Immediate effects of the new modified UCBL foot orthosis on electrical muscle activity and kinetic parameters of gait in adults with symptomatic flexible flat foot.

Abstract

Objective

Symptomatic flexible flat foot is a common disease of the lower extremities in which the medial longitudinal arch of the foot is reduced or eliminated when weight is applied on it. One of the prescribed methods is orthotics treatment. The purpose of this study was to design a new UCBL foot orthosis with greater flexibility in midfoot area. The electromyography (EMG) and kinetics evaluation of the patients during walking with the new UCBL orthosis was done afterwards.

Materials and Methods

34 subjects with flexible flat foot (15 men and 19 women) aged 19 to 37 with BMI range of 18.5 -25 and 7-11 foot posture index with foot and leg discomfort were chosen. The new custom orthotics insole, a conventional UCBL, a prefabricated functional foot orthosis and a pair of sport shoe was delivered to patients. After two weeks of wearing orthosis, electromyography activity of calf muscles and ground reaction forces (GRF) was measured during walking. Conditions of the tests were barefoot, bare shoes, functional orthosis, orthotics UCBL and the new UCBL foot orthosis. Surface electromyography was measured by Biometric system and ground reaction force was measured by Kistler force plate.

Results

The new UCBL with greater flexibility in mid-foot area and a higher arch caused a change in the components of the ground reaction forces. Significant increase of fz1, fz3 (p <0/005), decrease of the posterior force (p<0/001), an increase in lateral force and the first medial peak (p < 0/05), reduction of medio-lateral displacement of the center of pressure (COP) (p < 0/05) were measured compared to other orthoses. The new UCBL orthosis also increased the activity of peroneus longus muscle more than other orthosis (p <0/005) and decreased the activity of tibialis anterior muscle significantly in the stance phase of walking compared with the bare feet (p < 0/05). All of orthoses were caused significant changes in the loading rates, stance time and component of the ground reaction forces compared with bare feet and shoes (p < 0/05). Functional orthosis was more comfortable than other orthoses (p < 0/05).

Conclusion

The results of this study indicate that, the foot orthosis will decrease loading rate and mediolateral displacement of COP, changing GRF and EMG of leg muscles and increases stance duration by comforting the feet. The new UCBL foot orthosis may be used for patients with flat feet that cannot tolerate the conventional rigid UCBL.