Principles of joint arthroplasty as applied to the ankle

The challenges for the development of a successful total ankle prosthesis are formidable. The forces at the ankle are large and the surface area for bone support is [figure: see text] small. The size and shape of the talus make expansion of the surface area for fixation very difficult and greatly minimize options for prosthetic revision. The quality of bone in the distal tibia frequently may be questionable, and the bone strength is not uniform across the distal tibia. Finally, the soft-tissue envelope at the ankle is poor. The distal location of the ankle magnifies the circulatory risk in any patient with peripheral vascular disease. Wound problems are more common and more dangerous than in more proximal sites. Fractures and other injuries are very common at the ankle and potentially can add to the frequency of complications. The proximity of the medial and anterior neurovascular structures also increases the likelihood of serious complication. Total ankle arthroplasty is much closer to the limit of what can be successfully accomplished with acceptable risk to the patient. There is little room for error. This, coupled with the larger compressive forces generated at the ankle, makes successful ankle arthroplasty a bigger challenge than arthroplasty at the hip or knee.