Supraclavicular Approach for Surgical Treatment of Thoracic Outlet Syndrome

Historical Background

Thoracic outlet syndrome (TOS) is recognized to encompass three conditions: (1) neurogenic TOS, caused by compression of the brachial plexus nerve roots within the scalene triangle, subcoracoid space, or both; (2) venous TOS, caused by compression of the axillary, subclavian, or both veins and leading to the effort thrombosis syndrome; and (3) arterial TOS, caused by compression of the subclavian artery and leading to arterial stenosis, aneurysm formation, and thromboembolism. The early history of surgical treatment for TOS is dominated by supraclavicular operations for cervical rib resection in the treatment of subclavian artery aneurysms. Operations initially developed for neurogenic TOS also used supraclavicular approaches, including first rib resection, scalenotomy, and anterior scalenectomy. Transaxillary first rib resection was introduced in 1966 and became widely used, particularly with the recognition of frequent anatomic variations and scalene muscle pathology contributing to neurogenic TOS, but its popularity waned in the 1980s with reports of significant morbidity because of brachial plexus nerve injury. Use of the supraclavicular approach was reintroduced in 1979, initially as a technique for recurrent neurogenic TOS, and was soon followed by descriptions of combined transaxillary or supraclavicular approaches and more refined techniques for supraclavicular decompression in primary operations. Subsequent reports have emphasized the usefulness of supraclavicular decompression for all forms of TOS, exemplified by several particularly large clinical series. The techniques described in this chapter are therefore built on rich and varied experience, with additional modifications that have enhanced the usefulness of the supraclavicular approach for all three forms of TOS.

Preoperative Preparation

The diagnosis of neurogenic TOS is based on clinical evaluation according to the criteria listed in Box 15-1 and supplemented by relevant testing procedures to exclude alternative conditions. The extent of brachial plexus compression attributable to either the scalene triangle or the subcoracoid space is also characterized by physical examination.
Box 15-1

DIAGNOSTIC FEATURES OF NEUROGENIC THORACIC OUTLET SYNDROME

Thompson RW: Development of consensus-based diagnostic criteria for NTOS. In Illig KA, Thompson RW, Freischlag JA, Donahue DM, Jordan SE, Edgelow PI, editors: Thoracic outlet syndrome , London, 2013, Springer, pp 143-155.
Unilateral or bilateral upper extremity symptoms present for at least 12 weeks that meet at least one criterion in each of the following three categories yet are not satisfactorily explained by another condition:
- Manifesting symptoms
  - Pain in the neck, anterolateral chest, medial upper back, shoulder, arm, and/or hand
  - Complaint of numbness or paresthesias in the hand, especially in digits 4 and 5
  - Complaint of weakness in the arm or hand
  - Paresthesias that radiate from the supraclavicular or infraclavicular space to the arm and/or hand
- Clinical history
  - Symptoms that began after head, neck, or upper extremity injury (occupational or recreational)
  - Symptoms exacerbated by overhead or work-related activities, including repetitive strain
  - Presence of a cervical rib or previous fracture of the clavicle or first rib
- Physical examination
  - Local tenderness on palpation over the scalene triangle and/or subcoracoid space
  - Reproduction of hand or digit paresthesias on palpation over the scalene triangle and/or subcoracoid space
  - Weak handgrip, intrinsic muscles, digit 5, or thenar or hypothenar atrophy
  - Positive upper limb tension test or 3-minute elevated arm stress test
Exclusion of other conditions typically includes nonspecific or negative findings on physical examination (Spurling’s test, axial compression test, Tinel’s sign over the carpal tunnel or cubital tunnel, and Phalen’s test), imaging studies (magnetic resonance imaging of the cervical spine and shoulder), and conventional electrophysiologic tests (upper extremity electromyography and nerve conduction studies). Adapted from the preliminary consensus diagnostic criteria developed by the Consortium for Research and Education on Thoracic Outlet Syndrome.
A chest radiograph is obtained to determine the presence or absence of a cervical rib, but other imaging studies of the brachial plexus are usually not helpful.
Conventional electromyography and nerve conduction studies (EMG/NCS) may be performed to exclude peripheral nerve compression disorders or cervical radiculopathy, but these tests are usually negative or nonspecific in neurogenic TOS.
After clinical diagnosis, almost all patients should undergo an anterior scalene or pectoralis minor muscle block with a short-acting local anesthetic to support the clinical diagnosis of neurogenic TOS and to help predict the reversibility of symptoms with treatment.
After an appropriate course of physical therapy that has been directed by a therapist with specific expertise of neurogenic TOS, surgical treatment is recommended for patients with substantial disability who have not made significant improvement. Surgical treatment may also be recommended in selected patients with persistent or recurrent symptoms of neurogenic TOS after a previous operation, when there has been no response to appropriate conservative measures. In each of these situations we find that supraclavicular decompression, with or without pectoralis minor tenotomy, provides the most definitive approach for surgical treatment.
Angiography with magnetic resonance imaging or computed tomography is performed to determine the presence or absence of a subclavian artery aneurysm in patients with a cervical rib or first rib anomaly suspected of having arterial TOS. Similar imaging studies are performed in patients who have presented with upper extremity arterial thromboembolism to detect a proximal source of embolism in the subclavian artery or the axillary artery. Surgical treatment based on supraclavicular decompression is recommended for all patients with subclavian artery aneurysms. This should include arterial reconstruction for subclavian aneurysms that have already produced distal emboli, those associated with imaging evidence of intimal ulceration or mural thrombus, or those greater than twice the normal diameter of the subclavian artery.
Upper extremity venography is the initial diagnostic step for patients with venous TOS who most frequently present with the axillary-subclavian vein “effort thrombosis” syndrome. Duplex imaging of the subclavian vein is usually inaccurate in this setting because of a high false-negative rate. Contrast venography is immediately followed by thrombolytic therapy, preferably with current pharmacomechanical approaches. Completion venograms typically reveal a focal area of residual subclavian vein stenosis or occlusion at the level of the first rib, often with enhancement by positional maneuvers. Balloon angioplasty of these residual stenoses is usually not helpful, and placement of stents in the subclavian vein is strongly discouraged.
First rib resection is recommended for patients with previous axillary-subclavian vein thrombosis who remain symptomatic despite anticoagulation and restricted activity, as well as for asymptomatic individuals in whom long-term anticoagulation and restrictions on upper extremity activity are undesirable. The addition of an infraclavicular incision can be used, if needed, along with the supraclavicular approach to ensure complete medial first rib resection and to facilitate direct subclavian vein reconstruction.

