title: The effects of low median nerve block on thumb abduction strength.
abstract: The relative contributions of the abductor pollicis longus (APL) and abductor pollicis brevis (APB) to thumb abduction strength (TAS) were determined after a selective nerve block in 21 normal volunteers. The median nerve was anesthetized (blocked) at the wrist. Needle electromyography verified paralysis of the APB and usually the opponens pollicis; in 6 study subjects, the superficial head of the flexor pollicis brevis (FPB) was also paralyzed. The APL, innervated by a branch of the posterior interosseous nerve, remained functionally intact. TAS was measured by a mechanical device before and after median nerve block. Median nerve block at the wrist resulted in a dramatic decrease in TAS in all volunteers. The mean loss of TAS was 70.3% in men and 74.3% in women. Postblock TAS tended to be greater in those subjects with retained function of the FPB. This study verifies that TAS is primarily a function of the APB.
authors.affiliation: Miller Orthopaedic Clinic, Charlotte, NC 28203, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Boatright
authors.forename: G M
authors.initials: GM
authors.lastname: Kiebzak
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004576:Electromyography / Q000187:drug effects; D005260:Female; D018737:Hand Strength; D006801:Humans; D007537:Isometric Contraction / Q000187:drug effects*; D008012:Lidocaine; D008297:Male; D008475:Median Nerve / Q000187:drug effects; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation; D009407:Nerve Block; D013933:Thumb / Q000294:innervation*
chemical_list: D008012:Lidocaine