Summary

MOWHTO yields satisfactory 10-year survivorship in patients with medial compartment isolated knee OA and mechanical overload. Age, preoperative stage of OA disease and cartilage wear, and postoperative alignment are relevant risk factors that need to be taken into consideration

Abstract

Background

Medial opening wedge high tibial osteotomy (MOWHTO) is a reliable joint-preserving surgical procedure in case of isolated medial compartment knee osteoarthritis (OA) and mechanical overload. Despite the mid- to long-term promising results, age, sex, body mass index (BMI), and the extent of cartilage degeneration have been identified as primary contributors to the failure of HTO. The aim of this study was to evaluate the long-term survivorship and clinical outcomes of patients undergoing MOWHTO and to identify the risk factors associated with an increased risk of failure.

Methods

This was a retrospective study of prospectively collected patients who underwent MOWHTO for isolated medial osteoarthritis and overload between 2002 and 2023. A preoperative MRI and diagnostic arthroscopy were performed on every patient to ensure the osteoarthritis was limited to the medial compartment and classified according to the International Cartilage Repair Society (ICRS). Clinical outcomes were evaluated using the knee injury and osteoarthritis outcome score (KOOS) and Tegner activity score. The radiographic analysis included postoperative hip-knee-ankle angle (HKA) and medial proximal tibial angle (MPTA). Survivorship was intended free from conversion to total knee arthroplasty using the Kaplan–Meier curve. Logistic regression was used to identify risk factors, and p values <0.05 were considered significant.

Results

Overall, 431 patients (right: 227) underwent a MOWHTO and were included in the analysis. Males were 82.5% (356 patients), and the mean age was 49.1±8.0 years. The mean BMI was 29.8± 5.4 kg/m2. Patients lost to follow-up were 56 (12.9%). The KOOS score significantly increased in any subsection at a mean 5.7±4.5 years follow-up (p<0.001). The complication rate was 35.9%, and the reoperation rate was 25.5% at a mean 9.6-year follow-up. Removal of metal hardware occurred in 22.0% of the cases (95 of 431 patients). DVT occurred in 21 patients (4.9%), with 3 presenting a PE (0.7%). The mean preoperative HKA was 6.4±3.4° varus, whilst the mean postoperative HKA was 2.6±2.1° valgus. The mean postoperative MPTA was 93.4±2.6°. Overall, 89 patients (out of 431, 20.64%) were converted to TKA at a mean of 9.6 years of follow-up. The cumulative conversion rate to TKA at 5 years was 2.2%; at 10 years, 17.8%; and at 15 years, 37.1%. Age (odd ratio [OR] 1.05, p=0.017), wedge thickness (OR 1.08, p=0.015), medial femoral condyle OA (OR 3.41, p=0.029), medial tibial plateau OA (OR 2.04, p=0.044), postoperative HKA (OR 1.25, p=0.031) and postoperative MPTA (OR 1.26, p=0.04) were associated with an increased risk of failure.

Conclusion

MOWHTO yields satisfactory 10-year survivorship in patients with medial compartment isolated knee OA and mechanical overload. Age, preoperative stage of OA disease and cartilage wear, and postoperative alignment are relevant risk factors that need to be taken into consideration.