Dean M. Donahue
INDICATIONS/CONTRAINDICATIONS
Vascular reconstruction techniques are required in the management of patients with thoracic outlet syndrome (TOS) when a vascular injury has occurred to either the subclavian vein or artery. Neurogenic TOS (NTOS) accounts for between 90% and 95% of clinical cases and is caused by compression or irritation of the brachial plexus. The remainder of cases is venous TOS (VTOS), which results from stenosis of the subclavian vein. Arterial TOS (ATOS) only occurs when compression of the subclavian artery results in arterial thrombosis and/or an aneurysm formation. This is very uncommon and accounts for less than 1% of all cases.
VTOS frequently presents with symptoms of upper extremity swelling with or without skin discoloration. Patients may report a heavy sensation or a feeling of “pressure” in the upper extremity. For suspected cases of VTOS, the initial management is immediate anticoagulation with subcutaneous low–molecular-weight or intravenous heparin. Venous ultrasound studies are often used in the initial diagnosis, but the high degree of false-negative studies limits its usefulness. A contrast venogram has much greater diagnostic accuracy and a therapeutic capability as well. Catheter-delivered chemical thrombolysis, and possibly mechanical thrombectomy may be used, the author’s preference is to avoid balloon venoplasty at the initial presentation. If balloon venoplasty is felt to be necessary, limiting this to an 8 mm or less balloon is preferable. The use of intravascular stents as a management for VTOS should be strictly avoided.
Some cases of VTOS may be treated nonoperatively. Patients who present in their mid-30s or older, have minimal or no narrowing of the subclavian vein after lytic therapy and remain asymptomatic may be treated with 3 to 6 months of anticoagulation and observed. This is a fairly small percentage of patients presenting with VTOS. The majority of patients will require surgical thoracic outlet decompression with or without vein reconstruction.
Patients with ATOS from a subclavian or axillosubclavian artery aneurysm represent an absolute indication for surgery, even if asymptomatic at the time of presentation.
PREOPERATIVE PLANNING
The surgical treatment of TOS requiring vascular reconstruction involves resection of the first thoracic rib through a supraclavicular or paraclavicular (combined supra- and infraclavicular) approach. The surgeon and the assistant would benefit from the use of surgical telescopes and a headlight to improve visualization. During the procedure, the degree of retraction on the spinal nerves, phrenic nerve, and brachial plexus trunks must be minimized to avoid a nerve traction injury. The author uses bipolar cautery for much of the procedure to avoid transmitting electrical current to the nerves in this area.
SURGERY
Positioning
General anesthesia is administered and the patient is intubated with the endotracheal tube taped to the side of the patient’s mouth opposite to the side of the procedure. The use of neuromuscular blocking agents is avoided following intubation so an electrical nerve stimulator can be used to assist in identifying and confirming the function of nerves.
The patient is placed in a modified semi-Fowler position with the head on a padded roll, rotated 45 degrees away from the operative side. Both arms are tucked to the side if possible. Otherwise, the operative side arm is tucked to the patient’s side and an arm board is placed on the nonoperative side as far down on the bed as possible to allow the assistant to stand close to the table. A roll of gauze is placed into the patient’s hands for padding. The operative-side shoulder is elevated off of the bed by placing a stack of folded surgical towels behind the shoulder to pivot the shoulder and lateral clavicle anteriorly and open the costoclavicular space. The field is draped so that a sternotomy can be performed in the unlikely event that additional exposure is needed.
Supraclavicular Exposure
A 5 cm long incision is made beginning at the lateral border of the sternocleidomastoid muscle (SCM). The incision extends laterally 1 to 2 cm above the clavicle. The subcutaneous tissue and platysma muscle are divided, and flaps are raised under this muscle with electrocautery. A Weitlaner retractor is placed below the level of the platysma and the scalene fat pad is mobilized off of the lateral border of the SCM using electrocautery. Small sensory nerve branches and anterior jugular veins are identified running approximately perpendicular to the incision. These structures are identified and mobilized laterally without tension. Another self-retaining retractor can be placed between the lateral wound edge and the SCM muscle to retract it medially. The scalene fat pad is now mobilized laterally. The omohyoid muscle is identified running approximately parallel to the incision. This is encircled with a vessel loop to allow for its retraction. Deep to the omohyoid muscle will lie the anterior scalene muscle.
