Orthopedic Approachs 2022, Nov, 19 | 12:00 am

Anterolateral (Retroperitoneal) Approach to the Lumbar Spine

Anterolateral (Retroperitoneal) Approach to the Lumbar Spine‌

 

 

The retroperitoneal approach to the anterior part of the lumbar spine has several advantages over the transperitoneal approach. First, it provides access to all vertebrae from L1 to the sacrum, whereas the transperitoneal approach is very difficult to use above the level of L4. Second, it allows drainage of an infection, such as a psoas abscess, without the risk of contaminating the peritoneal cavity and causing a postoperative ileitis. Because of the arrangement of the vascular anatomy of the retroperitoneal space, however, it is slightly more difficult to reach the L5-S1 disc space using this retroperitoneal approach.

The uses of this approach include the following:

  1. Spinal fusion

  2. Drainage of psoas abscess and curettage of infected vertebral body

  3. Resection of all or part of a vertebral body and/or intervertebral disc and associated bone grafting

  4. Biopsy of a vertebral body when a needle biopsy is either not possible or hazardous

  5. Insertion of disc prosthesis

 

Position of the Patient

 

Place the patient on a radiolucent operating table in the semilateral position. The patient’s body should be at about a 45- to 90-degree angle to the horizontal, facing away from the surgeon. Keep the patient in this position throughout the surgery by placing sandbags under the hips and shoulders or by using a kidney rest brace to hold the patient. The angle allows the peritoneal contents to fall away from the incision. Alternatively, place the patient supine on the operating table and tilt the table at 45 degrees to the horizontal away from the surgeon. This position has the advantage of not putting the psoas muscle on stretch (Fig. 6-37). Ensure that you can obtain adequate radiographs of the area of the spine to be approached before prepping and draping.

 

 

 

Figure 6-37 Place the patient in the semilateral position for the anterolateral (retroperitoneal) approach to the lumbar spine.

 

The approach can be done with the left or right side up depending on whether the surgeon prefers to work on the “aortic side” or the “caval side.”

 

Landmarks and Incision

Landmarks

Palpate the 12th rib in the affected flank and the pubic symphysis in the lower part of the abdomen. Palpate the lateral border of the rectus abdominis muscle about 5 cm lateral to the midline.

Incision

Make an oblique flank incision extending down from the posterior half of the 12th rib toward the rectus abdominis muscle and stopping at its lateral border, about midway between the umbilicus and the pubic symphysis (Fig. 6-38).

 

Internervous Plane

 

No internervous plane is available for use. The three muscles of the abdominal wall (the external oblique, internal oblique, and transversus abdominis) are divided in line with the skin incision. Because all three muscles are innervated segmentally, significant denervation does not occur (Fig. 6-39).

 

Superficial Surgical Dissection

 

Deepen the incision through subcutaneous fat to expose the aponeurosis of the external oblique muscle. Divide the aponeurosis of this muscle in the line of its fibers, which is in line with the skin incision. The muscle fibers of the external oblique rarely appear below the level of the umbilicus except in very muscular patients. If they are found there, the muscle should be split in the line of its fibers (Fig. 6-40).

Next, divide the internal oblique muscle in line with the skin incision which is perpendicular to the line of its muscular fibers. This division causes partial denervation, but if the muscle is closed properly, postoperative hernias can be avoided (Fig. 6-41). Under the internal oblique muscle lies the transversus abdominis muscle. Divide this in line

with the skin incision to expose the retroperitoneal space (Figs. 6-42, 6-43, 6-47, and 6-48).

 

 

 

Figure 6-38 Make an oblique flank incision extending down from the posterior half of the 12th rib toward the rectus abdominis muscle.

 

Using blunt finger dissection, develop a plane between the retroperitoneal fat and the fascia that overlies the psoas muscle (Fig. 6-44). Gently mobilize the peritoneal cavity and its contents and retract them medially (Fig. 6-45). Carry out this dissection from either the left lower quadrant or the right upper quadrant, depending on the side that needs to be exposed.

Place a Deaver-type retractor over the peritoneal contents and retract them to the right upper quadrant. The ureter, which is attached loosely to the peritoneum, is carried forward with it.

