Different femoral origins of valgus deformity affect aspect ratios of resected distal femurs in total knee arthroplasty

This study aimed to evaluate the anthropometry of resected distal femurs in valgus knees at the level of standard cuts during total knee arthroplasty (TKA), and to compare these measurements to neutrally aligned knees.

Anteroposterior and mediolateral measurements of the distal femur were performed on three-dimensional computed tomography reconstructions of 57 valgus knees (34 intra-articular valgus and 23 juxta-articular valgus) and 40 neutrally aligned knees. The measured dimensions and calculated aspect ratios (ARs) were subsequently compared.

Juxta-articular valgus knees had similar ARs when compared with neutrally aligned knees (1.14 ± 0.06 vs. 1.12 ± 0.05, P = 0.103). However, intra-articular valgus knees had smaller ARs (1.09 ± 0.07) when compared with juxta-articular valgus (P = 0.002) or neutrally aligned knees (P = 0.023).

Different origins of valgus deformity in the femur can significantly affect the AR values on the resected surface of the distal femur. Pre-operative evaluation of a valgus deformity may assist in estimating the morphology of the resected distal femur during TKA.