Dislocation of the rotating platform after low contact stress total knee arthroplasty

From a one-surgeon series of 2485 patients, we report on 10 patients with rotating platform dislocation after primary Low Contact Stress total knee arthroplasty. All dislocations occurred within 2 years of the index procedure. Of the 10 patients, nine required open reduction. Five of these patients also had exchange of the original insert. One patient was treated by closed reduction. All knees were immobilized in a cast for 8 weeks. Eight of the 10 patients had no additional dislocation and at followup (average, 35 months; range, 12 months-5 years), had a stable functional joint. Two patients had recurrent spinout of the rotating platform develop. One patient had arthrodesis whereas the other patient had the insert cemented to the tibial tray as a salvage procedure. Increasing age, a preoperative valgus deformity, and prior patellectomy were significantly associated with rotating platform spinout. Surgical experience and an improved understanding of the soft tissue constraints, particularly in the valgus knee, are important in minimizing this complication.