And Lumbar Spine

Mohammad E. Majd, MD, Douglas H. Musser, DO, and Richard T. Holt, MD

1. What are the indications for an anterior surgical approach to the thoracic and lumbar spine?

• Anterior spinal decompression and stabilization (e.g. tumor, infection, fracture)

• Anterior correction of spinal deformity (e.g. scoliosis)

• To enhance arthrodesis (e.g. for treatment of posterior pseudarthrosis)

• Anterior release or destabilization to enhance posterior spinal deformity correction (e.g. for treatment of severe, rigid spinal deformities)

• To improve biomechanics of posterior implant constructs (e.g. to restore anterior column load sharing when anterior spinal column integrity has been compromised)

• To enhance restoration of sagittal alignment

• To eliminate asymmetric growth potential (e.g. congenital scoliosis)

2. List situations in which an anterior thoracic or lumbar surgical approach may not be advised.

• Patients who have undergone prior anterior surgery to the same spinal region. Dissection will be difficult because of adhesions and will increase the risk of visceral or vascular injury

• Patients with poor pulmonary function may have an unacceptable risk of complications after an anterior thoracic approach

• Patients with extensive calcification of the aorta are not ideal candidates for anterior lumbar approaches. Extensive mobilization of the great vessels is required and is associated with an increased risk of vascular complications

3. What anterior surgical approaches may be used to expose the upper thoracic spine (T1-T4)?

Access to the T1 vertebral body is generally possible through a standard anterior cervical approach medial to the sternocleidomastoid muscle. Anterior exposure between T1 and T3 is challenging. Options for exposure include a modified sternoclavicular approach, a third-rib thoracotomy, or a median sternotomy. Each approach has advantages and disadvantages, depending on patient anatomy, type of spinal pathology, number of levels requiring exposure, and type of surgery required.

4. What standard surgical approach is used to expose the anterior aspect of the spine between T2 and T12?

The anterior aspect of the thoracic spine between T2 and T12 is approached by a thoracotomy.

5. What is the preferred method of positioning a patient for an approach to the anterior thoracic spine?

The lateral decubitus position with an axillary roll under the down-side axilla (Fig. 26-1). Many surgeons prefer approaching the thoracic spine from the left side because it is easier to work with the aorta than the vena cava.

Figure 26-1. Positioning of the patient for an anterior approach to the thoracic spine. (From Majd ME, et al. Anterior approach to the spine. In: Margulies JY, Aebi M, Farcy JP, editors. Revision Spine Surgery. St. Louis: Mosby; 1999. p. 139.)

However, the type of spinal pathology may dictate the side of approach. For example, in the anterior treatment of scoliosis, the surgical approach should be on the convex side of the curve.

6. What factors determine the level of rib excision when the thoracic spine is exposed through a thoracotomy approach?

If the procedure requires exposure of a long segment of the thoracic spine (e.g. for treatment of scoliosis or kyphosis), a rib at the proximal end of the region requiring fusion is removed. For example, removal of the fifth rib allows exposure from T5 to T12.

If the patient requires treatment of a single vertebral body lesion, the rib two levels proximal to the involved vertebral body is removed. Alternatively, the rib directly horizontal to the target vertebral level at the mid-axillary line on the anteroposterior (AP) thoracic spine x-ray is removed.

If the surgeon requires only a limited exposure (e.g. to excise a thoracic disc herniation), the rib that leads to the disc should be removed (e.g. the eighth rib is removed for a T7-T8 disc herniation).

7. What are some tips for counting ribs after the chest cavity has been entered during a thoracotomy?

The first cephalad palpable rib is the second rib. The first rib is generally located within the space occupied by the second rib and cannot be easily palpated. The distance between the second and third rib is wider than the distance between the other ribs. Application of a marker on a rib with subsequent radiographic verification is important to identify the level of exposure.

8. During an anterior exposure of the thoracic spine, the parietal pleura is divided longitudinally over the length of the spine. What landmarks may be used for identification of critical anatomic structures?

