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Lowry V.1, Caravias M.1,2, Desroches G.2,3, Fournier-Belley A.4, Gagnon D.H.2,3, Roy J.-S.4,5, Desmeules F.1,2
1Maisonneuve-Rosemont Hospital Research Center, University of Montréal Affiliated Research Center, Orthopaedic Unit, Montreal, Canada, 2University of Montreal, School of Rehabilitation, Montreal, Canada, 3Center for Interdisciplinary Research in Rehabilitation of Greater Montreal, Montreal Rehabilitation Institute, Montreal, Canada, 4Center for Interdisciplinary Research in Rehabilitation and Social Integration, Quebec, Canada, 5Laval University, Department of Rehabilitation, Quebec, Canada
Background: Rotator cuff (RC) disorders are a common source of shoulder pain. RC disorder is thought to be the result of a progressive degeneration of the RC tendons evolving from tendinopathy to full-thickness tear. One commonly described pathophysiological mechanism of RC disorder is the reduction or dynamic narrowing of the subacromial space due to upward migration of the humeral head during arm elevation, that in turn leads to compression of the subacromial structures. Ultrasound imaging (US) measurement of the acromiohumeral distance (AHD) has been recognized as a reliable and valid method to measure the width of subacromial space at rest and during arm elevation.
Purpose: To compare US measures of the AHD during active abduction in individuals with a RC tendinopathy, a full-thickness RC tear and in asymptomatic individuals.
Methods: Participants were included based on physical examination and, for the full-thickness group, on magnetic resonance imaging results confirming a full-thickness RC tear. The US AHD was defined as the tangential distance between the humeral head and the inferior edge of the acromion. US AHD measurements were performed at 0°, 45° and 60° of active shoulder abduction. A two-way repeated measures mixed-model analysis of variance and post-hoc comparisons were performed to compare groups.
Results: Twenty-one asymptomatic individuals, 48 with chronic RC tendinopathy and 17 with a full-thickness RC tear were included. Mean age was 43.7 ± 11.3 years old and 60% were male. At 45° of abduction, the AHD was significantly smaller in the full-thickness RC tear group (mean AHD: 0.66 cm; 95%CI: 0.57-0.75) when compared to the asymptomatic (mean AHD: 0.82 cm; 95%CI: 0.76-0.87) and RC tendinopathy groups (mean AHD: 0.84 cm; 95%CI: 0.79-0.89). At 60° of abduction, the AHD remained significantly smaller in the full-thickness RC tear group (mean AHD: 0.56 cm; 95%CI: 0.47-0.65) compared to the asymptomatic (mean AHD: 0.77 cm; 95%CI: 0.71-0.83) and RC tendinopathy groups (mean AHD: 0.81 cm; 95%CI: 0.75-0.86). There were no other statistically significant differences between groups (p≥0.05).
Conclusion(s): The reduced AHD in participants with full-thickness RC tear strengthens the evidence with regard to the key coupling force role played by RC muscles to counteract the superiorly directed force of the deltoid during active shoulder abduction. However, RC tendinopathy may not necessarily lead to a reduction or a narrowing of the AHD when RC muscles are recruited at low intensity during active shoulder abduction, calling for a prudent generalization of previous evidence.
Implications: Further research should continue investigating AHD measurements in individuals with RC disorders to gain a better understanding of the reduction or dynamic narrowing of the subacromial space since recent studies suggests that only a subgroup of individuals suffering from RC tendinopathy may have a reduction in subacromial space. US measurements may allow physiotherapists to quantify glenohumeral arthrokinematics changes during arm elevation and better tailor rehabilitation interventions and evaluate their efficacy in terms of normalisation of AHD.
Funding acknowledgements: This study was funded by the research fund of the Maisonneuve-Rosemont Hospital.
Topic: Musculoskeletal: upper limb
Ethics approval: Ethics committee of the Quebec Rehabilitation Institute.
Ethics committee at the Hospital Cité de la Santé of Laval
All authors, affiliations and abstracts have been published as submitted.
