Foot and ankle joint fusion and ankle replacement

Fusion or replacement: what’s the difference?

Fusion (arthrodesis) removes the damaged cartilage from the joint surfaces, positions the bones in a corrected alignment, and holds them together with screws, plates, staples or a rod until they knit. The joint no longer moves, so the pain that came from bone rubbing on bone is relieved. The neighboring joints take on some of the work.^[1]

Replacement (arthroplasty) removes the damaged joint surfaces and puts metal and plastic components in their place. Total ankle replacement aims to relieve pain, improve function and maintain motion in people with end-stage ankle arthritis. Fusion was historically the mainstay of treatment for this, and the use of replacement has been increasing.^[2]

Where each is used

• Big toe joint (first MTP joint). For advanced hallux rigidus, and for some severe bunion deformities, fusion gives a stable, pain-free toe. A systematic review of modern fixation techniques for fusion reported a union rate of 95.7% and a complication rate of 5.8%, with plates preferred over screws or staples for several outcomes.^[6] Minimally invasive fusion has also been described; a review of six small studies found a fusion rate of 87% with about 12% complications.^[7] See hallux rigidus.
• Midfoot joints. Fusion is used for painful midfoot arthritis, unstable injuries, and deformity, including Lisfranc injuries (see Lisfranc surgery) and Charcot collapse.^[8,9]
• Hindfoot joints. Fusion of one, two or three joints of the hindfoot (subtalar, or “triple” arthrodesis) is used for arthritis and for stiff flatfoot deformities.^[10] See flatfoot reconstruction.
• Ankle joint. Fusion or total ankle replacement is used for end-stage ankle arthritis. See ankle arthritis.

Ankle fusion or ankle replacement?

Both are established options, with different strengths, and the choice depends on you and your ankle.

• What studies show. A meta-analysis of recent studies found no significant difference in pain and alignment scores between them. Replacement was associated with better function scores and range of motion, and with more complications and reoperations.^[3] A later meta-analysis that pooled trials and matched studies found no significant difference in the total complication rate (moderate-certainty evidence).^[4] Uncemented replacements followed for an average of ten years showed sustained improvement in pain and function scores.^[11]
• Factors that favor fusion can include a younger, heavier or more active patient, significant deformity or bone loss, poor bone quality or ligament stability, previous infection, nerve or circulation problems, and a preference for a durable, single-procedure solution.
• Factors that favor replacement can include an ankle with good alignment and bone, arthritis of the neighboring joints, stiff neighboring joints, and a strong preference to maintain motion.
• Adjacent-joint arthritis. There is a concern that fusion overloads the joints below it. A systematic review found no consensus on whether ankle fusion causes adjacent-joint arthritis, and imaging changes didn’t always match symptoms.^[12]

Recovery

A fusion needs time for the bone to heal, and healing is the main determinant of recovery. Traditionally this meant weeks without weight on the foot. Some fusions can be loaded earlier: a systematic review of 898 first-MTP fusions with early weight-bearing (within two weeks) reported an overall nonunion rate of about 6%, which the authors considered acceptable, though those were mostly non-randomized studies and each surgeon’s protocol differs.^[13] Recovery from surgery for arthritis of the foot and ankle can take four to nine months for full recovery.^[1] See recovery after foot and ankle surgery.

Risks

• Nonunion (the bones don’t knit) or delayed union, which may need further surgery, is a risk of any fusion, and it is more likely in smokers. A systematic review found that smoking increases the risk of nonunion and wound infection after foot and ankle surgery.^[5]
• Infection and wound problems, which are more frequent in people with diabetes and neuropathy.^[14,15]
• Stiffness and arthritis in neighboring joints after fusion.^[12]
• For ankle replacement: implant loosening or wear, and the need for revision surgery.^[3]
• Blood clots, nerve and vessel injury, and anesthesia risks, which are discussed before any surgery.

Questions to ask before deciding

• Which joints are involved, and what are my options at each?
• What can I do without this surgery, and for how long?
• If I choose fusion, how will the neighboring joints and my walking be affected?
• If I choose replacement, what is the implant’s track record, and what are the chances I’ll need further surgery?
• How do my smoking status, diabetes and weight affect my risks?

When to seek care