It is usually attached to the first rib, close to the insertion of scalenus anterior muscle
The key points in both the approaches are (1) complete resection of bony, cartilaginous, and fibrous parts of (2) complete resection of the scalenus anterior muscle
at the scalene tubercle on the first rib and (3) arterial exploration and reconstruction.
The scalenus anterior muscle
pulls the lateral portion of the first rib proximally and posteriorly and the scalenus medius muscle pulls the medial portion of the first rib proximally and medially.
It descended downwards and laterally to merge with the tendon of scalenus anterior muscle towards its insertion.
These anomalous muscular slips sometimes arose from scalenus medius muscle and ran into scalenus anterior muscle or vice-versa (Yamamoto, 1992).
Murakami et al (2003) even report a case of total absence of the right scalenus anterior muscle
, a rare occurrence also observed by Le Double (1897).
In the root of neck each artery arches across the dome of pleura behind the scalenus anterior muscle which divides it into three parts viz.
Daseler and Anson came across a bilateral malposition of subclavian artery both situated anterior instead of posterior to scalenus anterior muscle (5).