Abstract
The Mobility (DePuy International) is a three-component, cobalt chrome, uncemented design.
Patients
Over an 18-month period 100 ankles, with end-stage arthritis and less than 20 degree valgus or varus deformity, were replaced. There were 95 patients (70 OA, 25 RA) with average age of 65 years (41-95). Five had bilateral replacements. Follow-up was 30 months (24 to 48).
Results
Average score on VAS pain line improved from 8.8 to 1.8. The average AOFAS pain score improved from 3 to 33. Average AOFAS function score improved from 31 to 48. Four patients were disappointed because pain relief was poor. Four ankles have undergone further surgery. One ankle was converted to fusion for recurrent deformity. One ankle required repeated washout for infection at six months but remains clinically and radiologically satisfactory 2 years later. One ankle required exchange of UHMWP insert at 4 weeks because of a technical error. One ankle required fixation of an ununited intraoperative medial malleolar fracture and subsequently developed ‘edge loading’, namely radiographs showed that a gap had opened up between the articular surfaces on the lateral side of the joint. The radiographs of 3 other ankles also showed ‘edge loading’. Two of these patients were symptom free but one wore a brace to control symptoms of instability. Radiographs showed bony incorporation in all surviving ankles. This was always complete around the tibial stem and under the talar component. However in 15 ankles there was a small non-progressive area of lucency adjacent to the tibial plate.
Conclusion
These early results are encouraging and an improvement on those previously reported by the same surgeon using other designs. We believe that this is attributable to the ongoing process of refining the indications and improving surgical technique and implant design.
