DEFINITION

The anterior approach can be used to access the thoracic spine for decompression, deformity correction, and stabilization.

This approach allows for access to treat conditions such as intervertebral disc herniation, infection, tumor, and trauma.1

 

 

ANATOMY

 

The thoracic spinal cord may have a tenuous blood supply, particularly in patients with congenital anomalies and kyphosis.

 

The midthoracic cord represents a watershed zone for vascularity. The artery of Adamkiewicz supplies the thoracic cord but can have a variable origin. Its origin is usually (80%) from the left side at the T10 level but can

vary from T5 to L5.2

 

Because of the thoracic spine's tenuous blood supply and the potential for anterior spinal artery compression caused by thoracic disc herniations, indirect approaches were developed, obviating the need for wide laminectomy and direct visualization of the cord. The goal of these techniques, including the posterolateral transpedicular and transthoracic anterior approaches, is to minimize direct cord manipulation via retraction and prevent subsequent microcontusion and cord ischemia.

 

SURGICAL MANAGEMENT

Preoperative Planning

 

Location of pathology is a key element to choosing the optimal approach to the thoracic spine.

 

 

In terms of disc pathology, evidence has shown that more axially located disc herniations are better treated with an anterior approach, whereas a posterolateral approach is better suited for lateral or foraminal disc herniations.

 

Radiographs of the thoracic spine and chest should be obtained to determine the level of surgery and help in “rib counting.”

 

 

It is often helpful to obtain lumbar radiographs also to determine the number of lumbar segments below the most distal thoracic rib. Knowing this information preoperatively helps in counting “up” from the sacrum intraoperatively if needed.

 

In the absence of obvious bony pathology such as fractures, infections, or tumors, it is very easy to inadvertently localize the wrong level in the thoracic spine. The surgeon should be sure to have a strategy for

intraoperative level identification based on careful scrutiny of radiographs and magnetic resonance imaging (MRI) or computed tomography (CT) scans before surgery, understanding that the quality of intraoperative fluoroscopy may not be optimal.

 

When obtaining an MRI to better understand the nature of the pathology in relation to the thoracic spinal cord, the surgeon should ask for a topogram to be performed so that there is no question as to the level or levels of involvement.

 

On CT or MRI scans, the surgeon should pay close attention to the position of the aorta and inferior vena cava, especially on the axial cuts, as this may affect the side from which the spine is approached, especially if a corpectomy will be performed.

 

Anesthesia considerations include the use of an oral gastric tube and double-lumen endotracheal tube, which allows for collapse of the ipsilateral lung.

 

 

If the surgical site is T10 or caudal, selective deflation of the ipsilateral lung is usually not necessary. Additionally, a left-sided approach may prove more advantageous at the thoracolumbar junction, as the elevated right hemidiaphragm may prevent adequate exposure.

 

If the surgical site is proximal to T10, selective deflation is helpful in keeping the lung out of the field, but it may lead to more postoperative issues with atelectasis.

 

We routinely use neurologic monitoring when performing thoracic operations.

 

Positioning

 

The patient should be in the lateral decubitus position with the arms in prayer position.

 

The thorax vertex should be positioned over the break of the bed, all pressure points should be padded, pillows should be placed between legs and arms, and an axillary roll should be used to prevent compression of the axillary vessels (FIG 1).

 

The operating surgeon typically stands behind the patient during the exposure. However, it may be helpful to stand in front of the patient when performing the decompression,

 

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as the line of sight into the spinal canal is better from that vantage point.

 

 

 

FIG 1 • Patient placed in the lateral decubitus position. It is important to ensure that all bony prominences are well padded.

 

Approach (Right versus Left)

 

Considerations for thoracic approaches include the following:

 

 

Approach from the side of herniation in cases of posterolateral or lateral herniation.

 

Look at the axial CT or MRI scans to determine the location of the heart and great vessels. In most thoracic cases, these structures are either on the left or central. Thus, all other factors being equal, a right-sided approach is favored in most cases.

 

In the distal thoracic spine (eg, T10-T12), the elevated right hemidiaphragm and liver may be in the way of a right-sided approach. Because it is a bit more difficult to retract the liver than the kidney or spleen, a left-sided approach may be favorable.

