method of treating knee localized osteoarthritis (OA). Additionally, the posterior cruciate ligament (PCL) is essential to maintaining the physiological kinematics and functions of the knee joint. Considering these factors, the purpose of this study was to investigate the biomechanical effects on PCL-deficient knees in medial UKA.

Methods

Computational simulations of five subject-specific models were performed for intact and PCL-deficient UKA with tibial slopes. Anteroposterior (AP) kinematics and contact stresses of the patellofemoral (PF) joint and the articular cartilage were evaluated under the deep-knee-bend condition.

Results

As compared to intact UKA, there was no significant difference in AP translation in PCL-deficient UKA with a low flexion angle, but AP translation significantly increased in the PCL-deficient UKA with high flexion angles. Additionally, the increased AP translation became decreased as the posterior tibial slope increased. The contact stress in the PF joint and the articular cartilage significantly increased in the PCL-deficient UKA, as compared to the intact UKA. Additionally, the increased posterior tibial slope resulted in a significant decrease in the contact stress on PF joint but significantly increased the contact stresses on the articular cartilage.

Conclusion

Our results showed that the posterior stability for low flexion activities in PCL-deficient UKA remained unaffected; however, the posterior stability for high flexion activities was affected. This indicates that a functional PCL is required to ensure normal stability in UKA. Additionally, posterior stability and PF joint may reduce the overall risk of progressive OA by increasing the posterior tibial slope. However, the excessive posterior tibial slope must be avoided.

Cite this article: Bone Joint Res 2020;9(9):593–600.

Medial unicompartmental knee arthroplasty to patients with a ligamentous deficiency can cause biomechanically poor outcomes

PURPOSE

The aims of this study were to investigate the biomechanical effects of the deficiency of the collateral ligament and cruciate ligament in medial unicompartmental knee arthroplasty in normal and varus knee patients using computational simulation.

METHODS

Validated finite-element (FE) models for conditions of various cruciate and collateral ligament deficiencies were developed to evaluate the biomechanical effects of ligamentous deficiency in UKA for normal and varus knee patients. Contact stresses on the polyethylene (PE) insert, contact stresses on the lateral articular cartilage, and quadriceps force were analyzed under gait-loading conditions.

RESULTS

Contact stresses on the PE insert and lateral articular cartilage as well as quadriceps force in a normal knee UKA FE model were increased in the order of anterior cruciate ligament (ACL) deficiency, medial collateral ligament (MCL) deficiency, lateral collateral ligament (LCL) deficiency, and posterior cruciate ligament (PCL) deficiency in the stance phase of gait cycle, as compared with those in the model without ligamentous deficiency. In two or more multiple ligamentous deficiencies, contact stresses on the PE insert and articular lateral cartilage and quadriceps force were significantly increased versus in the case of single-ligament deficiency.

CONCLUSION

Poor outcomes of medial UKA in patients with ACL or MCL deficiency can be predicted. Care should be taken to extend the indications when performing medial UKA in patients with ligamentous deficiency, especially when varus knee with ACL or MCL deficiency is present.

Patellofemoral Mechanics: a Review of Pathomechanics and Research Approaches

PURPOSE OF REVIEW

The patellofemoral joint is a complicated articulation of the patella and femur that is prone to pathologies. The purpose of this review is to report on the current methods of investigating patellofemoral mechanics, factors that affect joint function, and future directions in patellofemoral joint research with emerging technologies and techniques.

RECENT FINDINGS

While previous hypotheses have suggested that the patella is only a moment arm extender, recent literature has suggested that the patella influences the control of knee moments and forces acting on the tibia as well as contributes to various aspects of patellar function with minimal neural input. With advancements in simulating a six-degrees-of-freedom patellofemoral joint, we have gained a better understanding of patella motion and have shown that geometry and muscle activations impact patella mechanics. Research into influences on patella mechanics from other joints such as the hip and foot has become more prevalent. In this review, we report current in vivo, in vitro, and in silico approaches to studying the patellofemoral joint. Kinematic and anatomical factors that affect patellofemoral joint function such as patella alta and tilt or bone morphology and ligaments are discussed. Moving forward, we suggest that advanced in vivo dynamic imaging methods coupled to musculoskeletal simulation will provide further understanding of patellofemoral pathomechanics and allow engineers and clinicians to design interventions to mitigate or prevent patellofemoral pathologies.

Anatomy-mimetic design preserves natural kinematics of knee joint in patient-specific mobile-bearing unicompartmental knee arthroplasty

PURPOSE

This study aims to evaluate whether different tibial-femoral conformities for patient-specific mobile-bearing unicompartmental knee arthroplasties (UKAs) preserve natural knee kinematics, using computational simulations.

METHODS

Different designs for patient-specific mobile-bearing UKAs were evaluated using finite element analysis. Three designs for the identical femoral component were considered: flat (non-conforming design), anatomy-mimetic, and conforming for the tibial insert.

