Modifiable musculoskeletal factors and their association with shoulder function in adults: A systematic review of risk and association
Authors: Briel Sonia , Brandt Corlia , Oliver Benita , Olivier Franso-Mari 
Published: June 2024

Objective:The objective of this systematic review of etiology and risk was to determine the association between modifiable musculoskeletal factors and shoulder dysfunction in an adult population.Background:There is still a paucity of evidence in the literature on shoulder function and the influence of modifiable musculoskeletal factors on function. The present study aimed to explore current and past research on all reported modifiable musculoskeletal factors to clarify the multifactorial etiology of shoulder dysfunction in an adult population.Methods:The methodology and meta-analysis process were performed as detailed in the JBI Reviewer’s Manual for Etiology and Risk, and the following guidelines were used according to the PRISMA (Preferred Items for Systematic Reviews and Meta-Analysis) statement. When a meta-analysis of the data was not possible, the SWiM (synthesis without meta-analysis) approach was used for the synthesis of pooled modifiable musculoskeletal factors. The outcome measure considered was shoulder dysfunction. The exposure parameters measured were modifiable musculoskeletal factors leading to the development of shoulder dysfunction. Patients aged between 18 and 75 years were included. A total of 7628 studies were identified worldwide through searching 12 databases. The results yielded by 91 studies were included in the systematic review. The risk of bias was low for 88 studies. Both females (2441) and males (3117) were included. The systematic review included cross-sectional and longitudinal studies investigating most sporting subpopulations (swimming, rugby, weightlifting, wheelchair, volleyball and baseball; 1003 participants) and members of the general population (4651). Pooling of the results into five meta-analyses was possible.Results:The results revealed that affected musculoskeletal factors led to a decrease in the strength of shoulder dysfunction during external rotation, with I2 = 0indicatinga large positive effect size of 0.59 (p = 0.00), a decreased external versus internal muscle strength ratio, with I2 = 46 indicating a large negative effect size of -0.69 (p = 0.002); decreased flexibility of the posterior capsule, with I2=0 indicating a small negative effect size of -0.0 (p = 0.45); decreased internal rotation, with a large negative effect size of -1.00 (p = 0); and a glenohumeral internal rotation deficit. Participants were 1.29 times more likely to develop shoulder dysfunction in the presence of decreased external rotation strength.Discussion:A comprehensive evaluation of the shoulder joint should include all identified musculoskeletal factors of the present systematic review at one point in time. Modifiable musculoskeletal factors include the strength of the external and internal rotators; the strength ratio of the external rotators: internal rotators; the internal rotation range of motion movement; the total range of motion; glenohumeral internal rotation deficit; pectoralis minor muscle length; posterior capsule and the glenohumeral posterior musculature flexibility; and scapular stabilizer strength and strength ratios. This protocol has been registered in PROSPERO (CRD 42021261719).