The influence of a hydraulic prosthetic ankle on residual limb loading during sloped walking

<div><p>In recent years, numerous prosthetic ankle-foot devices have been developed to address the demands of sloped walking for individuals with lower-limb amputation. The goal of this study was to compare the performance of a passive, hydraulic ankle-foot prosthesis to two related, non-hydraulic ankles based on their ability to minimize the socket reaction moments of individuals with transtibial amputation during a range of sloped walking tasks. After a two-week accommodation period, kinematic data were collected on seven subjects with a transtibial amputation walking on an instrumented treadmill set at various slopes. Overall, this study was unable to find significant differences in the torque at the distal end of the prosthetic socket between an ankle-foot prosthesis with a hydraulic range-of-motion and other related ankle-foot prosthesis designs (rigid ankle, multiaxial ankle) during the single-support phase of walking. In addition, socket comfort and perceived exertion were not significantly different for any of the ankle-foot prostheses tested in this study. These results suggest the need for further work to determine if more advanced designs (e.g., those with microprocessor control of hydraulic features, powered ankle-foot designs) can provide more biomimetic function to prosthesis users.</p></div

Demographic data of subjects with unilateral transtibial amputation.

<p>Demographic data of subjects with unilateral transtibial amputation.</p

(A) Minimum and (B) maximum SVA (+ 1 standard deviation) during single-limb support (control = white, RIGID = light gray, MULTI = gray, HYDRA = black).

<p>Positive angles correspond to a reclined shank posture (i.e., the posture that would be expected at initial contact). An asterisk (*) indicates a statistically significant within-group difference (p<0.05) between level and the sloped walking condition across all prosthetic feet.</p

Mean rating of perceived exertion (+ 1 standard deviation) across sloped walking conditions (control = white, RIGID = light gray, MULTI = gray, HYDRA = black).

<p>This scale allows subjects to rate their level of effort from 0 (no exertion) to 10 (maximum possible exertion). An asterisk (*) indicates a statistically significant within-group difference (p<0.05) between level and the sloped walking condition across all prosthetic feet.</p

Mean socket comfort score (+ 1 standard deviation) across sloped walking conditions (RIGID = light gray, MULTI = gray, HYDRA = black).

<p>This 11-point scale ranges from 0 (worst comfort imaginable) to 10 (greatest comfort imaginable).</p

Mean socket reaction moments of subjects with transtibial amputation (n = 7) during single-limb support for the following sloped walking conditions: (A) 10° decline, (B) level, and (C) 10° incline.

<p>Dashed band corresponds to the mean reaction moment (± 1 standard deviation) of an able-bodied control group (n = 7) at a shank location equal to the mean, normalized residual-limb length of the amputee group. External extension moments are defined as positive.</p

Schematic drawings of the: (A) Endolite Esprit ankle-foot system (RIGID) with a dynamic-response foot (i.e., carbon toe and heel spring as shown in manufacturer’s specifications) and rigid ankle, (B) Endolite Epirus ankle-foot system (MULTI) with a dynamic-response foot and multi-axial ankle, and (C) Endolite Echelon ankle-foot system (HYDRA) with a dynamic-response foot and hydraulic ankle with adjustable damping.

<p>Schematic drawings of the: (A) Endolite Esprit ankle-foot system (RIGID) with a dynamic-response foot (i.e., carbon toe and heel spring as shown in manufacturer’s specifications) and rigid ankle, (B) Endolite Epirus ankle-foot system (MULTI) with a dynamic-response foot and multi-axial ankle, and (C) Endolite Echelon ankle-foot system (HYDRA) with a dynamic-response foot and hydraulic ankle with adjustable damping.</p

(A) Minimum and (B) maximum socket reaction moments (+ 1 standard deviation) during single-limb support (control = white, RIGID = light gray, MULTI = gray, HYDRA = black).

<p>External extension moments are defined as positive. An asterisk (*) indicates a statistically significant within-group difference (p<0.05) between level the sloped walking condition across all prosthetic feet. A carrot (^) indicates a statistically significant between-group difference (HYDRA vs control; p<0.05) within each sloped walking condition.</p

Markers placed on the distal end of the socket were used to define a socket coordinate system.

<p>Markers placed on the distal end of the socket were used to define a socket coordinate system.</p