Three-dimensional motion analysis for the patella of the natural and artificial knee joints.

Abstract

In the field of biomechanics in vivo, functional assessment of the natural and artificial knee joints has been investigated. Therefore, the artificial knee joints have acquired a new support construction and wear resistance. To further improve the functionality of the artificial knee joints, it is important to analyze the patella. Because, we believe patella is involved in deep flexion and stability of the knee joints. This study focused on the patella of the natural and artificial knee joints during squat activity. Motion analysis techniques were image correlation method for the natural joints and shape matching method for the artificial joints. Average errors of these technique were within 1.0 mm for the translation, and within 1.0 degrees for the rotation. The subjects were three natural knee joints and four artificial knee joints (Zimmer NexGen LPS-Flex). We evaluated the six-degree-of-freedom motion of the patella, and the contact location of patellofemoral joints. In the results, the patellar components of the artificial knee joints were positioned medial side compared to the patella of the natural knee joints. Furthermore, the artificial knee joint was confirmed contact with patellar component edge. Therefore, we were concerned about uneven wear of the artificial knee joints. From these results, we showed the importance of considering the design of the patellofemoral joint surface.