Individualised distal femoral cut improves femoral component placement and limb alignment during total knee replacement in knees with moderate and severe varus deformity.

Abstract

Our aim was to determine the variation in valgus correction angle and the influence of individualised distal femoral cut on femoral component placement and limb alignment during total knee replacement (TKR) in knees with varus deformity. The study was done prospectively in two stages. In the first stage, the valgus correction angle (VCA) was calculated in long-limb radiographs of 227 patients and correlated with pre-operative parameters of femoral bowing, neck-shaft angle and hip-knee-ankle angle. In the second part comprising of 240 knees with varus deformity, 140 (group 1) had the distal femoral cut individualised according to the calculated VCA, while the remaining 100 knees (group 1) were operated with a fixed distal femoral cut of 5°. The outcome of surgery was studied by grouping the knees as varus <10°, 10-15° and >15°. Of the 227 limbs analysed in stage I, 70 knees (31%) had a VCA angle outside 5-7°. Coronal bowing (p < 0.001), neck-shaft angle (p < 0.001) and preoperative deformity (p < 0.001) significantly influenced VCA. Results of the second phase of the study showed a significant improvement in both femoral component placement and postoperative alignment when VCA was individualised in the groups of knees with varus 10-15° (p 0.002) and varus >15° (p 0.002). Valgus correction angle is highly variable and is influenced by femoral bowing, neck-shaft angle and pre-operative deformity. Individualisation of VCA is preferable in patients with moderate and severe varus deformity. Level 2.