Strength reduction in unilateral shoulder pain: Is the healthy side really healthy in rotator cuff disease?

Objective The primary aim was to ascertain if unilateral shoulder pain is implicated in strength reduction both on the ipsilateral and contralateral side. Secondarily, we aimed to determine whether strength was affected by sonographic tendon abnormalities. Design A total of 122 subjects were evaluated. Sixty-six female subjects with unilateral shoulder pain in the dominant arm were recruited. Abduction strength was measured in both the dominant and non-dominant arm. High-resolution ultra-sonography was also conducted on both shoulders. A match-paired control group (n=66) composed of healthy volunteers underwent the same strength and sonography tests. Subjects with any radiographic anomaly were excluded from the control group. A mixed analysis of variance was performed to test the effect of unilateral shoulder pain on abduction strength. The effect of tendinopathy on shoulder strength was investigated using a mixed 2X2 ANOVA. Results ANOVA showed that patients with dominant shoulder pain had lower shoulder strength (11.65±4.05 kg) when compared to controls (14.37±4.00 kg; F=10.454, p=0,002). No statistically significant effects were found when comparing subjects with and without tendinopathy among the study group. Conclusion In patients with unilateral shoulder pain, abduction strength was found to be lower both on the ipsilateral and contralateral side. The presence of tendinopathy did not affect the reduction in strength. Future research is needed to substantiate these findings. Corresponding author: Valerio Sansone: valerio.sansone@unimi.it, IRCCS Istituto Ortopedico Galeazzi, Via Riccardo Galeazzi, 4, 20161 Milan, Italy. telephone: +39 6621 4921 Funding: No funding was received regarding the preparation of this manuscript. Declaration of Interest: The authors whose names are listed above certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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