The reported outcomes of unicompartmental knee replacement (UKR) for spontaneous osteonecrosis of the knee (SPONK) often derive from small series with an average followup of 5 years, enabling to generate meaningful conclusions. Therefore, we determined the long-term functional results and the 10-years survivorship of the implant in all patients with advanced SPONK of the medial tibio-femoral compartment treated with a unicompartmental knee arthroplasty at our institute. We retrospectively evaluated 84 consecutive patients with late stage SPONK. All patients received a pre-operative MRI to confirm the diagnosis, to exclude any metaphyseal involvement and to assess the absence of significative degenerative changes in the lateral and PF compartment. Mean age at surgery was 66 years and mean body mass index (BMI) was 28.9. In all cases, SPONK involved the medial compartment; in 77 cases the medial femoral condyle (MFC) was involved, while in 7 cases the pathology site was the medial tibial plateau (MTP). Radiological evaluation was conducted by 3 different radiologists and clinical evaluation according to KSS and WOMAC score was performed by 3 fellows from outside institutions, with no previous clinical contact with the patients, at a mean followup of 98 months.Background
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