Experimental Study On Femoral Prosthesis Internal And External Maltranslations In Total Knee Arthroplasty And The Influence On Knee Joint Biomechanics Changes

Total knee arthroplasty has treated many patients with serious knee problems or suffered late phase of knee diseases successfully, and then could make them return to normal lives. Experts has been focusing on total knee arthroplasty all over the world. Experts still make studies and researches on the anatomy, biomechanics, kinetics of human knee extensively to improve prosthesis design, surgical techniques in order to achieve more reliable and better results. Two main problems surgeons which experts concern are surgical complications and polyethylene wear after operation. How to prevent and reduce the two forementioned problems is what orthopaedic surgeons concern of. This study is designed to identify the proper external and internal position of femoral component by researching the contact pressures and areas.Objectives To study the effect of alignment of femoral component on the patellofemoral and tibiofemoral biomechanics in total knee arthroplasty demonstrated on autopsy specimens, as the guide for surgeons to choose the correct reference of proper lateral and medial positions of femoral component and to reduce postoperative complications.Method 1.Select five frozen fresh human cadaver knees without gross deformities or instabilities as subjects.2.Design a patellofemoral and tibiofemoral testing jig and mount specimens onto it. Then, connect it to a KQL biomechanics machine (China) and make up a knee simulator. The study simulated the action of squatting from the standing position with the foot firmly planted. 3.Standard TKA was performed in each specimen by the same senior surgeon using PFC total knee system (Depuy Corporation, Warsaw Indiana). Alter lateral alignment of femoral component with reference on the maltranslations of 4mm lateral,2mm lateral,2mm medial and 4mm medial.4.Measure the biomechanics of patellofemoral and tibiofemoral joints using I-scan sensor (Tekscan Inc., Boston, USA )at 0°, 30°, 60°, 90°, and 120°of knee flexion. The digital values were obtained by the Autocad software.Results The group of external 4mm and internal 4mm maltranslations of femoral component lead to the higher peak value of tibiofemoral contact force at 90°and 120°of knee flexion (P<0.05). The peak value of the lateral patellofemoral contact force decreases as femoral component was placed at external positions. (P<0.05),while increasing as femoral component was placed at internel positions. (P<0.05).The peak value of the medial patellofemoral contact force decreases as femoral component was placed at 4mm internel positions at 60°, 90°, and 120°of knee flexion. (P<0.05).Conclusions It's reliable for surgeons to position femoral component between 4mm external maltranslation and neutural position with a proper rotation alignment.