Radiographic parameters and a novel fluoroscopic control view for posterior screw fixation of coracoid base fractures...

Coracoid fractures have the potential to lead to inadequate shoulder function. Most coracoid base fractures occur with scapular fractures and the posterior approaches would be utilized for surgical treatment. We investigated the possibility of fixing the coracoid through the same approach without an additional anterior approach.

Multi-slice CT scans of 30 shoulders were examined and the following measurements were performed by an independent specialized radiologist: posterior coracoid screw entry point measured form infraglenoid tubercle, screw trajectory in coronal plane in relation to scapular spine and lateral scapular border, screw trajectory in sagittal plane in relation to glenoid face bisector line and screw length. We used the results from the CT study to guide postero-anterior coracoid screw insertion under fluoroscopic guidance on two fresh frozen cadaveric specimens to assess the reproducibility of accurate screw placement based on these parameters. We also developed a novel fluoroscopic projection, the anteroposterior (AP) coracoid view, to guide screw placement in the para-coronal plane.

The mean distance between entry point and the infraglenoid tubercle was 10.8 mm (range: 9.2-13.9, SD 1.36). The mean screw length was 52 mm (range: 46.7-58.5, SD 3.3). The mean sagittal inclination angle between was 44.7 degrees (range: 25-59, SD 5.8). The mean angle between screw line and lateral scapular border was 47.9 degrees (range: 34-58, SD 4.3). The mean angle between screw line and scapular spine was 86.2 degrees (range: 75-95, SD 4.9). It was easy to reproduce the screw trajectory in the para-coronal plane; however, multiple attempts were needed to reach the correct angle in the parasagittal plane, requiring several C-arm corrections.

This study facilitates posterior fixation of coracoid process fractures and will inform the "virtual visualization" of coracoid process orientation.