RESULTS

The conforming design for the patient-specific mobile-bearing UKAs exhibited a 1.2 mm and 0.7° decrease in the translation and rotation, respectively, in the swing phase compared with those of the natural knee. In addition, the femoral rollback and internal rotation were 2.6 mm and 1.2° lower, respectively, than those of the natural knee, for the conforming design under the deep-knee-bend condition. The flat design for the patient-specific mobile-bearing UKAs exhibited a 2.2 mm and 1.4° increase in the femoral rollback and rotation compared with the natural knee under the deep-knee-bend condition. The anatomy-mimetic patient-specific mobile-bearing UKAs best preserved the natural knee kinematics under the gait and deep-knee-bend loading conditions.

CONCLUSIONS

The kinematics of the loading conditions in patient-specific mobile-bearing UKAs was determined to closely resemble those of a native knee. In additional, by replacing the anatomy-mimetic design with a mobile-bearing, natural knee kinematics during gait and deep-knee-bend motions is preserved. These results confirm the importance of tibiofemoral conformity in preserving native knee kinematics in patient-specific mobile-bearing UKA.

Biomechanical effect of a lateral hinge fracture for a medial opening wedge high tibial osteotomy: finite element study

BACKGROUND

This study aimed to investigate the biomechanical effect on the Takeuchi classification of lateral hinge fracture (LHF) after an opening wedge high tibial osteotomy (HTO).

METHODS

We performed an FE simulation for type I, type II, and type III in accordance with the Takeuchi classification. The stresses on the bone and plate, wedge micromotion, and forces on ligaments were evaluated to investigate stress-shielding effect, plate stability, and biomechanical change, respectively, in three different types of LHF HTO and with the HTO without LHF model (non-LHF) models.

RESULTS

The greatest stress-shielding effect and wedge micromotion were observed in type II LHF (distal portion fracture). The type II and type III (lateral plateau fracture) models exhibited a reduction in ACL force and an increase in PCL force compared with the HTO without LHF model. However, the type I (osteotomy line fracture) and HTO without LHF models did not exhibit a significant biomechanical effect. This study demonstrates that Takeuchi type II and type III LHF models provide unstable structures compared with the type I and HTO without LHF models.

CONCLUSIONS

HTO should be performed while considering a medial opening wedge HTO to avoid a type II and type III LHF as a potential complication.

EMG-Assisted Muscle Force Driven Finite Element Model of the Knee Joint with Fibril-Reinforced Poroelastic Cartilages and Menisci

Abnormal mechanical loading is essential in the onset and progression of knee osteoarthritis. Combined musculoskeletal (MS) and finite element (FE) modeling is a typical method to estimate load distribution and tissue responses in the knee joint. However, earlier combined models mostly utilize static-optimization based MS models and muscle force driven FE models typically use elastic materials for soft tissues or analyze specific time points of gait. Therefore, here we develop an electromyography-assisted muscle force driven FE model with fibril-reinforced poro(visco)elastic cartilages and menisci to analyze knee joint loading during the stance phase of gait. Moreover, since ligament pre-strains are one of the important uncertainties in joint modeling, we conducted a sensitivity analysis on the pre-strains of anterior and posterior cruciate ligaments (ACL and PCL) as well as medial and lateral collateral ligaments (MCL and LCL). The model produced kinematics and kinetics consistent with previous experimental data. Joint contact forces and contact areas were highly sensitive to ACL and PCL pre-strains, while those changed less cartilage stresses, fibril strains, and fluid pressures. The presented workflow could be used in a wide range of applications related to the aetiology of cartilage degeneration, optimization of rehabilitation exercises, and simulation of knee surgeries.

EMG-Assisted Muscle Force Driven Finite Element Model of the Knee Joint with Fibril-Reinforced Poroelastic Cartilages and Menisci

Abnormal mechanical loading is essential in the onset and progression of knee osteoarthritis. Combined musculoskeletal (MS) and finite element (FE) modeling is a typical method to estimate load distribution and tissue responses in the knee joint. However, earlier combined models mostly utilize static-optimization based MS models and muscle force driven FE models typically use elastic materials for soft tissues or analyze specific time points of gait. Therefore, here we develop an electromyography-assisted muscle force driven FE model with fibril-reinforced poro(visco)elastic cartilages and menisci to analyze knee joint loading during the stance phase of gait. Moreover, since ligament pre-strains are one of the important uncertainties in joint modeling, we conducted a sensitivity analysis on the pre-strains of anterior and posterior cruciate ligaments (ACL and PCL) as well as medial and lateral collateral ligaments (MCL and LCL). The model produced kinematics and kinetics consistent with previous experimental data. Joint contact forces and contact areas were highly sensitive to ACL and PCL pre-strains, while those changed less cartilage stresses, fibril strains, and fluid pressures. The presented workflow could be used in a wide range of applications related to the aetiology of cartilage degeneration, optimization of rehabilitation exercises, and simulation of knee surgeries.

Effect of sagittal femoral component alignment on biomechanics after mobile-bearing total knee arthroplasty

BACKGROUND

Recently, there has been increasing interest in mobile-bearing total knee arthroplasty (TKA). However, changes in biomechanics with respect to femoral component alignment in mobile-bearing TKA have not been explored in depth. This study aims to evaluate the biomechanical effect of sagittal alignment of the femoral component in mobile-bearing TKA.

