The intermetacarpal distance method for assessment of active thumb radial abduction has excellent test-retest agreement, reliability, and precision in persons with non-operative thumb carpometacarpal osteoarthritis.
Halil Ibrahim Ergen, Karl Dischinger, Corey McGee
PMID 39814634WHAT IT FOUND
Measuring thumb abduction with a digital caliper is highly reliable in people with thumb arthritis.
Using the average of two trials provides better precision than a single trial, requiring only ten extra seconds to ensure accurate tracking of patient progress.
Key findings
01The intermetacarpal distance method showed excellent test-retest reliability, with Intraclass Correlation Coefficients ranging from .942 to .970.
02Averaging two trials provided significantly better reliability than a single trial, while averaging three trials offered no additional benefit over two.
03For a change in measurement to be considered clinically meaningful rather than measurement error, the distance must exceed 3.74 mm when using the average of two trials.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The sample was largely homogeneous regarding race and ethnicity, limiting generalizability. Participants with concomitant conditions like carpal tunnel syndrome or rheumatological issues were excluded, so results may not apply to more complex clinical presentations. The method measures distance in millimeters, which varies by hand size, preventing direct comparison of absolute scores between different individuals. The study only assessed active radial abduction; findings do not apply to passive range of motion measurements.
The easy way to misread this
Do not compare absolute millimeter scores between different patients. The intermetacarpal distance depends on individual hand anatomy, such as metacarpal length, so a score of 40 mm in one person does not represent the same degree of abduction as 40 mm in another.