EARLY RESULTS OF 200 TOTAL ANKLE ARTHROPLASTIES (MOBILITY DEPUY)

Abstract

Material: 100 consecutively performed Total Ankle Arthroplasties (TAA) of the Mobility design carried out at Schultess Clinic Zurich and 100 from Wrightington Hospital Wigan were entered into the study. The male: female ratio was 1:1. Age 62 (range 24 to 95 years). The diagnosis was primary OA (59%), OA resulting from a major injury in the past (20%) and rheumatoid arthritis (21%). We considered more than 20 degrees varus or valgus to be a contraindication to TAA.

Methods: The Mobility TAA is three component, cobalt chrome uncemented design. The tibial component has a stem and the talar component has two fins for secure bony incorporation. At the time of TAA ancillary procedures such as gastrocnemius lengthening were performed if required.

Results: The follow-up was 36 months (24 to 50). The most frequently performed ancillary procedure was gastro-soleus lengthening and this was carried out in 20% of cases. Osteotomy of os calcis and talo-navicular or other hindfoot fusion was performed in approximately 8%. The severity of pain was measured on the visual analogue scale before and at follow-up and this improved from 8.5 to 1.6. The average range of motion measured radiographically improved from 25 deg to 30 deg. The most frequent persistent complaint was that of occasional troublesome antero-medial pain. 92% patients were satisfied with the outcome. Complications were 6% intra-operative malleolar fractures. These did not lead to long term problems. Delayed wound healing occurred in 4% but all healed fully by three months. Late medial malleolar fractures occurred in 2%. Early infection occurred in one patient and was successfully treated by washout and antibiotics. Revision to fusion or change of tibilal and/or talar implant was required in 2.5% (5 patients) due to aseptic loosening and a technical error in one further patient treated three years ago led to subluxation of the insert. This was changed for an 11mm insert with a successful outcome to present time.

Conclusion: These results are an improvement on those acheived by the same surgeons prior to this study using other types of implant. We believe this is due to improved instrumentation and implant design and a better understanding of the indications particularly the need to be very cautious in recommending replacement to patients with severe varus or valgus deformities.