title: Strength measurements of the lumbrical muscles.
abstract: This study was designed to measure the strength of the lumbrical muscles in the index and long fingers in patients with ulnar nerve paralysis. A hand-held dynamometer was used. The results show that in ulnar nerve damage the index and long fingers have a mean metacarpophalangeal (MCP) joint flexion strength of 0.8 kg (range 0.3-1.5), compared with 6.4 kg (range 4.6-7.9) in the noninvolved hand. Thus, the damaged fingers have only about 12% of the strength of those of the noninvolved hand. In the hand with ulnar paralysis, the loss of intrinsic strength (dorsal and palmar interosseous muscles) is considerable (almost 90%). The contribution of the interosseous muscles in maintaining the intrinsic position is considerably greater than that of the lumbricals. Comparing the Medical Research Council (MRC) scale (0-5) with the dynamometry measurements shows that MRC grade 3 correlates with about 0.8 kg, while grade 5 correlates with about 6.5 kg of MCP joint flexion strength.
authors.affiliation: Department of Rehabilitation, University Hospital Rotterdam-Dijkzigt, The Netherlands.
authors.forename: T A
authors.initials: TA
authors.lastname: Schreuders
authors.forename: H J
authors.initials: HJ
authors.lastname: Stam
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D005385:Fingers; D006226:Hand Deformities / Q000534:rehabilitation / Q000601:surgery; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology*; D010243:Paralysis; D014459:Ulnar Nerve / Q000293:injuries