Résumé
Objective A three-dimensional （3D） printing precise pressure device was designed specifically targeted at cambered limbs according to the requirement of postoperative rehabilitation of total knee replacement(TKR), and its effectiveness and safety was verified by finite element analysis. Methods Based on gastrocnemius muscle of lower limbs as the pressurized objects, the precise pressure device was designed, which contained an air pressure generating module, an inflatable airbag and a 3D printing brace. Through the closed loop control algorithm, the device stably supplied different pressures in the airbag. Distributed pressure data of the airbag-skin within contact surface were collected under different experimental conditions and imported into biomechanical simulation software which combined CT images to reconstruct 3D model of the lower limb mechanics. Finally, the effective compression area fraction and the joint micro-motion angle under each condition were obtained, to verify the effectiveness and safety of the system. Results Using generally preferred 4 cm-size offset and 4-barrel airbag configurations, under different intracapsular pressure of 5.32，6.65，7.98，9.31，10.64 kPa, the simulated knee joint micro-motion angles were 5.3°, 6.1°, 7.2°, 9.5°, 10.6°， respectively, and the effective compression area fraction could be up to 90-8%-95-2%. Conclusions For the optimized scheme, the dynamic range of joint micro-motion angle and the effective compression area fraction caused by different airbag pressure values were the best and met the design requirements of effectiveness and safety. The research findings can contribute to analyzing the influence of compression system on limb biomechanics, which are of great significance for effective and safe rehabilitation training after TKR.
Résumé
Objective To establish a personalized musculoskeletal multi-body dynamics model of total knee replacement (TKR) by two software nmsBuilder and OpenSim, and verify this established model by using bouncy and medthrust gait patterns. Methods Based on skeletal data from a patient, the body, skeletal landmark clouds and muscular landmark clouds were established for automatically generating reference systems and muscles. The musculoskeletal model generated by nmsBuilder was introduced into OpenSim, and inverse kinematics, static optimization and knee joint force analysis were performed successively. Finally, the model was driven by bouncy gait and medthrust gait respectively, and the results were compared with experimental measurements. Results Except for the lateral joint contact forces, the predicted magnitude and trend of knee joint contact forces by the model had a good agreement with the experimental data, and the constructed skeletal muscle multi-body dynamics model could be used for knee joint research. Conclusions The established musculoskeletal multi-body dynamics model could predict the medial, lateral and total tibiofemoral joint contact forces simultaneously by inputting the marker positions and the ground reaction forces. The research ideas of this study can provide references for designing personalized knee prostheses for TKR patient.
Résumé
Objective To study the effect of stair ascent on insert wear of total knee replacement (TKA) by finite element model, which is of great theoretical and practical significance for improvement of wear evaluation method and guidance of design of artificial knee joint prosthesis. Method A finite element analysis model of TKR wear based on Archard’s law was established and validated. The model was applied with loads under normal level walking (ISO14243) and stair ascent, respectively, to compare and analyze the influence of stair ascent on TKR wear. Results The predicted wear during level walking was consistent with experimental results reported in the literature. The volumetric wear rate during stair ascent was 37.10 mm3 per million cycles (MC), which was significantly higher than that during level walking (16.94 mm3/MC). The linear wear during stair ascent was significantly higher than that during level walking as well. Wear during stair ascent was mainly distributed in the backward area of medial platform, which was obviously different from that during level walking. Conclusions As a common daily activity with high loads and high flexion angles, stair ascent contributes an important part in TKR wear, and more attention should be paid to the testing and evaluation of TKR wear.
Résumé
Objective To develop a musculoskeletal multi-body dynamic model of the patient-specific total knee replacement (TKR), and to simulate knee joint biomechanical characters of the patient during right-turn gait. Methods Based on the musculoskeletal dynamic software AnyBody and the method of force-dependent kinematics as well as the related data from a patient with TKR, the corresponding patient specific lower extremity musculoskeletal multi-body dynamic model was constructed and then used to simulate the right-turn gait of the patient. The knee contact forces, motion, muscle activations and ligament forces were predicted simultaneously by inverse dynamics analysis on such right-turn gait. ResultsThe root mean square error of the predicted average tibiofemoral medial contact force and lateral contact force were 285 N and 164 N, respectively, and the correlation coefficients were 0.95 and 0.61, respectively. The predicted average patellar contact force was 250 N. The predicted contact forces and muscle activations were consistent with those in vivo measurements obtained from the patient. In addition, the model also predicted the average range of tibiofemoral rotations of flexion-extension, internal-external, varus-valgus as 3°-47°, -3.4°-1.5°, 0.2°--1.5°, and the average range of tibiofemoral translations of anterior-posterior, inferior-superior, medial-lateral as 2.6-9 mm, 1.6-3.2 mm, 4.2-5.2 mm, respectively. The predicted average peak value of the medial, lateral collateral ligament force and posterior cruciate ligament force were 190, 108, 108 N, respectively. Conclusions The developed model can predict in vivo knee joint biomechanics, which offers a robust computational platform for future study on the failure mechanisms of knee prosthesis in clinic.