Electromyographic Activity of Shoulder Girdle Muscles in Patients With Symptomatic and Asymptomatic Rotator Cuff Tears: A Systematic Review and Meta-Analysis

Abstract

ObjectivesTo compare electromyographic activity in patients with symptomatic rotator cuff tears with healthy controls or to those with asymptomatic cuff tears. TypeSystematic review and meta-analysis. Literature SurveyPubMed, Scopus, Ovid Medline, and Web of Science were searched from inception to August 1, 2014, and a search update was performed on June 8, 2015. MethodologyCase-control studies or intervention studies that had baseline comparisons for symptomatic versus healthy shoulders or those with asymptomatic rotator cuff tear were searched. Methodological quality was assessed with a modified Critical Appraisal Skills Programme score and meta-analyses were performed when 2 or more studies explored the same outcome measures. SynthesisNine studies were included, with the quality ranging from 1 to 3 (maximum 6). Electromyographic outcomes included amplitudes and ratios thereof, activity duration, and median frequency of shoulder girdle muscles during isometric contractions (4 studies) and functional tasks (5 studies). Longer activity duration was found for upper trapezius during glenohumeral movements, and greater fatigability of anterior and middle deltoids during isometric hand gripping for patients with rotator cuff tears compared to controls. The meta-analysis (3 studies) showed that patients with rotator cuff tears had lower activation ratios for latissimus dorsi during isometric abduction contraction compared to controls (P < .001), indicating greater co-contraction of adductors for the injured shoulders. ConclusionsAlthough various electromyographic domains were explored, these were generally limited to one publication or research group. Current evidence for muscle activity differences between the rotator cuff tear group and controls is thus limited.