Title: Thoracic Outlet Decompression.
Published: 5/17/2011, Updated: 5/17/2011.

Author(s): Susan E. Mackinnon MD, Andrew Yee BS, Osvaldo Laurido-Soto BS.
Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, St. Louis, MO.

Thoracic outlet syndrome (TOS) is controversial and difficult to diagnose due to the wide-range of symptomology (vascular and/or neurogenic) that are involved, may it be vascular and/or neurogenic, and there not being a distinct examination method (1). The superior thoracic outlet, anatomically known as the thoracic inlet, is composed of the anterior and middle scalene between which the brachial plexus, subclavian artery, and subclavian vein courses distal, superior to the 1st rib and passes obliquely and inferiorly to the clavicle. Impingement of the brachial plexus can involve these structures. As there can be a neurogenic, arterial, and/or venous component of TOS, the most common is neurogenic and constitute the majority of patients with complaints of diffuse shoulder weakness, postural abnormalities, and pain/numbness in the affected upper extremity. Non-invasive treatment for TOS can involve posture correction, shoulder muscles strengthening, and stretching to promote nerve gliding and relieve pressure off of the brachial plexus through the thoracic outlet. Therefore, diagnosis of TOS is made frequently; rarely do these patients require surgical decompression (1). If conservation management fails, our institution’s preferred approach for decompression of the brachial plexus for neurogenic TOS is a supraclavicular approach to release the scalene muscles. Initially, the procedure included a first rib resection, but over the last two decades, literature has shown that the release of the scalene muscles is as satisfactory in results as with the first rib resection. Resection of the first rib is not necessary, unless there is a vascular component to the thoracic outlet syndrome or an underlining pathology in the bony structures. Decompression of the brachial plexus for neurogenic TOS primarily involves dividing the anterior and middle scalene muscles and inspecting the brachial plexus and its nerve branches for possible compression points by adjacent structures.

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  Figure 5 – Anterior Scalene and Brachial Plexus 230.0 KB
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  Figure 6 – Middle Scalene 255.2 KB
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  Figure 8 – Middle Scalene and Brachial Plexus 217.5 KB
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  Figure 9 – Thoracic Outlet Decompression. 335.4 KB

PROCEDURE: Thoracic Outlet Decompression.

Incision Description:

• Incision is marked a finger breath supraclavicular and is approximately 8cm in length.
• The supraclavicular notch and lateral border of the sternocleidomastoid are marked.

Sugical Steps:
Exposure and Dissection:

1. The entire arm, chest, neck, and the lower aspect of the ear are prepped and draped. The supraclavicular notch and lateral border of the sternocleidomastoid are marked and the lobule of the ear is noted.
2. An incision is made a finger breath above the clavicle and approximately 8cm in length.
3. The dissection is carried down through the platysma muscle to identify the supraclavicular nerves that are encountered beneath it. Once identified, these nerves are carefully protected and two vessel loops are placed around the nerves. These loops are used as retractors for the nerves to prevent injury. Additionally, there are several supraclavicular nerves that can be encountered and are protected.

Thoracic Outlet Decompression:

4. The fat above the brachial plexus is elevated superiorly.
5. The omohyiod is identified and divided through a plane lateral to the sternocleidomastoid. This small muscle is not repaired.
6. Digital palpation is used to feel the smooth anterior and middle scalene muscles and the “rope-like” brachial plexus in between these muscles for orientation.
7. The fat is elevated above the scalene muscles and the brachial plexus to be able to visualize these structures. Transverse cervical vessels, that are identified, are divided and ligated.
8. The phrenic nerve is identified on the anterior surface of the anterior scalene and courses in a unique direction from lateral to medial. It is frequently found on the very most medial aspect of the anterior scalene. No vessel loop is used to protect it due to the sensitivity and critical function of this nerve. Once visually identified and stimulated to confirm its function, the phrenic nerve is visually protected throughout the procedure.
9. The brachial plexus is separated from the anterior scalene, from which the anterior scalene is slowly and carefully divided using micro-bipolar cautery, and taking into account the subclavian artery inferiorly. The phrenic nerve is carefully protected throughout the division.
10. The brachial plexus is mobilized medially to identify the middle scalene muscle laterally. A nerve stimulator is used to identify the long thoracic nerve, which will appear to have a course through the middle scalene or posterior to it. Due to its C5, C6, and C7 contributions, occasionally a couple of branches are visualized to originate from the root level and course together distally to compose the long thoracic nerve. The long thoracic nerve is protected with a vessel loop.
11. Micro-bipolar cautery is used to remove the middle scalene from its attachment to the first rib. The middle scalene has a long distance to its attachment to the first rib. Its long attachment is elevated over this distance.
12. The brachial plexus is then neurolyzed to the point where the Bands of Fontana can be visualized on the surface of the plexus trunks. The Bands of Fontana represent redundancy in the nerve fibers. Micro-instrumentation and straight micro-spring scissors are used for this neurolysis. This minimal neurolysis is described by just opening the epineurium to ensure that there is no compression due to thickened epineurium on the brachial plexus. In situations, where thoracic outlet syndrome is the result of trauma, neurolysis is recommended and useful. In other situations, neurolysis will not be necessary as it depends on the thickness of the epineurium and visualization of the Bands of Fontana. The visualization of the Bands of Fontana will help determine the necessity of neurolysis.
13. In patients that exhibit scapular winging due to weakness of the serratus anterior, the entire length of the long thoracic nerve is examined to verify that there are no vascular structures compressing the nerve. If compression of the long thoracic nerve is identified, these structures are divided to decompress the nerve.
14. Marcaine is then placed in the incision, which is usually drained and closed with subcuticular monocryl.
15. Within two or three days post-operatively, patients are allowed gentle range of movements.

Cited References:

1. Mackinnon SE, Novak CB. Thoracic outlet syndrome. Curr Probl Surg. 2002 Nov;39(11):1070-145.

Related References:

1. Mackinnon SE, Novak CB. Thoracic outlet syndrome. Orthop Clin North Arm. 1996 Oct;27(4):747-62.
2. Mackinnon SE, Patterson GA. Supraclavicular first rib resection. Semin Thorac Cardiovasc Surg. 1996 Apr;8(2):208-13.
3. Mackinnon SE, Patterson GA, Novak CB. Thoracic outlet syndrome: a current overview. Semin Thorac Cardiovasc Surg. 1996 Apr;8(2):176-82
4. Mackinnon SE, Novak CB. Evaluation of the patient with thoracic outlet syndrome. Semin Thorac Cardiovasc Surg. 1996 Apr;8(2):190-200.
5. Novak CB, Collins ED, Mackinnon SE. Outcome following conservative management of thoracic outlet syndrome. J Hand Surg Am. 1995 Jul;20(4):542-8.