Ankle Joint Replacement Versus Ankle Fusion Surgery
Richard A. Zell, M.D.
Hip and knee replacement surgeries have very good results for the great majority of patients with arthritis. There are many studies showing the longevity of these implants with low complication rates. While orthopaedic surgeons always attempt to treat patients initially with non-operative modalities (which includes anti-inflammatory medications, physical therapy, and injections with corticosteroid or hyaluronic acid), joint replacement surgery can be required if these modalities do not provide significant relief. Research has shown that joint replacement is a reliable surgery that provides patients with good function and pain relief.
While not as common as knee or hip arthritis, the ankle can also develop arthritis. Ankle arthritis affects many patients and can occur after injuries such as ankle fractures. Recent studies have shown that the disability resulting from ankle arthritis is just as debilitating as that from hip or knee arthritis (Glazebrook, 2008). These studies were done using the SF36 functional score which is a standard measure to determine a patients outcomes both before and after surgery. Unlike the hip or knee where joint replacements have had good results, the optimal operative treatment for ankle arthritis has not been as clear.
The traditional treatment for ankle arthritis has been arthrodesis or fusion. In this procedure, the ankle joint is exposed, any remaining cartilage on the ends of the bone is removed, and the bone surfaces of the talus and tibia are compressed using screws and/or plates. This allows the bones of the ankle to heal in a manner similar to the way that the bones in a fracture heals. This procedure eliminates the pain from the joint at the expense of decreased ankle motion. Most patients do reasonably well with ankle fusion even given this loss of motion. We have progressed our ankle fusion technique to an arthroscopically assisted procedure in some patients which allows the surgery to be done with smaller incisions and a shorter healing time. While an ankle fusion is a good operation that significantly decreases patients’ pain, there are disadvantages to the procedure. The ankle becomes stiff due to the lack of motion and subsequent arthritis can develop in surrounding joints of the foot due to the increased weight they need to bear and increased motion they need to perform.
An alternative to an ankle fusion is an ankle joint replacement. In this procedure, the bones of the ankle (the tibia and the talus) are replaced with a metal cap. A piece of plastic between the ends of the bone acts as the gliding surface of the joint allowing the ankle to move. This design is similar to a knee replacement.
There have been many attempts at ankle replacement through the years. In the 1970s and 1980s, there were various replacement implants designed and trialed, however the results of these surgeries were poor. Many patients required further surgery and eventual removal of the implants. Such complications led to the eventual abandonment of ankle replacement surgery in the United States until a more viable surgery was discovered.
Foot and ankle surgeons, in both Europe and the US, continued to work on ankle replacements and, by the late 1990s, there was one US ankle replacement that was approved by the FDA. This implant was called the Agility ankle replacement and was significantly better than the previous ankle replacements. However, there were still many failures of the implant, most notably involving the talus or lower ankle component.
Over the last 15 years, more advanced ankle replacements were initially introduced in Europe and have been gradually approved in the United States. These improved implants more accurately reproduce the anatomy and biomechanics of the ankle which have led to better clinical results following surgery and long lasting durability. One such implant is the STAR ankle replacement that has been found to have a 95% survival rate of the implant 10 years status-post surgery (Kofoed, 2004). Several studies have been completed comparing ankle replacement and ankle fusion surgery. The results of these studies imply that pain relief is comparable with both surgeries, however the ankle replacements patients have improved function (Saltzman, 2009). While it has been a long time in the making, ankle replacement surgery has finally become a good alternative to ankle fusion in select patients.