| CLINICAL EXPERIENCES WITH THREE DIFFERENT DESIGNS OF ANKLE PROSTHESES |
Rippstein
PF
Department of Foot and Ankle Surgery, Schulthess Clinic, Lengghalde
2, Zürich CH-8008, Switzerland
ABSTRACT
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.
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