 

Considerations for thoracolumbar approaches include the following:

 

 

The left-sided approach is generally favored, as it is easier to mobilize the great arteries (aorta, iliacs) from their left central position to the right rather than mobilizing the great veins (which tend to be further to the right).

 

TECHNIQUES

• Anterior Thoracic Approach from T1 to T4

For upper thoracic exposures, a right-sided approach is preferred to avoid the heart.

 

 

The surgeon makes a curved skin incision below the tip of the scapula (TECH FIG 1A).

 

This incision is carried down to the latissimus dorsi muscle and then the latissimus is incised, leaving a cuff of the muscle on the scapula for later closure (TECH FIG 1B).

 

A large retractor (ie, Richardson retractor) can then be held by the assistant while the surgeon incises the periosteum over the appropriate rib and then resects the rib as far anteriorly and posteriorly as possible (TECH FIG 1C).

 

 

 

TECH FIG 1 • Anterior thoracic approach from T1 to T4. A. A curved incision should be made just under the tip of the scapula. B. The incision is carried down to the latissimus dorsi. A cuff of muscle is left attached to the scapula for repair upon closure. (continued)

 

 

At this point, the chest is entered through the rib bed and a Finochietto or Omni retractor can be placed, with one of the blades holding the scapula up and out of the way.

 

Now the lung can be deflated and retracted anteriorly and inferiorly (TECH FIG 1D).

 

The pleura overlying the spine is now sharply incised. Placing suture into the edges of the pleura makes subsequent closure easier.

 

Segmental vessels are identified and ligated as needed, and the vertebral bodies (the “valleys”) and disc spaces (the “hills”) are identified.

 

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TECH FIG 1 • (continued) C. The surgeon incises the periosteum over the rib. D. The deflated lung is retracted anteriorly and inferiorly while protecting the esophagus and great vessels.

• Anterior Thoracic Approach from T5 to T12

   

  The surgeon should plan the incision directly over the desired rib (ie, 10th rib for T9-T10 disc). A curvilinear skin incision is made along the path of the rib from the anterior border of the latissimus dorsi to the costochondral junction anteriorly (TECH FIG 2A).

   

  Due to the downslope of the ribs, it is generally preferable to make an incision that is more proximal rather than distal. If the incision is too distal, the ribs may impede access to the more proximal segment, necessitating a second thoracotomy. In contrast, it is easier to access levels that are distal to the rib that is resected. Thus, if in doubt as to the exact rib to be resected, the incision should be made more proximal.

   

  Skin and subcutaneous fat are incised to expose the trapezius and latissimus dorsi.

   

  The trapezius and latissimus dorsi are divided in line with the incision using electrocautery. The rhomboids may need to be split to gain more exposure cephalad.

   

  Once the correct rib is identified, the surgeon divides the periosteum over the upper border of the rib to avoid injury to the intercostal nerve and vessels (TECH FIG 2B).

   

  The rib is stripped subperiosteally anteriorly to the costochondral angle and as far posteriorly as possible (TECH FIG 2C).

   

  The rib is removed with a rib cutter and passed off the field. The rib is cut at the midaxillary line anteriorly and as far posteriorly as possible. The rib can be used as a strut graft or autologous bone graft.

   

  The periosteal rib sleeve and parietal pleura are incised to enter the thorax. A rib spreader is placed to hold the ribs apart (TECH FIG 2D).

   

  The ipsilateral lung is deflated and retracted medially to expose the parietal pleura overlying the spine.

   

  The parietal pleura overlying the spine is incised and retracted medially. Stitches can be placed in the parietal pleura to make closure easier. The underlying segmental vessels are visualized (TECH FIG 2E).

   

  The segmental arteries arising from the aorta can run in an ascending, recurrent, horizontal, or descending direction depending on the level of involvement.

   

  The surgeon carefully ligates as few segmental vessels as possible to gain adequate exposure to the spine. Ligating more segmental vessels than necessary places the spinal cord at increased risk for ischemia because the thoracic spinal cord has a tenuous blood supply (TECH FIG 2F).

   

  In cases of suspected vascular anomalies, such as congenital kyphosis, the surgeon should consider temporary occlusion of the segmental vessels and check evoked potentials before vessel ligation. If a patient has had a prior spine exposure on one side, the surgeon should be wary of ligating the contralateral segmental vessels. Instead, the surgery should be performed through the previously exposed side, or a preoperative angiogram should be obtained to identify the important arterial feeders to the spinal cord.

