Modifiable Musculoskeletal Factors and their Association With Shoulder Function in Adults: A Systematic Review of Etiology and Risk.
Authors: Briel Sonia , Brandt Corlia , Olivier 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: A paucity of evidence still exists 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 of all reported modifiable musculoskeletal factors to clarify the multifactorial etiology of shoulder dysfunction in an adult population. Methods: The methodology and meta-analysis process as detailed in the JBI Reviewer’s Manual for Etiology and Risk, were followed, and the guidelines as proposed by the PRISMA (Preferred Items for Systematic Reviews and Meta-Analysis) statement were adhered to. Where meta-analysis of data was not possible the SWiM (Synthesis without meta-analysis) approach was followed for synthesis of pooled modifiable musculoskeletal factors.The outcome measure considered was shoulder dysfunction. Exposure measured was modifiable musculoskeletal factors leading to the development of shoulder dysfunction. Age groups between 18 to 75 years of age were included. A total number of 7628 studies were identified worldwide through searching of 12 databases. The results yielded by 91 studies were included in the systematic review. The risk of bias was low for 88 studies. Females (2441) and males (3117) were both included. The systematic review included cross-sectional and longitudinal studies investigating most sporting sub-populations (swimming, rugby, weightlifting, wheelchair, volleyball and baseball (1003 participants) and members of the general population (4651). Pooling of results into five meta-analyses was possible. Results: Results concluded that musculoskeletal factors leading to shoulder dysfunction to be decreased external rotation strength, with I2=0a large positive effect size 0.59 with p=0.00, decreased external versus internal muscle strength ratio, with I2=46 a large negative effect size -0.69 with p=0.002, decreased flexibility of the posterior capsule, with I2=0 small negative effect size -0.0 p=0.45, decreased internal rotation with I2=0, with a large negative effect size -1.00 p=0, and 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 comprise of the strength of the external and internal rotators; the strength ratio of the external rotators: internal rotators; the internal rotation range of motion movement; total range of motion; glenohumeral internal rotation deficit; pectoralis minor muscle length, posterior capsule and the glenohumeral posterior musculature flexibility and scapular stabilisers strength and strength ratios. This protocol has been registered in PROSPERO (CRD 42021261719).