2025 ISAKOS Congress in Munich, Germany

2025 ISAKOS Biennial Congress Paper


The Role of the Critical Coronoid Angle in Simple Elbow Dislocation

Paolo Angelo Arrigoni, MD, Milan ITALY
Francesco Luceri, MD, Milano, Italy/Lombardia ITALY
Enrico Rosagrata, MD, Milan ITALY
Andrea Zagarella, MD, Milano ITALY
Simone Cassin, MD, Milan ITALY
Valeria Vismara, MD, Milan ITALY
Alessandra Colozza, MD, Faenza ITALY
Carlo Eugenio Zaolino, MD, Milan ITALY
Pietro S. Randelli, MD, Prof., Milan ITALY

ASST Gaetano Pini CTO, Milan, Milan, ITALY

FDA Status Not Applicable

Summary

How CT Indexes can stratify the risk of Elbow Dislocation

Abstract

Introduction

Elbow primary stability is guaranteed by the anatomical congruency between the humeral trochlea
and the Greater Sigmoid Notch (GSN). Elbow dislocation typically happens in a semi-extended
position, but Computed Tomography (CT) scans are usually performed at 90° of flexion, supporting
the false idea that the apex of the coronoid is covering the trochlea centre of rotation. The purpose of
this study is to evaluate the anatomical features of the coronoid and GSN in a dislocated versus nondislocated
group, demonstrating that a more prominent coronoid would be more frequently found in
non-dislocated elbows compared to dislocated ones.

Material And Methods

50 CT scans, equally divided between dislocated elbows and non-dislocated elbows were analyzed
and the critical coronoid angle (CCA) was measured on a specific slice of the CT scan (level of
evidence 3). The CCA was calculated from two lines that arise in the center of GSN with the first one
crossing the coronoid tip and the second one being parallel to the posterior olecranon cortex.

Results

A significant difference in CCA (p<0.001) between the two groups was highlighted. In detail, it was
found that 14/25 patients from the dislocated elbow group had a CCA ≤ 27° and all the non-dislocated
subjects had a CCA ≥ 27°. These preliminary results suggest that a CCA ≤ 27° could be a threshold
for requiring further imaging of soft tissues or closer follow-up. This can happen both because the
coronoid is less prominent or because the radius of the GSN is shallow. A regression model has been
proposed (DAM model) to address different clinical choices.
Manuscript

Conclusion

Low CCA is statistically more frequent in dislocated elbows versus non-dislocated ones creating a
specific anatomical condition. The CCA should be carefully evaluated by elbow surgeons to guide
patient-specific treatment. The DAM model can permit the stratification of patients eligible for
further diagnostic analysis.