• T Nakajima, R E Hughes, and K-N An.
• Orthopedic Biomechanics Laboratory, Mayo Clinic, 200 First Street, S.W., Rochester, MN 55905, USA.
• Clin Biomech (Bristol, Avon). 2004 Jul 1;19(6):579-85.

ObjectiveThe purpose of this study was to evaluate the effects of glenohumeral rotations and humeral head translations on supraspinatus tendon morphology.DesignA convenience sample of cadaver shoulders was used to measure supraspinatus tendon shape and dimensions from MRI images.BackgroundEpidemiological evidence has indicated that shoulder elevation and external rotation may be risk factors for rotator cuff tendon pathology, but little is known about how these postures affect tendon morphology.MethodsMeasurements of supraspinatus tendon morphology were made from three-dimensional reconstructions based on T2-weighted fast spin-echo magnetic resonance images. Seven cadaver arms were imaged at neutral, 45 degrees external and 45 degrees internal rotations at 0 degrees, 30 degrees, and 60 degrees of glenohumeral abduction. Measurements of the anterior, middle, and posterior portions of the tendon were made using ANALYZE software.ResultsThe supraspinatus tendon was twisted at the muscle-tendon junction of the middle and posterior portions in 45 degrees external and 45 degrees internal axial rotations of the humerus, especially over 30 degrees of abduction. Abduction over 30 degrees shortened the entire supraspinatus tendon. External and internal rotation motions elongated the anterior and posterior portions, respectively.ConclusionsArm posture affects morphology of the supraspinatus tendon.RelevanceThe results support the epidemiologic evidence linking external rotation and abduction to supraspinatus tendon disorders.Copyright 2004 Elsevier Ltd.

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