Examining the role of intrinsic and reflexive contributions to ankle joint hyper-resistance treated with botulinum toxin-A.
Ronald C Van't Veld, Eline Flux, Wieneke van Oorschot and 6 others
PMID 36750869WHAT IT FOUND
In nine people with ankle spasticity, the clinical Modified Ashworth Scale showed a significant drop in resistance six weeks after botulinum toxin injections.
However, precise instrumented measures of reflex and tissue stiffness failed to confirm this group-wide effect, leaving the specific mechanism of action unclear.
Key findings
01The clinical Modified Ashworth Scale showed a statistically significant reduction in overall joint resistance at six weeks, returning towards baseline by twelve weeks.
02Instrumented measures of reflexive and intrinsic resistance did not show a significant group-level reduction, despite some individual participants responding.
03Participants with low baseline reflex activity showed little to no reduction in resistance, suggesting the treatment may be less effective for those without significant spasticity.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The sample size was very small (nine participants), limiting the generalizability of the findings. The clinical assessments were performed by a non-blinded physiotherapist, which could introduce bias in the Modified Ashworth Scale scores. Participants' passive range of motion varied across sessions, which complicates the interpretation of instrumented measures that are sensitive to joint angle. The study was exploratory and not powered to detect small differences in specific resistance components. Three participants had low baseline reflexive resistance, meaning they had little potential to show a reduction, which may have diluted the group-level effect.
Declared interests
The authors declared no competing interests. The study was funded by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (Dutch Research Council).
The easy way to misread this
Do not conclude that the treatment failed because instrumented measures were negative. The study was underpowered, and the clinical scale (MAS) did show a significant group improvement. The discrepancy suggests the MAS may be measuring overall resistance changes that the specific reflex/tissue breakdowns in this pilot did not capture, or that the effect is driven by a subset of patients with high baseline spasticity.