The vertebral bodies are located in the depressions, and the discs are located over the prominences (Fig. 26-2). The segmental vessels are identified as they cross the vertebral bodies (depressions). This has been referred to as the hills-and-valleys concept (i.e. discs are the hills and vertebral bodies are the valleys).

Figure 26-2. Intraoperative view of the anterior exposure of the thoracic spine. (From Majd ME, Harkess JW, Holt RT, et al. Anterior approach to the spine. In Margulies JY, Aebi M, Farcy JP, editors. Revision Spine Surgery. St. Louis: Mosby; 1999. p. 142.)

Figure 26-2. Intraoperative view of the anterior exposure of the thoracic spine. (From Majd ME, Harkess JW, Holt RT, et al. Anterior approach to the spine. In Margulies JY, Aebi M, Farcy JP, editors. Revision Spine Surgery. St. Louis: Mosby; 1999. p. 142.)

9. After the initial surgical exposure, what study should be obtained by the surgeon before proceeding with an anterior discectomy or corpectomy?

A radiograph or fluoroscopic view should be obtained to confirm that the correct spinal level has been exposed. Even if one knows anatomy very well, mistakes can be made. This strategy is very important because wrong-level surgery is not an uncommon claim in malpractice lawsuits against spine surgeons.

10. Are there any risks associated with ligation of the segmental artery and vein as they cross the vertebral bodies?

Ligation of the segmental vessels is required to obtain comprehensive exposure of the vertebral body. Unilateral vessel ligation is safe. However, ligation too close to the neural foramina may damage the segmental feeder vessels to the spinal cord. Temporary and reversible occlusion of segmental vessels may be used when the risk of paraplegia is high (congenital kyphoscoliosis, severe kyphosis, patients who have undergone prior anterior spinal surgery with vessel ligation). If there is no change in spinal potential monitoring after temporary vessel occlusion, permanent ligation may be carried out safely.

11. After thoracotomy, placement of a chest tube is necessary. What are the proper placement criteria?

The chest tube should be placed at the anterior mid-axillary line at least two interspaces from the incision. Placement of the chest tube too posteriorly has potential for kinking and can cause subsequent blockage of drainage in the supine position. In addition, posterior placement is uncomfortable and painful when the patient lies supine.

12. During a thoracic spinal exposure via thoracotomy, a creamy discharge is noted in the operative field. What anatomic structure has been violated?

The thoracic duct. Thoracic duct injuries are uncommon. Most injuries heal without intervention. Repair or ligation of the area of leakage can be attempted. Leaving the chest tube in place for several additional days can be considered. This strategy may help to avoid a chylothorax by allowing the thoracic duct to heal. If a chylothorax should develop postoperatively, treatment options include chest tube drainage, a low-fat diet, or hyperalimentation.

13. What is the standard surgical approach for exposure of the anterior aspect of the spine between T10 and L2 (thoracolumbar junction)?

Exposure in this region is achieved through a transdiaphragmatic thoracolumbar approach, also termed a thoracophrenolumbotomy (Fig. 26-3). The patient is positioned as for a thoracotomy. The incision typically begins over the tenth rib and extends distally to the costochondral junction, which is transected. The incision extends distally into the abdominal region as required. Dissection through the layers of the abdominal wall is carried out, and the peritoneum is mobilized from the undersurface of the diaphragm. The diaphragm is then transected from its peripheral insertion. The peritoneal sac and its contents are mobilized off the anterolateral aspect of the lumbar spine. This strategy provides the surgeon with wide continuous exposure of the spine across the two major body cavities (thoracic cavity and abdominal cavity).

Figure 26-3. A, Positioning of the patient for an anterior approach to the thoracolumbar junction. B, Intraoperative view of exposure of the thoracolumbar region. Note how the diaphragm requires detachment from its insertion along the lateral chest wall. (From Majd ME, et al. Anterior approach to the spine. In Margulies JY, Aebi M, Farcy JP, editors. Revision Spine Surgery. St. Louis: Mosby; 1999. p. 146, 147.)

