Non–Velocity-Related Effects of a Rigid Double-Stopped Ankle-Foot Orthosis on Gait and Lower Limb Muscle Activity of Hemiparetic Subjects With an Equinovarus Deformity

Abstract

Background and Purpose —This study investigated the non–velocity-related effects of a 1-bar rigid ankle-foot orthosis on the gait of hemiparetic subjects, with particular emphasis on the muscle activity of the paretic lower limb. Methods —Twenty-one hemiparetic subjects who had been using an ankle-foot orthosis for equinovarus deformity for <1 week participated. Patients walked cued by a metronome at a comparable speed with and without the orthosis. Dependent variables were basic, limb-dependent cycle parameters, gait symmetry, vertical ground reaction forces, sagittal ankle excursions, and kinesiological electromyogram of several lower limb muscles. Results —The use of the caliper was associated with more dynamic and balanced gait, characterized by longer relative single-stance duration of the paretic lower limb, better swing symmetry, better pivoting over the stationary paretic foot, and better ankle excursions ( P <0.05). The functional activity of the paretic quadriceps muscles increased, while the activity of the paretic tibialis anterior muscle decreased ( P <0.05). Conclusions —The orthosis led to a more dynamic and balanced gait, with enhanced functional activation of the hemiparetic vastus lateralis muscle. The study further supports the functional benefits of a rigid ankle-foot orthosis in hemiparetic subjects as an integral part of a comprehensive rehabilitation approach. However, the reduced activity in the tibialis muscle may lead to disuse atrophy and hence long-term dependence on the orthosis.