 

Deep Surgical Dissection

Identify the psoas fascia, but do not enter the muscle. Any existing psoas abscess is easily palpable at this point. If one is found, it should be entered from its lateral side with finger dissection. Follow the abscess cavity with a finger directly to the infected disc space or spaces. If there is no psoas abscess, follow the surface of the psoas muscle medially to reach the anterior lateral surface of the vertebral bodies.

The aorta and vena cava effectively are tied to the waist of the vertebral bodies by the lumbar arteries and veins. These smaller vessels must be located individually on the involved vertebrae and tied so that the aorta and vena cava can be mobilized and the anterior part of the vertebral body reached. Make sure that the lumbar vessels are not cut flush with the aorta; a slipped tie then would prove hard to deal with (Figs. 6-46 and 6-49).

Place a needle into the involved lumbar vertebra or disc, and take a radiograph to identify the exact location.

 

 

 

Figure 6-39 The anterior abdominal musculature and viscera have been transected and removed at the level of the iliac crest. The arrow indicates the route of surgery between the peritoneum anteriorly and the retroperitoneal structures posteriorly.

 

 

Dang

 

 

Nerves

The sympathetic chain lies on the lateral aspect of the vertebral body and on the most medial aspect of the psoas muscle. It is easy to identify as the tissue is cleared from the front of the vertebrae.

The genitofemoral nerve lies on the anterior medial surface of the psoas muscle, attached to its fascia. Easily identifiable, it should be preserved (see Figs. 6-45 and 6-49).

Vessels

The segmental lumbar arteries and veins must be tied or excessive bleeding will occur (see Fig. 6-46).

The vena cava may be injured if the peritoneal contents are retracted vigorously when the approach is made from the right side. The aorta is a much tougher structure that is more resistant to injury.

The aorta is easy to identify. Its pulsating length can be palpated (see Fig. 6-49).

Ureter

The ureters run in the medial aspect of the field between the peritoneum and the psoas fascia. Because the ureter is attached not to the psoas fascia, but loosely to the peritoneum, it normally falls forward with the peritoneum and its contents, away from the operative field. If doubt exists regarding the identity of the ureter, it should be stroked gently to produce peristalsis (see Fig. 6-49).

 

 

Figure 6-40 Incise the external oblique muscle and aponeurosis in line with its fibers and in line with the skin incision.

 

 

Figure 6-41 Divide the internal oblique in line with the skin incision and perpendicular to the line of its muscular fibers.

 

 

Figure 6-42 Divide the underlying transversus abdominis muscle in line with the skin incision.

 

 

Figure 6-43 In the anterior part of the wound, identify the peritoneum and its contents. Posteriorly, identify the retroperitoneal fat.

 

 

Figure 6-44 Using blunt finger dissection, develop the plane between the retroperitoneal fat and fascia that overlie the psoas muscle.

 

 

Figure 6-45 Mobilize the peritoneal cavity and its contents, and retract them medially.

 

 

 

Figure 6-46 Ligate the lumbar vessels (segmental branches of the aorta). Mobilize the aorta and vena cava to reach the anterior part of the vertebral body.

 

How to Enlarge the Approach

Local Measures

Chest wound retractors are the key to providing good visibility. They are self-retaining and offer excellent cephalad and caudad exposure. If the incision does not comfortably expose the involved vertebra, continue dissecting more posteriorly, taking additional fibers of the latissimus dorsi, and even possibly the quadratus lumborum, to allow more posterior exposure.

Extensile Measures

This incision generally is limited to the lower lumbar vertebrae. Parallel incisions may be made at higher levels for access to the upper lumbar vertebrae, but they involve rib resection and potentially are hazardous because of the proximity of the pleura and the kidney. They should be performed in conjunction with a general surgeon unless the orthopedic

surgeon has considerable experience in this area.

 

 

 

Figure 6-47 The external and internal oblique have been resected to reveal their relationship to each other and to the transversus abdominis muscle.

 

 

Figure 6-48 The transversus abdominis muscle is resected to reveal the peritoneum and the retroperitoneal fat.

 

 

Figure 6-49 The abdominal muscles and viscera have been removed proximal to the level of the iliac crest to reveal retroperitoneal structures. Note the interval between the psoas muscle and the aorta. This interval provides access to the sympathetic chain and the anterior portion of the vertebral bodies.