A fusion is the creating of a bone where there used to be a motion segment (a joint). The derivation of the word arthrodesis is from the Latin word arthron, meaning joint, and the Greek word desis, meaning binding. The subtalar joint is about a thumbs breadth below the ankle joint and is responsible for about half the side-to-side motion of the hindfoot.
Symptoms and Clinical Presentation
Most patients complain of lateral “ankle” pain. Many have had previous trauma or prior deformity. Some patients have a history of inflammatory arthritis, such as rheumatoid arthritis or a previous ankle fusion. Flat foot deformity is frequently also present.
Cause (including risk factors)
Anything that injures the joint cartilage surface may result in arthritic type pain and eventually need to be treated by a subtalar arthrodesis. This could include trauma such as a fracture, abnormal wear such as with a flat foot deformity, or a process which attacks the cartilage such as rheumatoid arthritis.
The subtalar joint is one of three joints that make up the subtalar complex. The other two joints in the complex are the talonavicular and calcaneocuboid. Together, they allow most of the side-to-side motion of the hind foot. The subtalar joint is oriented obliquely, with an axis at an angle different from that of the ankle and that of the plantar aspect of the foot. The subtalar joint has three facets or parts.
Clinical examination and X-ray evaluation can lead to the diagnosis and rule out other diagnostic possibilities. Further work-up may include a bone scan, CAT scan, or an MRI. Selective injection of the joint with a local anesthetic (sometimes with a steroid) may also be used.
*Source: American Orthopaedic Foot & Ankle Society® http://www.aofas.org