Hydroxyapatite Augmentation for Bone Atrophy in Total Ankle Replacement in Rheumatoid Arthritis

Although total ankle replacement is routinely used for rheumatoid arthritis of the ankle, it has been hampered by early implant failures such as loosening and subsidence of the tibial component due to poor bone quality. To prevent this complication, total ankle replacement augmented by a specially designed hydroxyapatite coating was used in 14 patients (16 feet). Patients were reviewed after an average follow-up of 23.1 months, and the mean clinical rating scale significantly improved from 30.7/100 points preoperatively to 65.9/100 at final follow-up, especially with respect to pain relief. Radiographs taken immediately postoperatively and at final follow-up were analyzed for the position and sinking of the tibial component. The position was evaluated by measurement of the alpha and beta angles, formed by the tibial long axis and tibial component on anteroposterior and lateral radiographs, respectively. The mean alpha and beta angles were 87.4° and 79.3° postoperatively and 87.7° and 81.0° at final follow-up, respectively. No significant change was noted in either angle between the immediate postoperative views and at final follow-up, and no significant subsidence was noted. Radiographs were also assessed for the presence of a lucent zone: 1 case demonstrated a clear zone between hydroxyapatite and bone, 9 cases between hydroxyapatite and the tibial component, and 6 cases between the tibial component and bone. These results suggest that hydroxyapatite helps to secure implant fixation firmly to the bone, making it a useful augmentation for tibial bone atrophy in total ankle replacement for rheumatoid arthritis.