Clinical experiences with three different designs of ankle prostheses.
Until 1995, fusion was in our institution the only rational surgical option for a severe ankle arthrosis. Consistent reports about good mid- and long-term results with ankle replacement allowed us to change our minds. Ankle replacement became the gold standard and fusion was then almost totally banished. Because ankle arthrosis can be morphologically different from one patient to another, we soon believed that one single type of ankle prosthesis would not be the universal optimal solution for all patients. We therefore divided the ankle arthrosis into three groups. Each group shows the best solution from each of the ankle prostheses with which we had gained experience (Agility, STAR, and BP). The Agility prosthesis, which was indicated for ankles with extremely damaged geometry, did not restore sufficiently the ankle motion. Preoperatively stiff ankles remained stiff postoperatively. Additionally, significant residual pain was more likely to occur in those patients. These cases did not show significant advantages compared with ankle fusion, especially from a functional point of view. Fusion for these stiff ankles is therefore today our first treatment of choice. In our experience, the malleolar joints do not have to be replaced. Even a severe arthrosis at this level does not produce significant pain, provided that osteophytes have been removed and joint height has been restored by the implanted prosthesis. It is our strong belief that these malleolar joints are also less sensitive to pain, similar to the femoropatellar joint. For these reasons, a replacement of the malleolar joints and the resurfacing of the talar sides is not necessary. Leaving the talar sides untouched requires less bone resection and makes the implantation of the talar component easier. Although we obtained good results with the STAR prosthesis, we progressively abandoned it because of these reasons, and we preferred the BP prosthesis. The BP prosthesis works on the same biomechanic principle as the STAR prosthesis. Some features, however, like the untouched malleolar joints, the large exposition of the joint, the easier adjustments of its position, the possibility of enhancing the press fit, and the good short- and midterm results we obtained with it led us to the decision of using it as our only design for cases of nice and acceptable arthroses. Even if mostly good and excellent results have been achieved with all prostheses currently used, some results are still disappointing. Some ankles become stiff postoperatively and some remain diffusely painful; the explanations for these problems are often difficult to attain. This clearly shows that despite all the progress made over the last few years, there is still a lot to be learned about ankle arthroplasty.
Rippstein
Pascal F
PF
Department of Foot and Ankle Surgery, Schulthess Clinic, Lengghalde 2, Zürich CH-8008, Switzerland. rip@kws.ch
D001168:Arthritis / Q000601:surgery*; D019643:Arthroplasty, Replacement / Q000379:methods; D005060:Europe; D006801:Humans; D007595:Joint Prosthesis / Q000009:adverse effects; D011474:Prosthesis Design; D014481:United States