Effects of tarsal coalition resection on dynamic plantar pressures and electromyography of lower extremity muscles.

The goal of this study was to evaluate kinetic abnormalities in feet after tarsal coalition resection using plantar pressure measurements and electromyography of 4 muscle groups in the lower limb. Eleven subjects (14 feet) with tarsal coalition (3 feet with calcaneocuboid, 6 feet with calcaneonavicular, and 5 feet with talocalcaneal) underwent coalition excision. Patients ranged in age from 9 to 17 years, and mean follow-up was 20 months. Two feet underwent subsequent subtalar fusion and 1 had a triple arthrodesis. Plantar pressure and electromyography measurements were compared with data taken from 68 normal (control) subjects between the ages of 6 to 16 years. Feet with tarsal coalition showed significant differences in the midfoot region, with increases in contact area (40.36 cm2 +/- 14.7 vs 18.02 cm2 +/- 8.0, P < .001), loading (5.63 N/cm2 sec +/- 3.4 vs 1.83 N/cm2 sec +/- 0.9, P < .001) and peak pressure (13.38 N/cm2 +/- 5.8, 6.81 N/cm2 +/- 2.8, P = .01). Tarsal coalition feet also displayed reduced peak pressure and loading at the region of the fifth metatarsal head as compared with uninvolved feet (P < .05). Electromyography measurements were also performed on both the affected and unaffected feet of 9 subjects who had undergone resection of their coalition. These measurements revealed nearly consistent abnormal activity in the peroneal, gastrocnemius, and soleus muscles on both the surgically operated foot and the contralateral side, including either prolonged monophasic activity or biphasic activity. These findings suggest that although resection of coalition may have relieved symptoms of discomfort, it did not restore normal foot alignment or muscular balance.