K. Postema et al., ENERGY-STORAGE AND RELEASE OF PROSTHETIC FEET .1. BIOMECHANICAL ANALYSIS RELATED TO USER BENEFITS, Prosthetics and orthotics international, 21(1), 1997, pp. 17-27
The energy storing and releasing behaviour of 2 energy storing feet (E
SF) and 2 conventional prosthetic feet (CF) were compared (ESF: Otto B
eck Dynamic Pro and Hanger Quantum; CF: Otto Beck Multi Axial and Otto
Beck Lager). Ten trans-tibial amputees were selected. The study was d
esigned as a double-blind, randomised trial. For gait analysis a VICON
motion analysis system was used with 2 AMTI force platforms. A specia
l measuring device was used for measuring energy storage and release o
f the foot during a simulated step. The impulses of the anteroposterio
r component of the ground force showed small, statistically non-signif
icant differences (deceleration phase: 22.7-23.4 Ns; acceleration phas
e: 17.0-18.4 Ns). The power storage and release phases as well as the
net results also showed small differences (maximum difference in net r
esult is 0.03 J kg(-1)). It was estimated that these differences lead
to a maximum saving of 3% of metabolic energy during walking. It was c
onsidered unlikely that the subjects would notice this difference. It
was concluded that during walking differences in mechanical energy exp
enditure of this magnitude are probably not of clinical relevance. Ank
le power, as an indicator for energy storage and release gave differen
t results to the energy storage and release as measured with the speci
al test device, especially during landing response. In the biomechanic
al model (based on inverse dynamics) used in the gait analysis the def
ormation of the material is not taken into consideration and hence thi
s method of gait analysis is probably not suitable for calculation of
shock absorption.