[The evolution of ankle arthroplasty]

The results of ankle arthroplasty have generally been disappointing compared to other forms of arthroplasty. The present survey of results of ankle arthroplasty deals with the anatomical, the kinemasiological the biomechanical and the biological features of the ankle joint. These features all seem important prerequisites for a successful total ankle prosthesis design. From the study of the results displayed in the literature and those of my own series it can be stated that a modern ankle arthroplasty should respect the normal anatomy and kinemasiology. Biomechanically it should work as a normal ankle joint i. e. cylindrical mobility, congruency and a possibility for normal torque within the ankle mortise. The prosthesis components should only be fixed in solid subchondral bone, and preferably without cement. Only compressible forces should act at the bone-prosthesis interface. The axis of the ankle joint as well as of that of the hindfoot should be aligned to normal. Meticulous surgery and special guide instruments are absolute necessities. Restoration of muscle power and gait postoperatively are essential for a good and lasting result. The indication for ankle arthroplasty is mainly cases of osteoarthritis (primary or traumatic) and rheumatoid arthritis. Contraindications are talus necrosis, Charcot joints, extreme osteoporosis, severe arteriosclerosis, and very aggressive arthritis. Mental disorders and neurological disorders may also be contraindications. Furthermore, the patients should agree not to perform sports involving jumping and running or other ankle demanding activities. The average annual failure rate should not exceed 1 % if these recommendations are followed.