Reducing stiffness of shock-absorbing pylon amplifies prosthesis energy loss and redistributes joint mechanical work during walking.
Jenny Anne Maun, Steven A Gard, Matthew J Major and 1 others
PMID 34548080WHAT IT FOUND
A softer pylon increased energy absorbed by pylon compression, but the prosthesis did not return more energy later.
The sound limb had less impact work, and residual hip work changed with stiffness. This is a mechanical finding, not a comfort outcome.
Key findings
01Reduced pylon stiffness increased energy absorbed by the pylon, with 18-229% more negative work. The pylon accounted for only 14% of prosthesis net work in stance and 22% in collision.
02Reduced pylon stiffness was associated with 11-17% less early impact work on the sound limb.
03Reduced pylon stiffness was associated with 21-73% more energy produced by the residual hip during early impact.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
Read the rest of this summary
You get three full summaries a month, free, and we do not ask for a card. Search, the TL;DRs and your library stay unlimited either way.
What it does not show
The analysis included 12 participants, so individual responses may vary and the sample was small. The study measured mechanical work only. It did not report patient comfort, pain, stability, falls, or metabolic cost. Analyses were exploratory, and no adjustment was made for multiple statistical tests. Participants needed at least six months of prosthesis experience and independent walking for 10 m, so results may not apply to new users or people who need assistance. The prosthesis included a shock-absorbing pylon, standard prosthetic foot, and flat shoes, so work from the foot and shoes could not be isolated. The residuum-socket interface could not be included in the prosthesis power calculation. Familiarization was at least 5 minutes, which may be short for adapting to stiffness changes. The pylon twisting was disabled, so transverse motion was not tested.
Declared interests
No author conflict-of-interest declaration appears in the supplied text. The publication types list NIH extramural and non-U.S. government research support.
The easy way to misread this
Do not conclude that a softer shock-absorbing pylon is clinically better for comfort, pain, stability, or metabolic cost. The study measured mechanical work in 12 people, tested the pylon with a standard prosthetic foot and flat shoes, and did not show that the pylon alone caused the prosthesis energy loss.