THE PATHOLOGY OF THE LOWER LEG MUSCLES IN PURE FOREFOOT PES CAVUS

Enlargement of the peroneus longus muscle is a common occurrence in pa tients with forefoot pes cavus, and may contribute to the cavus deform ity, The present study compares the morphology of up to five lower leg muscles from 17 patients with forefoot pes cavus with those of normal muscles, Eight cases had an identifiable neurogenic cause for the cav us. In four cases of hereditary motor-sensory neuropathy, the tibialis anterior showed more severe damage than the peroneus longus. In two c ases of cerebral palsy, fibre atrophy and increased oxidative enzyme a ctivity were observed. In nine clinically idiopathic cases, the histol ogical appearances ranged from normal to generalised fibre atrophy or hypertrophy in individual muscles. There was a trend for the mean fibr e area to be greater in peroneus longus than in tibialis anterior in s ix of the idiopathic group of patients. The muscle cross-sectional are a on magnetic resonance imaging was correlated closely with the mean f ibre area measured on tissue sections. In idiopathic forefoot pes cavu s, fibre hypertrophy in peroneus longus (relative to tibialis anterior ) may contribute to the cavus deformity. Muscle fibre hyperplasia may contribute to the peroneal muscle enlargement in Friedreich's ataxia, In none of the cases was peroneus longus enlargement due to fat or fib rous tissue replacement.