23 research outputs found
Subject-specific knee ligaments modeling approaches in finite element analysis: 1D and 3D
Knee ligaments are among the most complicated structures and have a large effect on knee biomechanics. There are different approaches to model the knee ligaments in FE models. In the knee joint, ligaments have been commonly modelled as 1D spring elements; moreover, some studies modelled the ligaments as 3D constitutive elements [2]. Using springs reduces computational costs compared to constitutive models of the ligaments. In turn, constitutive models closer approximate the anatomy, and facilitate the prediction of local quantities and interactions with surrounding tissues, such as wrapping [1]. To the best of our knowledge, there is no direct/practical comparison study between two FE ligament modelling approaches. The aim of this study is to develop and compare two separate subject-specific finite element knee models in terms of ligament modelling approaches, based on cadaveric validation experiments
The effect of posterior tibial slope on simulated laxity tests in cruciate-retaining TKA
INTRODUCTION: Tibial slope can affect the outcomes of Total Knee Arthroplasty (TKA). More posterior slope potentially helps releasing a too tight flexion gap and it is generally associated with a wider range of post-operative knee flexion. However, the mechanism by which tibial slope affects the function of TKA during dynamic activities of daily living is rather complex and not well documented. The aim of this study was to investigate the effect of tibial slope on the kinematics of the tibiofemoral (TF) contact point, quadriceps muscle forces, and patellofemoral (PF) joint contact forces during squat. In addition, we studied the effect of anterior tibial cortex-referencing (ACR) versus center of tibial plateau-referencing (CPR), as two possible techniques to obtain the desired degree of tibial slope. METHODS: A previously validated musculoskeletal model of a 86-year-old male subject, having a cruciate-retaining (CR) TKA prosthesis, was used to simulate a squat activity [1]. Motion-capture data were input to a motion optimization algorithm to find the full body kinematics. Quadriceps muscle forces were then calculated using inverse-dynamics. The kinematics of the TF contact point and PF joint contact forces were simultaneously calculated using force-dependent kinematics. A baseline case with 0° tibial slope was simulated, plus four additional cases with anterior (-3°), and posterior (+3°, +6°, +9°) tibial slope using the ACR technique (Fig. 1a), and four using the CPR technique (Fig. 1b). RESULTS: Compared to the baseline, more posterior tibial slope with ACR technique resulted in a larger excursion of the TF contact point, which shifted to a more anterior position, on the lateral side, and a more posterior position, on the medial side, in extension (Fig. 2). With the CPR technique, the contact point in extension shifted gradually more posterior on both sides with more posterior slope, and in flexion it shifted gradually more posterior mainly on the lateral side. The peak quadriceps force decreased on average by 1.7 and 1.2 % BW per degree of more posterior slope, with the ACR and CPR techniques, respectively. However, due to the different relative position of patella and femur, the peak PF contact force was mainly reduced by increasing the posterior slope with the CPR technique (-3.9 % BW/degree), rather than with the ACR technique (-1.5 % BW/degree) (Fig. 3). DISCUSSION: Increasing the tibial slope using the ACR technique produced large changes in the TF kinematics: the pattern of the contact point became more unstable, with a larger AP movement observed on the lateral side, denoting increased anterior-posterior laxity. On the other hand, variations of tibial slope with CPR technique resulted in more stable TF kinematics, more posterior position of the TF contact point, and a greater reduction of the PF contact forces. It is advisable to pre-plan the desired amount of tibial slope and execute it using the CPR technique. The surgeon should be very careful applying too much tibial slope with the ACR technique in CR-TKA, as it may have devastating effects on the TF kinematics, laxity and PF forces. SIGNIFICANCE: This study provides new insights into the effect of variation of tibial slope in TKA using different surgical techniques, which were not documented before, and used a highly controlled and parameterized study design and dynamic loading conditions. Orthopedic surgeons can directly use these results as an indication for the clinical practice. The presented tool can also be very useful for educational/medical training purposes
