RESUMEN
BACKGROUND: Unicompartmental knee arthroplasty (UKA) is an option for the treatment of spontaneous osteonecrosis of the knee (SONK). However, there are limited studies focusing on this area. This study presents medium-term clinical outcome data of UKA for SONK. METHODS: We reviewed 50 SONK knees in 48 patients that were treated by UKA. The mean age, height, and body weight were 73â¯years, 153â¯cm, and 57â¯kg, respectively. The mean follow-up was 8.4â¯years (range, four to 15â¯years). Preoperatively, we measured the size and the volume (estimated by widthâ¯×â¯lengthâ¯×â¯depth) of the necrotic bone mass on T1-weighted magnetic resonance imaging. The clinical results were evaluated serially at follow-up visits radiographically and with the Knee Society Scoring (KSS) and Oxford Knee Scoring (OKS) systems. RESULTS: There were no revisions, re-operations, or major complications. The mean sizes of the necrotic lesions were 17.2â¯mm (14.7-22.3â¯mm) in width, 28.2â¯mm (6.2-34.7â¯mm) in length, and 11.3â¯mm (3.2-14.5â¯mm) in depth. The mean volume was approximately 5.4â¯cm3 (0.7-10.3â¯cm3). The mean flexion of the knee, KSS Knee Score, Function Score, and OKS increased from a preoperative 128.7-137.5°, 52.3-91.3, 39.7-90.2, and 21.6-40.2, respectively, at the latest follow-up. At the last follow-up, all patients had good or excellent OKS. CONCLUSIONS: This study demonstrates that UKA is a good option and is reliable for the treatment of SONK irrespective of necrotic bone mass size.