METHODS

We developed femoral sagittal alignment models with - 3°, 0°, 3°, 5°, and 7°. We also examined the kinematics of the tibiofemoral (TF) joint, contact point on the TF joint, contact stress on the patellofemoral (PF) joint, collateral ligament force, and quadriceps force using a validated computational model under a deep-knee-bend condition.

RESULTS

Posterior kinematics of the TF joint increased as the femoral component flexed. In addition, contact stress on the PF joint, collateral ligament force, and quadriceps force decreased as the femoral component flexed. The results of this study can assist surgeons in assessing risk factors associated with femoral component sagittal alignment for mobile-bearing TKA.

CONCLUSIONS

Our results showed that slight flexion implantation may be an effective alternative technique because of its advantageous biomechanical effect. However, excessive flexion should be avoided because of potential loosening of the TF joint.

Biomechanical Effect of UHMWPE and CFR-PEEK Insert on Tibial Component in Unicompartmental Knee Replacement in Different Varus and Valgus Alignments

The current study aims to analyze the biomechanical effects of ultra-high molecular weight polyethylene (UHMWPE) and carbon-fiber-reinforced polyetheretherketone (CFR-PEEK) inserts, in varus/valgus alignment, for a tibial component, from 9° varus to 9° valgus, in unicompartmental knee replacement (UKR). The effects on bone stress, collateral ligament force, and contact stress on other compartments were evaluated under gait cycle conditions, by using a validated finite element model. In the UHMWPE model, the von Mises’ stress on the cortical bone region significantly increased as the tibial tray was in valgus >6°, which might increase the risk of residual pain, and when in valgus >3° for CFR-PEEK. The contact stress on other UHMWPE compartments decreased in valgus and increased in varus, as compared to the neutral position. In CFR-PEEK, it increased in valgus and decreased in varus. The forces on medial collateral ligaments increased in valgus, when compared to the neutral position in UHMWPE and CFR-PEEK. The results indicate that UKR with UHMWPE showed positive biomechanical outputs under neutral and 3° varus conditions. UKR with CFR-PEEK showed positive biomechanical outputs for up to 6° varus alignments. The valgus alignment should be avoided.

Biomechanical influence of lateral meniscal allograft transplantation on knee joint mechanics during the gait cycle

Background

This study evaluated the influence of meniscal allograft transplantation (MAT) on knee joint mechanics during normal walking using finite element (FE) analysis and biomechanical data.

Methods

The study included 20 patients in a transpatellar group and 25 patients in a parapatellar group. Patients underwent magnetic resonance imaging (MRI) evaluation after lateral MAT as a baseline input for three-dimensional (3D) and FE analyses. Three different models were compared for lateral MAT: intact, transpatellar approach, and parapatellar approach. Analysis was performed using high kinematic displacement and rotation inputs based on the kinematics of natural knees. ISO standards were used for axial load and flexion. Maximum contact stress on the grafted menisci and maximum shear stress on the articular surface of the knee joint were evaluated with FE analysis.

Results

Relatively high maximum contact stresses and maximum shear stresses were predicted in the medial meniscus and cartilage of the knee joint during the loading response for all three knee joint models. Maximum contact stress and maximum shear stress in the meniscus and cartilage increased on the lateral side after lateral MAT, especially during the first 20% of the stance phase of the gait cycle. The transpatellar approach was most similar to the intact knee model in terms of contact stresses of the lateral grafted and medial meniscus, as well as maximum shear stresses during the gait cycle. In addition, the transpatellar model had lower maximum contact stress on the menisci than did the parapatellar model, and it also had lower maximum shear stress on the tibial cartilage.

Conclusions

Therefore, the transpatellar approach may reduce the overall risk of degenerative osteoarthritis (OA) after lateral MAT.

Biomechanical effect with respect to the sagittal positioning of the femoral component in unicompartmental knee arthroplasty

BACKGROUND

Component malalignment in unicompartmental knee arthroplasty (UKA) has been related to the concentration in tibiofemoral joint of contact stress and to poor post-operative outcomes. Few studies investigated a biomechanical effect of femur component position in sagittal plane. The purpose of this study was to evaluate the biomechanical effect of the femoral components on the sagittal alignment under flexion and extension conditions using computational simulations.

METHODS

The flexion and extension conditions of the femoral component were analyzed from 10° extension to 10° flexion in 1° increments. We considered the contact stresses in the polyethylene (PE) inserts and articular cartilage, and the force on the collateral ligament, under gait cycle conditions.

RESULTS

The contact stress on the PE insert increased as flexion of the femoral component increased, but there was not a remarkable difference in the amount of increased contact stress upon extension. There was no difference in the contact stress on the articular cartilage upon extension of the femoral component, but it increased in flexion during stance and double support periods. The forces on the medial collateral ligaments increased with the extension and decreased with the flexion of the femoral component, whereas the forces on the lateral collateral ligaments showed opposite trends.

CONCLUSIONS

Surgeons should be concerned with femoral component position on UKA not only in frontal plane but also in the sagittal plane, because flexion or extension of the femoral component may impact the PE or opposite compartment along with the surrounding ligaments around knee joint.