The effect of tibial slope on the biomechanics of cruciate-retaining total knee arthroplasty:A musculoskeletal simulation study
Introduction/Aim: More posterior tibial slope (PTS) can prevent flexion gap tightness in cruciate-retaining Total Knee Arthroplasty (TKA) and help achieving better knee function. However, the influence of PTS on knee function during activities of daily living (ADLs) is scarcely documented. The aim of this study was to investigate the effect of PTS and surgical referencing technique on tibiofemoral joint (TFJ) kinematics, quadriceps force, and patellofemoral joint (PFJ) force during ADLs. Materials and Methods: We used a previously validated musculoskeletal model of cruciate-retaining TKA [1] to simulate a squat activity. A baseline case with the original post-operative PTS (0°) was simulated, plus four PTS cases (-3°, +3°, +6°, +9°) obtained using anterior tibial cortex-referencing (ACR, Fig. 1a) technique and four using centre of tibial plateau-referencing (CPR, Fig. 1b) technique. Results: More PTS with ACR technique caused a larger and more anterior excursion of the TFJ contact point on the lateral side, and more posterior, on the medial side, in extension (Fig. 2). More PTS with the CPR technique caused the contact point in extension to shift gradually more posterior on both medial and lateral sides, and in flexion to shift gradually more posterior mainly on the lateral side. The peak quadriceps force decreased on average by 1.7 and 1.2 % BW for every degree of more PTS, with the ACR and CPR techniques, respectively. The peak PFJ contact force decreased more importantly with more PTS with the CPR technique rather than with the ACR technique (-3.9 vs. -1.5 % BW/degree more PTS, Fig. 3). Discussion: The ACR technique loosens the TFJ, thus leading to more unstable TFJ kinematics and anterior shift on the lateral side. More PTS also reduces the quadriceps force to squat. More PTS with the CPR technique resulted in stable and more posterior TFJ kinematics, and a greater reduction of the PFJ contact force, due to preservation of patellar height. Conclusions: TFJ stability should be maximally preserved to improve knee function. More PTS with the ACR technique has severe consequences on knee kinematics and function, whilst CPR technique results in more effective reduction of quadriceps and PFJ forces, while preserving TFJ stability. References: [1] Marra MA, Vanheule V, Fluit R, et al. A Subject-Specific Musculoskeletal Modeling Framework to Predict In Vivo Mechanics of Total Knee Arthroplasty. ASME. J Biomech Eng. 2015;137(2):020904-020904-1
The effect of flexion of the femoral component in TKA:A musculoskeletal simulation study
Introduction/Aim: More flexion of the femoral component (FFC) is a surgical option to better restore the femur anatomy in the sagittal plane in Total Knee Arthroplasty (TKA), and to prevent notching of the anterior femoral cortex. However, its true effects on the patellofemoral joint (PFJ) during activities of daily living (ADLs) remain unknown. We studied the effect of FFC on quadriceps and PFJ forces during ADLs. We hypothesised that more FFC has advantages for the knee extensor mechanism. Materials and Methods: A previous validated musculoskeletal model of cruciate-retaining TKA was used (Fig. 1) to simulate a rising-from-a-chair activity [1]. We simulated a baseline case with the original post-operative FFC (0°). We then increased the FFC by 3°, 6°, 9°, by referencing the posterior femoral condyles (Fig. 2) and repeated the simulation. Quadriceps forces, PFJ ligament forces and PFJ contact forces were calculated. Results: Peak quadriceps force decreased by 48 N (6.5 %BW), on average, for every 3° of FFC at 90° flexion (Fig. 3a). The peak PFJ contact force decreased by 64 N (8.7 %BW), on average, for every 3° of FFC at 90° flexion. Conversely, peak medial and lateral PFJ ligament forces increased by 23 N and 25 N, respectively, on average, for every 3° more FFC (Fig. 3c-d). Discussion: FFC moderately affects the PFJ mechanics. Reduced PFJ contact force with more FFC is explained by reduced