Assessing weakness in patients with ulnar neuropathy: comparison between a custom hand muscle dynamometer and a pinch dynamometer.

Abstract

The aim of this study was to compare the use of a custom intrinsic hand dynamometer (HD) with that of a standard pinch dynamometer (PD) in assessing strength in patients with ulnar neuropathy at the elbow. Nine patients (age, 53 ± 3 yrs) with clinical and electrophysiological features of ulnar neuropathy at the elbow with conduction block (CB) were studied. All underwent bilateral ulnar motor nerve conduction studies recording from the first dorsal interosseous and a quantitative measurement of strength of the first dorsal interosseous using a custom-made HD and a standard PD. The maximal strength of the ulnar neuropathy at the elbow-affected side (16.2 ± 8.0 N) was found to be significantly lower than that of the unaffected side (27.9 ± 11.2 N), as measured by HD. Strength differences were not significant between the affected (62.7 ± 26.4 N) and unaffected sides (48.0 ± 20.5 N) using PD. HD force decrement (in comparison with the unaffected limb) correlated strongly with CB percentage (r = 0.74). No relationship was found between PD and CB (r = 0.05). HD was better able to measure the weakness of affected muscles than did PD, and its results correlated well with the extent of electrophysiological CB. Therefore, a custom HD would provide a better indication of disease severity, progression, or improvement in strength in studies of ulnar neuropathy at the elbow with CB.