Running patterns of juveniles wearing SACH and single-axis foot components

Concerns have been raised about the capability of conventional prosthetic foot components to provide adequate support and function for activities other than walking to persons with lower limb amputations. Degenerative changes of the lumbar spine and knee joints have been linked to prolonged asymmetric loading, which may be accentuated when force magnitudes are high, as in running. This study evaluated the extent and location of kinematic and kinetic asymmetries relative to the foot component worn. The running patterns of six children with unilateral below-knee amputations were evaluated on two occasions: first, while wearing the solid ankle-cushioned heel (SACH) component, and second, wearing the single-axis (SA) component. Cinematographic and forceplate data yielded bilateral temporal data, vertical ground reaction forces, joint angular trajectories, and moments. Results indicated that the SACH and SA components performed almost identically, despite the greater excursion allowed by the SA foot. Slower step speed on the affected side was related to significantly lower vertical ground reaction forces (p less than .01). The ankle angular displacement and moment curves revealed the incapacity of either component to stimulate natural foot-ankle function, with resulting significant interlimb asymmetries. The ipsilateral knee displayed marked reduction of the initial flexor wave, paired with a reduced extensor moment. Compensations predominated ipsilaterally, as evidenced by the similarity of the contralateral patterns to those of an able-bodied runner, except for a decreased hip flexor moment before toe-off. This study showed that interlimb asymmetries were attributable to the inadequacies of both components.