14. A patient with an L1 lesion underwent an uneventful left-sided thoracoabdominal approach and corpectomy of L1. After surgery the patient complained of weakness of left hip flexion and difficulty in climbing stairs. What is the most probable cause of this problem?

In this case, the most probable cause is retraction and mobilization of the psoas muscle causing trauma to the muscle during surgery. The patient's symptoms should gradually improve without further treatment. The psoas major muscle attaches on both sides to the last thoracic and all five lumbar vertebral bodies. The psoas major is innervated by the anterior rami of the upper lumbar nerves. Its principal actions are flexion and medial rotation of hip joint. In addition,

Figure 26-3. A, Positioning of the patient for an anterior approach to the thoracolumbar junction. B, Intraoperative view of exposure of the thoracolumbar region. Note how the diaphragm requires detachment from its insertion along the lateral chest wall. (From Majd ME, et al. Anterior approach to the spine. In Margulies JY, Aebi M, Farcy JP, editors. Revision Spine Surgery. St. Louis: Mosby; 1999. p. 146, 147.)

Diaphragm the muscle flexes the lumbar spine both anteriorly and laterally. In the sitting position, the psoas muscle is relaxed and permits kyphosis of the lumbar spine. In the standing position, the psoas muscle is taut and thus induces physiologic lumbar lordosis.

15. What are the surgical approach options for exposure of the lumbar spine and lumbosacral junction?

The most commonly used open surgical approaches to the lumbar spine and lumbosacral junction are the retroperitoneal flank approach and the medial incision retroperitoneal approach. A minimal incision direct lateral approach has recently been popularized and is applicable to all lumbar levels except L5-S1. Less commonly used approaches include the transperitoneal approach and the laparoscopic approach.

16. Describe a medial incision retroperitoneal approach to the lumbar spine.

In a medial incision retroperitoneal approach (Fig. 26-4), the patient is positioned supine. A vertical left paramedian or midline incision is commonly used. Transverse or oblique incisions are also options. The rectus sheath is incised, and the muscle is retracted to expose the transversalis fascia. The fascia is incised to enter the retroperitoneal space. Alternatively, if exposure of only L5-S1 is required, the retroperitoneal space can be entered below the arcuate line, thus avoiding the need for incising any fascia. The peritoneal sac is swept off the abdominal wall and anterior aspect of the spine to complete initial exposure.

Figure 26-4. Anterior exposure of the lumbar spine through a paramedian retroperitoneal approach. A, A longitudinal incision is made through the fascia overlying the rectus muscle to expose the muscle belly. B, The arcuate ligament marks the point of entry into the retroperitoneal space. Using a sponge stick caudad to the ligament in a gentle sweeping motion, the surgeon pushes down and toward the midline to free the peritoneal sac from the fascia and displace it toward the midline, thereby exposing the spine. (From Majd ME, et al. Anterior approach to the spine. In Margulies JY, Aebi M, Farcy JP, editors. Revision Spine Surgery. St. Louis: Mosby; 1999. p. 151.)

Figure 26-4. Anterior exposure of the lumbar spine through a paramedian retroperitoneal approach. A, A longitudinal incision is made through the fascia overlying the rectus muscle to expose the muscle belly. B, The arcuate ligament marks the point of entry into the retroperitoneal space. Using a sponge stick caudad to the ligament in a gentle sweeping motion, the surgeon pushes down and toward the midline to free the peritoneal sac from the fascia and displace it toward the midline, thereby exposing the spine. (From Majd ME, et al. Anterior approach to the spine. In Margulies JY, Aebi M, Farcy JP, editors. Revision Spine Surgery. St. Louis: Mosby; 1999. p. 151.)

