Reproducibility and Relevance of Acromial Morphology Measurements in Shoulder Pathologies: A Critical Review of the Literature

TL;DR

This paper reviews how the shape of the acromion affects shoulder disorders, highlighting inconsistencies in measurements and suggesting the need for standardized 3D methods.

Contribution

The paper introduces a critical analysis of acromial morphology measurements, emphasizing the need for standardized 3D reference models to improve reproducibility.

Findings

Acromion morphology varies in posterior instability and massive cuff tears, but measurements lack consistency.

Current 2D methods and differing definitions limit reproducibility and clinical use of acromial parameters.

Standardized 3D models anchored to stable scapular landmarks are recommended for future research.

Abstract

Background: The morphology of the acromion has long been implicated in shoulder pathology, particularly in relation to subacromial impingement and rotator cuff disease. More recently, interest has shifted toward the posterior acromion, with studies examining its potential role in posterior instability, eccentric glenohumeral osteoarthritis, and massive rotator cuff tears. Methods: A critical literature review of nine studies assessing sagittal acromial tilt, posterior coverage, and acromial height was conducted, emphasizing reproducibility and clinical significance across different shoulder disorders. Results: In posterior instability and eccentric osteoarthritis, the acromion is generally described as more horizontally oriented, less covering posteriorly, and positioned higher. Conversely, in massive cuff tears, it tends to appear more posteriorly covering without consistent change in tilt. Although these trends suggest a possible biomechanical role for the acromion, reported values vary widely between studies, and significant overlap exists between pathological and control groups. Such variability is compounded by differences in imaging modality, definitions of anatomical landmarks, and the frequent reduction of three-dimensional structures into two-dimensional projections. These methodological inconsistencies undermine reproducibility and limit the clinical applicability of posterior acromial parameters. Conclusions: Posterior acromial morphology appears to influence shoulder biomechanics, but existing measurements should be considered population-level markers rather than diagnostic thresholds. Future research should adopt standardized, three-dimensional, pathology-independent reference models anchored to stable scapular landmarks and validated across imaging modalities to improve reproducibility and clinical utility.

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