Thoracic Outlet Syndrome: Definition and Foundational Concepts
Thoracic outlet syndrome (TOS) is a group of clinical disorders caused by compression, irritation or traction of the neurovascular structures as they pass from the cervicothoracic region to the upper limb through one of the thoracic outlet spaces. The structures at risk are the lower trunk of the brachial plexus (C8–T1), the subclavian artery and the subclavian vein. The term is therefore anatomical rather than a single disease entity.
The commonly involved sites are the interscalene triangle, the costoclavicular space and the retropectoralis minor or subcoracoid space. The interscalene triangle is bounded anteriorly by scalenus anterior, posteriorly by scalenus medius and inferiorly by the first rib; the brachial plexus and subclavian artery pass through it, whereas the subclavian vein lies anterior to scalenus anterior. The costoclavicular space lies between the clavicle and first rib. The retropectoralis minor space is situated beneath pectoralis minor near the coracoid process and is particularly important in overhead activity.
Clinical Classification of Thoracic Outlet Syndrome
The accepted clinical classification is based on the structure predominantly compressed. It is useful because symptoms, investigations and treatment differ between the groups. Mixed forms may occur, and symptoms…