ABSTRACT
Objective Aiming at the medial prosthetic loosening failure and lateral cartilage degeneration after unicompartmental knee arthroplasty ( UKA), the effects of prosthetic installation errors of joint line in UKA on knee contact mechanics and kinematics during different physiologic activities were studied using musculoskeletal multi-body dynamic method. Methods Taking the medial natural joint line as 0 mm error, six installation errors ofjoint line including ±2 mm, ±4 mm and ±6 mm were considered respectively, and seven musculoskeletal multi body dynamic models of medial UKA were established, to comparatively study the variations in knee contact mechanics and kinematics during walking and squatting. Results At 70% of walking gait cycle, compared with 0 mm error, the medial prosthetic contact force was increased by 127. 3% and the contact force of the lateral cartilage was decreased by 12. 0% under 2 mm elevation in joint line, the medial prosthetic contact force was close to 0 N, but the lateral cartilage contact forces were increased by 10. 1% under 4 mm reduction in joint line. The tibiofemoral total contact forces were increased by 19. 7% and decreased by 14. 2% under 2 mm elevation and 2 mm reduction in joint line, respectively. At the 100°knee flexion during squatting, compared with 0 mm error, the medial prosthetic contact force and the tibiofemoral total contact force increased by 31. 6% and 11. 1% under 2 mm elevation in joint line, and decreased by 24. 5% and 8. 5% under 2 mm reduction in joint line, respectively. The change in the lateral cartilage contact force was not marked. Moreover, at 70% of walking gait cycle, the varus angle decreased, the internal rotation and the anterior translation increased along with the elevation of joint line in UKA, while it was just the opposite along with the reduction of joint line in UKA. The trends of the varus valgus movement and anterior-posterior translation during squatting were consistent with those during swing phase of walking, but the trend of the internal-external rotation was opposite. Conclusions In order to reduce the risk of medial prosthetic loosening failure and lateral cartilage degeneration, it is recommended that the installation error of joint line in UKA should be controlled in the range of -2 mm to +2 mm. This study provides theoretical basis for UKA clinical failure caused by changes in joint line
ABSTRACT
Objective To investigate the method of modeling, finite element modeling and AnyBody musculoskeletal multi-body dynamics simulation technique analyze the biomechanics of clinical orthopaedic surgery. Methods The AnyBody software was used to establish the musculoskeletal motor model of the individualized upper limbs according to the height, weight and CT data of the volunteers. The flexion motion of the elbow in normal people was simulated, and the muscle force, joint force, torque, constraint condition of the humerus during the flexion movement were derived and used as the boundary conditions of finite element analysis.Then, the 3D reconstruction was conducted in the MIMICS software based on CT data. In the Geomagic Studio software, the humeral curved surface and position coordinate matching were completed, and grid division and material assignment were done in the HyperMesh software. Finally, the 3D reconstruction for finite element model of the humerus was introduced into ABAQUS software. The boundary condition data derived from the AnyBody software were applied and the stress calculation analysis was performed. Results The results of the stress and displacement of the humerus during elbow flexion motion were calculated in the ABAQUS software. The maximum stress and displacement of the humerus were 0.76 MPa and 20 μm when flexion of the elbow joint was about 90°. Conclusions A continuous dynamic analysis of humeral stress and displacement during elbow flexion motion was realized, which was more consistent with the requirements of human physiological anatomy and could provide an efficient analysis platform and a new way for studying clinical orthopedic problems.
ABSTRACT
Objective To establish the musculoskeletal multi-body dynamic foot-ground contact model and explore its applicability at different speed. Methods The gait data of the subjects at different speed were collected, and the foot-ground contact model was established based on the full body model from the musculoskeletal multibody dynamic software AnyBody. Then the calculated ground reaction forces (GRFs) and ground reaction moments (GRMs) at different speed (slow walking, normal walking, fast walking and jogging) were compared with the measurements from the force plates. Results The predicted GRFs and GRMs correlated well with the experimental measurements at slow, normal and fast speed (stride speed ranged from 0.69 to 1.68 m/s). The correlation coefficients between predicted and measured GRFs were greater than 0.875 and the correlation coefficients for GRMs were greater than 0.9. Conclusions The developed foot-ground contact model could simultaneously predict GRFs and GRMs with good accuracy, thus eliminating the dependency on force plates. The model could be applied to low-speed gait conditions, such as the elderly and pathological gait.
ABSTRACT
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.