Abstract
Background Unicompartmental knee arthroplasty (UKA) is an effective treatment for end-stage, symptomatic unicompartmental osteoarthritis (OA) of the knee joint. However, patellofemoral (PF) joint degeneration is a contraindication to medial UKA. Therefore, the objective of this study is to evaluate the biomechanical effect on the PF joint in medial UKA using fixed-bearing (FB) and mobile-bearing (MB) design prostheses. Methods A three-dimensional finite-element model of a normal knee joint was developed using medical image data. We performed statistical analysis for each model. The differences in the contact stress on the PF joint and the quadriceps force between the FB and MB designs were evaluated under a deep-knee-bend condition. Results At an early flexion angle, the results of the contact stress were showed that there was no significant difference between the FB and MB medial UKA models compared with the intact model. However, at a large flexion angle, we observed a significant increase in the contact stress of FB models. On the contrary, in the case of the MB models, there was no statistically significant increment compared to the intact model. Our results indicate that with medial UKA, the contact stress increased, and a greater quadriceps force was applied to the PF joint. However, there should be no difficulty in performing UKA on a PF joint with OA, unless there is anterior knee pain. This is because the increase in the contact stress is negligible. Conclusions Our results showed that there was no significant difference in contact stress on the PF joint between medial UKA and intact knee joints. In particular, such a mechanism was easily found in mobile-bearing medial UKA. Therefore, this study biomechanically showed that degenerative changes in the PF joint should not be considered an absolute contraindication for treatment with medial UKA.
Effects of contact stress on patellarfemoral joint and quadriceps force in fixed and mobile-bearing medial unicompartmental knee arthroplasty