   

  The intrathoracic vertebral bodies and intervertebral discs are now exposed. To gain access to the posterior intervertebral disc, the rib head may need to be removed.

   

   

  The costotransverse and costovertebral articulations are removed to excise the rib head (TECH FIG 2G). The soft tissues overlying the transverse process, pedicle, and vertebral body are removed.

   

  The superior edge of the pedicle is identified and followed back to the intervertebral space.

   

  The superior edge of pedicle is burred to expose the posterior intervertebral disc and lateral margin of the dura (TECH FIG 2H).

   

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  TECH FIG 2 • Anterior thoracic approach from T5 to T12. (In these images, the patient's head is to the upper left and the patient's back is toward the surgeon.) A. The incision is planned directly over the rib. Injecting the subcutaneous tissues with a combination of anesthetic and epinephrine aids in hemostasis. B. The skin and subcutaneous tissues have been divided, exposing the desired rib. C. Subperiosteal exposure of the rib before excision. Note the thin parietal pleura beneath the rib bed. D. After excision of the rib the parietal pleura is entered, exposing the ipsilateral lung. E. The parietal pleura and the underlying segmental vessels.

  F. (continued)

   

   

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  TECH FIG 2 • (continued) The vertebral bodies and intervertebral discs are exposed after segmental arteries are ligated, and the overlying soft tissues are removed. Once the costotransverse and costovertebral articulations are excised (G), the rib head can be removed with a high-speed burr (H).

• Mini Transthoracic Anterior Approach

  Exposure

   

  Patient is positioned in lateral decubitus.

   

  Fluoroscopic evaluation is used to identify desired levels to gain access to, and the level of these vertebral bodies are marked with a skin pen directly over their position on a lateral projection.

   

  A skin incision is made parallel to the ribs medially extending 5 to 10 cm laterally.

   

  Using a pair of curved scissors, bluntly split the latissimus dorsi and serratus anteriorly in line with their fibers until you encounter the underlying rib.

   

  Using the rib spreading, create a space between the two ribs.

   

  The rib need only be resected if exposure is not adequate with the rib spreader

   

  Deflate the lung and sharply split the visceral pleura and retract it medially to expose the desired vertebra

  and confirm with fluoroscopy.

   

  Bring the microscope into the field and identify the costovertebral junction.

   

  Using a high-speed burr, resect the rib head, superolateral portion of the caudal vertebral body and the inferolateral portion of the cranial vertebra and the superior portion of the pedicle below the desired disc, exposing the longitudinal ligament, which is incised to provide clear visualization of the intervertebral disc (TECH FIG 3).

  Detaching the Diaphragm

   

  Exposure of T12-L1 may require detaching the diaphragm.

   

   

  The diaphragm inserts and originates from the xiphoid and the inferior six ribs. The lateral arcuate ligament arises from the transverse process of L1.

   

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  TECH FIG 3 • In the mini transthoracic approach, a 5- to 10-cm incision is made just cranial to the 10th rib through the parietal and visceral pleura, bypassing the inflated lung. This approach provides access to the T9-T10 disc space to allow for a variety of procedures, including corpectomy and plating, interbody fusion, and discectomy.

   

   

  The crura extend more distally on the right.

   

  The diaphragm is innervated centrally by the phrenic nerves.

   

  The surgeon starts at the costal angle and incises the costodiaphragmatic reflection until extraperitoneal fat is visualized.

   

  The diaphragm is divided off the anterior chest wall (TECH FIG 4). The surgeon should leave a 1- to 2-cm cuff of diaphragm on the anterior chest wall to allow for diaphragm repair at closure. To avoid diaphragm denervation, the diaphragm should be incised only at its periphery. The diaphragm is split up to the lateral arcuate ligament.

   

   

   

  TECH FIG 4 • The diaphragm is incised circumferentially 2 cm from its peripheral attachment to the chest wall. Marker stitches should be placed for resuturing upon closure.

   

   

   

  The medial and lateral crura are detached, exposing the underlying peritoneum. The peritoneum is swept medially until the retroperitoneal space is visualized.

   

  The surgeon bluntly dissects and sweeps the fascia of Gerota medially to expose the spine and the overlying parietal pleura.

   

  The aorta and vena cava are identified.

   

   

  The surgeon can elevate the psoas muscle if needed. The parietal pleura is incised to expose the spine.

