Anterior (Transperitoneal and Retroperitoneal) Approach to the Lumbar Spine
Anterior (Transperitoneal and Retroperitoneal) Approach to the Lumbar Spine
The transperitoneal anterior approach to the lumbar spine usually is reserved for fusing L5 to S1. It also may be used for fusing L4 to L5, although it then involves mobilization of the great vessels. Although the approach is simple in concept, the occasional user may appreciate the assistance of a general surgeon who is more familiar with the area exposed.8,10
The approach can also be used for the treatment of spinal tuberculosis and the insertion of disc prostheses. Endoscopic transperitoneal approaches have been described but these are beyond the scope of this
book.
Position of the Patient
Place the patient supine on the operating table (see Fig. 6-14). Make sure that two areas remain bare for incision if the approach is used for spinal fusion; one for the abdominal incision, and one for harvesting an anterior iliac crest bone graft. Insert a urinary catheter to keep the bladder empty. Use of mechanical calf compression and/or chemical prophylaxis is recommended to decrease the risk of thromboembolism.
Landmarks and Incision
Landmarks
The umbilicus normally is opposite the L3-4 disc space, but varies in level depending on how heavy the patient is.
Palpate the pubic symphysis at the lower end of the abdomen through the fatty mons pubis. The pubic tubercle, on the upper border of the pubis just lateral to the midline, may be easier to palpate than the superior surface of the symphysis itself.
Incision
Make a longitudinal midline incision from just below the umbilicus to just above the pubic symphysis. Extend it superiorly, curving it just to the left of the umbilicus and ending about 2 to 3 cm above it. Heavier patients will require longer incisions (Fig. 6-15).
Internervous Plane
The midline plane lies between the abdominal muscles on each side, segmentally supplied by branches from the seventh to the 12th intercostal nerves. Therefore, this incision can be extended from the xiphisternum to the pubic symphysis.
 |
 |
 |
 |
 |
 |
Figure 6-14 With the patient in the supine position (A), the anterior lumbar spine can be approached by a transperitoneal, left retroperitoneal, or right retroperitoneal
path (B).
 |
 |
Figure 6-15 Make a longitudinal midline incision from just below the umbilicus to just above the pubic symphysis. Extend it superiorly, to the left of the umbilicus.
Superficial Surgical Dissection
Deepen the wound in line with the skin incision by cutting through the fat to reach the fibrous rectus sheath. Incise the sheath longitudinally, beginning in the lower half of the incision, to reveal the two rectus abdominis muscles (Fig. 6-16). Separate the muscles with the fingers to expose the peritoneum (Fig. 6-17). Then, pick up the peritoneum carefully between two pairs of forceps and, after making sure that no viscera are trapped beneath it, incise it with a pair of scissors (Fig. 6-18). Extend the incision distally, but take care not to incise the dome of the bladder at the inferior end of the wound. With one hand inside the abdominal cavity to protect the viscera, carefully deepen the upper half of the incision, staying in the midline and cutting through the linea alba, the band of fibrous tissue that separates the two rectus abdominis muscles in the upper half of the abdomen. Complete the exposure by cutting through the peritoneum in the upper half of the wound (Fig. 6-19).
Deep Surgical Dissection
Use a self-retaining Balfour retractor to retract the rectus abdominis muscles laterally and the bladder distally (Fig. 6-20). Perform a routine abdominal exploration. Next, put the operating table in Trendelenburg position at 30 degrees and carefully pack the bowel in a cephalad position, keeping it inside the abdominal cavity. Spread a moist lap pad (swab) over it to prevent loops of bowel from slipping free. It is much safer to keep the bowel within the abdominal cavity, but do not pack it so tightly that vascular compromise is induced. In women, the uterus may be retracted forward with a 0 silk suture placed in its fundus and tied to the Balfour retractor.
Infiltrate the tissue over the anterior surface of the sacral promontory with a few milliliters of saline solution to make dissection easier and to allow identification of the presacral parasympathetic nerves that run down through this area. For the L5-S1 disc space, incise the posterior peritoneum in the midline over the sacral promontory. The sacral artery runs down along the anterior surface of the sacrum and must be ligated or clipped. The ureters should be well lateral to the surgical approach.
 |
 |
Figure 6-16 Deepen the wound in line with the skin incision by cutting through the
fat to reach the fibrous rectus sheath. Incise the sheath longitudinally.
 |
 |
Figure 6-17 With your fingers, separate the rectus abdominis muscles in the midline to expose the peritoneum.
 |
 |
Figure 6-18 Pick up the peritoneum with forceps and incise it.
 |
 |
 |
Figure 6-19 With one hand inside the abdominal cavity to protect the viscera, carefully deepen the upper half of the incision, staying in the midline and cutting through the linea alba.
 |
 |
 |
 |
Figure 6-20 Use a self-retaining retractor to retract the rectus abdominis muscles laterally and the bladder distally. Carefully mobilize and retract the bowel in a cephalad position, keeping it inside the abdominal cavity. Observe the posterior peritoneum overlying the bifurcation of the great vessels and the promontory of the sacrum. Incise the peritoneum longitudinally.
