Introduction: Hemiplegic cerebral palsy (CP) children are often treated with ankle-foot orthoses (AFO′s) in order to resist abnormal motion patterns and to restore normal function. It has been shown that AFOs are successful in improving pre-positioning of the foot for initial heel strike in CP patients. The myoelectric signal (EMG) during gait provides valuable information with respect to timing of muscular activity. The aim of this study was to evaluate changes in timing of muscle activation in children with hemipelegic CP during gait with and without wearing AFOs.

Patients/Materials and Methods: Eight Children (5 boys, 3 girls; mean age 9.5±1.4 years) with mild to moderate hemiplegic CP and no prior surgeries or fixed contractures were studied. The children were tested barefoot and wearing a hinged AFO and shoes. Only children with an initial toe-strike barefoot and a physiological heel-strike with the AFO were included. All children performed a 3-dimensional gait analysis. At least six trials with clear forceplate data have to be collected for each of the two testing condition. Frontal and sagittal video recording took place. A sSurface EMG of vastus medialis/lateralis, rectus femoris, biceps fem-oris, semimembranosus/semitendinosus, gastrocnemius lateralis (only barefoot), and tibialis anterior was collected.

Results: Mean ankle plantarflexion at initial foot contact was 16.1° when walking barefoot and 3.4° with the AFO. EMG data showed reduced tibialis anterior muscle activity with the AFO in all patients, especially in early to mid swing phase. Muscle activation pattern was corrected towards normal for knee extensors and hamstrings.

Discussion: Our results show that tibialis anterior muscle activity is reduced by a hinged AFO with plantarflexion block in hemiplegic CP children. These results indicate that the pathological muscle activation pattern present in CP patients are not only due to spastic activation but also to a compensation for the abnormal gait pattern.