The Mobility (DePuy International) is a three-component, cobalt chrome, uncemented design.

Methods

There were 106 men and 94 women (mean age 65 years; 22 - 85). 69 patients had inflammatory arthritis and 131 osteo-arthritis. 27 patients (13 B-P, 14 STAR) had a pre-operative varus/valgus deformity greater than or equal to 20 degrees. Mean follow-up was 48 months (36-72).

Twenty-four replacements were performed in 19 patients (13 female: 6 male), with average age of 33 years (18-40). All had severe polyarticular rheumatoid arthritis. Pre-operatively 12 ankles had no angular deformity, 9 were in valgus and 3 in varus. All had associated hindfoot disease. Some of these patients are part of two larger studies of the Scandinavian Total Ankle Replacement (STAR) and the Buechel-Pappas (BP) replacement. In this group there were 20 STAR and 4 BP replacements. Average follow-up was 62 months (36 to 120). Twenty-one replacements had good pain relief and function. The AOFAS hindfoot score for pain improved from 0 to 36 (max 40) and for function from 25 to 35 (max 60). Three have failed. One ankle had a 25-degree valgus deformity pre-operatively and this recurred and caused failure at 11 months. The second failed at 34 months due to aseptic loosening of the talar component. Both of these were converted to tibio-talo-calcaneal fusions with an intra-medullary nail. The third failure had never provided satisfactory pain relief in spite of appearing satisfactory on clinical and radiological examination. Exploratory surgery was carried out at 36 months but failed to produce an improvement and at 61 months the decision was made to revise the replacement to a fusion. However, due to concurrent health problems, this has not yet been done. We offer replacement to patients with severe polyarticular rheumatoid disease especially if there is a stiff but well aligned hindfoot. In the light of increased experience, we now consider valgus or varus deformity of greater than 20 degrees to be a contra-indication to replacement. This is because the deformity tends to recur leading to pain, loosening and failure.

We aim to assess the outcome of ankle arthrodesis performed for painful osteoarthritis in the presence of a coronal plane deformity of 20 degrees or more.

To our knowledge this is the first reported series of such a cohort of patients. We have a consecutive and complete series of 24 patients with 26 ankle arthrodeses which were all performed for painful osteoarthritis in the presence of large coronal plane deformity. These patients have a minimum of twelve months clinical follow-up. The results showed a low non-union rate of 8% (2 ankles). These have subsequently been re-fused satisfactorily, and are excluded from further analysis. The results of the remaining 24 ankles, which united primarily, show that patients were very pleased with the outcome of their surgery. AOFAS scores were used to measure pain and function, both pre-operatively and post-operatively. These scores showed large improvements for both pain and function, and had a high statistical significance (p<0.0001). All patients improved in their walking distance and many patients reduced their need for walking aids. Stair climbing ability was also improved in some patients. It is recognised that an ankle arthrodesis usually relieves pain but does not result in a normal gait and full function.

We feel that the high level of patient satisfaction in this series was due to the combination of deformity correction, restoring a functional foot position, and achieving a painless ankle. Arthroplasty of the ankle is a good procedure for relief of pain and restoration of function. However, in the presence of a large coronal plane deformity, ankle arthroplasty is known to fare badly with early failure. Therefore for patients with painful osteoarthritis and a coronal plane deformity of 20 degrees or more, we recommend ankle arthrodesis as the procedure of choice.