# Association Between Osseous Shoulder Morphology and Pathoanatomical Characteristics of Calcific Deposits in Rotator Cuff Calcific Tendinitis

## TL;DR

This study found that the shape of the acromion in the shoulder is linked to the characteristics of calcific deposits in rotator cuff tendinitis.

## Contribution

The study identifies specific acromial morphological parameters associated with calcific deposit features in RCCT patients.

## Key findings

- Deposit size correlated with critical shoulder angle and acromiohumeral interval.
- Acromion index correlated with Gartner–Heyer classification types of calcific deposits.
- Significant differences in acromial morphology were found across deposit groups.

## Abstract

Background/Objectives: Rotator cuff calcific tendinitis (RCCT) is a common cause of shoulder pain. The role of acromial morphology in RCCT pathogenesis remains unclear. This study aimed to evaluate association between acromial morphological parameters and calcific deposit characteristics in patients with RCCT. Methods: We retrospectively analyzed 1185 patients who underwent shoulder radiography between January 2015 and January 2025 at Merkur University Hospital, Zagreb, Croatia. After excluding 281 radiographs of insufficient quality, 904 patients (503 females, 401 males; mean age 57.5 ± 13.6 years) were included. Calcific deposits were classified according to Bosworth and Gartner–Heyer systems. Acromial morphology was assessed using the acromion index (AI), critical shoulder angle (CSA), lateral acromial angle (LAA), and acromiohumeral interval (AHI). Non-parametric statistical tests were used with statistical significance set at p < 0.05. Results: The mean deposit diameter was 13.29 mm. According to Gartner–Heyer classification, 295 patients had type 1, 339 type 2, and 270 type 3 deposits. Significant correlations were found between deposit size and CSA (ρ = −0.08, p < 0.05), and AHI (ρ = 0.12, p < 0.001), while AI correlated with Gartner–Heyer type (ρ = 0.09, p < 0.01). No significant correlations were found for LAA. Kruskal–Wallis testing showed significant differences across deposit groups for AI, AHI, and LAA. Conclusions: Acromial morphology is significantly associated with calcific deposit characteristics in RCCT, supporting a potential biomechanical role in disease manifestation. These findings may refine diagnostic assessment and warrant further prospective validation.