The Rigidity of Plastic Ankle-Foot Orthoses: Effect of Ankle Width

ABSTRACT

OBJECTIVE: This study was designed to analyse quantitatively the change in rigidity of plastic ankle foot orthoses (AFOs) corresponding with regulated ankle width and to find the appropriate ankle width for spastic ankles. METHOD: Five different plastic AFOs were fabricated according to the regulated ankle width. The resistance to dorsiflexion and plantar flexion movements was measured by bending the plastic AFOs at intervals of 2 degrees with the measuring device. Plantar flexion moments of hemiplegic spastic ankles were also measured. RESULTS: The rigidity of plastic AFOs increased nearly in proportion to the increase of the ankle width. The plantar flexion moments of hemiplegic spastic ankles increased in proportion to the severity of the spasticity. If the plastic AFOs would be used only for the prevention of toe dragging in swing phase, the ankle width of plastic AFOs could be reduced up to 60% which was enough to support the ankle in swing phase. CONCLUSION: These findings suggested that the degree of rigidity of plastic AFOs could be adjusted by trimming about the ankle to meet the individual patient's requirement. And this study could be helpful to quantify empirical approach of the prescription of plastic AFOs.