A radiographic analysis of anterior-posterior translation in total knee arthroplasty

Abstract

We performed radiological analyses to examine the relationship between the knee flexion angle and the anteroposterior translation movement relative to the prosthetic components (NexGen type) after total knee arthroplasty (TKA). Cruciate-retaining (CR) type TKA was performed in 12 knees with osteoarthritis (OA) and 9 knees with rheumatoid arthritis (RA) in which no posterior cruciate ligament (PCL) tear was present. Posterior-stabilized (PS) type TKA was performed in 7 OA knees and 7 RA knees in which the PCL was defective or resected. The measurements were performed according to the methods of Watanabe. The contact point ratio (percentage) was calculated by dividing the distance to the contact point (CP; the closest point of contact between the femoral and tibial components) by the antero-posterior length of the tibial component. After TKA, the CP at full extension was positioned more posteriorly than in the normal knee both under weight-bearing and non-weight-bearing conditions. Except for the RA knees in the PS group, the CP translated anteriorly in the early phase of flexion and then posteriorly. Under weight-bearing conditions, the posterior translation occurred earlier and was smaller in magnitude. For RA knees in the PS group, the CP moved gently posteriorly right from the beginning.