Abstract: Objective To compare the short- and long-term effects of unicondylar replacement with medial fixed platform and movable platform on spontaneous osteonecrosis of the knee(SONK). Methods A retrospective analysis of 72 SONK patients who underwent unicondyle replacement in our hospital from February 2016 to March 2020 was divided into medial fixed platform group(35 cases) and movable platform group according to the difference of the unicondyle replacement prosthesis used by the patients(37 cases).The operation time,intraoperative blood loss,knee range of motion(ROM),Knee Society(KSS) score,American Hospital for Special Surgery(HSS) score and lower extremity alignment were compared between the two groups.After a 2-year follow-up,the prosthesis survival of the two groups was analyzed.Results There was no significant difference in the operation time and intraoperative blood loss between the two groups(P>0.05).At 6 months after operation,the ROM,KSS score,HSS score,hip,knee and ankle angle of the two groups were all increased(P < 0.05),while the tibiofemoral angle was decreased(P<0.05).There was no significant difference in ROM,KSS score,HSS score,hip-knee-ankle angle,tibiofemoral angle and tibial retroversion angle between the two groups at 6 months after operation(P>0.05).There was no significant difference in the survival curve of prosthesis between the two groups(P>0.05). ConclusionThe treatment of SONK with medial fixed platform and movable platform unicondyle replacement is quite effective.

Key words: spontaneous knee osteonecrosis, medial fixed platform, movable platform, unicondylar replacement, curative effect