Which space is not typically involved in TOS etiologies?

• A. Interscalene triangle
• B. Costoclavicular triangle
• C. Subcoracoid/sub-pec minor
• D. Supraclavicular space

Answer: (D)

Thoracic Outlet Syndrome happens when the neurovascular bundle is squeezed as it passes from the thorax to the upper limb. The classic sites where this compression occurs are the interscalene triangle (between the anterior and middle scalene muscles), the costoclavicular space (between the clavicle and first rib), and the subcoracoid or pectoralis minor space (between the coracoid process and the pec minor). These spaces are the typical bottlenecks where overhead motion, posture, or muscular tightness can narrow the passageways for the brachial plexus and blood vessels. The supraclavicular space, while nearby, is not a common primary site of compression in TOS etiologies. Therefore, it is not typically involved in TOS.