Total Ankle Replacement: Back to the Future?

Abstract

When total ankle replacement began in 1970 [1] the trend was soon followed by lots of others. All designs were two-component replacements with Fixed Bearings (FB) intended for fixation with bone cement. Already at 5-year follow-ups most designs were given up because of major problems with loosening. A few continued to solve the problems, and from the beginning of the 1980s the three component designs with Mobile Bearing (MB) were introduced [2,3]. With results superior to the former two-piece devices, a new era was started, and nearly all new designs from the late 1990s were three component devices, and intended for non-cemented use. The good survival rates have been confirmed also with these devices. They have all lend features from the two original designs [2-4], and much more attention has been paid to restoring alignment and stability of the ankle and hindfoot. Recently, for unclear reasons, the trend is to use two-piece (FB) designs again. Maybe this is inspired by the possibility, on a 5-10 K basis, to introduce two-piece designs to the American market. These two piece designs are now hitting the market in numbers that equals the many designs in the 1970s. This is a cause of concern. The reason for introducing the MB designs was the inability for FB designs to find the correct position of the components. There is a widespread diversity not only in the normal anatomy and kinematics of the ankle, but especially in the pathological and degenerated ankles. The MB is a way to overcome this, and let the ankle find its best position by gliding and rotation of the meniscus. Has this been in vain? In a recent lecture, it was claimed in a prospective study with short-term follow-up that the FB of prosthesis originally introduced as a MB design gave the better results in terms of optimal