The contributions of anterior and posterior tibialis dysfunction to varus foot deformity in patients with cerebral palsy.

BACKGROUND: According to traditional teaching, the posterior tibialis is the main cause of varus foot deformity in patients with cerebral palsy. However, the relative frequency of anterior and posterior tibialis dysfunction has only been reported with use of dynamic electromyography in relatively small series of patients, with contrasting results. The purpose of the current study was to determine the relative prevalence of posterior and anterior tibialis dysfunction with use of gait analysis in a large group of patients with cerebral palsy and varus foot deformity.
METHODS: The muscular contributors to varus foot deformity in seventy-eight patients (eighty-eight feet) who had cerebral palsy were evaluated with use of computerized motion analysis and dynamic electromyography. Data also were examined to identify any relationships between the timing of varus during gait and the contributing muscle.
RESULTS: The muscular contributor to varus deformity was the anterior tibialis in thirty feet, the posterior tibialis in twenty-nine feet, both the anterior tibialis and the posterior tibialis in twenty-seven feet, and another contributor in two feet. Seventy feet had varus deformity during both stance phase and swing phase. Of these seventy feet, twenty-five exhibited dysfunction of the anterior tibialis, twenty exhibited dysfunction of the posterior tibialis, and twenty-three exhibited dysfunction of both muscles. Therefore, the timing of varus was not predictive of the contributing muscle or muscles.
CONCLUSIONS: The current study demonstrated a higher prevalence of anterior tibialis dysfunction, both alone and in combination with posterior tibialis dysfunction, as a contributor to pes varus in patients with pes varus and cerebral palsy than had been reported previously. Dynamic electromyography provides clinically useful information for the assessment of such patients.