Abstract
Objective: One major challenge encountered by exomodular prosthetic users is walking in uneven terrain and sloped surfaces. This difficulty arises from the restricted mobility of the ankle joint on the prosthetic side and the absence of distal muscles and sensory input from the lower limb. Looking forward to design prostheses that are better adapted to this type of terrains, it is necessary to establish the existing differences in the spatiotemporal variables of gait and in the kinematics of the ankle, knee and hip during walking on sloping uneven ground of transtibial amputees with exomodular prostheses and control users, in order to help identify areas where existing prostheses can be ameliorated.
Methods: An experiment was conducted with a sample of 20 transtibial amputees with exomodular prostheses and 20 control users, who walked on a platform with stones at level ground (without inclination) and in sloping ground with an inclination of 10°. Spatiotemporal measurements and gait kinematics were taken by means of noninvasive sensors. The variables were compared between the amputee group and the control group in the different ground inclinations and in the distinct phases of the gait cycle.
Results: Overall, in terms of spatiotemporal variables we found that during gait in uneven surfaces, amputee subjects reduced the stride length, gait speed and cadence in comparison with control subjects. Lower stance time and higher swing time of the prosthetic leg for amputees were also found.
During both the ramp-up and the ramp-down condition, amputee users showed decreased flexion than control users in the ankle and the knee joints during the heel strike, single limb support and pre-swing sub-phases in the prosthetic leg. This pattern of lower flexion was also seen in the single limb support in the level ground surface. No significant differences were found in the loading response and swing phases. For the healthy leg, less flexion of the knee joint of the amputees was found for level ground, ramp-up and ramp-down gait during the swing phase. No significant differences were found in the heal strike, single limb support and pre-swing phases.
Conclusions: Due to the use of exomodular prostheses with stiff ankle joints, individuals who have undergone amputation lack the ability to actively manipulate the position of the ankle in their prosthetic limb, consequently, they rely on adjusting the knee and hip positions to regulate the orientation of the foot. This is why some variations are found in the values of ankle, knee and hip flexion and abduction angles, and in the spatiotemporal parameters of gait of amputees compared to controls while walking on uneven surfaces, although the movement pattern found was similar.
In order to reduce the adaptations that amputees must use to be able to walk on these terrains, the possibility of increasing the range of motion of the foot of exomodular prostheses should be considered, so that the new prostheses adapt better to the changes of inclination and slope characteristic of the uneven terrains that are the most common in Colombia and some Latin American countries.