Design optimization of high tibial osteotomy plates using finite element analysis for improved biomechanical effect

Background

High tibial osteotomy (HTO) is a common treatment for moderate osteoarthritis of the medial compartment in the knee joint by the translation of the force center toward the lateral compartment. However, the stability of a short plate such as Puddu used in this procedure was not as effective as other long plates such as Tomofix. No previous studies have used a rigorous and systematic design optimization method to determine the optimal shape of short HTO plate. Therefore, the purpose of this study is to evaluate the improved biomechanical stability of a short HTO plate by using design optimization and finite element (FE) analysis.

Methods

A FE model of HTO was subjected to physiological and surgical loads in the tibia. Taguchi-style L27 orthogonal arrays were used to identify the most significant factors for optimizing the design parameters. The optimal design variables were calculated using the nondominated sorting genetic algorithm II. Plate and bone stresses and wedge micromotions in the initial and optimized designs were chosen as the comparison indices.

Results

Optimal designed HTO plate showed the decreased micromotions over the initial HTO plate with enhanced plate stability. In addition, increased bone stress and decreased plate stress supported the positive effect on stress shielding compared to initial HTO plate design. The results yielded a new short HTO design while demonstrating the feasibility of design optimization and potential improvements to biomechanical stability in HTO design. The newly developed short HTO plate throughout the optimization and computational simulation showed the improved biomechanical effect as good as the golden standard, TomoFix, does.

Conclusions

This study showed that plate design has a strong influence on the stability after HTO. This study demonstrated that the optimized short plates had low stress shielding effect and less micromotion because of its improvement in biomechanical performances. Our result showed that design optimization is an effective tool for HTO plate design. This information can aid future developments in HTO plate design and can be expanded to other implant designs.

Development of mussel-inspired 3D-printed poly (lactic acid) scaffold grafted with bone morphogenetic protein-2 for stimulating osteogenesis

3D printing is a versatile technique widely applied in tissue engineering due to its ability to manufacture large quantities of scaffolds or constructs with various desired architectures. In this study, we demonstrated that poly (lactic acid) (PLA) scaffolds fabricated via fused deposition not only retained the original interconnected microporous architectures, the scaffolds also exhibited lower lactic acid dissolution as compared to the freeze-PLA scaffold. The 3D-printed scaffolds were then grafted with human bone morphogenetic protein-2 (BMP-2) via the actions of polydopamine (PDA) coatings. The loading and release rate of BMP-2 were monitored for a period of 35 days. Cellular behaviors and osteogenic activities of co-cultured human mesenchymal stem cells (hMSCs) were assessed to determine for efficacies of scaffolds. In addition, we demonstrated that our fabricated scaffolds were homogenously coated with PDA and well grafted with BMP-2 (219.1 ± 20.4 ng) when treated with 250 ng/mL of BMP-2 and 741.4 ± 127.3 ng when treated with 1000 ng/mL of BMP-2. This grafting enables BMP-2 to be released in a sustained profile. From the osteogenic assay, it was shown that the ALP activity and osteocalcin of hMSCs cultured on BMP-2/PDA/PLA were significantly higher when compared with PLA and PDA/PLA scaffolds. The methodology of PDA coating employed in this study can be used as a simple model to immobilize multiple growth factors onto different 3D-printed scaffold substrates. Therefore, there is potential for generation of scaffolds with different unique modifications with different capabilities in regulating physiochemical and biological properties for future applications in bone tissue engineering.

The biomechanical effect of tibiofemoral conformity design for patient-specific cruciate retainging total knee arthroplasty using computational simulation

Background

Alterations to normal knee kinematics performed during conventional total knee arthroplasty (TKA) focus on the nonanatomic articular surface. Patient-specific TKA was introduced to provide better normal knee kinematics than conventional TKA. However, no study on tibiofemoral conformity has been performed after patient-specific TKA. The purpose of this study was to compare the biomechanical effect of cruciate-retaining (CR) implants after patient-specific TKA and conventional TKA under gait and deep-knee-bend conditions.

Methods

The examples of patient-specific TKA were categorized into conforming patient-specific TKA, medial pivot patient-specific TKA and anatomy mimetic articular surface patient-specific TKA. We investigated kinematics and quadriceps force of three patient-specific TKA and conventional TKA using validated computational model. The femoral component designs in patient specific TKA were all identical.

Results

The anatomy mimetic articular surface patient-specific TKA provided knee kinematics that was closer to normal than the others under the gait and deep-knee-bend conditions. However, the other two patient-specific TKA designs could not preserve the normal knee kinematics. In addition, the closest normal quadriceps force was found for the anatomic articular surface patient-specific TKA.

Conclusions

Our results showed that the anatomy mimetic articular surface patient-specific TKA provided close-to-normal knee mechanics. Other clinical and biomechanical studies are required to determine whether anatomy mimetic articular surface patient-specific TKA restores more normal knee mechanics and provides improved patient satisfaction.

