Quantification of hand function by power grip and pinch strength force measurements in ulnar nerve lesion simulated by ulnar nerve block.

INTRODUCTION: In the assessment of hand and upper limb function, grip strength is of the major importance. The measurement by dynamometers has been established. PURPOSE OF THE STUDY: In this study, the effect of a simulated ulnar nerve lesion on different grip force measurements was evaluated. METHODS: In 25 healthy volunteers, grip force measurement was done by the JAMAR dynamometer (Fabrication Enterprises Inc, Irvington, NY) for power grip and by a pinch strength dynamometer for tip pinch strength, tripod grip, and key pinch strength. STUDY DESIGN: A within-subject research design was used in this prospective study. Each subject served as the control by preinjection measurements of grip and pinch strength. Subsequent measurements after ulnar nerve block were used to examine within-subject change. RESULTS: In power grip, there was a significant reduction of maximum grip force of 26.9% with ulnar nerve block compared with grip force without block (P < .0001). Larger reductions in pinch strength were observed with block: 57.5% in tip pinch strength (P < .0001), 61.0% in tripod grip (P < .0001), and 58.3% in key pinch strength (P < .0001). DISCUSSION: The effect of the distal ulnar nerve block on grip and pinch force could be confirmed. However, the assessment of other dimensions of hand strength as tip pinch, tripod pinch and key pinch had more relevance in demonstrating hand strength changes resulting from an distal ulnar nerve lesion. CONCLUSIONS: The measurement of tip pinch, tripod grip and key pinch can improve the follow-up in hand rehabilitation. LEVEL OF EVIDENCE: II.