Coalitions are fusions between tarsal bones that cause a loss of inversion and eversion motion. They are often familial, may be unilateral or bilateral, and occur in both sexes equally. Coalitions may involve more than one joint. The fusion imposes increased stress on adjacent joints and sometimes causes degenerative arthritis, pain, and peroneal spasm. These symptoms usually develop during early adolescence. Often coalitions remain silent. Treatment is indicated only for intractible pain, not the mere existence of a coalition. Two common forms are present.
Calcaneonavicular (C-N) Coalitions
C-N coalitions are most common and sometimes identified on a lateral radiograph but are readily shown by an oblique radiograph of the foot. Incomplete coalitions may show only narrowing or irregularity of the calcaneonavicular articulation.
Manage symptomatic coalitions with a trial of immobilization. Apply a short-leg walking cast for 4 weeks. The pain should disappear. If pain recurs soon after removal, operative correction is usually necessary. Resect the coalition (see next page) and interpose extensor hallucis brevis muscle to prevent recurrence.
Talocalcaneal (T-C) Coalitions
T-C coalitions usually involve the middle facet of the subtalar joint. Conventional radiographs are often normal, but sometimes the C-sign of Lateur may be present. A special calcaneal or Harris view may show the fusion. The coalition is best demonstrated by CT scans of the foot.
Manage symptomatic coalitions with a trial using a short-leg cast. If pain recurs, consider operative resection. Assess the size of the coalition by CT imaging. Technical problems are common. Heel valgus may be increased by resection. Sometimes a calcaneal lengthening will be needed to correct this component. Outcomes for resection of subtalar coalitions are much less predictable than for the more common calcaneonavicular fusions. Advise the family of the potential for an unsatisfactory result and the possibility that additional procedures may be necessary.
It may occur at the talonavicular and naviculocuneiform joint. More extensive coalitions may be present in children with clubfeet, fibular hemimelia, and proximal focal femoral deficiencies. Pain and stiffness of the subtalar joint may occur with arthritis, tumors, and articular fractures. Consider these uncommon causes of pain if calcaneonavicular and talocalcaneal fusions are ruled out by radiography.
Tarsal Coalition Resection
Resection of tarsal coalitions is optimal management for refractory symptomatic coalitions. Resection of calcaneonavicular coalitions is much simpler and more consistently satisfactory than subtalar coalition resection. Subtalar coalitions often require secondary procedures due to continued pain, excessive valgus, or recurrence.
Calcaneonavicular Coalition Resection
This resection is based on the technique of Cowell, as described by Gonzalez and Kumar. Under tourniquet hemostasis, make a 4 cm incision over the sinus tarsi. Avoid the sural nerve and peroneal tendons in the inferior aspect of the wound. Deepen the incision to expose the extensor digitorum brevis muscle. Detach the origin of the muscle from the calcaneus and elevate it from the underlying coalition. Identify the coalition with a Freer elevator. If the location or extent of coalition is uncertain, identify it with the aid of imaging. Resect the coalition with an osteotome as a single block. The resected block should be rectangular, not triangular in shape. Remove any cartilagenous remnants of the coalition from both the calcaneal and navicular sides of the resection. Confirm the resection with an oblique radiograph. Apply bone wax to cut bony surfaces and place a heavy absorbable suture in the origin of the extensor muscle. Thread this suture on a straight. Secure the suture through a pad and button. Tie the suture with sufficient tension to maintain the position of the interposition but not so tight as to cause skin necrosis. The muscle interposed between the navicular and calcaneus prevents recurrence of the coalition.
Talocalcaneal Coalition Resection
Based on Olney and Asher, this is a description of the resection of middle facet coalitions. Identify the coalition by CT scan. Consider mapping the extent of the coalition, as success is related to size. Make a 5 cm incision over the sustentaculum tali. Reflect the abductor hallucis plantar-ward and divide the flexor retinaculum. Retract the flexor digitorum and the neurovascular bundle. Between these structures, identify the coalition by elevating the periosteum and marking the margins of the subtalar joint with Keith needles. If uncertain about the location of the coalition, use imaging. Resect the coalition with a power burr, osteotomes, or rongeurs. Make the resection 5–7 mm wide. Be certain that the entire coalition is resected by visualizing joint cartilage around the resected area and demonstrating increased subtalar motion. Place bone wax on the cut surfaces and harvest autogenous fat from the buttock crease. Place this graft into the defect. Secure the graft with sutures under the overlying periosteal margins. Repair the flexor retinaculum, reattach the abductor origin, and close the skin in layers. Apply a short-leg non-weight-bearing cast. Remove the cast in the clinic in 3 weeks.