Clinical Evaluation and Radiographic Assessment of Bone Lysis of the AES Total Ankle Replacement

Background: AES mobile-bearing total ankle replacement is evolved from the Buechel Pappas model. We report medium-term results of a prospective study with AES. Materials and Methods: All patients who underwent AES TAR for ankle arthritis, by a single surgeon, from 2003 to 2006 were included, excluding neurologic disease, talar osteonecrosis and malalignment more than 20 degrees. All were reviewed at 6 months, I year, and at yearly intervals thereafter. X-rays were analyzed by three observers, using a 10-zone protocol. Fifty consecutive AES implants in 47 patients (mean age, 56 years; range, 21 to 79 year) were included, with at least 2 years' followup (mean 40 months). Preoperative diagnosis was mainly post-traumatic (50%) and osteoarthritis secondary to instability (36%). Associated procedures were performed in 38%. Results: Eighty-two percent had good functional results. The mean AOFAS score rose from 36.9 +/- 1.7 preoperatively to 85.4 +/- 12, dorsiflexion from 3 degrees to 7.3 degrees, and plantarflexion from 30.8 degrees to 37.8 degrees. Two ankles underwent secondary arthrodesis for talar subsidence and mechanical dislocation. Ninety-eight percent of implants were well positioned at 90 degrees +/-4. Mean prosthesis ROM on X-ray was 22.1 degrees. There were tibia/implant interface cysts (greater than 5 mm) in 62% of cases, and talar/implant interface cysts in 43%. Conclusion: Although functional outcomes were comparable to the other mobile TAR in the literature, bone lysis with the AES prosthesis was more frequent with risk of subsidence. We therefore stopped implantation of this prosthesis and recommend preventive grafting for severe lysis.