Reliability of Hand Strength Measurements Using the Rotterdam Intrinsic Hand Myometer in Children

Purpose Grip strength and pinch strength measurements are often used to assess hand function. However, both measure a number of muscle groups in combination, and grip strength in particular is dominated by extrinsic hand muscles. The Rotterdam Intrinsic Hand Myometer (RIHM) was recently introduced to measure the force that individual fingers and thumb can exert in different directions. The aim of this study was to establish the reliability of these measurements with use of the RIHM in children. Methods Sixty-three healthy children between 4 and 12 years of age participated in this study. The RIHM was used to measure thumb palmar abduction, thumb opposition, thumb flexion at the metacarpal-phalangeal (MP) joint, index finger abduction, and little finger abduction. A retest was performed with an average test-retest interval of 26 days. Results For the thumb, palmar abduction strength had intraclass correlation coefficients (ICCs) of .98 for both hands. For both thumb opposition and flexion at the MP joint, ICCs were .97 for the dominant hands and .98 for the nondominant hands. Index finger abduction had ICCs of .94 and .95 and little finger abduction had ICCs of .90 and .92 for the dominant and nondominant hands, respectively. The smallest detectable differences for dominant and nondominant hands respectively were thumb palmar abduction, 15% and 15%; thumb opposition, 12% and 9%; thumb flexion (at the MP joint), 12% and 9%; abduction of the index finger, 17% and 17%; and little finger abduction, 26% and 26%. Conclusions We found that the RIHM was reliable for use in children. Intraclass correlation coefficients and smallest detectable differences were comparable with those obtained with use of the RIHM in adults and with values found for pinch and grip strength in children. Because the RIHM measures more specific aspects of hand function than grip and pinch, adding the RIHM to measurement protocols may contribute to a more complete overview of a child's hand function.