S8 THE STEP FROM ARTHRODESIS TO ARTHROPLASTY – EARLY RESULTS WITH THE MOBILITY ANKLE PROSTHESIS

Abstract

For many decades ankle fusion has been the only option for treatment of symptomatic osteoarthritis of the ankle joint. From the late 60’s on the crusade of joint replacement for hip and knee led to successful functional restoration for severe destruction of these joints. Because of a lack of understanding the biomechanical principals of the ankle a similar approach in reconstructing the ankle arthritis was doomed to fail. On the other side very good functional outcome after fusion of the ankle seemed to make needless further development. Although first encouraging results with non-constrained designs and cementless fixation were obtained in mid-late 70’s a wider acceptance within the orthopaedic society was found only almost 20 years later whereas today many surgeons wouldn’t give up the ankle arthroplasty for several indications. Despite good and very good midterm results we still need to understand limits and further develop operative techniques especially soft-tissue balancing.

In our institution we have been using TAR since 1995 on a regular basis and by now overlook a total of almost 400 TAR’s. The experience with different designs (Agility, S.T.A.R. and Buechel-Pappas) led to the development of the Mobility-TAR in collaboration with two surgeons from England and the U.S. It is a 3-component TAR, non-constrained. As a unique feature the instrumentation allows an accurate centring of the implants both in the frontal and the saggital plane. In a prospective trial in Wrightington and Zurich we clinically and radiographically evaluate the outcome. The first 42 cases in Zurich with a follow-up of more than 1 year showed a significant pain reduction from av. 8.1 on a visual analogue scale to av. 1.4 after one year. The ROM assessed radiographically could be improved from 26° preoperatively to 33° after one year. We have seen 4 fractures/osteotomies of the medial malleolus and one neuropathy of the tibial nerve as intraoperative complications. Postoperative complications included two superficial wound healing problems, one deep infection and finally two stress fractures of the medial malleolus. One case had to be revised because of aseptic loosening after 6 months. All but one of the first 42 patients would undergo the same procedure again.

The first results are encouraging because of good overall results with significant pain reduction and good ROM combined with only few complications.