Changes in dynamic foot pressure after surgical treatment of valgus deformity of the hindfoot in cerebral palsy.

BACKGROUND: Calcaneal lengthening osteotomy and extra-articular arthrodesis of the subtalar joint are two methods used for the correction of valgus deformity of the heel and forefoot abduction. The purpose of this study was to compare the operative results of these procedures in patients with cerebral palsy who were able to walk. We focused primarily on changes in radiographic parameters and how altered mobility of the subtalar joint by the two operative methods would modify pressure distribution over the plantar surface of the foot.
METHODS: A total of eighty-one feet in forty-seven patients were included in the study. The mean age at the time of surgery was eight years and one month, and the mean follow-up period was thirty-nine months. The subjects were divided into two groups; Group I consisted of thirty-seven feet in twenty-two patients who underwent a calcaneal lengthening osteotomy, and Group II comprised forty-four feet in twenty-five patients who underwent an extra-articular subtalar arthrodesis. Preoperative and final follow-up radiographs and dynamic pedobarographs were used to evaluate the results.
RESULTS: The feet in both groups were found to be similarly deformed before surgery, by radiographic measurements and dynamic foot-pressure analysis. Both operative procedures led to improved radiographic indices; however, calcaneal pitch failed to improve after the subtalar arthrodesis. After surgery, the relative vertical impulse was decreased for the hallux, first metatarsal head, and medial aspect of the midfoot in both groups, while it was increased for the lateral aspect of the midfoot and calcaneus. On the other hand, postoperatively, the relative vertical impulse of the medial aspect of the midfoot was higher and the relative vertical impulse of the first through fourth metatarsal heads was lower in the group that had subtalar arthrodesis compared with the group that had a calcaneal lengthening osteotomy and the normal control subjects.
CONCLUSIONS: Extra-articular subtalar arthrodesis appears to be an effective means to achieve predictable correction of severe valgus deformity of the heel in patients with cerebral palsy who are able to walk; however, supination deformity of the forefoot remains and calcaneal equinus is not corrected. On the other hand, we believe that the calcaneal lengthening osteotomy is the treatment of choice because postoperative foot-pressure distribution more closely approximates the normal foot-pressure distribution.