This generalized systemic disease can affect the ankle joint as well as the hindfoot, namely subtalar joint. The erosive arthropathy destroys the joint surfaces, resulting in loss of bone stock, osteopaenia, collapse of bony architecture and resulting hindfoot deformity. This is usually a valgus hind-foot and is secondary not only to destruction of the joint surfaces but also damage to the associated ligaments and soft tissues. This affects both the ankle and subtalar joint and the deformity is generally rigid if the disease process is well established.
Clinically, an abnormal wear pattern is found in the patient's shoes. On standing behind the patient, there may be marked valgus of the hindfoot which does not correct when the patient stands on his toes. The ankle and subtalar joints may be stiff and irritable to movement. There may also be hindfoot swelling, tenderness to palpation and tenosynovitis of the peroneal or posterior tibial tendons and tendon rupture may occur.
Conservative treatment consists of modifying footwear to try and relieve weight on pressure points and give some added support to the hindfoot. If the hindfoot deformity is still mobile, as it may be early in the disease, then bracing with special orthoses may be appropriate to try and maintain the hindfoot in normal alignment. Due to the relentless nature of the disease, conservative measures often prove fruitless and therefore surgical intervention is necessary. There are three main categories:
• Osteotomy: usually involves realigning the os calcis beneath the tibia to correct hindfoot valgus. This does not affect the joint surfaces and the deformity can recur.
• Arthroplasty: involves resurfacing the joint; however, due to the stresses placed through the joint, this often fails and the prosthesis can loosen.
• Arthrodesis: involves bony fusion across the ankle, hind-foot or midfoot joints. 'Double arthrodesis' may be preferred in younger, more active patients. It involves arthrodesis of calcaneocuboid and talonavicular joints. 'Triple arthrodesis' is a popular procedure which involves
Figure 22.26. Kohler's disease of the tarsal navicular (right).
arthrodesis of subtalar, calcaneocuboid, and talonavicular joints. It has a high union rate in rheumatoid arthritis and can improve ambulatory status in more than 80% patients and can provide pain relief in up to 90% patients. 'Pantalar' arthrodesis is the term used for fusion of the ankle, subtalar, talonavicular and calcaneocuboid joints. This is often used to permanently stabilize the hindfoot.
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