Subtalar Fusion and Arthroereisis Procedures
Procedures for arthrodesis, stiffening, or limiting motion of the subtalar joint are numerous and commonly performed. These procedures are often used to stabilize valgus feet secondary to cerebral palsy and to correct various types of flatfeet.
Types of Procedures
The procedures fall into several categories: arthrodesing procedures, such as the interaarticular Dennyson–Fulford and bone dowel procedures; extraarticular fusions, such as the Grice–Green procedure; subtalar procedures, which stabilize the joint with a staple, plug of silastic, or bioabsorbable material; and subtalar blocking procedures that limit eversion by implanting bone, metal, or plastic, such as the Smith subtalar arthroreisis implant (STA-peg) procedure. These procedures are simple and commonly performed.
The simplicity of these procedures often leads to misuse by expanding the indications to include children with physiologic flexible flatfeet. Be aware that fusion of the subtalar joint increases stress on adjacent unfused joints and may lead to premature degenerative arthritis of the ankle and tarsal joints. Procedures that stiffen the subtalar joint may cause joint damage and eventual arthritis of the subtalar joint itself.
Subtalar stabilizing procedures have limited indications. These include feet with deformity, causing significant disability that cannot be corrected by joint preserving procedures such as calcaneal lengthening. Typical indications include feet with established osteoarthritis of the subtalar joint and deformity associated with stiffness of the midfoot, eliminating the option of calcaneal lengthening.
Prep and drape the extremity free. Make a curved skin line incision over the sinus tarsi. Expose the sinus tarsi by freeing the short extensor from the calcaneus and remove the soft tissues to expose the joint. With the foot in the neutral inversion–eversion position, decorticate the adjacent surfaces of the talus and calcaneus or use a dowel cutter to remove a segment of bone across the joint. Obtain bone chips or a dowel graft from the ilium. Place the graft across the subtalar joint. While maintaining the neutral subtalar position, pass a drill vertically through the subtalar joint and fix the joint with a cancellous screw to maintain the neutral position. Confirm the position of the screw by radiography. Lengthen triceps if contracted.
Complications of Foot Surgery in Cerebral Palsy
Nonunion is best prevented by neutral positioning, autogenous grafting, and firm fixation.
Over- or undercorrection is avoided by careful positioning of the foot during grafting and fixation.