quadriceps force. More FFC, thus, benefits the knee extensor mechanism, due to increased quadriceps moment arm. More FFC over-tightens both medial and lateral PFJ ligaments, due to a wider PFJ gap, although the effect on ligament forces is not dramatic. Conclusions: More FFC reduces the quadriceps and PFJ force to rise from and sit on a chair. This surgical option can potentially help preventing anterior femoral notching, while at the same time provide a better knee function. References: [1] Marra MA, Vanheule V, Fluit R, et al. A Subject-Specific Musculoskeletal Modeling Framework to Predict In Vivo Mechanics of Total Knee Arthroplasty. ASME. J Biomech Eng. 2015;137(2):020904-020904-1
The effect of posterior tibial slope on simulated laxity tests in cruciate-retaining total knee arthroplasty
Introduction/Aim: More posterior tibial slope (PTS) can potentially prevent flexion gap tightness in Total Knee Arthroplasty (TKA). However, the effects of more PTS on knee laxity remain unclear. The aim of this study was to investigate the effect of PTS on the anterior-posterior (AP) and varus-valgus (VV) laxity in TKA. We hypothesised that the effects also depend on whether an anterior tibial cortex-referencing (ACR) technique or a centre of tibial plateau-referencing (CPR) technique is used. Materials and Methods: A previous validated musculoskeletal model of cruciate-retaining TKA was configured to simulate AP and VV laxity tests [1]. First the model was simulated without any external loads applied, with the knee spanning a 0-90° flexion range of motion (ROM). Subsequently, anterior and posterior loads of 70 N were applied alternately to the proximal tibia, and the resulting AP tibial displacement recorded throughout the knee ROM. Similarly, varus and valgus loads of 15 Nm were applied alternately to the tibia, and the resulting knee VV rotation recorded. The simulations were repeated with -3°, +3°, +6°, +9° of PTS both with the ACR and CPR techniques (Fig. 1). Laxity were calculated as the unloaded case curves minus the loaded case curves. Results: More PTS with the ACR technique increased dramatically the anterior, varus and valgus laxities, throughout the knee flexion ROM. The anterior laxity was maximal (23 mm) at 60° of knee flexion in the +9° ACR case. Conversely, variations of PTS with the CPR technique hardly affected the AP and VV laxities. Discussion: More PTS with the ACR technique compromises the overall knee stability, throughout the knee flexion-extension ROM and, most interestingly, also in extension. This is due to an increase of the flexion gap. In contrast, the CPR technique preserves the translational and rotational laxities of the knee, throughout the ROM. CPR could be achieved by pre-planning the PTS and by accurately executing the tibial cut or by using inserts with built-in PTS. Conclusions: More PTS with the ACR technique has large effects on knee stability and laxity, therefore surgeons should avoid increasing PTS using the ACR technique and, instead, reference the tibial cut height and slope from the posterior one third of the tibia. References: [1] Marra MA, Vanheule V, Fluit R, et al. A Subject-Specific Musculoskeletal Modeling Framework to Predict In Vivo Mechanics of Total Knee Arthroplasty. ASME. J Biomech Eng. 2015;137(2):020904-020904-1
The effect of tibial slope on the biomechanics of cruciate-retaining TKA:a musculoskeletal simulation study
INTRODUCTION: Tibial slope can affect the outcomes of Total Knee Arthroplasty (TKA). More posterior slope potentially helps releasing a too tight flexion gap and it is generally associated with a wider range of post-operative knee flexion. However, the mechanism by which tibial slope affects the function of TKA during dynamic activities of daily living is rather complex and not well documented. The aim of this study was to investigate the effect of tibial slope on the kinematics of the tibiofemoral (TF) contact point, quadriceps muscle forces, and patellofemoral (PF) joint contact forces during squat. In addition, we studied the effect of anterior tibial cortex-referencing (ACR) versus center of tibial plateau-referencing (CPR), as two possible techniques to obtain the desired degree of tibial slope. METHODS: A previously validated musculoskeletal model of a 86-year-old male subject, having a cruciate-retaining (CR) TKA prosthesis, was used to simulate a squat activity [1]. Motion-capture data were input to a motion optimization algorithm to find the full body kinematics. Quadriceps muscle forces were then calculated using inverse-dynamics. The kinematics of the TF contact point and PF joint contact forces were simultaneously calculated using force-dependent kinematics. A baseline case with 0° tibial slope was simulated, plus four additional cases with anterior (-3°), and posterior (+3°, +6°, +9°) tibial slope using the ACR technique (Fig. 1a), and four using the CPR technique (Fig. 1b). RESULTS: Compared to the baseline, more posterior tibial slope with ACR technique resulted in a larger excursion of the TF contact point, which shifted to a more anterior position, on the lateral side, and a more posterior position, on the medial side, in extension (Fig. 2). With the CPR technique, the contact point in extension shifted gradually more posterior on both sides with more posterior slope, and in flexion it shifted gradually more posterior mainly on the lateral side. The peak quadriceps force decreased on average by 1.7 and 1.2 % BW per degree of more posterior slope, with the ACR and CPR techniques, respectively. However, due to the different relative position of patella and femur, the peak PF contact force was mainly reduced by increasing the posterior slope with the CPR technique (-3.9 % BW/degree), rather than with the ACR technique (-1.5 % BW/degree) (Fig. 3). DISCUSSION: Increasing the tibial slope using the ACR technique produced large changes in the TF kinematics: the pattern of the contact point became more unstable, with a larger AP movement observed on the lateral side, denoting increased anterior-posterior laxity. On the other hand, variations of tibial slope with CPR technique resulted in more stable TF kinematics, more posterior position of the TF contact point, and a greater reduction of the PF contact forces. It is advisable to pre-plan the desired amount of tibial slope and execute it using the CPR technique. The surgeon should be very careful applying too much tibial slope with the ACR technique in CR-TKA, as it may have devastating effects on the TF kinematics, laxity and PF forces. SIGNIFICANCE: This study provides new insights into the effect of variation of tibial slope in TKA using different surgical techniques, which were not documented before, and used a highly controlled and parameterized study design and dynamic loading conditions. Orthopedic surgeons can directly use these results as an indication for the clinical practice. The presented tool can also be very useful for educational/medical training purposes. REFERENCES: [1] Marra MA, Vanheule V, Fluit R, et al. A Subject-Specific Musculoskeletal Modeling Framework to Predict In Vivo Mechanics of Total Knee Arthroplasty. ASME. J Biomech Eng. 2015;137(2):020904-020904-12 ACKNOWLEDGEMENTS: The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 323091 awarded to N. Verdonschot
Dutch translation and validation of the Norwich Patellar Instability score and Banff Patella Instability Instrument in patients after surgery for patellar instability
PurposeRecently, two new English specific patient reported outcome measures (PROMs) to evaluate treatment of patients with patellofemoral complaints have been developed: the Banff Patella Instability Instrument (BPII) and the Norwich Patellar Instability (NPI) score. This study was designed to translate and validate the BPII and NPI in Dutch patients after surgical treatment for patellar instability.MethodsForward and backward translation of the outcome measures was performed. Patients who had been surgically treated for patellar instability filled out the NPI and BPII together with the Kujala Knee Score, numeric rating scales, Knee disability and Osteoarthritis Outcome Score (KOOS) and SF-36. We assessed internal consistency and construct validity. We evaluated the presence of ceiling and floor effects.ResultsNinety-seven patients completed the online questionnaires. The internal consistency of the NPI and BPII score was excellent for both outcome measures. The BPII and NPI had good correlations with other PROMs. For the BPII we found no floor nor ceiling effect. For the NPI we found a floor effect but no ceiling effect. ConclusionOur results indicate that the Dutch version of the BPII and the NPI can be used for patients with patellar instability. Both PROMs have specific (dis)advantages.