Accuracy and Reliability of Single-Camera Measurements of Ankle Clonus and Quadriceps Hyperreflexia.
Keith Macon, Dustin Hoang, Lauren Elizondo and 3 others
PMID 34977536WHAT IT FOUND
A smartphone camera system with green stickers measured ankle and knee reflex angles as accurately as expensive motion capture sensors.
Students and experienced therapists got similar results, meaning this cheap, portable method can reliably track spasticity changes in clinic.
Key findings
01The smartphone Reflex Tracker system showed agreement with high-fidelity motion capture sensors within clinically acceptable limits for both ankle clonus and knee hyperreflexia.
02Reliability was high for both student and experienced physical therapists, with no significant difference in measurement accuracy between the two groups.
03The system's minimum detectable change was smaller than the typical improvements seen after treatment in previous studies, suggesting it can track real clinical progress.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
The study used inertial motion capture as the reference standard, not the gold-standard optical motion capture, so there is some inherent error in the comparison baseline. Not all participants could walk, which meant the motion capture sensors were calibrated differently for non-ambulatory patients, potentially affecting agreement in that subgroup. The order of raters was not randomized (students always first), so the interaction effect found between rater type and repetition might be due to testing order rather than experience. The study only assessed same-day reliability, not test-retest reliability over time. Lighting conditions and marker clarity varied across sites, which could affect the smartphone tracking algorithm's performance in real-world clinics.
Declared interests
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The easy way to misread this
Do not assume this system measures true spasticity severity. It measures agreement with another sensor system. Also, the study included only 14 people, so while promising, it does not yet prove this tool works across all patient populations or lighting conditions.