• Arjen Kolk, Jan Ferdinand Henseler, Pieter Bas de Witte, Erik W van Zwet, Peer van der Zwaal, Visser Cornelis P J CPJ Department of Orthopaedics, Alrijne Hospital, Postzone RZL-22, Simon Smitweg 1, 2353GA Leiderdorp, the Netherlands. Electronic address: C.Visser@r, Jochem Nagels, Nelissen Rob G H H RGHH Department of Orthopaedics, Leiden University Medical Center, Postzone J-11-R, PO Box 9600, 2300RC Leiden, the Netherlands. Electronic address: R., and Jurriaan H de Groot.
• Department of Orthopaedics, Leiden University Medical Center, Postzone J-11-R, PO Box 9600, 2300RC Leiden, the Netherlands; Laboratory for Kinematics and Neuromechanics, Department of Orthopaedics and Rehabilitation, Leiden University Medical Center, Postzone J-11-R, PO Box 9600, 2300RC Leiden, the Netherlands. Electronic address: a.kolk@lumc.nl.
• Clin Biomech (Bristol, Avon). 2017 Jun 1; 45: 43-51.

BackgroundRotator cuff-disease is associated with changes in kinematics, but the effect of a rotator cuff-tear and its size on shoulder kinematics is still unknown in-vivo.MethodsIn this cross-sectional study, glenohumeral and scapulothoracic kinematics of the affected shoulder were evaluated using electromagnetic motion analysis in 109 patients with 1) subacromial pain syndrome (n=34), 2) an isolated supraspinatus tear (n=21), and 3) a massive rotator cuff tear involving the supraspinatus and infraspinatus (n=54). Mixed models were applied for the comparisons of shoulder kinematics between the three groups during abduction and forward flexion.FindingsIn the massive rotator cuff-tear group, we found reduced glenohumeral elevation compared to the subacromial pain syndrome (16°, 95% CI [10.5, 21.2], p<0.001) and the isolated supraspinatus tear group (10°, 95% CI [4.0, 16.7], p=0.002) at 110° abduction. Reduced glenohumeral elevation in massive rotator cuff tears coincides with an increase in scapulothoracic lateral rotation compared to subacromial pain syndrome (11°, 95% CI [6.5, 15.2], p<0.001) and supraspinatus tears (7°, 95% CI [1.8, 12.1], p=0.012). Comparable differences were observed for forward flexion. No differences in glenohumeral elevation were found between the subacromial pain syndrome and isolated supraspinatus tear group during arm elevation.InterpretationThe massive posterosuperior rotator cuff-tear group had substantially less glenohumeral elevation and more scapulothoracic lateral rotation compared to the other groups. These observations suggest that the infraspinatus is essential to preserve glenohumeral elevation in the presence of a supraspinatus tear. Shoulder kinematics are associated with rotator cuff-tear size and may have diagnostic potential.Copyright © 2017 Elsevier Ltd. All rights reserved.

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