Biomechanical Evaluation of the Effect of Mesenchymal Stem Cells on Cartilage Regeneration in Knee Joint Osteoarthritis

Numerous clinical studies have reported cell-based treatments for cartilage regeneration in knee joint osteoarthritis using mesenchymal stem cells (MSCs). However, the post-surgery rehabilitation and weight-bearing times remain unclear. Phenomenological computational models of cartilage regeneration have been only partially successful in predicting experimental results and this may be due to simplistic modeling assumptions and loading conditions of cellular activity. In the present study, we developed a knee joint model of cell and tissue differentiation based on a more mechanistic approach, which was applied to cartilage regeneration in osteoarthritis. First, a phenomenological biphasic poroelastic finite element model was developed and validated according to a previous study. Second, this method was applied to a real knee joint model with a cartilage defect created to simulate the tissue regeneration process. The knee joint model was able to accurately predict several aspects of cartilage regeneration, such as the cell and tissue distributions in the cartilage defect. Additionally, our results indicated that gait cycle loading with flexion was helpful for cartilage regeneration compared to the use of simple weight-bearing loading.

Flexed femoral component improves kinematics and biomechanical effect in posterior stabilized total knee arthroplasty

PURPOSE

The kinematics and biomechanics of the knee joint are important in ensuring patient satisfaction and functional ability after total knee arthroplasty (TKA). There has been no study on knee joint mechanics with regard to the sagittal alignment of the femoral component. The objective of this study is to determine the extent of the impact of the femoral component's sagittal alignment on kinematics and biomechanics.

METHODS

A validated computational TKA model was used. The femoral component was simulated at - 3°, 0°, 5°, and 7° of flexion in the sagittal plane. This study evaluated the tibiofemoral (TF) joint kinematics, contact point, quadriceps force, and contact stress on the patellofemoral (PF) joint under a deep-knee-bend condition.

RESULTS

The kinematics of the TF joint in the posterior direction increased with the flexion of the femoral component position. For all tasks, the overall posterior locations of the TF contact points were observed in the medial and lateral compartments as the femoral component flexion angle increased. The quadriceps force and contact stress on the PF joint decreased with the femoral component flexion.

CONCLUSION

This study found that the femoral component sagittal position is an important factor in knee joint mechanics. In this study, the flexion of femoral component showed a stable reconstruction of the knee extensors' mechanism. Surgeons may consider neutral-to-mild flexed femoral component position, without concerns of anterior notching of the femoral cortex.

Effect of geometric variations on tibiofemoral surface and post-cam design of normal knee kinematics restoration

Background

Restoration of natural knee kinematics for a designed mechanism in knee implants is required to achieve full knee function in total knee arthroplasty (TKA). In different posterior-stabilized TKAs, there are wide variations in tibiofemoral surfaces and post-cam design. However, it is not known whether these design variations preserve natural knee kinematics. The purpose of this study was to determine the most appropriate tibiofemoral surface and post-cam designs to restore natural knee kinematics of the TKA.

Methods

A subject-specific finite element knee modal was used to evaluate tibiofemoral surface and post-cam design. Three different posts in convex, straight, and concave geometries were considered with a fixed circular cam design in this study. In addition, this post-cam design was applied to three different surface conformities for conforming, medial pivot, and subject anatomy mimetic tibiofemoral surfaces. We evaluated the femoral rollback, internal-external rotation, and quadriceps muscle force under a deep-knee-bend condition.

Results

The three different tibiofemoral conformities showed that the convex post provided the most natural-knee-like femoral rollback. This was also observed in internal rotation. In surface conformity, subject anatomy mimetic tibiofemoral surfaces showed the most natural -knee-like kinematics and quadriceps force.

Conclusions

This study confirmed that convex post design and subject anatomy mimetic tibiofemoral surfaces provided the most natural-knee-like kinematics. This study suggested that post-cam design and tibiofemoral surface conformity should be considered in conventional and customized TKA.

Biomechanical evaluation of opening-wedge high tibial osteotomy with composite materials using finite-element analysis

BACKGROUND

Medial opening-wedge high tibial osteotomy (HTO) has been used to treat osteoarthritis of the medial compartment of the knee. However, this makes the proximal tibia a highly unstable structure and causes the plate to be a potential source of mechanical failure. Consequently, proper design and material use of the fixation device are essential in HTO, especially for overweight or full-weight-bearing patients.

METHODS

This study investigated the biomechanical effects of the TomoFix plate composed of conventional titanium (Ti) in comparison to plates composed of carbon short-fiber-reinforced (CSFR) polyetheretherketone (PEEK) and carbon long-fiber-reinforced (CLFR) PEEK, in medial opening-wedge HTO. A medial opening was simulated with various HTO plate models subjected to a 2500 N vertical load simulating the peak walking force using a validated knee-joint finite-element (FE) model. The stress on the plate and the bone, the contact stress on the menisci and articular cartilage, as well as wedge micromotion were measured.

RESULTS

The results of the FE analysis indicated that the Ti plate showed the best functional outcome in terms of micromotion. However, the CSFR PEEK plate showed a positive effect on relieving stress shielding. In addition, there was less contact stress on the meniscus and articular cartilage with the CSFR PEEK plate in comparison to CLFR PEEK and Ti plates.

CONCLUSION

These results can provide insights into the design of high-performing composite HTO plates to produce more desirable biomechanical effects.

