Safe drilling angles and depths for plate-screw fixation of the clavicle: avoidance of inadvertent iatrogenic subclavian neurovascular bundle injury.

Background: Plate fixation is frequently used to repair clavicle fractures, but over drilling can cause subclavian neurovascular bundle damage. The aims of this study were to investigate the anatomic relationship between the clavicle and subclavian neurovascular bundle and to determine safe drilling angles and depths.

Methods: Twenty-six healthy subjects underwent magnetic resonance imaging. Coronal and sagittal images of the periclavicular region including the whole clavicle and nearby vital anatomic structures were obtained. The clavicle was divided into three sections: section I: between the sternoclavicular joint and point N (where the subclavian neurovascular bundle coursed below the midaxial level of the clavicle); section II: from N to the projection point of the coracoid process to the clavicle (CP'); and section III: from CP' to the acromioclavicular joint. Dangerous drilling depths and angles were determined for each section.

Results: In section I, the safe drilling angle was >59.7 degrees cephalad and >95.3 degrees caudad, while safe drilling depth was <17.0 +/- 2.4 mm. Corresponding values in section II were <1.2 degrees caudad and >142.4 degrees caudad. Safe drilling depth was no more than 36.2 mm +/- 12.4 mm. Depth and direction limitations were not assessed for section III, because the neurovascular bundle coursed well below the level of the coracoid process.

Conclusions: We have used magnetic resonance imaging to determine safe drilling directions and depth for plate-screw fixation of the clavicle. On confirmation, these findings could be used in the clinical setting to reduce the risk of inadvertent iatrogenic subclavian neurovascular bundle injury during surgical clavicle fracture repair.