Total knee arthroplasty after formal knee fusion using unconstrained and semiconstrained components: a report of 7 cases.

Seven cases of total knee arthroplasty (TKA) after formal knee fusion were reviewed at a mean follow-up of 56 months (range, 12-161 months). The mean modified Hospital for Special Surgery score improved from 54 (range, 16-65) preoperatively to 68 (range, 57-80) at the latest follow-up. Mean range of motion was 74 degrees (range, 55-90 degrees ). Patient subjective rating was excellent or satisfied in 5 of 7 cases. Two patients underwent secondary refusion (1 for chronic infection, 1 for ligamentous instability). Six patients (86%) had to undergo reoperation for postoperative complications: 3 patients had open arthrolysis for adhesion and arthrofibrosis, 2 patients had a gastrocnemius flap for skin necrosis, and 1 patient had neurolysis of the peroneal nerve for painful paresis. Despite the presence of increased postoperative pain while walking, all 5 patients with the TKA still in place declared that they would undergo the same procedure again. The procedure of TKA in fused knees is technically demanding and has a considerable complication rate. Renewed mobility of the fused knee joint appears to correlate with increased pain on walking in this group of patients. Four types of postoperative problems were noted in the evaluation: skin necrosis, extensor mechanism contracture, insufficient collateral ligaments, and adhesion and arthrofibrosis. Takedown of a formal knee fusion with TKA should be performed only in carefully selected cases and in highly motivated patients with realistic expectations.