Multi-objective design optimization of high tibial osteotomy for improvement of biomechanical effect by using finite element analysis

Medial opening wedge high tibial osteotomy (HTO) makes the proximal tibia a highly unstable structure and causes plates and screws to be the potential sources for mechanical failure. However, asymmetrical callus and incomplete bone formations underneath the plates (TomoFix) have been recent concerns in clinical and experimental studies related to HTO due to the high stiffness. The purpose of this study was to evaluate the biomechanical effect of the TomoFix plate system with respect to changes in design using a computational simulation. A parametric three-dimensional model of HTO was constructed from medical image data. The design parameters for the HTO plate were evaluated to investigate their influence on biomechanical effects, and the most significant factors were determined using Taguchi-style L27 orthogonal arrays. Multi-objective optimization was used to identify the wedge micromotion stability without the stress shielding effect that occurs in the bone plate. The initial design showed that the high stiffness of the plate caused stress shielding on the bone and plate. However, the optimal design led to sharing the stress and load with the bone plate to eliminate stress shielding. In addition, the stability required for the plate could be found in the micromotions of the wedge for the optimal design. The optimal condition of design parameters was successfully determined using the Taguchi and multi-objective optimization method, which was shown to eliminate stress shielding effects. The results showed that an optimal design demonstrated the feasibility of design optimization and improvements in biomechanical stability for HTO. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2956-2965, 2018.

Patient-specific design for articular surface conformity to preserve normal knee mechanics in posterior stabilized total knee arthroplasty

BACKGROUND

Contemporary total knee arthroplasty (TKA) provides remarkable clinical benefits. However, the normal function of the knee is not fully restored. Recent improvements in imaging and manufacturing have utilized the development of customized design to fit the unique shape of individual patients.

OBJECTIVE

The purpose of the present study is to investigate the preservation of normal knee biomechanics by using specific articular surface conformity in customized posterior stabilized (PS)-TKA.

METHODS

This includes customized PS-TKA, PS-TKA with conforming conformity (CPS-TKA), medial pivot conformity with PS-TKA (MPS-TKA), and PS-TKA with mimetic anatomy femoral and tibial articular surface (APS-TKA). In this study, kinematics, collateral ligament force and quadriceps force were evaluated using a computational simulation under a deep knee bend condition.

RESULTS

A conventional TKA did not provide the normal internal tibial rotation with flexion leading to abnormal femoral rollback. The APS-TKA exhibited normal-like femoral rollback kinematics but did not exhibit normal internal tibial rotation. However, APS-TKA exhibited the most normal-like collateral ligament and quadriceps forces.

CONCLUSIONS

Although the APS-TKA exhibited more normal-like biomechanics, it did not restore normal knee biomechanics owing to the absence of the cruciate ligament and post-cam mechanism.

Effects of posterior condylar offset and posterior tibial slope on mobile-bearing total knee arthroplasty using computational simulation

BACKGROUND

Postoperative changes of the femoral posterior condylar offset (PCO) and posterior tibial slope (PTS) affect the biomechanics of the knee joint after fixed-bearing total knee arthroplasty (TKA). However, the biomechanics of mobile-bearing is not well known. Therefore, the aim of this study was to investigate whether alterations to the PCO and PTS affect the biomechanics for mobile-bearing TKA.

METHODS

We used a computational model for a knee joint that was validated using in vivo experiment data to evaluate the effects of the PCO and PTS on the tibiofemoral (TF) joint kinematics, patellofemoral (PF) contact stress, collateral ligament force and quadriceps force, for mobile-bearing TKA. The computational model was developed using ±1-, ±2- and ±3-mm PCO models in the posterior direction and -3°, 0°, +3°, and +6° PTS models based on each of the PCO models.

RESULTS

The maximum PF contact stress, collateral ligament force and quadriceps force decreased as the PTS increased. In addition, the maximum PF contact stress and quadriceps force decreased, and the collateral ligament force increased as PCO translated in the posterior direction. This trend is consistent with that observed in any PCO and PTS.

CONCLUSIONS

Our findings show the various effects of postoperative alterations in the PCO and PTS on the biomechanical results of mobile-bearing TKA. Based on the computational simulation, we suggest that orthopaedic surgeons intraoperatively conserve the patient's own anatomical PCO and PTS in mobile-bearing TKA.

Effect of Post-Cam Design for Normal Knee Joint Kinematic, Ligament, and Quadriceps Force in Patient-Specific Posterior-Stabilized Total Knee Arthroplasty by Using Finite Element Analysis

