Summary

Our technique of obtaining extension gap balancing using trial components led to safe and effective balancing by avoiding unnecessary extensive release in severe varus deformity during total knee arthroplasty.

Abstract

Introduction

Extensive medial soft tissue release may be necessary to correct severe varus deformity during total knee arthroplasty (TKA). However, this procedure may result in instability. The aims of this study were: (1) to describe our novel technique to achieve a proper gap balancing with minimal soft tissue release, using trial components in severe varus deformity with hip-knee-ankle (HKA) angle of more than 20° of varus during TKA; (2) to evaluate whether this technique ensured appropriate medial release in all knees with severe varus deformity; and (3) to compare the mediolateral (ML) stability of these knees with those having mild deformity following TKA. For the third purpose, a comparative study in terms of ML stability, clinical and radiographic results was conducted in a control group of patients who underwent deep medial collateral ligamnet release only during primary TKA.

Methods

Fifty knees (40 patients) with hip-knee-ankle angle of more than 20° of varus were corrected using this technique (group 1). After achieving flexion gap balancing by needle puncturing and spreading of the medial collateral ligament, extension gap balancing was obtained by gradual extension with the trial components in place. After group 1 was set, a one to one patient-matched control group who had mild varus deformity was selected by propensity score matching (50 knees, 48 patients, group 2). At postoperative one year, ML laxity was compared between the two groups using the stress radiographs. Clinical outcomes were also compared using the Knee Society Score (KSS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score.

Results

There were significant differences in preoperative knee alignments, i.e., Femorotibial angle (FTA) and HKA angle between the groups (both, p < 0.001). However, there were no differences in FTA and HKA angle between groups at postoperative one-year follow-up (p = 0.552 and p = 0.334, respectively). There were no differences in mean medial and lateral laxities between groups 1 and 2 at one year after the operation (medial laxity; 2.3 ± 1.4° and 2.7 ± 1.3°, respectively, p = 0.310) (lateral laxity; 3.6 ± 1.7° and 3.2 ± 2.0°, respectively, p = 0.459). Group 1 showed significantly worse KSS and WOMAC score than group 2 preoperatively (p = 0.024 and p = 0.008, respectively). There were significant differences in function subscore and total score of KSS. The statistically significant differences in function subscore and total score of WOMAC were also noted. However, postoperative KSS and WOMAC score showed no significant differences between the groups. The mean polyethylene thickness was 12.3 ± 2.0 in group 1 and 10.9 ± 1.1 in group 2. Group 1 needed significantly thicker polyethylene insert than group 1 (p < 0.001).

Discussion

& Conclusion: Our technique of obtaining extension gap balancing using trial components led to safe and effective balancing by avoiding unnecessary extensive release in severe varus deformity during TKA.