Description of orthotic properties and effect evaluation of ankle-foot orthoses in non-spastic calf muscle weakness
Niels F.J. Waterval, Merel-Anne Brehm, Jaap Harlaar, Frans Nollet
Rehabilitation, Amsterdam UMC, 1105AZ Amsterdam, The Netherlands. E-mail: firstname.lastname@example.org
Objective: To describe the orthotic properties and evaluate the effects of ankle-foot orthoses for calf muscle weakness in persons with non-spastic neuromuscular disorders compared with shoes-only.
Design: Cross-sectional study.
Subjects: Thirty-four persons who used ankle-foot orthoses for non-spastic calf muscle weakness.
Methods: The following orthotic properties were measured: ankle-foot orthosis type, mass, and ankle and footplate stiffness. For walking with shoes-only and with the ankle-foot orthoses, walking speed, energy cost and gait biomechanics were assessed.
Results: Four types of ankle-foot orthosis were identified: shaft-reinforced orthopaedic shoes (n = 6), ventral ankle-foot orthoses (n = 10), dorsal leaf ankle-foot orthoses (n = 12) and dorsiflexion-stop ankle-foot orthoses (n = 6). These types differed significantly with regards to mass, ankle-and footplate stiffness. Compared with shoes-only, all ankle-foot orthoses/orthopaedic shoes groups combined increased walking speed by 0.18 m/s (95% confidence interval (95% CI) 0.13–0.23), reduced energy cost by 0.70 J/kg/m (95% CI 0.48–0.94) and limited ankle dorsiflexion by –3.0° (95% CI 1.3–4.7). Higher ankle-foot orthoses ankle stiffness correlated with greater reductions in walking energy cost and maximal ankle dorsiflexion angle.
Conclusion: Ankle-foot orthoses for persons with non-spastic calf muscle weakness vary greatly in properties and effects on gait. The large variation in effectiveness may be due to differences in ankle stiffness, although this requires further prospective evaluation.
Ankle-foot orthoses are used to improve walking in persons with non-spastic calf muscle weakness. For best results the mechanical properties of the device should be matched with the patient’s impairments. However, there are currently no guidelines about the optimal mechanical properties of ankle-foot orthoses, due to a lack of studies evaluating their effects and properties. In order to establish a baseline and guide further research, we conducted an overview of the mechanical properties and effects of the ankle-foot orthoses provided in usual care in the Netherlands. The results show that, in usual orthotic care, ankle-foot orthoses that are not optimally matched with the patient’s impairments are provided to persons with non-spastic calf muscle weakness. Differences in ankle-foot orthoses ankle stiffness were related with their effects. In general, persons wearing ankle-foot orthoses with the greatest ankle and footplate stiffness showed the largest benefits with regard to improved walking ability, although this warrants further prospective research.
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