THE DYNAMICS OF LONGITUDINAL IMPACT TRANSMISSION AND ATTENUATION IN AMPUTEES RUNNING WITH BELOW-KNEE PROSTHESES

Abstract

Lower limb amputees who want to stay physically active and rely on activities such as jogging to improve their fitness level often encounter limitations related to the prosthesis they are wearing. The loss of an important amount of the biological tissues attenuating the foot-ground repetitive impact shocks can possibly lead to severe health problems like cartilage degeneration, stress fractures and even be a contributing factor in the development of low back pain. Since the wearing of a prosthesis is considered to alter the overall locomotion dynamics of an individual it becomes imperative to study the different aspects of the human body response in such a situation. The present research on the longitudinal impact attenuation dynamics of amputees running with below-knee prostheses was undertaken in order to determine shock transmission phenomenons above and below the ankle and knee joints. A group of seven (7) below-knee amputees, wearing a prosthesis since two (2) years or more and exhibiting a flight phase in their running pattern, was used for the study. Five (5) trials for each leg were evaluated while running at a speed between 2.8 and 3.2 ms-1. Impact shock was measured with accelerometers placed at ankles and hips as well as with a force platform. A kinematic study of sequences filmed with three video cameras complemented the kinetic study. Results have shown that the impact shock transmitted from ankle to hip is attenuated in both the prosthetic and the sound limb, even if the materials and the mechanisms responsible for the absorbtion are different. It was also demonstrated that subjects who had attained higher running ability through the readaptation process were applying larger loads on the prosthetic limb, rather than protecting it, as many amputees do. Conclusions of the present study as well as from recent literature indicate that amputees wearing prostheses well adapted to their specific needs can effectively participate in many physical activities involving repetitive longitudinal impacts after adequate readaptation.