title: Strain on the ulnar nerve at the elbow and wrist during throwing motion.
abstract: BACKGROUND
  It is well known that cubital tunnel syndrome frequently occurs in throwing athletes. The cause of cubital tunnel syndrome is considered to be mechanical stimuli on the ulnar nerve in the cubital tunnel. The hypothesis of the present cadaveric study was that the ulnar nerve is subjected to longitudinal strain in the cubital tunnel during the throwing motion.
  
  
  METHODS
  Four phases of throwing (stance, wind-up, middle cock-up, and early acceleration) were passively simulated in seven fresh-frozen transthoracic cadaveric specimens that were fixed in an upright position to allow free arm movement. In each throwing phase, the elbow was sequentially flexed from 45 degrees to 90 degrees to 120 degrees to maximum flexion. The longitudinal movement of and strain on the ulnar nerve were measured with use of a caliper and a strain gauge at the proximal aspects of both the cubital tunnel and the canal of Guyon.
  
  
  RESULTS
  The movement of the ulnar nerve at the proximal aspect of the cubital tunnel was significantly increased during all throwing phases with increased elbow flexion (p < 0.05). An average maximum movement of 12.4 +/- 2.4 mm was recorded during the wind-up phase with maximum elbow flexion. The movement at the proximal aspect of the canal of Guyon was approximately two-thirds of that at the proximal aspect of the cubital tunnel. The strain on the ulnar nerve at the proximal aspect of the cubital tunnel was significantly increased with elbow flexion in the stance, wind-up, and middle cock-up phases (p < 0.05). An average maximum strain of 13.1% +/- 6.1% was recorded during the early acceleration phase with maximum elbow flexion. The strain at the proximal aspect of the canal of Guyon was approximately half of that at the proximal aspect of the cubital tunnel.
  
  
  CONCLUSIONS
  In the present study, the maximum strain on the ulnar nerve during the acceleration phase was found to be close to the elastic and circulatory limits of the nerve.
authors.affiliation: Departments of Physical Therapy, Sapporo Medical University School of Health Sciences and School of Medicine, South-3, West-17, Chuo-ku, Sapporo 060-8556, Japan. maoki@sapmed.ac.jp
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Aoki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takasaki
authors.forename: Takayuki
authors.initials: T
authors.lastname: Muraki
authors.forename: Eiichi
authors.initials: E
authors.lastname: Uchiyama
authors.forename: Gen
authors.initials: G
authors.lastname: Murakami
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Yamashita
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001265:Athletic Injuries / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D002102:Cadaver; D004550:Elbow; D005260:Female; D006801:Humans; D008297:Male; D020196:Trauma, Nervous System / Q000503:physiopathology; D014459:Ulnar Nerve / Q000293:injuries*; D017769:Ulnar Nerve Compression Syndromes / Q000503:physiopathology*; D014953:Wrist