Varus-valgus stress radiograph as a predictor for extensive medial release in total knee arthroplasty

Purpose

The purpose of this study was to identify the risk factors for predicting the reduction osteotomy as extensive medial release during total knee arthroplasty (TKA) using multivariate logistic regression.

Methods

A total of 404 TKAs were enrolled and sorted into two groups according to the extent of medial release and then analysed for the statistical significance of various risk factors including age, gender, body mass index (BMI), pre-operative knee mechanical axis angle (KMAA), mechanical varus stress angle (MVrSA), mechanical valgus stress angle (MVgSA), and sum of the mechanical varus and valgus stress angles (SMVVA) with use of multivariate logistic regression analysis.

Results

SMVVA to a more varus direction was found to be a significant risk factor for the reduction osteotomy (p < 0.0001, adjusted odds ratio (OR) = 2.705 with 95 % CI 2.126–3.443). KMAA and MVgSA to a more varus direction were also significant risk factors (p = 0.010, adjusted OR = 1.189 with 95 % CI 1.041–1.357, and p = 0.005, adjusted OR = 1.401 with 95 % CI 1.109–1.767). The other variables were not significant risk factors.

Conclusions

The overall results suggest that careful attention should be given to the need for extensive medial release and failure of the conventional soft tissue release technique during TKA in patients with a greater varus angle in the pre-operative SMVVA, MVgSA, and KMAA, especially with a greater varus SMVVA, which was the strongest predictor of reduction osteotomy.

Level of evidence: Level III, retrospective comparative study