The purpose of this study is to investigate post-cam design via finite element analysis to evaluate the most normal-like knee mechanics. We developed five different three-dimensional computational models of customized posterior-stabilized (PS) total knee arthroplasty (TKA) involving identical surfaces with the exception of the post-cam geometry. They include flat-and-flat, curve-and-curve (concave), curve-and-curve (concave and convex), helical, and asymmetrical post-cam designs. We compared the kinematics, collateral ligament force, and quadriceps force in the customized PS-TKA with five different post-cam designs and conventional PS-TKA to those of a normal knee under deep-knee-bend conditions. The results indicated that femoral rollback in curve-and-curve (concave) post-cam design exhibited the most normal-like knee kinematics, although the internal rotation was the closest to that of a normal knee in the helical post-cam design. The curve-and-curve (concave) post-cam design showed a femoral rollback of 4.4 mm less than the normal knee, and the helical post-cam design showed an internal rotation of 5.6° less than the normal knee. Lateral collateral ligament and quadriceps forces in curve-and-curve (concave) post-cam design, and medial collateral ligament forces in helical post-cam design were the closest to that of a normal knee. The curve-and-curve (concave) post-cam design showed 20% greater lateral collateral ligament force than normal knee, and helical post-cam design showed medial collateral ligament force 14% greater than normal knee. The results revealed the variation in each design that provided the most normal-like biomechanical effect. The present biomechanical data are expected to provide useful information to improve post-cam design to restore normal-like knee mechanics in customized PS-TKA.

Comparison of Kinematics in Cruciate Retaining and Posterior Stabilized for Fixed and Rotating Platform Mobile-Bearing Total Knee Arthroplasty with respect to Different Posterior Tibial Slope

Reconstructed posterior tibial slope (PTS) plays a significant role in kinematics restoration after total knee arthroplasty (TKA). However, the effect of increased and decreased PTS on prosthetic type and design has not yet been investigated. We used a finite element model, validated using in vitro data, to evaluate the effect of PTS on knee kinematics in cruciate-retaining (CR) and posterior-stabilized (PS) fixed TKA and rotating platform mobile-bearing TKA. Anterior-posterior tibial translation and internal-external tibial rotation were investigated for PTS ranging from -3° to 15°, with increments of 1°, for three different designs of TKA. Tibial posterior translation and external rotation increased as the PTS increased in both CR and PS TKAs. In addition, there was no remarkable difference in external rotation between CR and PS TKAs. However, for the mobile-bearing TKA, PTS had less effect on the kinematics. Based on our computational simulation, PTS is the critical factor that influences kinematics in TKA, especially in the CR TKA. Therefore, the surgeon should be careful in choosing the PTS in CR TKAs.

Effect of joint line preservation on mobile-type bearing unicompartmental knee arthroplasty: finite element analysis

In this study, we performed a virtual mobile-bearing unicompartmental knee arthroplasty (UKA) on the contact pressure in the tibial insert and articular cartilage by using finite element (FE) analysis to understand clinical observations and elaborate on the potential risks associated with a joint line preservation such as wear on tibial insert and osteoarthritis on other compartment. Neutral position of the knee joint was defined in 0 mm joint line, and contact pressure between tibial insert and articular cartilage varies with respect to changes of joint line. Therefore, evaluation of contact pressure may provide the degree of joint line preservation. The FE model for the joint line was developed using a perpendicular projection line from the medial tibial plateau to the anatomical axis. Seven FE models for joint lines in cases corresponding to ± 6, ± 4, ± 2, and 0 mm were modeled and analyzed in normal level walking conditions. The maximum contact pressure on the superior and inferior surfaces of the polyethylene insert increased when the joint line became positive while the maximum contact pressure on the articular cartilage increased when the joint line became negative. The increase in the maximum contact pressure in the positive joint line exceeded that in the negative joint line, and this lead to an unsymmetrical maximum contact pressure distribution with respect to the joint line from a 0 reference. The joint line elevation was sensitive to increases or decreases in maximum contact pressures in the mobile-bearing UKA. The findings of the study determined that postoperative joint line preservation is important in mobile-type bearing UKA.

Influence of Increased Posterior Tibial Slope in Total Knee Arthroplasty on Knee Joint Biomechanics: A Computational Simulation Study

BACKGROUND

The reconstructed posterior tibial slope (PTS) plays a significant role in restoring knee kinematics in cruciate-retaining-total knee arthroplasty (TKA). A few studies have reported the effect of the PTS on biomechanics.

METHODS

This study investigates the effect of the PTS on tibiofemoral (TF) kinematics, patellofemoral (PF) contact stress, and forces at the quadriceps, posterior cruciate ligament (PCL) and collateral ligament after cruciate-retaining-TKA using computer simulations. The simulation for the validated TKA finite element model was performed under deep knee bend condition. All analyses were repeated from -3° to 15° PTS in increments of 3°.

RESULTS

The kinematics on the TF joint translated increasingly posteriorly when the PTS increased. Medial and lateral contact points translated in posterior direction in extension and flexion as PTS increased. The maximum contact stress on the PF joint and quadriceps, and collateral ligament force decreased when the PTS increased. An implantation of the tibial plate with increased PTS reduced the PCL load. Physiologic insert movement led to an increasingly posterior position of the femur and reduced quadriceps force especially for knee flexion angles above high flexion (120°) when compared to TKA with a decreased slope of the tibial base plate.

CONCLUSION

An increase in the PTS increased medial and lateral movements without paradoxical motion. However, an excessive PTS indicated progressive loosening of the TF joint gap due to a reduction in collateral ligament tension during flexion.