17. What are the advantages and disadvantages of a medial incision retroperitoneal approach?

ADVANTAGES

• Provides excellent exposure from L2 through S1

• This muscle-sparing approach is less painful than a muscle-incising approach

• The direct anterior exposure facilitates graft placement and anterior decompression

DISADVANTAGES

• It cannot easily provide exposure above L2

• The anterior peritoneum is thin and easily perforated in this area

• Use of this approach is best limited to cases with moderate spinal deformity (scoliosis <40° or kyphosis <25°)

18. Describe a retroperitoneal flank approach.

In the retroperitoneal flank approach (Fig. 26-5), the patient is typically positioned in the lateral decubitus position with the left side upward. After an oblique skin incision, the layers of the abdominal wall are transected (external oblique, internal oblique, and transversus abdominis). The transversalis fascia is incised, and the peritoneum is mobilized medially to permit exposure of the psoas muscle, which overlies the anterolateral aspect of the spine.

Psoas m.

Aorta

Figure 26-5. The retroperitoneal flank approach to the lumbar spine may be performed with the patient in the lateral position or the supine position. Dissection passes anterior to the psoas muscle to expose the spine. (From An HS. Surgical exposure and fusion techniques of the spine. In An HS, editor. Principles and Practice of Spine Surgery. Baltimore: Williams & Wilkins; 1985. p. 56.)

Aorta

Figure 26-5. The retroperitoneal flank approach to the lumbar spine may be performed with the patient in the lateral position or the supine position. Dissection passes anterior to the psoas muscle to expose the spine. (From An HS. Surgical exposure and fusion techniques of the spine. In An HS, editor. Principles and Practice of Spine Surgery. Baltimore: Williams & Wilkins; 1985. p. 56.)

19. What are the advantages and disadvantages of the retroperitoneal flank approach?

ADVANTAGES

• Allows exposure of the entire lumbar spine and lumbosacral junction

• The extensile nature of this approach allows exposure above L2

• Useful for cases of severe spinal deformity (scoliosis >40° or kyphosis >25°)

DISADVANTAGES

• This muscle-incising approach is more painful than a muscle-splitting approach

• Muscle hernias can occur

• Exposure of the L5-S1 disc can be more difficult than with the medial incision approach

20. What are the disadvantages of a transperitoneal approach?

Extensive mobilization of the abdominal organs and packing of the intestinal contents out of the operative field increases operative time and complications. Manipulation of the abdominal contents increases the risk of postoperative ileus and intestinal adhesions. There is also a higher risk of retrograde ejaculation in male patients compared with the retroperitoneal approach.

21. What are some of the potential complications of an anterior approach to the lower lumbar and lumbosacral spine?

• Surgical sympathectomy • Deep vein thrombosis

• Vascular injury • Incisional hernia

• Ureteral injury • Retrograde ejaculation

22. During the retroperitoneal exposure of the lumbosacral spine, approximately what percentage of cases is complicated by vascular injuries?

Vascular injury rates during anterior lumbar spine surgery range from 1% to 15%. These intraoperative injuries are usually recognized during surgery and repaired with simple suture techniques. The rates of postoperative morbidity and major complications from deep venous thrombosis or arterial embolization are low.

23. What is the most important factor in avoiding vascular injury during anterior lumbar spine surgery?

Knowledge of the relationship of vascular structures to the anterior lumbosacral spine is the key to avoiding vascular complications during anterior exposure of the spine (Fig. 26-6).

First, the surgeon should plan exactly how many anterior disc spaces require exposure. If exposure of only the L5-S1 disc is required, the necessary dissection is limited. However, if exposure of the L4-L5 level or multiple anterior disc levels is required, extensive vascular mobilization is necessary and the exposure will be complex.

Next, the surgeon should assess the level of the bifurcation of the aorta and vena cava. Most commonly the great vessels bifurcate at the L4-L5 disc space or at the upper part of the L5 vertebral body. However, the location of the bifurcation may vary from L4 to S1.

For exposure of the L5-S1 disc, it is necessary to ligate the middle sacral artery and vein, which lie directly over the L5-S1 disc. Exposure of the L5-S1 disc is usually achieved by working in the bifurcation of the aorta and vena cava.