• Thoracoabdominal Retroperitoneal Lumbar Spine Approach from T10 to L3

 

The patient is positioned in the lateral decubitus position with the right side down. The approach should be

 

made from the left side to avoid the liver and inferior vena cava. The crura of the diaphragm are detached as described earlier.

 

An oblique incision is made from the quadratus lumborum to the lateral border of the rectus abdominis (TECH FIG 5).

 

This approach can be extended to L5 in most patients and even to S1 in those with low-riding iliac crests.

 

The subcutaneous tissue is incised, and the fascia of the external oblique is divided.

 

 

The external and internal obliques, transverse abdominis, and transversalis fascia are incised. The peritoneum is exposed and bluntly reflected anteriorly.

 

 

The ureter is identified and reflected anteriorly with retroperitoneal fat. The vertebral bodies, psoas, and great vessels are identified.

 

 

The genitofemoral nerve lies on anterior psoas muscle, and excessive traction should be avoided. The segmental vessels that lie over the middle of the vertebral bodies are identified and ligated.

 

 

The psoas is bluntly dissected off the vertebrae and retracted laterally. The vertebral body, pedicle, and neuroforamen can be visualized.

 

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TECH FIG 5 • Thoracoabdominal approach. A. A curvilinear incision is made over the 10th rib, and the muscle layers are identified. B. The retroperitoneal space is entered through the costal cartilage after

removing the 10th rib. C. The light areolar tissue that signifies the retroperitoneal space is identified, and the

peritoneum is mobilized from the undersurface of the diaphragm and abdominal wall as well as the aorta. D.

Exposure of the spine is done after ligation of segmental vessels.

 

 

 

PEARLS AND PITFALLS

 

Neurologic compromise

• The surgeon should consider preoperative angiography before left-sided approaches between T8 and T12 to identify the artery of Adamkiewicz and prevent spinal cord infarction.

• The surgeon should consider temporarily clamping the segmental arteries before ligation and assessing for changes in evoked potentials to avoid vascular catastrophe because blood supply to the spinal cord is tenuous in the thoracic region, especially in the “critical zone” from T4 to T9.

   

  Avoiding wrong-level surgery

• The surgeon should place a hand under the scapula and count rib spaces. The first rib is often difficult to feel, but the second rib space is the largest.

• Preoperative anteroposterior and lateral chest radiographs can aid in rib counting, especially in kyphotic patients.

   

  Exposure ▪ Using a double-lumen endotracheal tube will allow deflation of the ipsilateral lung and improve exposure.

  • Detaching the psoas muscle off the transverse processes can improve exposure of the intervertebral disc space and neuroforamen. The transverse processes can also be removed to further increase exposure.

  • Flexing the patient's hips can decrease tension on the psoas and improve visualization of the lumbar spine.

  • More ribs may need to be excised to gain better exposure, especially in older patients, in whom the ribs may not be as compliant to the rib spreader.

  • From T2 to T5, it may help to detach the serratus anterior muscle from the anterior chest wall and reflect it cephalad to gain better exposure. The surgeon should avoid cutting the long thoracic nerve at this level.

  • If scapular manipulation is needed to gain better exposure, the rhomboids, trapezius, and dorsal scapular muscles can be divided, allowing the scapula to be mobilized laterally.

 

Visceral injury

• When approaching from the right side, the surgeon should dissect the soft tissues away from the spine as close as possible to the bone with a blunt gauze or finger to prevent injury to the cisterna chyli and thoracic duct.

 

 

 

POSTOPERATIVE CARE

 

Chest tubes are left in place until output is less than 150 mL over 24 hours.

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COMPLICATIONS

The exiting nerve root can be injured while removing the pedicle. Vascular injury

Intercostal neuralgia Atelectasis Neurologic injury Wrong-level surgery

Significant bleeding can be encountered when entering the epidural space. Visceral injury

 

 

REFERENCES

1. Arts MP, Bartels RHMA. Anterior or posterior approach of thoracic disc herniation? A comparative cohort of mini-transthoracic discectomy versus transpedicular discectomy. Spine J 2014;4(8):1654-1662.

    

    

2. Grace RR, Mattox KL. Anterior spinal artery syndrome following abdominal aortic aneurysmectomy. Case report and review of the literature. Arch Surg 1977;112:813-815.