Publication type: Article in scientific journal
Type of review: Peer review (publication)
Title: Inclination-dependent changes of the critical shoulder angle significantly influence superior glenohumeral joint stability
Authors: Moor, B.K.
Kuster, Roman
Osterhoff, G.
Baumgartner, Daniel
Werner, C.M.L.
Zumstein, M.A.
Bouaicha, S.
DOI: 10.1016/j.clinbiomech.2015.10.013
Published in: Clinical Biomechanics
Volume(Issue): 32
Page(s): 268
Pages to: 273
Issue Date: 2016
Publisher / Ed. Institution: Elsevier
ISSN: 0268-0033
Language: English
Subjects: Cadaver; Compressive strength; Humeral head; Joint instability; Anatomic models; Skeletal muscle; Rotator cuff; Shear strength; Shoulder joint; Shoulder pain
Subject (DDC): 610: Medicine and health
Abstract: Background: The critical shoulder angle combines the acromion index and glenoid inclination and has potential to discriminate between shoulders at risk for rotator cuff tear or osteoarthritis and those that are asymptomatic. However, its biomechanics, and particularly the role of the glenoid inclination, are not yet fully understood. Methods: A shoulder simulator was used to analyze the independent influence of glenoid inclination during abduction from 0 to 60°. Spindle motors transferred tension forces by a cable-pulley on human cadaveric humeri. A six-degree-of-freedom force transducer was mounted directly behind the polyethylene glenoid to measure shear and compressive joint reaction force and calculate the instability ratio (ratio of shear and compressive joint reaction force) with the different force ratios of the deltoid and supraspinatus muscles (2:1 and 1:1). A stepwise change in the inclination by 5° increments allowed simulation of a critical shoulder angle range of 20° to 45°. Findings: Tilting the glenoid to cranial (increasing the critical shoulder angle) increases the shear joint reaction force and therefore the instability ratio. A balanced force ratio (1:1) between the deltoid and the supraspinatus allowed larger critical shoulder angles before cranial subluxation occurred than did the deltoid-dominant ratio (2:1). Interpretation: Glenoid inclination-dependent changes of the critical shoulder angle have a significant impact on superior glenohumeral joint stability. The increased compensatory activity of the rotator cuff to keep the humeral head centered may lead to mechanical overload and could explain the clinically observed association between large angles and degenerative rotator cuff tears.
Fulltext version: Published version
License (according to publishing contract): Licence according to publishing contract
Departement: School of Engineering
Organisational Unit: Institute of Mechanical Systems (IMES)
Appears in collections:Publikationen School of Engineering

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