Pitfalls and Danger Points

Inadequate decompression and recurrence
- Incomplete scalenectomy
- Incomplete brachial plexus neurolysis
- Incomplete first rib resection
- Insufficient methods to prevent perineural fibrosis
- Residual subclavian vein stenosis or occlusion
Nerve injury
- Brachial plexus nerve roots
- Phrenic nerve
- Long thoracic nerve
- First intercostal nerve
Vascular and lymphatic injury
- Subclavian artery
- Subclavian vein
- Thoracic duct

Operative Strategy

Surgical Anatomy of the Thoracic Outlet

Successful surgical treatment for all three types of TOS depends on a sound understanding of the relationships between musculoskeletal and neurovascular structures in this region, as well as the many anatomic variations likely to be encountered ( Fig. 15-1 ). One of the principal advantages of the supraclavicular approach is excellent exposure of the relevant anatomy, allowing more complete decompression compared with alternative approaches. To accomplish this with the greatest margin of safety, we have defined six “critical views” of the surgical anatomy that should be sequentially obtained during the course of supraclavicular decompression ( Box 15-2 ).

Figure 15-1, Anatomy of the thoracic outlet, focusing on the scalene triangle, the costoclavicular space, and the subcoracoid space. A, The scalene triangle is bounded by the anterior scalene muscle, the middle scalene muscle, and the first rib. The brachial plexus and subclavian artery pass through this space and over the first rib, whereas the subclavian vein passes over the first rib immediately in front of the scalene triangle. B, The costoclavicular space lies between the clavicle and the first rib and is bordered superiorly by the subclavius muscle, medially by the costoclavicular ligament, and posteriorly by the insertion of the anterior scalene muscle tendon on the first rib. The brachial plexus and subclavian artery pass over the first rib behind the costoclavicular space, whereas the subclavian vein passes over the first rib through the front part of the costoclavicular space. C, The subcoracoid space lies inferior to the clavicle and underneath the pectoralis minor muscle tendon, just below its insertion on the coracoid process. All of the structures of the neurovascular bundle pass through this space before reaching the axilla. D, Overview of the anatomy of the thoracic outlet.

Box 15-2

SIX CRITICAL VIEWS DURING SUPRACLAVICULAR THORACIC OUTLET DECOMPRESSION

1.
View of the operative field after lateral reflection of the scalene fat pad, with visualization of the anterior scalene muscle, phrenic nerve, brachial plexus, subclavian artery, middle scalene muscle, and long thoracic nerve.
2.
View of the lower part of the anterior scalene muscle where it attaches to the first rib, with space sufficient to allow a finger to pass behind the anterior scalene muscle and in front of the brachial plexus and subclavian artery, before division of the anterior scalene muscle insertion from the top of the first rib.
3.
View of the upper part of the anterior scalene muscle at the level of the transverse process of the cervical spine, in relation to the C5 and C6 nerve roots, before division of the origin of the anterior scalene muscle.
4.
View of the insertion of the middle scalene muscle on the first rib, with each of the five nerve roots of the brachial plexus and the subclavian artery retracted medially and the long thoracic nerve retracted posteriorly, before division of the insertion of the middle scalene muscle from the top of the lateral first rib.
5.
View of the posterior neck of the first rib, with the T1 nerve root passing from underneath the rib to join the C8 nerve root and form the inferior trunk of the brachial plexus, before division of the posterior first rib.
6.
View of the anterior portion of the first rib, with placement of the rib shears medial to the scalene tubercle, before division of the anterior first rib.

