Unicompartmental knee arthroplasty for spontaneous osteonecrosis

Background: Unicompartmental knee arthroplasty (UKA) is an effective treatment option for medial compartment osteoarthritis (OA) of the knee. Whether spontaneous osteonecrosis of the knee (SPONK) can be successfully treated with UKA remains controversial. This study evaluated the clinical and radiological results of patients with SPONK who were treated by UKA using Oxford phase III prostheses. Methods: We compared a prospective series of 23 UKA cases operated for SPONK with 235 UKA cases operated for OA. All patients underwent Magnetic Resonance Imaging (MRI) to confirm the diagnosis and exclude any major lesion in the lateral compartment. The stage, condylar ratio, and volume of the necrotic lesion were evaluated. The pre and postoperative Oxford knee scores (OKSs) were compared. Results: The mean follow-up was 60 months. No statistical differences in complication rates between the groups were found. The mean OKS improved from 39.48 ± 5.69 to 18.83 ± 3.82 (p < 0.05). There were no significant differences in the pre and postoperative OKS between the different groups. Conclusion: SPONK can be successfully treated with UKA, with a favorable short- to mid-term follow-up.