Comparison of five different methodologies for evaluating ankle-foot orthosis stiffness.
Benjamin R Shuman, Deema Totah, Deanna H Gates and 3 others
PMID 36683044WHAT IT FOUND
The same ankle-foot orthoses measured very different stiffness values depending on the testing method.
The simple hanging-weight method gave the lowest readings. Without a shared testing standard, stiffness values may not be comparable across labs.
Key findings
01Across all tested AFOs, the median difference in absolute stiffness between methods was 1.06 Nm/deg, with a range from 0.40 to 2.35 Nm/deg.
02The hanging-weight method produced the lowest stiffness values, a median of 0.66 Nm/deg lower than EMPIRE, 0.42 Nm/deg lower than SMApp, 0.91 Nm/deg lower than KST, and 0.18 Nm/deg lower than BRUCE.
03Only 2 of the 13 AFOs had stiffness values that agreed within 15% of the average stiffness across methods.
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 study tested 13 right-foot, size-large, carbon composite, non-articulated AFOs, so it does not address other AFO materials, sizes, left-foot models, or articulating designs. The methods differed in mounting, rotation-axis height, fore-aft position, transverse alignment, surrogate shank, footplate clamping, speed, filtering, and number of cycles; the study did not isolate which difference caused the variability. The hanging-weight method allowed out-of-plane rotation and a shifting rotation center, but those effects were not quantified. The BRUCE speed varied between 14 and 50 deg/s, unlike the other fixtures, which may have affected stiffness. The paper reports bench testing only, not patient outcomes, so it does not show which method is most accurate or which stiffness value best predicts patient response. Differences in methods do not prove one method is more or less accurate.
Declared interests
Funding was from the Congressionally Directed Medical Research Programs and the DoD-VA Extremity Trauma and Amputation Center of Excellence. The supplied text does not list author conflicts.
The easy way to misread this
Do not conclude that AFO stiffness values from different manufacturers, papers, or labs can be directly compared. The study tested bench methods, not patients, and it did not identify which method is most accurate.