Biomechanical effects of posterior tibial slope on unicompartmental knee arthroplasty using finite element analysis

Abstract

BACKGROUND: The effects of the posterior slope of the tibial prosthesis on unicompartmental knee arthroplasty have not been fully evaluated and controversies still exist.

OBJECTIVE: This study evaluates the effects of the posterior slope of the tibia on contact stresses in polyethylene inserts and articular cartilage using finite element analysis.

METHODS: We generated a computational model followed by the development of a posterior tibial slope (PTS) from -1° to 15° cases with increments of 2° PTS models. Using a validated finite element (FE) model, we investigated the influence of the changes in PTS on the contact stress in the medial polyethylene insert and lateral cartilage. The FE model's loading condition is level walking, a normal daily activity.

RESULTS: The contact stress increased on the lateral articular cartilage as the PTS increased. The contact stress on the polyethylene insert differed from the contact stress on the lateral articular cartilage, and it generally increased as the PTS decreased. However, in the initial stance phase when an axial force was exerted, it increased as the PTS increased.

CONCLUSIONS: Our results show that an offset of ±2° from the initial anatomical tibial slope does not biomechanically affect the outcome.