Dissection through the deep part of the fat pad is done with bipolar cautery to protect the phrenic nerve and brachial plexus. The suprascapular and transverse cervical arteries are identified and preserved. They typically run parallel to the incision, with the suprascapular artery below the level of the incision, and the transverse cervical artery above it. The dissection continues with bipolar cautery until the scalene muscle is identified deep and slightly medial to the lateral edge of the SCM muscle. Mobilization of the scalene fat pad continues from medial to lateral exposing the upper and middle trunks of the brachial plexus, as well as the subclavian artery. The lower trunk is deeper to these structures, and not usually identified at this point. The suprascapular artery is dissected off of the scalene fat pad laterally to complete the mobilization. A 2-0 silk traction suture is placed on the tip of the fat pad, which is retracted laterally.
The phrenic nerve is then identified on the surface of the anterior scalene muscle running from lateral to medial. A nerve stimulator (current setting 0.5 to 1 mA, frequency setting 30 Hz) is used to confirm the location and function of the nerve. The areolar plane between the surface of the scalene muscle and the phrenic nerve is developed, and tissue adjacent to the nerve is grasped and gently retracted to mobilize the nerve medially. Occasionally, an accessory phrenic nerve branch located at the lateral edge of the anterior scalene muscle is preserved if present. Near the cephalad portion of the scalene muscle, the phrenic nerve receives a contribution from the C5 spinal nerve, which limits the degree that the phrenic nerve can be mobilized. After mobilization, the nerve stimulator is used to confirm intact phrenic nerve function. Once the phrenic nerve is mobilized off of the anterior surface of the scalene muscle, the plane along the medial border of the muscle is developed using bipolar cautery. The subclavian artery is identified medially, and the dissection around the anterior scalene is continued down to the scalene tubercle of the first rib. A Richardson or Cloward retractor placed below the clavicle facilitates exposure. There may be muscle fibers running between the anterior and middle scalene muscles that must be divided to facilitate mobilization of the brachial plexus trunks.
The lower portion of the anterior scalene muscle is partially divided medially and laterally directly on the scalene tubercle exposing part of the first rib. The central part of the muscle is preserved at this time to facilitate the division of the cephalad portion of the anterior scalene muscle. The scalene muscle is then divided with bipolar cautery as far cephalad as possible while protecting the phrenic nerve and its C5 spinal nerve. Once the cephalad border of the muscle is divided, the remaining muscle attachments to the first rib are divided and the muscle is removed.
The brachial plexus trunks and the subclavian artery are then dissected. The upper trunk and subclavian artery are often the first two structures identified. The middle scalene muscle is deep to the brachial plexus trunks, and is easiest to identify cephalad and deep to the upper trunk. The subclavian artery is then mobilized to improve the exposure of the lateral aspect of the first rib. The dorsal scapular artery originating along the cephalad border of the subclavian artery is identified and preserved. This branch is typically 1 to 2 cm lateral to the lateral border of the anterior scalene muscle. It is important to remember that the brachial plexus trunks are oriented obliquely, with the middle trunk lying more dorsal (or deeper) to the upper trunk, and the lower trunk lying further dorsal to the middle trunk. While not consistently present in cases of vascular TOS, there may be scar tissue around the brachial plexus, which is removed to increase nerve mobility for the remainder of the dissection. Removal of this scar tissue is frequently done sharply, with fine-tip bipolar cautery forceps used for hemostasis. Identification of the proper plane can be difficult, but the goal is to not disrupt the epineurium layer containing the blood supply to each nerve. Tissue adjacent to each nerve is grasped with atraumatic forceps and gently retracted to assist in identifying the proper dissection plane. Occasionally, blunt dissection with a no. 4 Penfield elevator is done to gently peel scar tissue away from the epineurium. During the dissection of the upper trunk, the dorsal scapular nerve may be identified originating from the cephalad border. This initially runs parallel to upper trunk before turning dorsally toward the suprascapular notch. Circumferential dissection of the middle and lower trunks are performed in a similar manner. It is important to completely remove any remaining scalene muscle fibers around the nerve trunks and artery.
