Lateral Distal Femoral Condyle as a Precise Reference for Distal Femoral Resection in Total Knee Arthroplasty for Severe Varus Knee Osteoarthritis

Abstract

Purpose Bone resection was highly valued in total knee arthroplasty (TKA), but how to determine the amount of distal femur resection is still controversial. The purpose of this study was to explore how to use lateral condyle as a reference for distal femoral osteotomy in TKA. Method Imaging data from 118 nonarthritic subjects and 123 osteoarthritis (OA) subjects were used to assess the cartilage wear pattern of the distal femur in varus knees. Measurements were performed on three-dimensional reconstruction after virtual bone cutting. The difference between the resection amount of distal (0°) and posterior (90°) was calculated when the medial condyle was used as a reference in OA patients. The osteotomy amount on lateral was calculated in nonarthritic subjects when the medial condylar osteotomy was consistent with the thickness of the implants. Results In 43% of OA patients, there was༞1mm difference between the 0° and 90° in medial condyle cartilage, and no difference was observed in lateral. When using medial condyle as a reference for osteotomy, there was a difference of 1.3 ± 0.56 mm between the resection amount of 0° and 90°, and the difference was 0.24 ± 0.27 mm when using lateral condyle. Statistical analysis showed that there was a linear correlation between the resection amount of lateral condyle and mechanical lateral distal femoral angle (mLDFA) in nonarthritic subjects (R = 0.72, p<0.001). Conclusions Using the lateral condyle as the reference for distal femoral osteotomy is more suitable for the cartilage wear pattern of the varus knee. The position of cutting guide can be adjusted by preoperative measurements of mLDFA.