Avoiding Inadequate Decompression and Recurrence

The potential for persistent or recurrent symptoms of brachial plexus compression remains one of the most challenging aspects of surgical treatment for neurogenic TOS. The supraclavicular approach is designed to avoid the most frequent causes of recurrence by addressing the following issues:

Extent of scalene muscle resection. Reattachment of the anterior scalene muscle is a well-documented cause of recurrent neurogenic TOS after simple scalenotomy, partial scalenectomy, or transaxillary first rib resection. In these circumstances the anterior scalene muscle may reattach to remaining portions of the first rib, to the bed of the resected first rib, to the extrapleural fascia, or directly to the brachial plexus nerve roots. Anomalous scalene muscles and fibrofascial bands may also persist as a source of brachial plexus compression if not removed. It is therefore recommended that both the anterior and the middle scalene muscles be resected, along with the anomalous scalene muscle and the fibrofascial bands that might be encountered, during supraclavicular thoracic outlet decompression.
Brachial plexus neurolysis. Most patients undergoing surgery for neurogenic TOS exhibit visual evidence of fibrous scar tissue surrounding the brachial plexus nerve roots, a reflection of previous injury and inflammatory tissue healing. This fibrous tissue may contribute to nerve fixation and irritation and when retained may be a cause for residual neurogenic symptoms. It is therefore recommended that perineural fibrous scar tissue be meticulously removed from around each of the brachial plexus nerve roots during the course of thoracic outlet decompression (external neurolysis).
First rib and cervical rib resection. There remains some room for debate regarding the necessity for first rib resection during supraclavicular thoracic outlet decompression, with some advocating routine first rib resection and others encouraging a more selective approach based on intraoperative findings after scalenectomy and brachial plexus neurolysis. It remains unclear whether there are distinct advantages attributable to retaining the first rib, and incomplete first rib resection is often cited as a factor contributing to recurrent neurogenic TOS. It is therefore recommended that first rib resection be included in supraclavicular decompression for neurogenic TOS, extending posteriorly as far as the level of the T1 nerve root and anteriorly to the costochondral junction (just medial to the scalene tubercle). The first rib is often abnormal in patients with a cervical rib and may serve as a source of persistent or recurrent nerve compression after isolated cervical rib resection. Thus first rib resection is also advocated in patients with cervical ribs, along with resection of the cervical rib, in order to ensure the most complete decompression feasible. In venous TOS, the subclavian vein is typically compressed at the point where it passes over the first rib and directly underneath the clavicle. Resection of the anteriormost portion of the first rib is therefore considered important in operations for venous TOS to prevent persistent or recurrent subclavian vein obstruction, but this cannot be achieved through the supraclavicular approach alone. For this reason, and to provide more complete access to the axillary-subclavian vein (in the event that direct venous reconstruction is warranted), a medial infraclavicular incision is added to the supraclavicular approach in operations for venous TOS.
Pectoralis minor tenotomy. Brachial plexus compression by the pectoralis minor muscle has become increasingly appreciated as a factor contributing to neurogenic TOS. In our experience up to 20% of patients with neurogenic TOS exhibit physical findings isolated to the subcoracoid space and another 30% to 40% have findings that colocalize to both the scalene triangle and the subcoracoid space. Even in patients with findings predominantly localized to the scalene triangle, residual nerve compression at the site of the pectoralis minor muscle may be a source of persistent or recurrent neurogenic TOS. Simple division of the pectoralis minor muscle tendon immediately below the coracoid process can provide substantial relief of brachial plexus compression while adding little to the operative procedure; thus pectoralis minor tenotomy should be included with supraclavicular decompression whenever suggested by preoperative clinical findings.
Hemostasis and fluid accumulations. Postoperative accumulation of blood and serum may enhance local wound healing responses that promote fibrosis, thereby contributing to the potential for late neural compression and recurrent symptoms after thoracic outlet decompression. Common local sources of bleeding include the ends of the divided first rib and the edges of the resected scalene or intercostal muscles. Although bleeding from these sites is typically minimal and self-limited, effort should be made to diminish fluid accumulation in the operative field. To this end, a topical hemostatic agent is placed along the edges of the resected muscles and the scalene fat pad is closely reapproximated over the brachial plexus to reduce potential space in the wound. The pleural apex is also purposefully opened to promote dependent drainage away from the operative field, and a closed-suction drain is placed within the supraclavicular space upon completion of the procedure.
Absorbable film barriers. Postoperative scarring around the brachial plexus nerve roots is inevitable after an operation for TOS, and dense perineural fibrosis is a potential cause of recurrent nerve entrapment and irritation. As in other operations involving direct nerve exposure, it is recommended that the brachial plexus nerve roots be covered with an absorbable antiadhesion film barrier, using one of several materials that have been developed for this purpose, to decrease the potential for later nerve encasement.

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