scalene tubercle scalene tubercle the scalene tubercle is a small projection that runs along the medial border of the first rib between two grooves, which travel anteriorly for the subclavian artery and posteriorly for the subclavian vein. it projects outward medially, and is the site of insertion for scalenus anterior. scalene tuberclefirst rib.detailsidentifierslatintuberculum musculi scaleni anteriorista98a02.3.02.015fma76639anatomical terms of bone