Total Ankle Replacements, What Will They Think of Next?!

            In a recent article we briefly went over ankle osteoarthritis. It is a unique condition that has significant differences from osteoarthritis of the hip or ankle, namely that it’s rare to have primary arthritis of the ankle (occurring without another cause). The most common cause of ankle arthritis is post-traumatic arthritis, also known as after injury arthritis.  One of the very interesting treatments of end-stage arthritis is total ankle replacement.

            Traditionally end-stage ankle arthritis has been treated with an ankle fusion. While effective as a pain-relieving surgery, the downside of ankle fusion is that it caused increased arthritis of adjacent joints in the foot, which eventually caused pain and decreased function. Ankle replacement was originally introduced in the late 1960s and 1970s as a way to relieve the pain of late stage arthritis while preserving motion in the ankle joint in the hopes of preserving the surrounding joints and avoiding the problems caused by ankle fusions. The original ankle replacements did not do so well. They had a very high early failure rate. Throughout the 1980s and 1990s the total ankle design and materials underwent significant revisions and the outcomes improved.

            A recent study of the Scandinavian Total Ankle Replacement (STAR) prosthesis shows promising results. The study followed one hundred and eleven patients that underwent a total ankle replacement surgery with the STAR prosthesis for over 10 years.

They found that the average 10-year survival of the prosthesis was 88%. Let’s take a minute to explain what “survival” means in clinical studies of orthopaedic implants. Survival refers to the implants that remained in the patients without the need for a revision surgery to replace the implant. Survival is typically discussed in terms of average time until revision or percent of patients that have kept the original prosthesis without revision at a certain time mark (for example 10-year survival as above).

            Approximately 6% of the patients required a conversion to an ankle fusion. 18% of patients required replacement of the plastic that lines the total ankle, but kept their total ankle replacement. An interesting fact that the study pointed out is that revision rate of each surgeon involved was higher for the first 20 ankle replacements that they performed. This suggests that this operation, like a lot of surgeries in orthopedics, has a learning curve. It should be noted that ankle replacements aren’t without their complications.

            In this study of 111 patients, a total of 8 patients developed major complications. These complications included a clot in the leg, infection, wound healing problems, as well as nerve compression. Other possible complications include tendon injury, fracture, sensory deficits (numbness), and stiffness. The most common complication is wound healing problems. The majority of the patients in the STAR study experienced significant improvements in pain and function.

According to the article by Dr. Chou and co-authors the outcomes of total ankle replacements are very much dependent on appropriate patient selection.

This is the case with most, if not all, orthopaedic surgeries. The review article states that patients with rheumatoid arthritis seem to do significantly better then patients that have arthritis of the ankle that developed secondary to trauma. Additionally, it seems that patients with significant deformity of the ankle tend to do worse with total ankle replacements than patients without such deformities. However, it is important to note that indications and patient selection for total ankle replacement is a complicated topic and best left for the doctor’s office. This article is meant as a brief, and broad, introduction to total ankle replacements as based on the 2008 review by Dr. Chou and colleagues published in the Journal of the American Academic of Orthopaedic Surgeons.

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