Achieving Anatomic Kinematics in a Noncruciate Total Knee Arthroplasty: Preclinical Evaluation Using a Crouching Machine.

Abstract

Studies on patients have shown that normal anatomic motion is often not achieved with current total knee arthroplasty (TKA) designs. The purpose of this study was to determine whether anatomic motion could be restored using a design where intercondylar guiding surfaces were positioned between the medial and lateral femoral condyles. A crouching machine was constructed, which included simulations of the collateral ligaments, the quadriceps mechanism, the hamstrings, and the gastrocnemius. Medial pivot, medially congruent, ultracongruent, and replica intercondylar TKAs were designed and 3-dimensionally printed. The femoral-tibial kinematics were measured by determining lateral and medial contacts, as the knee underwent flexion and extension from 12 to 130°. The replica intercondylar design showed an almost constant position of the medial contact, with a progressive posterior displacement laterally during flexion. In contrast, the other designs showed nearly parallel motion with minimal variation in contact location. It was concluded that intercondylar guiding surfaces could produce anatomical motion in a TKA where the cruciate ligaments were resected.