Anatomical landmarks and angulation of the subclavian vessels: a CT-based morphometric study of the clavicular safety corridor.

The present study aims to describe the morphometric relationship of the subclavian vein and artery to the clavicle and their angular orientation, with a particular focus on improving the safety of interventional procedures by bringing new anatomical landmarks. The costoclavicular region is a critical anatomical corridor where the subclavian vein, subclavian artery, and brachial plexus cords pass beneath the clavicle, partially protected by the subclavius muscle. Precise knowledge of clavicle-vessel relationships is essential, as previous studies have reported considerable variability in the measured distances between the clavicle and adjacent vascular structures, particularly in the context of trauma or surgical fixation. This study aimed to define morphometric parameters to establish a safer anatomical corridor for clinical interventions. A cross-sectional study was conducted using contrast-enhanced computed tomography (CT) scans of adult patients (≥ 18 years). Each clavicle was divided into 13 reference points. At each point, we measured clavicular thickness, the distance from the inferior border of the clavicle to the anterior surface of the subclavian vein and artery, vessel diameters, and the angular relationship between the clavicle and vessels. Side- and sex -related differences were analyzed. A total of 150 participants (75 men, 75 women) were included. All participants were of Hispanic ethnicity, representative of the northeastern Mexican population. The greatest clavicular thickness was observed in men on the right side (14.4 ± 1.6 mm), whereas the shortest distance to the subclavian vein occurred in women on the right side (5.9 ± 2.1 mm). The subclavian vein was significantly larger in men on the right side (14.8 ± 2.7 mm). Significant sex- and side-dependent variations were identified in clavicle dimensions, vessel diameters, and vessel-clavicle distances and angulations. The point of closest proximity between the clavicle and the subclavian vein was consistently located at reference point 3/13 which corresponds to the medial third of the clavicle, located approximately at the costoclavicular region. At this site, the vein was reached at an average depth of ~ 13 mm when the needle was directed 20° cranially relative to the inferior clavicular border. These parameters define a practical "safety cone" that may improve the success and safety of subclavian vein catheterization, particularly in settings where ultrasound guidance is unavailable.