Shock absorption during transtibial amputee gait: Does longitudinal prosthetic stiffness play a role?
Erin Boutwell, Rebecca Stine, Steven Gard
PMID 27117010WHAT IT FOUND
At normal walking speeds, changing prosthetic stiffness showed no differences in force timing or joint patterns, and a peak force difference coincided with a speed difference.
At fast speeds, lower stiffness did not reduce peak force as expected.
Key findings
01Twelve subjects with unilateral transtibial amputation walked with four prosthetic stiffness conditions at normal and fast self-selected speeds.
02At normal self-selected walking, knee flexion and pelvic obliquity did not differ across stiffness conditions, and time to peak force did not differ; peak force differed between NORMAL and MEDIUM, but walking speed also differed between those conditions.
03At fast walking, NORMAL had lower peak force than SOFT, and RIGID had shorter time to peak than SOFT and MEDIUM.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study included twelve subjects, so it may not represent the range of transtibial prosthesis users. Walking speed was controlled only within 10% of baseline, and the NORMAL condition was tested first, so speed and order effects may have affected the normal-speed results. The significant peak force difference between NORMAL and MEDIUM at normal speed coincided with a significant walking speed difference between those conditions. The stiffness of the residual limb and socket interface was not measured, so the tested prosthetic stiffness values may not have changed total limb stiffness. The fast walking findings may not apply to most daily walking because the average fast speed was 1.57 m/s and many transtibial users likely walk slower.
Declared interests
The authors declared no conflict of interest. The supplied text does not identify a funder.
The easy way to misread this
Do not conclude that softer prosthetic components reduce shock absorption during usual walking. This study changed spring stiffness within one pylon system while the socket, suspension, foot, and shoe were held constant, and lower stiffness did not consistently lower peak force.