After the brachial plexus trunks are mobilized, modified Love nerve root retractors are used to work between the trunks to identify the middle scalene muscle lying immediately deep to the brachial plexus. It is important to minimize the degree of retraction on the nerves to avoid injury. By palpating above and below the middle trunk, the posterior aspect of the first rib can be identified. This is exposed by dividing the attached middle scalene fibers above the rib with bipolar cautery. Because of individual anatomic variability, there is no consistent plane to the posterior first rib. Typically, this is approached by working between the upper and middle trunks, but occasionally this is accomplished between the middle and lower trunks. If a cervical rib or an elongated C7 transverse process is to be removed, then the best approach is often by working above and below the upper trunk. The dorsal scapular nerve (from the C5 spinal nerve) and the long thoracic nerve (from the C5, C6, and C7 spinal nerves) run dorsally and laterally to penetrate the middle scalene muscle. It is, therefore, important to divide the posterior middle scalene fibers inserting on the first rib less than 1 to 2 cm away from the upper surface of the rib to avoid injuring these nerves. The inner edge of the posterior first rib is then exposed, and dense tissue bands are divided off of this part of the rib using bipolar cautery to avoid injury to the T1 spinal nerve as it arises from below the first rib. The costotransverse ligaments between the neck of the first rib and the transverse process are then divided with bipolar cautery to separate the rib from the transverse process of the first thoracic vertebrae.
Muscle fibers are divided off of the cephalad and dorsal surfaces of the first rib working from medial to lateral. The exposure of the lateral aspect of the rib is facilitated by working both above and below the lower trunk with minimal traction on this nerve. The middle scalene muscle and fibers from the upper part of the serratus anterior muscle are divided off of the rib posterior to the subclavian artery.
Once the muscle tissue completely divides off of the cephalad surface of the first rib, the plane along the undersurface of the rib is developed. This is started with either sharp dissection or with bipolar cautery, and then continued under the rib with blunt dissection of Sibson’s fascia using a small sponge or the surgeon’s finger. The goal is to avoid entry into the pleural space, but there is little consequence if it is entered. The remaining attachments to the first rib are now the intercostal muscle fibers between the first and second ribs. These are divided with electrocautery using an insulated extended tip with a slight angle created by bending the tip with a snap. Ventilation should be held intermittently during the division of this muscle to avoid cautery injury to the lung. If exposure of the remaining soft tissue attachments is limited, then dividing the first rib allows it to be mobilized to improve this exposure.
The rib is divided at its neck medial to the end of the T1 transverse process using a straight Kerrison rongeur ranging from 3 to 5 mm. The smooth synovial joint between the transverse process of the T1 vertebrae and the angle of the first rib is exposed during this maneuver.
Infraclavicular Exposure for VTOS
Division of the medial portion of the anterior rib may be difficult because of limited exposure from the supraclavicular approach. In cases where a vascular reconstruction is necessary, an infraclavicular incision will be required for vascular exposure and control. This also greatly facilitates exposure to the anterior rib. For VTOS cases, a 5- to 6-cm incision is made 1 to 2 cm below the clavicle beginning at the lateral border of the manubrium. The underlying soft tissues are divided with electrocautery exposing the pectoralis major muscle. These muscle fibers run obliquely, and are split between the upper and middle portions of this muscle. The underlying intercostal muscle fibers between the first and second rib are divided, and the subclavius muscle and tendon are partially resected off of the anterior surface of the rib preserving the costoclavicular ligaments. The cartilage of the first rib is then divided close to the manubrium with an angled duckbill rongeur or a Kerrison rongeur being careful to avoid the internal mammary vessels. With the rib completely free of soft tissue attachments, it is removed intact while avoiding any traction on the brachial plexus or subclavian artery. The subclavian vein is now exposed above and below the clavicle. A circumferential removal of surrounding tissue is then performed with sharp dissection and electrocautery. Following this, the vein is inspected and palpated to evaluate the extent of residual narrowing due to intrinsic vein injury. If the vein appears contracted and fibrotic, and is palpably thickened, a vascular reconstruction is indicated.
