1. Introduction / Plain Theory

Thoracic Outlet Syndrome (TOS) refers to a group of conditions in which the nerves or blood vessels of the upper limb become compressed as they pass from the neck to the armpit, through a narrow region called the thoracic outlet.

This outlet is bordered by the first rib, clavicle, and scalene muscles, and serves as the passageway for the brachial plexus, subclavian artery, and vein.
When these structures are compressed or irritated, it can lead to pain, tingling, or weakness in the shoulder, arm, or hand.

TOS can be classified into three main types:

1. Neurogenic TOS – compression of the brachial plexus (≈90% of cases).

2. Venous TOS – compression of the subclavian vein.

3. Arterial TOS – compression of the subclavian artery (rare but serious).

This condition often affects individuals with postural strain, repetitive upper-limb activity, or previous trauma, and is more common in women aged 20–50 years.

2. Typical Symptoms and Functional Impact

• Pain, tingling, or numbness in the neck, shoulder, arm, or hand.

• Heaviness, weakness, or fatigue with overhead use.

• Coldness, swelling, or colour changes in the hand (vascular involvement).

• Symptoms aggravated by lifting, reaching, or prolonged sitting.

• Tightness in the chest or scalene region; occasional headaches or dizziness.

Functional impact:
TOS can interfere with daily life, exercise, and work tasks requiring arm elevation or sustained posture.
Chronic irritation can cause protective tension in the shoulder girdle, scapula, and upper thoracic spine — perpetuating the cycle of compression.

Red flags:
Sudden arm swelling, bluish colour, or loss of pulse should be assessed urgently for possible vascular obstruction.

3. Contributing Factors / Underlying Causes

TOS develops when structures passing through the thoracic outlet are narrowed or irritated by surrounding tissues.
Common contributing factors include:

• Postural imbalance: rounded shoulders, forward head posture.

• Tight scalene or pectoralis minor muscles.

• First-rib elevation or restriction.

• Clavicular or upper-thoracic joint dysfunction.

• Repetitive overhead activity or carrying heavy loads.

• Previous trauma or whiplash injuries.

• Congenital anomalies: cervical rib or fibrous band.

From an osteopathic perspective, TOS represents a regional adaptation problem — where dysfunction in the cervical spine, ribs, and diaphragm alters mechanical and circulatory dynamics through the thoracic inlet and outlet.

4. Osteopathic Approach

Osteopathic management aims to reduce compression, restore mobility, and normalise circulation through the thoracic outlet and upper limb.

An osteopathic assessment may include:

• Evaluation of posture, breathing mechanics, and cervical-thoracic motion.

• Palpation of scalene, clavicular, and pectoral muscle tension.

• Gentle mobilisation of the first rib, cervical, and upper-thoracic segments.

• Myofascial release for the scalene triangle, pectoralis minor, and axillary fascia.

• Functional and indirect techniques to reduce neural and vascular tension.

• Breathing and diaphragm work to improve venous and lymphatic return.

• Guidance on posture, workstation setup, and gentle home exercises.

Treatment is always tailored to the individual and avoids aggressive stretching or manipulation that could aggravate neurovascular compression.
The goal is to restore freedom and balance to the structures surrounding the thoracic outlet, supporting natural recovery and long-term comfort.

5. Scientific Evidence & References

Evidence supports manual therapy, posture correction, and targeted exercise as conservative approaches for neurogenic and functional TOS.
Studies show that treatment addressing scalene tension, first-rib mobility, and scapular control can reduce symptoms and improve upper-limb circulation.

Osteopathic and physiotherapy-based interventions have demonstrated safety and efficacy in improving range of motion, reducing neural irritation, and enhancing quality of life.

References

1. Hooper TL, Denton J, McGalliard MK, Brismee JM, Sizer PS Jr. Thoracic outlet syndrome: a controversial clinical condition. Part 1: anatomy, and clinical examination/diagnosis. J Man Manip Ther. 2010;18(2):74–83. Link

2. Hooper TL, Denton J, McGalliard MK, Brismee JM, Sizer PS Jr. Part 2: conservative management of thoracic outlet syndrome. J Man Manip Ther. 2010;18(3):132–138. Link

3. Balderman J, et al. Outcomes of conservative management of neurogenic thoracic outlet syndrome: systematic review and meta-analysis. Ann Vasc Surg. 2019;54:260–273. Link

4. Novak CB, Collins ED, Mackinnon SE. Outcome following conservative management of thoracic outlet syndrome. J Hand Surg Am. 1995;20(4):542–548. Link

5. Tozzi P. A unifying neuro-fasciagenic model of somatic dysfunction — underlying mechanisms and treatment. J Bodyw Mov Ther. 2015;19(2):254–265. Link

6. Degenhardt BF, Johnson JC, Fossum C, et al. Osteopathic manipulative treatment for cervicothoracic pain and upper-limb dysfunction: pragmatic pilot study. J Bodyw Mov Ther. 2017;21(4):857–865. Link

7. Povlsen B, Hansson T, Povlsen SD. Treatment for thoracic outlet syndrome. Cochrane Database Syst Rev. 2014;(11):CD007218. Link

8. Xie Y, Chen Z, Yang Z, et al. Comparative efficacy of manual therapy interventions for thoracic outlet syndrome: network meta-analysis. Front Pain Res. 2024;15:1507401. Link