Why do ankle arthrodeses fail in patients with rheumatic disease?

Solid and painless fusion was achieved in 117/130 patients (90%) with rheumatic diseases after primary ankle arthrodesis at the authors' institution. Operations were performed using internal fixation according to the Adams technique. Critical retrospective analysis of failures in 13 patients (11 nonunions, one postoperative low-grade infection, and one painful arthrodesis) revealed errors in the primary operative technique in 10/13 ankles (77%), resulting typically from the surgeon's attempt to overcompensate a malaligned ankle while ignoring correction of the hindfoot deformity (subtalar complex). The optimum of 0-5 degrees of valgus was found in only 5/13 patients (38%). All four patients with varus alignment presented with malleolar pain. Bone grafting was adequate even in those patients with failure, whereas immobilization time was suboptimal in one patient (eight weeks). Patient satisfaction was lowered in every case of nonunion. Revision arthrodesis of failed primary fusion was successful in 10/13 patients (77%), however three additional stress fractures, two painful ankles without nonunions, and one superficial wound infection were detected. Ankle arthrodesis is a demanding procedure, and the operation should always be performed by an experienced surgeon, taking into account the alignment, ligament, and muscle balance of the rheumatoid ankle and hindfoot. Correction and rebalancing of these factors and the use of bone grafts are of crucial importance when considering the optimal conditions for fusion. Nonunions, infections, and stress fractures occurring after the primary arthrodesis are severe complications, leading eventually to revision operations and problems with osteoporotic bone, fragile soft tissues, and skin.