Infraclavicular Exposure for ATOS
For ATOS cases, exposure of the axillary artery for distal vascular control requires that the incision begin at the medial third of the clavicle and continue laterally to the deltopectoral groove. The exposure through the pectoralis major muscle is similar to the VTOS approach, but the underlying pectoralis minor muscle is frequently divided off of the coracoid process. The underlying axillary sheath is opened exposing the axillary vein. This is gently dissected away to expose the artery lying deep to the vein.
Vascular Reconstruction for VTOS
Once it is determined that a vein reconstruction is required, the patient is anticoagulated with a 5,000 unit bolus of intravenous heparin. Proximal venous control is achieved at two locations. One clamp is placed across the innominate vein from the infraclavicular incision using a Satinsky or other curved vascular clamp. Attention must be paid to the location of the phrenic nerve during this maneuver. A second curved vascular clamp is used medial at the internal jugular vein medial to its junction with the subclavian vein. A DeBakey clamp is then used to control the vein distally.
There are two options for vein reconstruction: Vein patch angioplasty, or vein replacement with an interposition bypass graft. To determine which option is appropriate, a longitudinal venotomy is made in the cephalad portion of the vein through the supraclavicular incision. The lumen of the vein is evaluated, and if the degree of intimal scar is not excessive, then a vein patch angioplasty is appropriate. The patch material can either be from the patients’ saphenous vein harvested from the thigh, or a piece of cryopreserved femoral vein. This is secured to the subclavian vein with running 5-0 or 6-0 polypropylene suture (Ethicon Inc. Sommerville, NJ).
If the lumen of the subclavian vein is densely fibrotic, then the segment is excised and a 10- to 14-mm conduit of cryopreserved femoral vein is inserted. A proximal end-to-side anastomosis is constructed between the conduit and the junction between the jugular and innominate veins using running 5-0 or 6-0 polypropylene suture. The conduit is then passed under the clavicle, and a beveled distal end-to-end anastomosis between the conduit and the subclavian vein is performed through the infraclavicular incision laterally.
Vascular Reconstruction for ATOS
Through the supraclavicular incision the subclavian artery is mobilized proximally to the level of the vertebral artery. A silastic vessel loop is passed around the artery at this level. Through the infraclavicular incision the distal subclavian artery is mobilized by releasing a tight fascial band often found around the outer portion of the artery. Small arterial branches may need to be divided and ligated with 5-0 polypropylene suture ligatures. Distally the axillary artery is controlled with a silastic vessel loop. The patient is then systemically heparinized with 5,000 units of intravenous heparin, which is allowed to circulate for 5 minutes. Vascular clamps are then placed on the proximal subclavian and axillary arteries. The artery is transected distal to the subclavian clamp, allowing an adequate cuff for creation of the proximal anastomosis. The artery including the aneurysm is then dissected out and removed from underneath the clavicle. The specimen is transected distally and removed. This is opened on the back table to inspect the aneurysm for signs of ulceration and thrombus.
The conduit of choice for replacement of the subclavian artery is ring-reinforced polytetrafluoroethylene (PTFE). Size of the conduit varies with the patient, but most commonly a 6-mm graft is used, which is passed through the infraclavicular tunnel. There may be bands of tissue that need to be divided to allow easy passage of the graft. A proximal end-to-end anastomosis to the subclavian artery is performed with two 5-0 polypropylene sutures, with one placed at the heel and one at the toe of the anastomosis. These sutures run in a nonlocking continuous fashion to complete the anastomosis. An antegrade flushing maneuver is then performed. Distally the graft is precisely trimmed to prevent both tension and kinking of the conduit. A distal end-to-end anastomosis between the axillary artery and the ringed PTFE graft is then performed in a similar fashion to the proximal one. Antegrade and retrograde flushing maneuvers are each performed, and the graft is flushed with heparinized saline. The clamps are then removed to re-establish flow to the axillary artery. The graft pulse is palpated, and flow in the distal artery is evaluated by Doppler signal.
