Application strategy of finite element analysis in artificial knee arthroplasty.

Artificial knee arthroplasty, as the most effective method for the treatment of end-stage joint diseases such as knee osteoarthritis and rheumatoid arthritis, is widely used in the field of joint surgery. At present, Finite element analysis (FEA) has been widely used in artificial knee replacement biomechanical research. This review presents the current hotspots for the application of FEA in the field of artificial knee replacement by reviewing the existing research literature and, by comparison, summarizes guidance and recommendations for artificial knee replacement surgery. We believe that lower contact stress can produce less wear and complications when components move against each other, in the process of total knee arthroplasty (TKA), mobile-bearing prostheses reduce the contact surface stress of the tibial-femoral joint compared with fixed-bearing prostheses, thus reducing the wear of the polyethylene insert. Compared with mechanical alignment, kinematic alignment reduces the maximum stress and maximum strain of the femoral component and polyethylene insert in TKA, and the lower stress reduces the wear of the joint contact surface and prolongs the life of the prosthesis. In the unicompartmental knee arthroplasty (UKA), the femoral and tibial components of mobile-bearing prostheses have better conformity, which can reduce the wear of the components, while local stress concentration caused by excessive overconformity of fixed-bearing prostheses should be avoided in UKA to prevent accelerated wear of the components, the mobile-bearing prosthesis maintained in the coronal position from 4° varus to 4° valgus and the fixed-bearing prosthesis implanted in the neutral position (0°) are recommended. In revision total knee arthroplasty (RTKA), the stem implant design should maintain the best balance between preserving bone and reducing stress around the prosthesis after implantation. Compared with cemented stems, cementless press-fit femoral stems show higher fretting, for tibial plateau bone defects, porous metal blocks are more effective in stress dispersion. Finally, compared with traditional mechanical research methods, FEA methods can yield relatively accurate simulations, which could compensate for the deficiencies of traditional mechanics in knee joint research. Thus, FEA has great potential for applications in the field of medicine.

The effects of different repair methods for a posterior root tear of the lateral meniscus on the biomechanics of the knee: a finite element analysis.

PURPOSE: To explore the impact of different repair methods for a lateral meniscus posterior root tear on the biomechanics of the knee joint using finite element analysis. METHODS: Finite element models of a healthy knee were established on the basis of MRI data from a volunteer using Mimics software, and the validity of the models was tested. The changes in the contact mechanics and kinematics of these finite element models under different repair approaches were then analyzed and compared. RESULTS: The normal meniscus had the maximum joint contact area, the minimum contact pressure, and the minimum contact stress. When total meniscectomy of the lateral meniscus was performed, the lateral compartment had the minimum joint contact area, the maximum contact pressure and the maximum contact stress. When complete avulsions of the posterior root of the lateral meniscus occurred, the maximum values of contact pressure and contact stress were between those of an intact meniscus and those of a meniscus treated with total meniscectomy. Lateral meniscal root attachment reconstruction by the single-stitch and double-stitch techniques resulted in a significant decrease in joint contact pressure and contact stress, leading to values comparable to those of a normal knee joint, and the double-stitch technique performed better than the single-stitch technique. CONCLUSIONS: Repair surgery for lateral meniscal posterior root avulsions can effectively restore the contact mechanics and kinematics of the knee joint, and the double-stitch technique can result in better clinical outcomes than the single-stitch technique.

The Effects of Lateral Meniscus Posterior Root Tear and its Repair on Knee Stability of Internal Rotation and Forward Shift: A Biomechanical Kinematics Cadaver Study.

Objective: Lateral meniscal posterior root (LMPR) is an important stabilizer for knee joint, providing the stability during tibia forward shifting and internal rotating. It is still controversial that whether the LMPR tear (LMPRT) should be repaired together with ACL reconstruction. This study aims to investigate the effects of LMPR on knee stability with intact ACL. Methods: Eight cadaver knees were used and performed the biomechanical kinematics tests in orders of: Group A: the LMPR was intact; Group B: the LMPR was cut off from its tibial end; Group C: the LMPRT has been repaired. 1) An internal rotation moment (5 Nm) was given to the tibia, then the internal rotation angle of the tibia was measured; 2) An forward shifting force (134 N) was given to the tibia, then the anterior displacement of the tibia was measured; 3) An internal rotation moment (5 Nm) and a valgus moment (10 Nm) were given to the tibia, then the internal rotation angle and the anterior displacement was measured. The stability was inferred from smaller rotation angle and displacement, and all of the angles and displacements were measured at knee flexion of 0°, 30°, 60° and 90°, respectively. Results: Comparing to Group A, the internal rotation angle in Group B was increased significantly at knee flexion of 30° (p = 0.025), 60° (p = 0.041), 90° (p = 0.002); the anterior tibia displacement in Group B was increased significantly at knee flexion of 30° (p = 0.015), 60° (p = 0.024); at knee valgus, the internal rotation angle was also increased significantly at knee flexion of 60° (p = 0.011), 90° (p = 0.037). Comparing to Group B, the internal rotation angle in Group C was decreased significantly at knee flexion of 30° (p = 0.030), 60° (p = 0.019), 90° (p = 0.021); the anterior displacement in Group C was decreased significantly at knee flexion of 30° (p = 0.042), 60° (p = 0.037); at valgus, the internal rotation angle was also decreased significantly at knee flexion of 60° (p = 0.013), 90° (p = 0.045). Comparing to Group A, only the internal rotation angle (p = 0.047) and anterior displacement (p = 0.033) in Group C were increased at knee flexion of 30°. Conclusion: In simulated knee with intact ACL, LMPRT can still lead to the notable internal rotational instability at knee flexion from 30° to 90°, as well as the anterior shift instability at knee flexion from 30° to 60°. LMPRT repair help to improve the internal rotation stability at 30° and restore it at 60° to 90°, and improve the anterior shift stability at 30° and restore it at 60°.