title: Comparison of the effects of flexion and extension of the thumb and fingers on the position and cross-sectional area of the median nerve.
abstract: OBJECTIVE
  To assess the separate effects of thumb and finger extension/flexion on median nerve position and cross-sectional area.
  
  
  METHODS
  Ultrasonography was used to assess median nerve transverse position and cross-sectional area within the carpal tunnel at rest and its movement during volitional flexion of the individual digits of the hand. Both wrists of 165 normal subjects (11 men, 4 women, mean age, 28.6, range, 22 to 38) were studied.
  
  
  RESULTS
  Thumb flexion resulted in transverse movement of the median nerve in radial direction (1.2 ± 0.6 mm), whereas flexion of the fingers produced transverse movement in ulnar direction, which was most pronounced during flexion of the index and middle fingers (3.2 ± 0.9 and 3.1 ± 1.0 mm, respectively). Lesser but still statistically significant movements were noted with flexion of the ring finger (2.0 ± 0.8 mm) and little finger (1.2 ± 0.5 mm). Flexion of the thumb or individual fingers did not change median nerve cross-sectional area (8.5 ± 1.1 mm(2)).
  
  
  CONCLUSIONS
  Volitional flexion of the thumb and individual fingers, particularly the index and middle fingers, produced significant transverse movement of the median nerve within the carpal tunnel but did not alter the cross-sectional area of the nerve. The importance of these findings on the understanding of the pathogenesis of the carpal tunnel syndrome and its treatment remains to be investigated.
authors.affiliation: Department of Rehabilitation Medicine, Wakayama Medical University, Wakayama, Wakayama, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Toge
authors.affiliation: Department of Rehabilitation Medicine, Wakayama Medical University, Wakayama, Wakayama, Japan.
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Nishimura
authors.affiliation: Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Basford
authors.affiliation: Department of Rehabilitation Medicine, Wakayama Medical University, Wakayama, Wakayama, Japan.
authors.forename: Takako
authors.initials: T
authors.lastname: Nogawa
authors.affiliation: Department of Rehabilitation Medicine, Wakayama Medical University, Wakayama, Wakayama, Japan.
authors.forename: Midori
authors.initials: M
authors.lastname: Yamanaka
authors.affiliation: Department of Rehabilitation Medicine, Wakayama Medical University, Wakayama, Wakayama, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakamura
authors.affiliation: Department of Orthopedic Surgery, Wakayama Medical University, Wakayama, Wakayama, Japan.
authors.forename: Munehito
authors.initials: M
authors.lastname: Yoshida
authors.affiliation: Department of Orthopedic Surgery, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Nagano
authors.affiliation: Department of Rehabilitation Medicine, Wakayama Medical University, Wakayama, Wakayama, Japan.
authors.forename: Fumihiro
authors.initials: F
authors.lastname: Tajima
mesh_terms: D000328:Adult; D005260:Female; D005385:Fingers / Q000000981:diagnostic imaging / Q000294:innervation* / Q000502:physiology*; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D016059:Range of Motion, Articular; D013933:Thumb / Q000000981:diagnostic imaging / Q000294:innervation* / Q000502:physiology*; D014463:Ultrasonography; D055815:Young Adult