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Design and Validation of a Hand Interossei Muscle Dynamometer (HIMDNA) for Finger Abduction and Adduction Strength
Seung Yeon Cho1, Geunwu Gimm2,3, Sungwoo Park1,4
1Interdisciplinary Program in Bioengineering, The Graduate School, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic of Korea.
Purpose:
Interossei muscles of the hand, innervated primarily by the ulnar nerve, are essential for coordinated finger abduction and adduction. Quantitative strength assessment of these key actions, which support precision grip and fine motor control, may aid in the diagnosis and monitoring of neuropathic conditions including cubital tunnel syndrome. This study aimed to develop and validate a novel Hand Interossei Muscle Dynamometer (HIMDNA) for quantifying finger abduction and adduction strength for the index to little fingers and to establish normative values for healthy adults.
Methods:
HIMDNA was designed based on hand morphology, incorporating a load cell within a fixed frame and a linear guide mechanism to ensure uniaxial, examiner-independent force measurements. The abduction and adduction strengths of 48 healthy adults aged 20-39 years were measured and validated against index and little finger abduction measurements obtained with a handheld dynamometer (HHD). The inter- and intra-rater reliabilities and overall usability of HIMDNA were then compared with those of HHD.
Results:
HIMDNA demonstrated excellent agreement with HHD (Pearson's r = 0.927 ~ 0.967; ICC = 0.911 ~ 0.956) and superior inter- and intra-rater reliabilities (ICC = 0.963 ~ 0.983). Normative values were approximately 4.5 ~ 23.4 N, with greater strength in the radial than ulnar direction except for the little finger. Participants rated HIMDNA higher in usefulness, effectiveness, and overall satisfaction than HHD.
Conclusion:
HIMDNA provided a reliable, valid, and user-friendly way of quantifying finger abduction and adduction strengths, suggesting its potential as a standardized and clinically applicable tool for evaluating the strength of interossei muscles quantitatively in patients with ulnar nerve disorders.
