Unicompartmental knee arthroplasty for avascular osteonecrosis

The data analyzing clinical and radiological outcomes after modern unicompartmental knee arthroplasty (UKA) for spontaneous and secondary avascular osteonecrosis are limited. We determined whether: (1) UKA for osteonecrosis was as reliable for alleviating pain and improving function (measured by Knee Society scores) as it is for osteoarthritis, (2) lower limb alignment could be restored after UKA for osteonecrosis, and (3) UKA for osteonecrosis is as durable as UKA for osteoarthritis (measured by survivorship at 12 years). We retrospectively reviewed 30 patients (31 knees) with osteonecrosis; 21 knees had spontaneous osteonecrosis and 10 had secondary osteonecrosis. Mean patient age was 71 years. Clinical and radiological evaluations were performed by an independent observer at a minimum followup of 3 years (mean, 7 years; range, 3-16 years). Reliable pain relief and function improvement were obtained in 30 knees (96%). Restoration of an appropriate lower-limb mechanical axis was achieved for 27 knees (88%). The Kaplan-Meier survivorship was 96.7% at 12 years. Our data suggest UKA is a reasonable solution for restoring clinical function and radiological lower-limb alignment for spontaneous or secondary osteonecrosis limited to one compartment of the knee, with a durable survivorship.