What is TOS?
Thoracic Outlet Syndrome (TOS) is a compression syndrome affecting the lower brachial plexus and subclavian axillary vessels, as it passes through the interscalene triangle (over the 1st rib and between the scalenes) and under the pectoral minor. It more commonly affects women rather than men (4:1 ratio), with a mean age of 30s to 40s, rarely affecting children. The two main categories of TOS are vascular (arterial or venous) and neurological. The latter accounting for 95-99% of all cases.
Signs and Symptoms:
- Pain and paraesthesia on the ulna side of the arm.
- Increase in symptoms after carrying bags or doing overhead activities.
- Fatigue and hand/arm weakness.
- Often worse at night.
- Discolouration and swelling (vascular TOS).
- Poor daily work habits and postures.
Relevant Anatomy
Interscalene triangle
The most proximal passage way of the thoracic outlet. This triangle is bordered by the anterior scalene muscle anteriorly, the middle scalene muscle posteriorly, and the medial surface of the first rib inferiorly.
Costoclavicular triangle
The second passage way is bordered anteriorly by the middle third of the clavicle, posteromedially by the first rib, and posterolaterally by the upper border of the scapula.
Subcorocoid or sub-pectoralis minor space
The borders of the thoraco-coraco-pectoral space include the coracoid process superiorly, the pec minor anteriorly, and ribs 2-4 posteriorly.
Causes of TOS
There are a variety of congenital factors that can lead to TOS such as a cervical rib, fibrous muscular bands, abnormalities of the insertion of the scalene muscles etc. However, the fact is that most cases are caused by poor posture, with examples including: shoulders rolling forward, a forward head position, a dropped shoulder, incorrect working postures, trauma, a clavicle/rib fracture, repetitive stress injuries (sitting at a keyboard for long hours), hypertrophy of the scalene muscles, decreased tone and weakness in the lower, levator scapulae, rhomboids, and/or shortening of scalenes, levator scapulae, pectoral muscles.
Treatment Options:
- Postural correction.
- Restrictions needing manual therapy (soft tissue massage, stretching of levator scapulae, scalenes and pec minor).
- Scapula retraining – strengthening of rhomboids, serratus anterior, lower and middle trapezius.
- Neural mobilisations.
- Taping to offload structures.
- Respiratory treatment training (diaphragmatic breathing).
