Chao-Hua Fang1, Chia-Ming Chang2, Yu-Shu Lai3, Wen-Chuan Chen3, Da-Yong Song4, Colin J McClean2, Hao-Yuan Kao5, Tie-Bing Qu6, Cheng-Kung Cheng7,8,9,10,11. 1. Department of Joint Surgery, The 6th Hospital of Ningbo, Ningbo, Zhejiang, China. 2. Department of Biomedical Engineering, National Yang Ming University, Taipei, Taiwan. 3. Orthopaedic Device Research Center, National Yang Ming University, Taipei, Taiwan. 4. Naton Institute of Medical Technology, Beijing, China. 5. School of Biological Science and Medical Engineering, Beijing University of Aeronautics and Astronautics, Beijing, China. 6. Department of Orthopaedics, Beijing Chao-Yang Hospital, Affiliated Hospital of Capital Medical University, 8 Gongren Tiyuchang Nanlu, Chaoyang District, Beijing, 100020, China. qtb@medmail.com.cn. 7. Department of Biomedical Engineering, National Yang Ming University, Taipei, Taiwan. ckcheng2009@gmail.com. 8. Orthopaedic Device Research Center, National Yang Ming University, Taipei, Taiwan. ckcheng2009@gmail.com. 9. Naton Institute of Medical Technology, Beijing, China. ckcheng2009@gmail.com. 10. School of Biological Science and Medical Engineering, Beijing University of Aeronautics and Astronautics, Beijing, China. ckcheng2009@gmail.com. 11. Institute of Biomedical Engineering, National Yang Ming University, No. 155, Sec. 2, Li-Nong St., Beitou Dist., Taipei, 112, Taiwan. ckcheng2009@gmail.com.
Abstract
PURPOSE: Excellent clinical and kinematical performance is commonly reported after medial pivot knee arthroplasty. However, there is conflicting evidence as to whether the posterior cruciate ligament should be retained. This study simulated how the posterior cruciate ligament, post-cam mechanism and medial tibial insert morphology may affect postoperative kinematics. METHODS: After the computational intact knee model was validated according to the motion of a normal knee, four TKA models were built based on a medial pivot prosthesis; PS type, modified PS type, CR type with PCL retained and CR type with PCL sacrificed. Anteroposterior translation and axial rotation of femoral condyles on the tibia during 0°-135° knee flexion were analyzed. RESULTS: There was no significant difference in kinematics between the intact knee model and reported data for a normal knee. In all TKA models, normal motion was almost fully restored, except for the CR type with PCL sacrificed. Sacrificing the PCL produced paradoxical anterior femoral translation and tibial external rotation during full flexion. CONCLUSION: Either the posterior cruciate ligament or post-cam mechanism is necessary for medial pivot prostheses to regain normal kinematics after total knee arthroplasty. The morphology of medial tibial insert was also shown to produce a small but noticeable effect on knee kinematics. LEVEL OF EVIDENCE: V.
PURPOSE: Excellent clinical and kinematical performance is commonly reported after medial pivot knee arthroplasty. However, there is conflicting evidence as to whether the posterior cruciate ligament should be retained. This study simulated how the posterior cruciate ligament, post-cam mechanism and medial tibial insert morphology may affect postoperative kinematics. METHODS: After the computational intact knee model was validated according to the motion of a normal knee, four TKA models were built based on a medial pivot prosthesis; PS type, modified PS type, CR type with PCL retained and CR type with PCL sacrificed. Anteroposterior translation and axial rotation of femoral condyles on the tibia during 0°-135° knee flexion were analyzed. RESULTS: There was no significant difference in kinematics between the intact knee model and reported data for a normal knee. In all TKA models, normal motion was almost fully restored, except for the CR type with PCL sacrificed. Sacrificing the PCL produced paradoxical anterior femoral translation and tibial external rotation during full flexion. CONCLUSION: Either the posterior cruciate ligament or post-cam mechanism is necessary for medial pivot prostheses to regain normal kinematics after total knee arthroplasty. The morphology of medial tibial insert was also shown to produce a small but noticeable effect on knee kinematics. LEVEL OF EVIDENCE: V.
Entities:
Keywords:
Kinematics; Medial pivot; Posterior cruciate ligament; Total knee arthroplasty