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. This technique is efficacious, but may lead to inadvertent subclavian neurovascular bundle damage due to over-drilling. The aims of this study were, using magnetic resonance imaging (MRI), to investigate the anatomical relationship between the clavicle and subclavian neurovascular bundle and to determine dangerous drilling angles and depths for different sections of the clavicle using clear anatomical landmarks.Methods: Twenty-six healthy subjects underwent MRI. Coronal and sagittal images of the periclavicular region, including the whole clavicle and nearby vital anatomical structures were obtained. The clavicle was divided into three sections. Section I: between the sternoclavicular joint (SJ) and point N (where the subclavian neurovascular bundle coursed below the mid-axial level of the clavicle). Section II: from N to the projection point of the coracoid process to the clavicle (CP'). Section III: from CP'to the acromioclavicular joint. Dangerous drilling depths and angles were determined for each section. Depth was determined by simulating straight line trajectories through the axial point of the clavicle in the sagittal plane and measuring the distance from the clavicular surface to the nearest neurovascular bundle sheath. Dangerous drilling angles were determined by simulating straight line trajectories and assessing the angle of the trajectory (with reference to a plumb-bob line) when the line was tangential to the inferior sheath and the superior tangent point of the neurovascular bundle.Results: In section I, the dangerous drilling angle was >59.7°cephalad and >95.3°caudad, while dangerous drilling depth was 17.0±2.4 mm. Corresponding values in section II were <1.2°caudad and >142.4°caudad. Dangerous drilling depth was 36.2±12.4 mm. Depth and direction limitations were not assessed for section III as the neurovascular bundle coursed well below the level of the coracoid process.Conclusions: It may be possible to accurately estimate safe drilling direction and depth and therefore reduce the risk of inadvertent iatrogenic subclavian neurovascular bundle injury during plate-screw fixation of the clavicle.