The cortical ring sign: a reliable radiographic landmark for percutaneous coracoclavicular fixation

For treatment of acute acromioclavicular separations, we have been using a reproducible radiographic view of the coracoid-the cortical ring sign-that we believe allows for placement of percutaneous coracoclavicular fixation safely and reliably in the center of the coracoid base, while avoiding the coracoid tip. This study evaluates the coracoid anatomy that the cortical ring sign represents, its utility for guiding fixation trajectory, and the proximity of neurovascular structures to this proposed trajectory.

Kirschner wires were used to measure the orientation of the fluoroscopic beam in relation to the scapula and the proposed fixation trajectory using this radiographic view.

The cortical ring sign is achieved by first directing the x-ray beam perpendicular to the medial border of the scapula in the parasagittal plane and 49 degrees off the axis of the scapular spine in the axial plane, then fine-tuning until the coracoid cortical ring becomes evident. The nearest neurovascular structures to the fixation trajectory are the suprascapular artery and nerve (< 2 cm).

The cortical ring sign view targets the coracoid base and, as such, allows reliable, safe, percutaneous fixation in the center of the coracoid base.

Basic Science.