For exposure of the L4-L5 disc it is generally necessary to mobilize branches originating from the distal aorta and vena cava as well as from the external iliac artery and vein. These branches tether the great vessels to the anterior aspect of the spine and limit safe left-to-right retraction of the vascular structures overlying the L4-L5 disc space.

Inf. vena cav; Common iliac a.

Abdominal a

Inf. vena cav; Common iliac a.

Abdominal a

Figure 26-6. Anterior anatomy at the lumbosacral junction. A, Anatomic structures related to the anterior L4 to S1 region—ureter, sympathetic plexus, aorta, vena cava, and bifurcation of these vessels. B, Exposure of the L5-S1 disc following ligation of the middle sacral vessels. Note that both the left and right ureters are retracted toward the right side. (From Majd ME, et al. Anterior approach to the spine. In Margulies JY, Aebi M, Farcy JP, editors. Revision Spine Surgery. St. Louis: Mosby; 1999. p. 152.)

Figure 26-6. Anterior anatomy at the lumbosacral junction. A, Anatomic structures related to the anterior L4 to S1 region—ureter, sympathetic plexus, aorta, vena cava, and bifurcation of these vessels. B, Exposure of the L5-S1 disc following ligation of the middle sacral vessels. Note that both the left and right ureters are retracted toward the right side. (From Majd ME, et al. Anterior approach to the spine. In Margulies JY, Aebi M, Farcy JP, editors. Revision Spine Surgery. St. Louis: Mosby; 1999. p. 152.)

It is especially critical to identify and securely ligate the iliolumbar vein and various ascending lumbar veins. Failure to control the vessels before attempting to retract the great vessels off the L4-L5 disc can result in uncontrolled hemorrhage and even death. The segmental vessels overlying the L4 vertebral body and proximal vertebral levels may also require ligation, depending on how many levels require exposure.

24. What is the transpsoas approach to the lumbar spine?

A surgical approach has been developed for lumbar interbody graft placement from a direct lateral approach passing through the posterior retroperitoneum and the anterior portion of the psoas muscle. Tubular retractors and electrophysiologic monitoring are integral to this approach. The technique is feasible for all lumbar levels except the L5-S1 interspace.

25. A 46-year-old man underwent implantation of two cylindrical fusion cages in the L5-S1 disc space through an anterior surgical approach. One year later, the surgeon decided to revise the cages through an anterior retroperitoneal approach because the fusion did not heal and the cages were migrating out of the disc space. During the procedure scar tissue made exposure difficult, and the surgeon was concerned that an injury to the ureter had occurred. What is the best way to evaluate for this problem? What treatment is indicated if a ureteral injury exists?

Intravenous injection of 5 mL of methylene blue can appear within 5 to 10 minutes in the surgical field and confirm the ureteral injury. Urologic consultation and repair or stenting of the ureter are required. Placement of a ureteral stent before surgery helps to identify the ureter during revision anterior surgical procedures and may help to prevent this complication.

26. A 40-year-old man underwent a L5-S1 anterior lumbar interbody fusion with implantation of an anterior fusion cage. He complains of erectile dysfunction after the procedure. What should the surgeon advise the patient?

The patient should be advised that prognosis for recovery is good because erection is not controlled by any of the neural structures that course over the anterior aspect of the L5-S1 disc. The patient's difficulty is not related to the anterior approach and other underlying causes should be evaluated.

Erection is predominantly a parasympathetic function through control of the vasculature of the penis. The parasympathetic fibers responsible for erection originate from the L1-L4 nerve roots and arrive at their target area via the pelvic splanchnic nerves. Somatic function from the S1-S4 levels is carried through the pudendal nerve.

Anterior spine surgery at the L5-S1 level has the potential to disrupt the superior hypogastric plexus. This sympathetic plexus crosses the anterior aspect of the L5-S1 disc and distal aorta. The superior hypogastric plexus controls bladder neck closure during ejaculation. Failure of closure of the bladder neck during ejaculation causes ejaculate to travel in a retrograde direction into the bladder and can result in sterility.

