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Several evolutionary phases in the design of total ankle replacement (TAR) implants have enabled these procedures to become surgical options for selected patients. In the past, first generation implants failed because they required bone cement for fixation. Being highly constrained causes a loosening around the cement and eventual failure. Newer generation implants have addressed these issues; they no longer require cement because the porous coated surfaces allow bone to grow into the joint. This can reduce the incidence of loosening that is sometimes seen with cemented implants. Furthermore, the techniques and instrumentation used with modern TAR implants are far more superior to the first-generation implants. These improvements provide patients with some ankle motion as compared with ankle fusions. In addition, they help protect the small joints below and in front of the ankle from developing arthritis.

In a review article published in the September 2008 Journal of the American Academy of Orthopaedic Surgeons (JAAOS), James K. DeOrio, MD, and I discuss the different types of TAR implants that are currently available. There are now four TAR implants that have been approved by the FDA, including the Agility (DePuy Orthopaedics, Inc.), INBONE (Wright Medical Technology, Inc.), Salto-Talaris (Tournier, Inc.), and Eclipse (Kinetikos Medical, Inc.), all of which are two-component designs that replace the tibial and talar surfaces of the ankle. Outside of the United States, however, many physicians have been using three-component ankles for several years. For example, the Scandinavian Total Ankle Replacement, or S.T.A.R. (Small Bone Innovations, Inc.), is a three-component implant that has been recommended for approval by the FDA. The three-component implant consists of a meniscus—a piece of polyethylene—that glides back and forth between the talar and tibula component. While a three-component ankle may provide more movement, there are insufficient data on whether it is superior to two-component implants.

Proper Patient Selection Is Key

Proper patient selection for ankle replacement is critical to surgical success. The new designs appear to work better in the short term as compared with first-generation models, but surgeons need to weigh the pros and cons based on the patient being treated. An alternative to TAR, ankle fusions are still available and are effective surgical options for some patients, but there are range-of-motion issues that must be considered. Surgeons may wish to perform TAR to overcome challenges observed with other procedures, but using this technique on the wrong patient can make subsequent ankle fusions much more difficult to perform. This is due to limited soft-tissue coverage across the ankle as well as bone loss from the ankle implant. Patients who have significant ankle deformities, a considerably unstable ankle, or a previous infection in the ankle are not indicated for TAR. Ideal patients include those with the following characteristics:

• A destroyed ankle (surfaces are gone)

• A stable ankle or one which can be made stable by repairing the ankle ligaments

• Ankle pain

Data are still emerging on TAR, and the goal of our JAAOS article was to provide a resource for surgeons as they treat diseased ankle joints. Surgeons need to recognize that improved TAR implants are available and should be aware of the promising developments in the field. TAR can be an effective surgical option, but patient selection remains the most important part of the equation. Revision TAR procedures are extremely challenging and cause significant burden to patients, but proper patient selection can reduce the impact of these problems.

Andrea Cracchiolo, MD, III, has indicated to Physician’s Weekly that he has no financial interests to report.