title: The collagen fibers of the anteroinferior capsulolabrum have multiaxial orientation to resist shoulder dislocation.
abstract: Instability of the glenohumeral joint can be associated with anteroinferior capsulolabral rupture. To understand its static stabilizing effect better, the collagen fiber orientation of the inferior glenohumeral ligament (IGHL), a component of the anteroinferior capsulolabrum, was studied with a small angle light scattering technique. Three rectangular samples (approximately 11 x 6 mm) were excised from the axillary pouch, one from the anterior band (AB) of the IGHL and one control sample from the long head of the biceps tendon of 7 cadaveric shoulders. The small angle light scattering technique scans the tissue with a helium-neon laser beam and quantifies the fiber alignment based on the resultant scattering pattern. The fiber orientation was quantified by an orientation index, defined as the angle within which 50% of the fibers lie. The axillary pouch had a random orientation, whereas the AB-IGHL was random with some regions of localized alignment. The percentage of tissue with an orientation index range of 25 degrees to 45 degrees was 23.2% +/- 8.5% and 29.0% +/- 13.1% for the axillary pouch and the AB-IGHL, respectively, whereas that for the long head of the biceps tendon was 61.6% +/- 15.2%. This suggests that the collagen fibers in the IGHL are not highly aligned and the anteroinferior capsulolabrum can be modeled as a continuous sheet. Moreover, a biomechanical evaluation of the anteroinferior capsulolabrum that investigates the possibility that the mechanical properties may be directionally independent should be conducted.
authors.affiliation: Musculoskeletal Research Center, Department of Orthopaedic Surgery, University of Pittsburgh, PO Box 71199, Pittsburgh, PA 15213, USA. genesis1@pitt.edu
authors.forename: Richard E
authors.initials: RE
authors.lastname: Debski
authors.forename: Susan M
authors.initials: SM
authors.lastname: Moore
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Mercer
authors.forename: Michael S
authors.initials: MS
authors.lastname: Sacks
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: McMahon
mesh_terms: D000328:Adult; D000368:Aged; D002102:Cadaver; D003094:Collagen / Q000648:ultrastructure*; D005260:Female; D006801:Humans; D017746:Joint Capsule / Q000473:pathology*; D007593:Joint Instability / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012421:Rupture / Q000517:prevention & control; D012783:Shoulder Dislocation / Q000150:complications* / Q000473:pathology*; D012785:Shoulder Joint / Q000033:anatomy & histology* / Q000473:pathology*
chemical_list: D003094:Collagen