An investigation of maximal strength of the upper limb bilaterally in individuals with lateral elbow tendinopathy: A systematic review with meta-analysis

Objective: To investigate whether there is evidence of bilateral upper limb strength deficits in individuals with unilateral lateral elbow tendinopathy (LET). Methods: The electronic databases, Medline-via Ovid, PubMed, and Scopus, were searched from inception to March 2020. Included studies encompassed maximal strength outcomes of any upper limb and appendicular musculature in those with LET and an asymptomatic comparator. Study quality was rated using a modified version of the Epidemiological Appraisal Instrument (EAI). Hedges’ g effect sizes (ES) and 95% confidence intervals were calculated for comparisons of maximal strength in the LET group compared to an asymptomatic control. Meta-analysis, using a random-effects model, was performed where possible. Results: Fourteen studies were included. Quality appraisal resulted in a mean EAI score of 46% (SD 10%). Meta-analysis revealed strength deficits in shoulder abduction (Pooled ES-0.37 [95%CI-0.62, -0.12]) and shoulder external rotation (Pooled ES-0.55 [95%CI-0.83, -0.28]) of the symptomatic limb compared to an asymptomatic control group. Meta-analysis also revealed maximal strength deficits in the upper trapezius (Pooled ES-0.26 [95%CI-0.49, -0.02) of the asymptomatic limb compared to an asymptomatic control group. There was also consistent evidence for strength deficits in the serratus anterior, lower trapezius, wrist extensors, and grip strength in the symptomatic limb and wrist extensor muscles in the asymptomatic limb of those with unilateral LET. Conclusion: In those with LET, maximal strength deficits exist in shoulder abduction, shoulder external rotation, serratus anterior, lower trapezius, wrist extension, and grip strength in the symptomatic limb compared to an asymptomatic control group. In addition, when compared to an asymptomatic control there appear to be strength deficits in upper trapezius, wrist extension, metacarpophalangeal joint flexion and extension, and grip strength in the asymptomatic limb of those with LET, compared to an asymptomatic control group, suggesting bilateral strength deficits.