Wound Closure
The surgical field is inspected, and hemostasis is achieved with bipolar cautery. This is critical, as a postoperative hematoma can lead to nerve irritation and potentially increased scar formation. The function of the phrenic nerve is again confirmed with a nerve stimulator. A no. 15 round closed suction drain is placed through a separate stab wound laterally to the supraclavicular incision, and positioned in the bed of the resected first rib. A second Blake drain can be used laterally to the infraclavicular incision if necessary. If there is an entry into the pleural space, a no. 14 red rubber catheter is placed through this entry into the pleural space.
After a final inspection for hemostasis, the omohyoid muscle and scalene fat pad are returned to their normal positions. The infraclavicular wound is closed by reapproximating the pectoralis major muscle fibers with running 3-0 Vicryl suture (Ethicon Inc. Sommerville, NJ). This is followed with a second layer of subcutaneous tissue closed in a similar fashion. The platysma muscle at the supraclavicular incision is reapproximated from medially to laterally with a running 3-0 Vicryl suture. Before tying this suture, the pleural space is evacuated by providing a sustained positive-pressure breath while suction is intermittently applied to the red rubber catheter. This catheter is then withdrawn from the wound. Suction is then applied to the wound drain via a vacuum bulb. The stitch for the platysma is then tied, and the skin of both incisions is closed with a subcuticular 4-0 Vicryl suture. A sterile dressing is then applied, which remains on for 24 hours.
POSTOPERATIVE MANAGEMENT
VTOS patients who have undergone vascular reconstruction require the initiation of anticoagulation once the risk of surgical bleeding has abated. Therapy with warfarin is typically started on the third or fourth postoperative day. Low–molecular-weight heparin is started at the same time and continued until the patient is in therapeutic range from the warfarin. ATOS patients are typically placed on an adult dose aspirin in this same time frame.
Patients with VTOS will undergo a venogram within the first few weeks postoperatively. During that procedure, a diagnostic venogram is performed on the contralateral side. While it is uncommon that significant disease is identified on the contralateral side, it occurs often enough to justify the mild inconvenience of this additional procedure. Immediate postoperative imaging is not required for ATOS patients, but the author’s practice has been to obtain a CT angiogram of the chest every 1 to 2 years.
COMPLICATIONS
Complications following surgical treatment of TOS are fortunately uncommon. Infections inherent to all surgical procedures such as bleeding and wound infection occur less than 2% of all cases. The more dreaded complication of nerve injury, from either traction injury or less commonly nerve transection, is reported to occur in 1% to 3% of all cases. This can involve the phrenic nerve (reportedly more common following supraclavicular approach) or the brachial plexus. A postoperative pneumothorax can occur regardless of approach, and is treated with either observation or tube decompression depending upon the size and clinical progression. An uncommon complication includes increased lymphatic drainage from either disruption of a small lymphatic branch or the thoracic duct. Low-volume lymphatic drainage (less than 200 mL) may be treated with a low-fat diet and continued observation. Outputs greater than 200 mL on a low-fat diet may require neck re-exploration for ligation of the leaking channel.
RESULTS
For VTOS, vein patency and freedom from symptoms occur in greater than 80% of cases, with most series approaching 100%. The cumulative experience for surgical treatment of ATOS also shows primary and secondary patency rates in the 90% to 100% range.
CONCLUSIONS
Familiarity with vascular reconstruction techniques is critical in the management of complex cases of VTOS and all cases of ATOS. Particularly for VTOS, where there may be uncertainty regarding the need for such techniques, preoperative awareness and preparation are mandatory in achieving a successful outcome.
Recommended References and Readings
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