RESUMEN
Objective To investigate the relative motion between the femoral component and the tibial insert through the technology of fluoroscopy and digital model.Methods Sixteen female patients (16 knees) with knee osteoarthritis were performed TKA (GENESIS Ⅱ) from July 2007 to June 2008.The mean age was 66.4 years (range from 56 to 76 years).All patients were followed up 48 months to 60 months,with the mean of 56±3 months.The postoperative clinical function was evaluated by Knee Society Score (KSS).To match the digital model to the imaging data of fluoroscopy using 2D-3D automatic registration technology and reconstruct motion of the knee after TKA.The movement of contact position between femoral medial and lateral condyle and tibial insert and tibial internal rotation during flexion were measured.The contact time and range between femoral cam and tibial post were analyzed.Results The cases were statistically improved in KSS postoperatively,knee score was 93±5 and function score 88±13.The range of movement for femoral medial condyle was 8.5±2.5 mm,and the lateral condyle was 9.5±4.8 mm,the range of tibial internal rotation was 2.5°±8.4°.The contact of cam and post was observed after 30°-40° flexion of the knee,and the range was 8.0±1.8 mm.The greater tilting angle of the tibial plateau was,the later contact between cam and post happened.Conclusion The kinematics of tibiofemoral joint after TKA is different from the kinematics of normal knee.With knee flexion within 10°-30°,femoral medial condyle moves forward.When flexion is greater than 40°,medial and lateral condyle begins rollback.The time of contact of cam and post is relative to tibial prosthesis slope.