A computational simulation study to determine the biomechanical influence of posterior condylar offset and tibial slope in cruciate retaining total knee arthroplasty

Objectives

Posterior condylar offset (PCO) and posterior tibial slope (PTS) are critical factors in total knee arthroplasty (TKA). A computational simulation was performed to evaluate the biomechanical effect of PCO and PTS on cruciate retaining TKA.

Methods

We generated a subject-specific computational model followed by the development of ± 1 mm, ± 2 mm and ± 3 mm PCO models in the posterior direction, and -3°, 0°, 3° and 6° PTS models with each of the PCO models. Using a validated finite element (FE) model, we investigated the influence of the changes in PCO and PTS on the contact stress in the patellar button and the forces on the posterior cruciate ligament (PCL), patellar tendon and quadriceps muscles under the deep knee-bend loading conditions.

Results

Contact stress on the patellar button increased and decreased as PCO translated to the anterior and posterior directions, respectively. In addition, contact stress on the patellar button decreased as PTS increased. These trends were consistent in the FE models with altered PCO. Higher quadriceps muscle and patellar tendon force are required as PCO translated in the anterior direction with an equivalent flexion angle. However, as PTS increased, quadriceps muscle and patellar tendon force reduced in each PCO condition. The forces exerted on the PCL increased as PCO translated to the posterior direction and decreased as PTS increased.

Conclusion

The change in PCO alternatively provided positive and negative biomechanical effects, but it led to a reduction in a negative biomechanical effect as PTS increased.

Cite this article: K-T. Kang, Y-G. Koh, J. Son, O-R. Kwon, J-S. Lee, S. K. Kwon. A computational simulation study to determine the biomechanical influence of posterior condylar offset and tibial slope in cruciate retaining total knee arthroplasty. Bone Joint Res 2018;7:69–78. DOI: 10.1302/2046-3758.71.BJR-2017-0143.R1.

Biomechanical Effects of Posterior Condylar Offset and Posterior Tibial Slope on Quadriceps Force and Joint Contact Forces in Posterior-Stabilized Total Knee Arthroplasty

This study aimed to determine the biomechanical effect of the posterior condylar offset (PCO) and posterior tibial slope (PTS) in posterior-stabilized (PS) fixed-bearing total knee arthroplasty (TKA). We developed ±1, ±2, and ±3 mm PCO models in the posterior direction and −3°, 0°, 3°, and 6° PTS models using a previously validated FE model. The influence of changes in the PCO and PTS on the biomechanical effects under deep-knee-bend loading was investigated. The contact stress on the PE insert increased by 14% and decreased by 7% on average as the PCO increased and decreased, respectively, compared to the neutral position. In addition, the contact stress on post in PE insert increased by 18% on average as PTS increased from −3° to 6°. However, the contact stress on the patellar button decreased by 11% on average as PTS increased from −3° to 6° in all different PCO cases. The quadriceps force decreased by 14% as PTS increased from −3° to 6° in all PCO models. The same trend was found in patellar tendon force. Changes in PCO had adverse biomechanical effects whereas PTS increase had positive biomechanical effects. However, excessive PTS should be avoided to prevent knee instability and subsequent failure.

Preservation of kinematics with posterior cruciate-, bicruciate- and patient-specific bicruciate-retaining prostheses in total knee arthroplasty by using computational simulation with normal knee model

Objectives

Preservation of both anterior and posterior cruciate ligaments in total knee arthroplasty (TKA) can lead to near-normal post-operative joint mechanics and improved knee function. We hypothesised that a patient-specific bicruciate-retaining prosthesis preserves near-normal kinematics better than standard off-the-shelf posterior cruciate-retaining and bicruciate-retaining prostheses in TKA.

Methods

We developed the validated models to evaluate the post-operative kinematics in patient-specific bicruciate-retaining, standard off-the-shelf bicruciate-retaining and posterior cruciate-retaining TKA under gait and deep knee bend loading conditions using numerical simulation.

Results

Tibial posterior translation and internal rotation in patient-specific bicruciate-retaining prostheses preserved near-normal kinematics better than other standard off-the-shelf prostheses under gait loading conditions. Differences from normal kinematics were minimised for femoral rollback and internal-external rotation in patient-specific bicruciate-retaining, followed by standard off-the-shelf bicruciate-retaining and posterior cruciate-retaining TKA under deep knee bend loading conditions. Moreover, the standard off-the-shelf posterior cruciate-retaining TKA in this study showed the most abnormal performance in kinematics under gait and deep knee bend loading conditions, whereas patient-specific bicruciate-retaining TKA led to near-normal kinematics.

Conclusion

This study showed that restoration of the normal geometry of the knee joint in patient-specific bicruciate-retaining TKA and preservation of the anterior cruciate ligament can lead to improvement in kinematics compared with the standard off-the-shelf posterior cruciate-retaining and bicruciate-retaining TKA.

Cite this article: Y-G. Koh, J. Son, S-K. Kwon, H-J. Kim, O-R. Kwon, K-T. Kang. Preservation of kinematics with posterior cruciate-, bicruciate- and patient-specific bicruciate-retaining prostheses in total knee arthroplasty by using computational simulation with normal knee model. Bone Joint Res 2017;6:557–565. DOI: 10.1302/2046-3758.69.BJR-2016-0250.R1.