27. During an anterior approach to the lumbosacral junction, the Bovie is used to coagulate the middle sacral artery and vein. This technique, as opposed to bipolar electrocoagulation or a suture ligation of the middle sacral artery and vessel, increases the risk for what complication?

Retrograde ejaculation. This complication has been reported more commonly with the endoscopic approach to the lumbosacral junction than with an open surgical approach. This finding has been attributed to use of a Bovie with subsequent damage to the sympathetic plexus. Male patients undergoing an anterior L5-S1 exposure should always be forewarned of this possible complication. Many surgeons do not offer an anterior exposure to men in their reproductive years for fear of this complication and its medical/legal ramifications.

28. After the left-sided retroperitoneal approach to the lumbar spine, the patient wakes up complaining of coolness in the right lower extremity compared with the left. Palpation of pulses demonstrates good dorsalis pedis and posterior tibia pulses bilaterally, and the right leg does appear to be cooler than the left leg. How are these clinical findings explained?

The sympathetic chain lies on the lateral border of the vertebral bodies and is often disrupted during an anterior surgical exposure. A sympathectomy effect occurs and allows increased blood flow to the left leg compared with the right. This process explains the temperature increase and occasional swelling noted in the lower extremity on the side of the surgical exposure. Patients should be forewarned of this possible result of an anterior spine procedure and told that it will not impair the ultimate outcome surgery.

29. After a left-sided retroperitoneal exposure of the lumbosacral junction, the patient awakens in the recovery room complaining of increased pain in the left lower extremity. The left leg is noted to be cooler than the right leg. What test should be ordered immediately?

An arteriogram should be ordered on an emergent basis. This clinical scenario cannot be explained on the basis of a sympathectomy effect by which the ipsilateral leg on the side of the exposure becomes warmer. When the distal extremity on the side of the exposure becomes cooler, it is usually due to dislodgement of an arteriosclerotic plaque. Thus, assessment of the vasculature with an arteriogram is the study of choice to determine whether the plaque has lodged in the trifurcation in the popliteal fossa. Immediate consultation with an experienced vascular surgeon is appropriate.

30. The technique for implantation of an artificial disc requires the surgeon to place the implant as far posteriorly as possible along the vertebral endplates. During the procedure for one type of artificial disc, sequential dilators are placed in the L5-S1 interspace until a loud pop is heard or felt. This noise represents the disruption of the posterior longitudinal ligament. Aside from fainting, what should the surgeon do if a large return of blood is noted in the wound after this popping noise?

In the case of rapid bleeding after distraction and disruption of the posterior longitudinal ligament, the presumptive diagnosis is disruption of the epidural venous plexus. The most appropriate technique at this point is to place gel foam soaked with thrombin into the posterior aspect of the interspace and then remove the distraction from the interspace. After several minutes the bleeding will stop, and the procedure may continue.

Key Point

1. Knowledge of the relationship of the visceral, vascular, and neurologic structures to the anterior and lateral aspect of the spine is the key to avoiding complications during surgical exposure.

Websites

Anterior exposure of the thoracic and lumbar spine: http://archsurg.ama-assn.org/cgi/content/full/141/10/1025 Thoracotomy for exposure of the spine: http://www.ctsnet.org/sections/clinicalresources/thoracic/expert_tech-37.html

BiBLiOGRAPHY

1. DeWald RL. Anterior exposures of the thoracolumbar spine. In: Bridwell KH, DeWald RL, editors. The Textbook of Spinal Surgery. 2nd ed. Philadelphia: Lippincott-Raven; 1997. p. 253-60.

2. Kim DH, Henn JS, Vaccaro AR, et al. Surgical Anatomy and Techniques to the Spine. Philadelphia: Saunders; 2006.

3. Majd ME, Harkess JW, Holt RT, et al. Anterior approach to the spine. In: Margulies JY, Aebi M, Farcy JP, editors. Revision Spine Surgery. St. Louis: Mosby; 1999. p. 138-55.

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