Centre of pressure displacements in trans-femoral amputees during gait.

The aim of this study was to describe and quantify centre of pressure (CoP) displacement during walking in 12 unilateral trans-femoral amputees who had worn a prosthesis for at least 10 years. All subjects wore the same type of prosthesis and seven healthy subjects acted as controls. The CoP was acquired by an F-scan system and the displacements along the longitudinal axis of the foot versus time were quantified. An asymmetry of both temporal and spatial parameters of CoP patterns occurred between the sound and the prosthetic foot. The double support time and the time during which the CoP remained in the heel and mid-foot region were longer for the prosthetic limb. Conversely, the stance phase was longer for the sound limb, as was the time spent by the CoP in the forefoot. There was a redistribution of the time during which the CoP remained within the different zones of the sound foot with respect to the normal feet of the control subjects. The asymmetry seen in trans-femoral amputee stance is due not only to an abnormal spatio-temporal distribution of the CoP under the prosthetic leg, but also to a modification of the spatio-temporal distribution of the CoP under the sound foot compared to the normal foot. We conclude that an adaptation occurs in the control of the stance phase on the sound side during amputee gait.