Effects of prosthetic mass distribution on the spatiotemporal characteristics and knee kinematics of transfemoral amputee locomotion

This study was designed to investigate the effect of changing the location of the center of mass (COM) of transfemoral prostheses on the spatiotemporal and kinematical characteristics of the amputee gait, while maintaining the prosthetic mass fixed. Ten men with unilateral traumatic transfemoral amputation participated in gait analysis, 2-min walk and subject preference tests. Weights were added to the original prosthetic legs in three conditions: 600 g added to the ankle, 600 g added at 10 cm distal to the prosthetic knee, and 300 g added to the ankle, and 300 g at 10 cm distal to the knee. For each prosthetic mass condition, the stride and step lengths, stepping speed, stance, swing and gait cycle durations, self-selected walking speed, cadence, and knee flexion angle, were measured. We found no significant change in the spatiotemporal variables and the knee kinematics with alteration of the prosthetic COM, for both the prosthetic and the intact limbs. With the mass added to the ankle, the stepping speed, and the step and stride lengths of the prosthetic limb were significantly larger than those of the intact limb. Subject's preference revealed that 8 of 10 preferred their original no-added mass prostheses or mass added prostheses with minimal change of the COM. It was concluded that a short-term intervention with changed prosthetic mass distribution has no significant effect on the spatiotemporal and knee kinematical characteristics of the transfemoral amputee gait, although it can affect the spatiotemporal symmetry of locomotion.

► The effect of prosthetic COM location on transfemoral amputee gait is studied.
► Amputees often recognize alteration of the COM and prefer their original prosthesis.
► The amputee gait kinematics does not change significantly when the COM is altered.
► Amputees adapt to mass perturbation using a kinematics invariance strategy.
► The gait kinetics is adjusted to maintain the original kinematical pattern.