Balance in lower limb child amputees.

Abstract

Postural stability of five unilateral above-knee amputee children was measured when wearing the SACH and the experimental Child Amputee Prosthetic Project (CAPP) prosthetic foot. Excursions of the centre of pressure of the supportive forces were recorded via force platform during sustained weight-shifting forward, backward, left, right, and during normal standing. Visual proprioception effects on upright stance were also demonstrated with these child amputees. Total base of support did not differ for the two types of prosthetic feet, but the functional base of support for SACH foot was significantly larger than CAPP. Fluctuations of centre of pressure about a mean position in normal standing were less when children used CAPP foot. Focusing on a static target had no effect on postural stability in either anterior-posterior or lateral direction for CAPP foot conditions, but lack of visual target had a deleterious effect on lateral stability when SACH foot was worn. Balance is one of the most difficult problems for a lower limb amputee (Hellebrandt et al, 1950; Moncur, 1969; Murdoch, 1969). The absence of part or all of a lower limb reduces the amount of proprioceptive information about the surfaces on which the foot is resting and the precise location of the prosthetic limb. While limited data have been reported on the balance and stability characteristics of adult amputees (Fernie and Holliday, 1978; Hellebrandt et al, 1950), information about balance of child amputees is almost non-existent. We have found only one report of the postural stability characteristics of a child amputee; Shambes and Waterland (1970) studied an 11-year-old quadrilateral amputee who had congenital Lisfranc amputations of both lower limbs, long above-elbow amputation of the left upper limb, and medium below-elbow amputation of the right upper limb. The purpose of this study was to detail the postural stability characteristics for lower limb child amputees. In addition, the conventional SACH prosthetic foot was compared with the experimental Child Amputee Prosthetic Project (CAPP) foot for various postural tasks. The SACH foot (Fig. la) is usually constructed with a moulded polyurethane material which incorporates a heel cushion to allow some compression of the heel during heel strike in walking to simulate plantar flexion of a normal foot. The CAPP foot (Fig. lb) is an experimental prosthesis undergoing development at the UCLA Child Amputee Prosthetic Project. It is designed to provide more knee stability during early stance phase during walking and also to respond to torsional loads occurring in the stance phase of walking. The heel projection of the CAPP foot is non-weight bearing and deflects upward at heelstrike. With the ground reaction forces shifted more anteriorly on the supporting foot there is an expected increase in dynamic knee stability during the stance phase of walking. While additional research is being conducted on the dynamic characteristics of the CAPP foot, the present study provides some preliminary information about the postural stability of child amputees using the experimental CAPP foot, as well as providing a comparison with the conventional SACH foot.