The patient is positioned supine on a regular operating room table. The iliac crest may be aligned with the break in the table to allow hyperextension of the lumbar region using the bed controls. Also, the plane of the left and right anterior supe- rior iliac spines should be parallel to the floor. Use of a leveling bar can aid in
Box 7-1 CONTRAINDICATIONS FOR TOTAL DISK REPLACEMENT • Active systemic infection or infection localized to the site of implantation
• Osteopenia or osteoporosis defined as dual energy x-ray absorptiometry (DEXA)–measured bone density T-score of less than –1.0
• Bony lumbar spinal stenosis
• Allergy or sensitivity to implant materials (cobalt, chromium, molybdenum, polyethylene, titanium)
• Isolated radicular compression syndromes, especially due to disk herniation • Pars defect
• Involved vertebral end plate dimensionally smaller that 34.5 mm in the medial-lateral and/
or 27 mm in the anterior-posterior direction
• Clinically compromised vertebral bodies at affected level due to current or past trauma • Lytic spondylolisthesis or degenerative spondylolisthesis higher than Grade 1
verification. The arms should be padded at the elbows and wrapped in front of the patient’s chest in mummy fashion. The folded arms are then secured by tap- ing to the bed. Both lower extremities should be in neutral position, with a pillow under the knees.
For anterior access, a paramedial, left-sided incision is preferred for a retroperi- toneal approach. A good strategy is to use right-sided approaches for L5-S1 when the patient has subthreshold degenerated disks at L4-5 or L3-4, so that the left retroperitoneum remains available for surgery at a later time. The paramedial inci- sion has been shown to have both a cosmetic and functional benefit compared with an anterolateral incision.22 The incidence of retrograde ejaculation is tenfold lower when a retroperitoneal approach is used compared to when a transperitoneal approach is used.23 Although access surgeons are commonly used in the United States, rates and types of complications are the same when a trained spine sur- geon performs the approach procedure.24 In a series of 1315 anterior access cases,
C
A B
FIGURE 7-10 A, Immediately postoperative AP radiograph of L4-5 artificial disk replacement. B and C, Five-year follow-up AP and lateral flexion and extension radiographs. Note the visible motion maintained at the L4-5 artificial disk.
Brau and colleagues25 reported a 0.45% incidence of iliac vein thrombosis and a 1.4% incidence of major vessel lacerations. Laparoscopic techniques have shown no functional advantage over the “mini-open” technique. In fact, use of a laparoscopic technique adds significant cost to the procedure.26
In smaller patients, the incision can usually be made horizontally for a one- level procedure. A 6- to 8-cm left-sided paramedial horizontal incision on the lower abdomen in line with the disk space is used. In more obese patients, a vertical incision should be used because it is more extensile (Figure 7-11). Based on the relation of the L4-5 disk space to the iliac crest on lateral radiographs, the incision may be situated either caudal or cephalad on the abdomen to the level of the crest. Some access surgeons like to verify the angle of the L5-S1 disk space using a lateral fluoroscopic image and radiopaque marker such as a pin, particularly early in their approach experience (Tips from the Masters 7-2).
After the skin incision is made, Bovie cauterization is used in the subcutane- ous tissue layer to expose the anterior rectus fascia. The fascia is incised slightly obliquely and to a greater length than the skin incision to allow easier mobilization.
The midline fascial raphe of the rectus is then identified, and the left rectus is mobi- lized to the left side with careful attention to avoid injury to the inferior epigastric vessels deep to the muscle. These vessels may need to be cauterized. Blunt finger dissection is then used to develop the retroperitoneal plane at the lateral edge of the fascial incision. The plane is bluntly dissected superficial to the peritoneum along the left abdominal wall around the sigmoid colon and taken posteriorly toward the psoas muscle (Figure 7-12). The entire peritoneal contents can be bluntly dissected and raised off the abdominal wall. A hand-held retractor can be useful. The ureter should be identified and retracted with the peritoneal contents, not dissected sepa- rate from the peritoneal sac. The genitofemoral nerve can usually be identified on the surface of the psoas muscle. Identification and ligation of the iliolumbar vein (or veins) is frequently necessary, because they may keep the iliac vein tethered anterior to the spine and inhibit proper mobilization of the great vessels. Once the peritoneum has been successfully mobilized, the vascular structures must be carefully dissected from the left anterolateral aspect of the spine to the right. Often there is inflammatory tissue anterior to the disk space, which makes mobilization of the vascular structures difficult. Identification and transection (between clips) of segmental vessels is sometimes necessary. Either table-held retractors or hand-held vein-type retractors can be used on each side of the spine to create a safe working area for the remainder of the procedure (Figure 7-13).
L3-4 L4-5 L5-S1
FIGURE 7-11 Illustration of the various incisions used for anterior mini–open retroperitoneal approach.
The extensile, vertical incision should be reserved for more obese patients to gain exposure.