Preserve any small nerve fibers that are found. Identify the L5-S1 disc space either by palpating its sharp angle or by inserting a metallic marker and taking a radiograph. The L5-S1 disc space lies below the bifurcation of the aorta; it should be possible to expose it fully without mobilizing any of the great vessels (Figs. 6-21 and 6-22).
Operating on the L4-5 disc space requires a larger exposure; mobilizing the great vessels is necessary, unless the vascular bifurcation occurs much higher. Carefully incise the peritoneum at the base of the sigmoid colon and mobilize the colon upward and to the right to expose the bifurcation of the aorta, the left common iliac artery and vein, and the left ureter. Identify the aorta just above its bifurcation and gently begin blunt dissection on its left side. Identify and ligate the fourth and fifth left
lumbar vessels, then divide them. Now, the aorta, vena cava, and left common iliac vessels can be moved to the right, exposing the L4-5 disc space. This exposure is difficult to achieve; a high incidence of venous thrombosis has been reported with anterior surgery at this level. Take care not to injure the left ureter, which crosses the left common iliac vessels roughly over the sacroiliac joint. The ureter may have to be moved laterally, but mobilize it only as much as necessary to reduce the risk of postoperative ischemic stricture formation.
An alternative method is to approach the L4-5 disc space from below, working upward into the apex of the vascular bifurcation. Isolate the left and right common iliac artery, placing umbilicus loops around them. Retract the two arteries cephalad and laterally to expose the common iliac veins. Dissect into the confluence of the veins and isolate the left common iliac vein with a loop. Gently retract the venous structures to expose the disc space. Use only minimal retraction to avoid injuring the intima, which may lead to venous thrombosis (see Fig. 6-22).
Dang
Nerves
The superior hypogastric plexus is critically important to sexual function. Injury to the plexus at L5-S1 may cause retrograde ejaculation and injury more distal on the sacrum or deep in the pelvis may cause impotence. Therefore, dissection should be carried out carefully, and only with a blunt peanut dissector. The incision over the anterior part of the sacrum should be made in the midline, and it should be long enough to allow for lateral mobilization of these nerves with minimal trauma. Injecting saline solution into the presacral tissue aids in identifying and preserving these nerves (see Figs. 6-21 and 6-34).11–13
 |
 |
 |
 |
Figure 6-21 Retract the posterior peritoneum to reveal the bifurcation of the aorta and vena cava. Ligate the middle sacral artery. Identify the superior hypogastric parasympathetic plexus overlying the aorta and the sacral promontory.
Arteries and Veins
The middle sacral artery can be a troublesome bleeder in the region of the L5-S1 disc space and must be tied off (see Fig. 6-21).
The aorta and inferior vena cava are tethered to the anterior surface of the lumbar vertebrae by the lumbar vessels. These smaller vessels must be ligated and cut to allow the great vessels to be lifted forward off the lumbar vertebrae, exposing the L4-5 disc space (see Fig. 6-12). It is important to dissect these vessels out carefully without cutting them flush with the aorta. If the vessels are cut flush, there will be, in effect, a hole in the aorta, and the bleeding may be extremely difficult to control. Mobilization of the venous structures should be undertaken very carefully, because they are fairly fragile and easily traumatized. Damage to these vessels may result in thrombosis; mobilization and retraction should be kept to a minimum.
Special Structures
The ureter must be mobilized laterally, particularly for exposure of the
How to Enlarge the Approach
Local Measures
Packing the bowel away carefully is the key to adequate exposure in the pelvis. Careful mobilization of the great vessels is crucial to exposure higher up (see Figs. 6-20 and 6-22).
Extensile Measures
In theory, this exposure can be extended to the xiphisternum, but the exposure of higher discs almost always is performed better through a retroperitoneal approach.
 |
 |
 |
 |
Figure 6-22 Mobilize the great vessels as needed for additional exposure. Expose the L5-S1 disc space subperiosteally.