2025 ISAKOS Biennial Congress ePoster
Comparable Early Conversion Rates To Total Knee Arthroplasty Among Different Bony Deformity Locations After Medial Opening Wedge High Tibial Osteotomy: A North American Cohort Study
Takaaki Hiranaka, MD, PhD, Sydney, NSW AUSTRALIA
Takeo Tokura, MD, Kobe, Hyogo JAPAN
Ryan M. Degen, MD, FRCSC, London, ON CANADA
Kevin R. Willits, MD, FRCS, London, ON CANADA
Robert Litchfield, MD, FRCSC, London, ON CANADA
Alan Getgood, MD, FRCS(Tr&Orth), DipSEM, Doha QATAR
Fowler Kennedy Sports Medicine Clinic, Western University, London, ON, CANADA
FDA Status Cleared
Summary
This North American cohort study found similar early TKA conversion rates across different varus deformity locations after MOWHTO, suggesting that patients without isolated tibial deformity may still benefit from the procedure.
Abstract
Purpose
To evaluate the center 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.
Methods
A retrospective analysis was performed on 271 digital full-leg standing radiographs of cases with varus alignment who underwent MOWHTO (mean age: 51.6 years; mean follow-up: 3.6 years). 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 analyzed 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.
Results
The mean HKA angle was 173.0° ± 3.1°. Among the 271 patients, 38% (n = 103), 18% (n = 48), 11% (n = 30), and 33% (n = 90) had tibial, femoral, combined, and no bony deformity, respectively. TKA conversion rates were 3% (n = 3/103), 0% (n = 0/48), 7% (n = 2/30), and 9% (n = 8/90) for the tibial, femoral, combined, and no bony deformity groups, respectively, with no significant difference among the groups (p = 0.080). Kaplan–Meier survival analysis showed no significant difference in TKA-free survival among the four groups (p = 0.185).
Conclusions
In this North American cohort, various varus deformity locations were observed, with isolated tibial deformity being the most prevalent. Additionally, two-thirds of cases exhibited bony deformity, while one-third had no identifiable bony deformity. Regardless of the specific deformity location, the conversion rate to TKA remained low, suggesting that even patients without isolated tibial deformity may still experience a beneficial treatment effect from MOWHTO.