title: Direct 3-dimensional measurement of scapular kinematics during dynamic movements in vivo.
abstract: The purpose of this study was to describe 3-dimensional scapular motion patterns during dynamic shoulder movements with the use of a direct technique. Direct measurement of active scapular motion was accomplished by insertion of 2 1.6-mm bone pins into the spine of the scapula in 8 healthy volunteers (5 men, 3 women). A small, 3-dimensional motion sensor was rigidly fixed to the scapular pins. Sensors were also attached to the thoracic spine (T3) with tape and to the humerus with a specially designed cuff. During active scapular plane elevation, the scapula upwardly rotated (mean [SD] = 50 degrees [4.8 degrees ]), tilted posteriorly around a medial-lateral axis (30 degrees [13.0 degrees ]), and externally rotated around a vertical axis (24 degrees [12.8 degrees ]). Lowering of the arm resulted in a reversal of these motions in a slightly different pattern. The mean ratio of glenohumeral to scapulothoracic motion was 1.7:1. Normal scapular motion consists of substantial rotations around 3 axes, not simply upward rotation. Understanding normal scapular motion may assist in the identification of abnormal motion associated with various shoulder disorders.
authors.affiliation: Department of Physical Therapy, Arcadia University, Glenside, Pa 19038, USA. mclure@arcadia.edu
authors.forename: P W
authors.initials: PW
authors.lastname: McClure
authors.forename: L A
authors.initials: LA
authors.lastname: Michener
authors.forename: B J
authors.initials: BJ
authors.lastname: Sennett
authors.forename: A R
authors.initials: AR
authors.lastname: Karduna
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001858:Bone Nails; D005260:Female; D006801:Humans; D008297:Male; D016059:Range of Motion, Articular / Q000502:physiology*; D012540:Scapula / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*; D013131:Spine