title: The anatomy and histology of the bicipital tunnel of the shoulder.
abstract: BACKGROUND
  The bicipital tunnel is the extra-articular, fibro-osseous structure that encloses the long head of the biceps tendon.
  
  
  METHODS
  Twelve cadaveric shoulder specimens underwent in situ casting of the bicipital tunnel with methyl methacrylate cement to demonstrate structural competence (n = 6) and en bloc harvest with gross and histologic evaluation (n = 6). The percentage of empty tunnel was calculated histologically by subtracting the proportion of cross-sectional area of the long head of the biceps tendon from that of the bicipital tunnel for each zone.
  
  
  RESULTS
  Cement casting demonstrated that the bicipital tunnel was a closed space. Zone 1 extended from the articular margin to the distal margin of the subscapularis tendon. Zone 2 extended from the distal margin of the subscapularis tendon to the proximal margin of the pectoralis major tendon. Zone 3 was the subpectoral region. Zones 1 and 2 were both enclosed by a dense connective tissue sheath and demonstrated the presence of synovium. Zone 3 had significantly greater percentage of empty tunnel than zones 1 and 2 did (P < .01).
  
  
  CONCLUSIONS
  The bicipital tunnel is a closed space with 3 distinct zones. Zones 1 and 2 have similar features, including the presence of synovium, but differ from zone 3. A significant bottleneck occurs between zone 2 and zone 3, most likely at the proximal margin of the pectoralis major tendon. The bicipital tunnel is a closed space where space-occupying lesions may produce a bicipital tunnel syndrome. Careful consideration should be given to surgical techniques that decompress both zones 1 and 2 of the bicipital tunnel.
authors.affiliation: Sports Medicine and Shoulder Service, Hospital for Special Surgery, New York, NY, USA. Electronic address: samueltaylor.md@gmail.com.
authors.forename: Samuel A
authors.initials: SA
authors.lastname: Taylor
authors.affiliation: Sports Medicine and Shoulder Service, Hospital for Special Surgery, New York, NY, USA.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Fabricant
authors.affiliation: Pathology and Laboratory Medicine, Hospital for Special Surgery, New York, NY, USA.
authors.forename: Manjula
authors.initials: M
authors.lastname: Bansal
authors.affiliation: Sports Medicine and Shoulder Service, Hospital for Special Surgery, New York, NY, USA.
authors.forename: M Michael
authors.initials: MM
authors.lastname: Khair
authors.affiliation: Sports Medicine and Shoulder Service, Hospital for Special Surgery, New York, NY, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: McLawhorn
authors.affiliation: Pathology and Laboratory Medicine, Hospital for Special Surgery, New York, NY, USA.
authors.forename: Edward F
authors.initials: EF
authors.lastname: DiCarlo
authors.affiliation: Sports Medicine and Shoulder Service, Hospital for Special Surgery, New York, NY, USA.
authors.forename: Mary
authors.initials: M
authors.lastname: Shorey
authors.affiliation: Sports Medicine and Shoulder Service, Hospital for Special Surgery, New York, NY, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: O'Brien
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010369:Pectoralis Muscles / Q000033:anatomy & histology; D017006:Rotator Cuff / Q000033:anatomy & histology; D012782:Shoulder / Q000033:anatomy & histology*; D012785:Shoulder Joint / Q000033:anatomy & histology*; D013710:Tendons / Q000033:anatomy & histology*; D055815:Young Adult
keywords: Long head; biceps tendinitis; biceps tendon; bicipital tunnel; tenodesis