The effect of medial condylar bone loss of the knee on coronal plane stability--a cadaveric study.

Overview

INTRODUCTION: The quantitative effects of medial bone loss of the knee on both leg alignment and coronal plane stability are poorly understood. MATERIALS AND METHODS: Utilizing computer navigation, 5mm bone defects of the medial distal femur (MDF), medial posterior femoral condyle (MPF), and medial tibial plateau (MT) were simulated in 10 cadaveric limbs, and alignment of the knee at various degrees of flexion were analyzed when applying standardized varus and valgus loads. RESULTS: The 5mm MPF defect significantly increased varus laxity at 90° of flexion by 3.3° ± 1.2° (p=0.019), a 5mm MDF defect resulted in a 2.2° ± 1.7° (p=0.037) and a 2.1° ± 1.3° (p=0.023) increase in laxity at 0° and 30° of flexion, respectively, and a 5mm MT defect increased varus laxity at all flexion angles by 4.0° to 7.0°, but was only statistically significant at 30° (p=0.026). DISCUSSION: This study confirms and quantifies the theories of flexion and extension gap balancing, and pseudolaxity of the medial collateral ligament in the varus knee, the results of which can be used in preoperative planning and intraoperative decision making for both total knee and unicondylar arthroplasty.