In vivo kinematics of mobile-bearing knee arthroplasty in deep knee bending motion

The current study aimed to analyze kinematics during deep knee bending motion by subjects with fully congruent mobile-bearing total knee arthroplasties allowing axial rotation and anteroposterior (AP) gliding. Twelve subjects were implanted with Dual Bearing Knee prostheses (DBK, slot type: Finsbury Orthopaedics, Surrey, UK). These implants include a mobile-bearing insert that is fully congruent with the femoral component throughout flexion and allows axial rotation and limited AP translation. Sequential fluoroscopic images were taken in the sagittal plane during loaded knee bending motion. In vivo kinematics were analyzed using a two- to three-dimensional registration technique, which uses computer-assisted design models to reproduce the spatial position of femoral and tibial components from single-view fluoroscopic images. The average femoral component demonstrated 13.4degrees external axial rotation for 0-120degrees flexion. On average, the medial condyle moved anteriorly 6.2 mm for 0-100degrees flexion, then posteriorly 4.0 mm for 100-120degrees flexion. On average, the lateral condyle moved anteriorly 1.0 mm for 0-40degrees flexion, then posteriorly 8.7 mm for 40-120degrees flexion. The typical subject exhibited a lateral pivot pattern from extension to 60degrees flexion and a central pivot pattern from 60degrees to 100degrees flexion, patterns that are not usually observed in normal knees. Subsequently from 100degrees to 120degrees flexion, a rollback pattern was reproduced in which bilateral condyles moved backward. (C) 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.