Measuring the strength of the intrinsic muscles of the hand in patients with ulnar and median nerve injuries: reliability of the rotterdam intrinsic hand myometer (RIHM)

Abstract

Purpose To determine the reliability and measurement error of measurements of intrinsic muscle strength of a new hand-held dynamometer (the Rotterdam Intrinsic Hand Myometer [RIHM]). Methods With the RIHM we obtained repeated measurements of the intrinsic muscle strength of the hand in 27 patients with peripheral nerve injury of the ulnar and/or median nerve in different stages of rehabilitation. The average time period after injury was 4.4 years (range, 99 days–11 years). Results Differences between 2 measurements greater than 6.3 N were interpreted as a real change in assessing the strength of the abduction of the little and index finger; for the median innervated muscles of the thumb this value was 16 N. Conclusions In patients with nerve injuries the muscle strength is usually assessed with manual muscle strength testing and grip- and pinch-strength dynamometers. Preferably the intrinsic muscle strength should be measured in isolation and quantitatively. The RIHM is a new dynamometer that allows for measurements of the intrinsic muscle strength in isolation with reliability comparable to grip and pinch measurements.