Three-dimensional kinematics in patients with anterior shoulder instability - A systematic review with meta-analysis

Anterior Shoulder Instability (ASI) is a common orthopedic condition often resulting in altered shoulder kinematics. Understanding the biomechanics of the unstable shoulder is critical to determine the most appropriate treatment. This study aims to conduct the first systematic review and meta-analysis of three-dimensional (3D) shoulder kinematic studies in ASI patients. A broad search was conducted within PubMed, Scopus, and Cochrane Library following the PRISMA guidelines. All cross-sectional or longitudinal studies with 3D motion analysis describing shoulder kinematics in patients with ASI were included. The quality of each study was assessed using the MINORS criteria. Qualitative and quantitative analyses were performed. Nine studies were included in the qualitative analysis and two in the meta-analysis. The qualitative review detected conflicting evidence for some parameters. The humeral head had a greater anterior translation in unstable shoulders in three of the studies analyzed, while the difference was not significant in one and another found higher variability for global humeral translation for instability patients. Two studies showed decreased rotation range of motion for unstable shoulders while one did not find significant differences. Conflicting results were also found regarding changes in scapulohumeral rhythm and scapular orientation. The meta-analysis indicated a greater scapulohumeral rhythm on the coronal plane for the instability group, suggesting a relatively greater contribution of motion at the glenohumeral joint compared with the scapulothoracic joint for arm abduction, and reduced glenohumeral peak angles for unstable shoulders. Identifying and quantifying kinematic changes associated with ASI are vital for refining treatment interventions.