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Abduction and External Rotation in Shoulder Impingement: An Open MR Study on Healthy Volunteers—Initial Experience¹

¹ From the Departments of Radiology (G.E.G., S.T.W., C.F.B.) and Orthopedic Surgery (G.C., T.M.), Stanford University School of Medicine, 300 Pasteur Dr, SO-68B, Stanford, CA 94305-5105; Harvard Combined Orthopaedics Program, Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, Mass (G.P.P.); and Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Va (S.S.B.). Received June 9, 2006; revision requested August 15; revision received November 11; accepted December 7; final version accepted February 2, 2007. Supported by NIH grants EB002524-01 and EB005790-01 and by the Whitaker and Lucas Foundations. Address correspondence to G.E.G. gold{at}stanford.edu).

Purpose: To prospectively evaluate rotator cuff contact with the glenoid in healthy volunteers placed in the unloaded and loaded abduction and external rotation (ABER) positions in an open magnetic resonance (MR) imager.

Materials and Methods: The study was institutional review board approved and HIPAA compliant, and informed consent was received. Eight male volunteers with no history of shoulder pain or pathology were imaged in a 0.5-T open MR imager. Volunteers were imaged in an unloaded ABER position with the arm at 90° abduction and in a loaded ABER position, with a 1-kg load that produced an average external rotation of 111° ± 6 (standard deviation). Two radiologists graded rotator cuff contact on a three-point scale. Three-dimensional anatomic models generated from the MR images were used to measure distances. Minimum distances were computed between the tendon insertion sites and the glenoid, acromion, and coracoid for the loaded ABER position. Minimum distances were compared by using a paired Student t test.

Results: In the unloaded ABER position, contact was seen between the infraspinatus and supraspinatus tendons and the glenoid in all eight volunteers. In the loaded ABER position, contact was also observed between the infraspinatus and supraspinatus and the posterior and posterosuperior glenoid, respectively. Deformation of the infraspinatus on the glenoid was seen in four volunteers, whereas supraspinatus deformation was only seen in one volunteer. The minimum distance between the supraspinatus insertion and acromion in the loaded ABER position decreased significantly (P < .01). Supraspinatus tendon to glenoid and infraspinatus tendon to glenoid minimum distances also decreased significantly (P < .01).

Conclusion: The unloaded and loaded ABER positions resulted in contact of the supraspinatus and infraspinatus with the glenoid in all volunteers. Distances between the rotator cuff insertion sites and the glenoid decreased in the loaded ABER position.

© RSNA, 2007

This article has been cited by other articles:

				A. M. Saleem, J. K. Lee, and L. M. Novak Usefulness of the Abduction and External Rotation Views in Shoulder MR Arthrography Am. J. Roentgenol., October 1, 2008; 191(4): 1024 - 1030. [Abstract] [Full Text] [PDF]