21 Thoracic Outlet Syndrome



Alexander Bitzer and Uma Srikumaran


Summary


Thoracic outlet syndrome (TOS) refers to a group of conditions that produce varying neurologic or vascular symptoms depending on the etiology. Etiologies include compression of neurologic or vascular structures at various anatomical sites in the upper extremity with neurologic involvement being far more common. The diagnosis of thoracic outlet syndrome is largely clinical, with clinical history and physical exam findings being the most sensitive and specific. The majority of cases can be treated successfully with nonoperative management. Surgery, which aims to decompress sites of anatomic compression, may be helpful in patients with symptoms refractory to nonoperative treatment.




21 Thoracic Outlet Syndrome



I. General overview




  1. Two separates entities:




    1. Neurogenic thoracic outlet syndrome (nTOS)



    2. Vascular thoracic outlet syndrome (vTOS).



  2. Caused by anatomical sites of compression of nervous structures/brachial plexus (nTOS) or shoulder girdle vessels (vTOS)



  3. Incidence is 1 to 2% of general population:




    1. nTOS is more common (19:1).



  4. More common in women than men (3.5:1):




    1. Theoretical risk factors are long neck and drooping shoulders.



  5. Clinical symptoms include upper extremity pain, paresthesias, numbness, weakness, fatigability, heaviness, swelling, discoloration, and Raynaud phenomenon:




    1. Pain and paresthesias most common.



  6. Treatment:




    1. Operative versus nonoperative management depending on cause.



II. Anatomy




  1. Nervous tissue:




    1. Brachial plexus:




      1. Five roots: C5, C6, C7, C8, T1



      2. Three trunks: Superior, middle, and inferior



      3. Six divisions: Anterior and posterior divisions of three trunks



      4. Three cords: Posterior, lateral, and medial



      5. Five branches: Median, axillary, radial, musculocutaneous, and ulnar nerves



      6. Lower trunk (C8–T1) > upper trunk (C5–C7) involvement in nTOS.



  2. Vasculature:




    1. Subclavian vein:




      1. Runs anterior to interscalene triangle proximally



      2. Becomes axillary vein after crossing first rib



      3. Joins artery and brachial plexus in costoclavicular and retropectoralis minor space.



    2. Subclavian artery:




      1. Branches off brachiocephalic trunk



      2. Becomes axillary artery after crossing first rib.



    3. Axillary artery (▶ Fig. 21.1 ):




      1. Divided into three parts:




        • i. First: Lateral border of first rib to superior border of pectoralis minor muscle



        • ii. Second: Lies deep to the pectoralis minor muscle



        • iii. Third: Extends from inferior border of the pectoralis minor muscle to the inferior border of the teres major muscle.

          Fig. 21.1 Anatomy of the thoracic outlet.


  3. Sites of compression from proximal to distal (▶ Fig. 21.2 ):




    1. Interscalene triangle:




      1. Anterior scalene muscle: Anterior border



      2. Middle scalene muscle: Posterior border



      3. First rib: Inferior border.



    2. Costoclavicular space:




      1. Clavicle: Anterior border



      2. First rib: Posteromedial border



      3. Costoclavicular ligament/scapula: Posterolateral border.



    3. Retropectoralis minor space:




      1. Pectoralis minor: Anterior border



      2. Ribs 2 to 4: Posterior border



      3. Coracoid: Superior border.



  4. Anatomical anomalies causing TOS:




    1. Congenital:




      1. Soft tissue:




        • i. Variation in scalene muscle origin or insertion



        • ii. Presence of scalenus minimus



        • iii. Fibromuscular bands constricting inlet spaces.

          Fig. 21.2 Common sites of neurologic or vascular compression are shown. From proximal to distal, these include the interscalene triangle, the costoclavicular space, and the retropectoralis space.


      2. Osseous:




        • i. Presence of cervical ribs



        • ii. Prominent C7 vertebrae transverse processes



        • iii. First rib anomalies



        • iv. Vertebral anomalies.



      3. Vascular:




        • i. Atypical vessel course and branching.



    2. Acquired:




      1. Osseous:




        • i. Osteochondroma of first rib/clavicle



        • ii. Malunion after fracture of first rib/clavicle



        • iii. Hyperostosis



        • iv. Posterior sternoclavicular dislocation.



      2. Occupational:




        • i. Repetitive overhead activity produces cumulative effects of micro trauma.



      3. Hypertrophy:




        • i. Hypertrophic scalene muscles.

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Feb 6, 2021 | Posted by in ORTHOPEDIC | Comments Off on 21 Thoracic Outlet Syndrome
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