Isolated tibial deformity is the most prevalent varus pattern in North American patients undergoing medial opening wedge high tibial osteotomy.

Abstract

To evaluate the location of deformity in varus alignment in a North American population and assess early total knee arthroplasty (TKA) conversion rates and TKA-free survival following medial opening wedge high tibial osteotomy (MOWHTO) based on the bony deformity location. A retrospective analysis was performed on patients with varus alignment who underwent MOWHTO. Deformity analysis measured the hip-knee-ankle (HKA) angle, mechanical medial proximal tibial angle (mMPTA) and mechanical lateral distal femoral angle (mLDFA) using automated software. An abnormal mMPTA was defined as <85° and an abnormal mLDFA was defined as >90°. Cases were classified into four groups based on deformity location: tibial, femoral, combined or no bony deformity. The differences in TKA conversion rates among groups were analysed using the chi-square test, while TKA-free survival was determined using Kaplan-Meier survival analysis, with between-group differences assessed using the log-rank test. A total of 271 patients were included (mean age: 51.6 years; mean follow-up: 3.6 years). The mean HKA angle was 173.0° ± 3.1°. Among the 271 patients, 38% (<i>n</i> = 103), 18% (<i>n</i> = 48), 11% (<i>n</i> = 30) and 33% (<i>n</i> = 90) had tibial, femoral, combined and no bony deformity, respectively. TKA conversion rates were 3% (<i>n</i> = 3/103), 0% (<i>n</i> = 0/48), 7% (<i>n</i> = 2/30) and 9% (<i>n</i> = 8/90) for the tibial, femoral, combined and no bony deformity groups, respectively, with no significant difference among the groups (<i>p</i> = 0.080). Kaplan-Meier survival analysis showed no significant difference in TKA-free survival among the four groups (<i>p</i> = 0.185). In this North American cohort, various varus deformity locations were analysed, with isolated tibial deformity being the most prevalent. Regardless of deformity location, TKA conversion rates remained low, suggesting that MOWHTO may be beneficial even in patients without isolated tibial deformity. Level III.