We evaluated the incidence of heterotopic ossification following total ankle replacement to determine whether the degree of ossification was associated with the clinical outcome. We evaluated 90 ankles in 81 consecutive patients who underwent total ankle replacement, and heterotopic ossification was assessed according to proportional involvement of the ankle joint. Correlation analysis was used to investigate the association between heterotopic ossification and outcome. No significant

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... n was found between the formation of heterotopic ossification and the clinical outcome. The degree of heterotopic ossification in the posterior ankle joint was not significantly correlated with posterior ankle pain (p = 0.929), the American Orthopaedic Foot and Ankle Society score (p = 0.454) or range of movement (p = 0.283). This study indicates that caution should be observed in attributing symptoms and functional limitation to the presence of heterotopic ossification in the posterior ankle joint when considering excision of heterotopic bone after total ankle replacement. Common symptoms after total ankle replacement (TAR) include pain, located particularly medially and posteriorly, and functional disabilities such as difficulty rising from a seat, climbing stairs and walking downhill. 1-7 However, the cause of these symptoms is unclear. Two common radiological findings at follow-up are osteolysis and heterotopic bone formation, which may be implicated as possible aetiological factors. Although osteolysis is a significant problem after TAR, 8-11 the natural history and clinical significance of the heterotopic ossification that develops after TAR have not been fully investigated. The goal of our study was to review pre-and post-operative radiographs to assess the incidence and aetiology of heterotopic ossification after TAR and its association with the outcome. We hypothesised that there would be no relationship between the formation of heterotopic ossification and outcome. Patients and Methods A total of 112 ankles in 103 patients who underwent TAR by a single surgeon (JWL) between 2004 and 2009 were retrospectively assessed. A total of 22 ankles were excluded because the follow-up was less than 24 months, leaving 90 ankles in 81 patients with a mean clinical and radiological followup of 44.8 months (24 to 77) for analysis. The HINTEGRA (Newdeal SA, Lyon, France) total ankle system was used in all patients. The mean age of the patients was 64 years (33 to 84). A total of 48 TARs were undertaken in men and 42 in women; three men and six women underwent bilateral TAR (Table I) . The operation was performed for osteoarthritis in 35 ankles, traumatic arthritis in 46 and rheumatoid arthritis in nine. The study was approved by the hospital's institutional review board. Operative technique. The technique of TAR has been previously described. 10 A tourniquet around the thigh was used in each case and was inflated to 320 mmHg and deflated before closure to ensure adequate haemostasis. Bone cutting guides were used to prepare the tibia and talus. Care was taken to remove any loose bone fragments, followed by copious irrigation to remove any debris. In order to restore neutral alignment and correct ligament instability or bony deformity, various additional procedures were performed according to the treatment algorithms of our institution: 10 deltoid ligament release in 44 ankles, percutaneous Achilles tendon triple hemisection lengthening 12 in 29, calcaneal valgus osteotomy in six, peroneus longus tendon transfer to peroneus brevis in six, gastrocnemius recession in six, modified Broström procedure 13 in five, dorsiflexion osteotomy of the first metatarsal bone in four,