Some reflections about the evolution of ankle prosthesis

Abstract

The aim with an ankle arthroplasty is to give freedom from pain, to retain or improve function and mobility. To achieve these goals it is necessary to know:

• underlying pathology of the degenerated ankle joint;

• the possibilities for a safe access to the ankle joint;

• fixation of the prosthetic components, and;

• the biological, biomechanical and kinematic behaviour of the hindfoot complex.

A successful result of an ankle arthroplasty will depend on all these features. The different arthroplastic designs seen since the seventies have more or less neglected vital parts of these goals. The results have been disappointing compared to the results of hip and knee arthroplasties. The reason is obviously that the ankle joint is a much more complex joint than the simple hip and the rather simple knee and the influence of the neighbouring joints. Thorough knowledge of the inside anatomy of the ankle joint is mandatory when considering an ankle arthroplasty. The shape of the talus, the possibility for talus rotation inside the ankle mortise, the rotation of the fibula, and the weight-bearing of not only the upper part of the talus but also the joints between the malleoli and the talus facets must be considered (14). Furthermore, the access to the ankle joint is difficult, and especially fixation with cement is a difficult task provided only limited bone resections are needed. The influence of the softtissue structures is of utmost importance as these guide the mobility, and allow function and stability.