Unicompartmental Knee Arthroplasty Versus Opening-Wedge High Tibial Osteotomy for Spontaneous Osteonecrosis of the Knee: A Retrospective Cohort Study.

Background: Unicompartmental knee arthroplasty (UKA) and high tibial osteotomy (HTO) are treatment options for patients with medial spontaneous osteonecrosis of the knee (SONK). Purpose: To compare the clinical outcomes after UKA and HTO in patients with SONK. Study Design: Cohort study; Level of evidence, 3. Methods: This retrospective study included 42 patients who had undergone Oxford UKA and 40 patients who had undergone opening-wedge HTO between 2014 and 2020. All patients were diagnosed with isolated medial SONK without subchondral collapse of the femoral condyle and tibial plateau. The patients were preoperatively and postoperatively evaluated using the Lysholm knee scoring system, the Western Ontario and McMaster Universities Osteoarthritis Index, and a numeric rating scale assessing patient satisfaction. Results: Patients in the UKA group were significantly older than those in the HTO group (median age, 71.5 years [IQR, 68.0-76.5 years] vs 65.0 years [IQR, 60.0-70.0 years], respectively; P <.001). The median follow-up time was 3.78 years (IQR, 2.45-4.53 years) for the UKA group and 3.87 years (IQR, 2.90-5.60 years) for the HTO group. Significant improvements in functional scores were observed in both the UKA and HTO groups (P <.001 for all), with no significant between-group differences in scores at the final follow-up (≥2 years after surgery). The satisfaction rate was similar (80.95% for UKA and 75.0% for HTO). Conclusion: According to the study results, significant improvements in clinical outcomes were seen after opening-wedge HTO with microfracture for a younger group of patients with SONK without subchondral collapse, while Oxford UKA had a comparable effect on an older group of patients. Both UKA and HTO were found to be viable surgical approaches for SONK at short- to midterm follow-up. [ABSTRACT FROM AUTHOR]