Analysis of mechanical and metabolic factors in the gait of congenital below knee amputees. A comparison of the SACH and Seattle feet.

Prosthetic feet have been developed with the intention that they deform during the first half of the stance phase to store energy that can be released at the end of stance and contribute to push-off. The purpose of this study was to examine the three-dimensional kinematics and kinetics of gait and metabolic energy cost in children and adolescents with below-knee amputations using the SACH and Seattle prosthetic feet. The metabolic test consisted of an 8-min walk around an oval track while expired gases were collected and analyzed. The biomechanical test consisted of 10 walking trials: 5 for each of the prosthetic and sound limbs. Stance and swing phase moments and powers were calculated for both the prosthetic and sound limbs. A four-camera VICON system recorded movements of the limb segments to calculate joint kinematics, and these were combined with ground reaction force data in a three-dimensional model to determine moments and powers about the hip, knee and ankle joints. The Seattle foot produced a small increase in stride length, which led to a small increase in walking velocity. Biomechanical data revealed that the Seattle foot was less resistant to passive dorsiflexion in midstance, and although there was no effect on the work done across the prosthetic ankle, a knee flexor moment dominated the stance phase when the SACH foot was tested, whereas the Seattle foot allowed a normal extensor moment. The profile of work was unaffected by the type of foot. On the sound side, the hip produced most of the positive work while the ankle output was below normal.(ABSTRACT TRUNCATED AT 250 WORDS)