What question did this study set out to answer?

This research aims to validate and assess the reliability and precision of intermetacarpal distance for measuring thumb abduction in osteoarthritis patients.

February 26, 2026Open Access

Assessing active thumb palmar and radial abduction in persons with thumb carpometacarpal osteoarthritis via intermetacarpal distance methods: an exploration of validity, reliability, and precision

Puntos clave

This research aims to validate and assess the reliability and precision of intermetacarpal distance for measuring thumb abduction in osteoarthritis patients.
Evaluated forty participants with confirmed carpometacarpal osteoarthritis.
Conducted intermetacarpal distance assessments using calipers and tape across two sessions, two weeks apart.
Recorded three trials per session to analyze reliability, precision, and construct validity.
Reliability scores (ICC 2,3) ranged from 0.90 to 0.97, indicating excellent reliability for the methods used.
All methods showed acceptable precision, with PABD-caliper demonstrating superior precision (MDC% = 9.1).
Strong correlations were found between radial abduction methods and self-reported disability scores from the Michigan Hand Questionnaire.

Resumen

Abstract Background Thumb carpometacarpal osteoarthritis (CMC1 OA) is a prevalent and disabling rheumatological condition. One impairment commonly described in the context of CMC1 OA is a loss of radial (RABD) and palmar (PABD) thumb abduction. Traditional goniometric measures are unreliable and poorly correlated with functional limitations. The intermetacarpal distance (IMD) method, using digital calipers, shows promise for better reliability, but its validity and the feasibility of using tape measures remain untested. Objective To evaluate the construct validity, test–retest reliability, and precision of IMD-based thumb abduction measurements using calipers and tape in individuals with non-operative, radiographically confirmed CMC1 OA. Methods Forty participants underwent standardized IMD assessments using both caliper and tape methods across two sessions, 2 weeks apart. Three trials were recorded per session. Reliability (ICC 2,3 ), precision (SEM, MDC, MDC%), and construct validity (correlation with Michigan Hand Questionnaire MHQ) were analyzed. Results Reliability (ICC 2,3 ) ranged from 0.90 (PABD-tape, 1 trial) to 0.97 (RABD-caliper, 2–3 trials). All methods had acceptable precision (MDC% < 22); PABD-caliper (3 trials) showed excellent precision (MDC% = 9.1). RABD-caliper and RABD-tape showed strong, significant correlations with MHQ ADL scores ( r = .38, p < .05; r = .40, p < .01). PABD methods showed weak or non-significant associations. Conclusion Caliper and tape-based IMD measurements offer similar reliability, but averaging multiple trials improves precision. RABD-IMD methods demonstrate moderate construct validity, supporting their use in clinical assessment of CMC1 OA. Standardized, repeatable IMD assessments may enhance monitoring and care planning in thumb CMC1 OA. Key Points In persons with carpometacarpal osteoarthritis:• Caliper and tape intermetacarpal distance measures of thumb radial and palmar abduction demonstrate excellent test-rest reliability and acceptable precision. • Averaging two or three intermetacarpal distance measurements is recommended over a single measure due to superior precision. • Radial abduction (via the intermetacarpal distance) is strongly associated with self-reported disability and may be more clinically meaningful than palmar abduction.

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