Ankle fusion (ankle arthrodesis) is a surgical procedure that permanently joins the bones of the ankle joint, typically the tibia and the talus. It is recommended to treat severe pain and instability caused by end-stage arthritis that has not responded to non-surgical treatments. Eliminating motion in the joint removes the bone-on-bone rubbing that causes chronic pain. The primary goal is to create a solid, pain-free platform for walking, but the long-term prognosis depends on the survival of the fusion and the functional lifespan of the entire foot complex.
Expected Lifespan and Success Rates
The structural lifespan of the ankle fusion site is generally excellent, with a high success rate for achieving a solid bony union. Studies report that successful bone fusion (union) ranges from approximately 85% to 95% in non-complicated cases. Once union is achieved, the long-term survival of this fused site is considered permanent.
However, the functional durability of the procedure is often limited by secondary issues rather than the failure of the fusion itself. The need for revision surgery due to non-union—where the bones fail to heal together—is low, typically occurring in 5% to 15% of cases over a 10- to 15-year period. For the initial decade post-surgery, the procedure offers reliable pain relief and improved function for most patients.
Factors Influencing Long-Term Durability
The long-term durability of the ankle fusion is influenced by patient-specific characteristics and technical aspects of the surgery. Patient health determines whether the fusion achieves its maximum structural lifespan. Smoking is a risk factor, as nicotine impairs healing, making non-union significantly more likely; rates in smokers can be up to four times higher than in non-smokers.
Underlying medical conditions, such as diabetes and obesity, also negatively impact the body’s ability to heal. Obesity is associated with higher odds of non-union, while diabetes is linked to an increased risk of post-surgical infection. Proper surgical technique is important, particularly the final alignment of the joint and the stability of the fixation method. Precise alignment is necessary to distribute weight properly and encourage successful bone growth across the fusion site.
Managing Adjacent Joint Stress
The primary long-term consideration following ankle fusion is the development of Adjacent Joint Arthritis (AJA) in the surrounding foot joints. Since the main ankle joint is immobilized, the joints immediately below it, particularly the subtalar and midtarsal joints, must compensate for the lost motion during walking. This biomechanical compensation leads to increased stress and accelerated wear on the cartilage of these adjacent joints.
This degeneration can manifest as pain and decreased function 10 to 20 years post-fusion. Long-term studies show that the incidence of subtalar joint arthritis rises significantly over time.
Managing this secondary issue involves strategies aimed at reducing stress on the foot. These include using custom orthotics to optimize foot mechanics and modifying high-impact activities. If the adjacent joint arthritis becomes severe, a secondary fusion or joint replacement of the affected joint may be considered to restore comfort and function.