Laparoscopic versus Mini Open Anterior Lumbar Interbody Fusion

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Michael G. Kaiser, Regis W. Haid, Jr., Brian R. Subach, Gerald E. Rodts, Jr.

Department of Neurosurgery, Emory Clinic, Atlanta, Ga., USA

The anterior approach for a lumbar interbody fusion was originally designed to treat Pott's disease [1]. Since that time, the anterior lumbar interbody fusion (ALIF) has evolved into an effective and popular alternative in the treatment of a variety of lumbar degenerative disorders, including degenerative disc disease, low-grade spondylolisthesis, and posterior pseudoarthrosis. Compared to traditional posterior fusion techniques, the ALIF operation is associated with shorter operative times, decreased blood loss, less postoperative pain, reduced hospital stay, and shorter recovery periods [2-5].

Supporters of the ALIF argue that reconstruction of the anterior column is biomechanically superior, avoids paraspinal muscle trauma and denervation, indirectly decompresses the intervertebral foramen, improves sagittal balance, and allows a more efficient restoration of disc interspace height compared to posterior fusion techniques [6-8]. The anterior position of the interbody graft increases the likelihood of fusion by exposing the graft to fusion-promoting forces in accordance with Wolff's law [9]. The interbody space also provides an increased surface area for fusion formation and robust blood supply following decortication of the vertebral endplates [10].

Early in the development of the ALIF technique, open approaches, such as the transperitoneal or retroperitoneal approach, were utilized to expose the anterior lumbar spine. Although providing adequate visualization, these more extensive exposures were associated with increased postoperative morbidity. As the ALIF technique evolved, emphasis was placed on exposing the spine through less invasive approaches. These minimally invasive techniques are intended to decrease postoperative morbidity, reduce hospitalization time, and shorten the recovery period with comparable or superior treatment outcomes compared to more traditional techniques.

Laparoscopic ALIF

Today's spine surgeon has two such options for approaching an ALIF: the laparoscopic approach and the 'mini-open' laparotomy. Zucherman et al. [11] were the first to report the use of the laparoscopic approach for an anterior interbody fusion. This technique is considered by many as the least invasive approach to the ventral lumbar spine and in many centers has become the standard technique when performing an ALIF, particularly at the L5/S1 disc interspace. The safety and efficacy of an anterior laparoscopic fusion have been reported in numerous reports [2, 3, 12-16].

The small incisions required for insertion of the laparoscopic working channels reduce the extent of abdominal wall muscle dissection and blood loss, both contributing to a decrease in postoperative pain. The laparoscopic approach is also associated with less direct manipulation of the abdominal contents, resulting in a decreased incidence of postoperative ileus. These characteristics are thought to reduce postoperative morbidity and contribute to a shorter length of hospitalization.

Mini-Open ALIF

More recently the traditional open transperitoneal approach has been modified into a mini-open technique that incorporates similar principles as the anterior cervical exposure. Originally reported by Mayer [17] in 1997, the mini-open technique reduces the degree of postoperative morbidity associated with the traditional open laparotomy by utilizing a smaller incision combined with a muscle splitting exposure, dividing the abdominal muscles in the direction of the fiber orientation. In this initial report, a total of 25 patients underwent an ALIF across various lumbar levels utilizing the mini-open laparotomy. It was the authors' belief that this technique was associated with negligible surgical trauma, decreased operative time and blood loss, decreased postoperative morbidity, and a shorter recovery time. The authors concluded that this approach could be employed for a variety of lumbar spinal disorders and fusion techniques. The mini-open approach has been described with both a transperitoneal and retroperitoneal route to the anterior lumbar spine [6, 17, 18]. Recently there has been evidence to suggest that the laparoscopic approach does not offer a significant advantage over the mini-open approach when performing an ALIF at the L4/5 interspace [5].

The mini-open approach provides direct access to the disc interspace and allows easier identification of the anatomical midline. The open technique allows complete disc removal, resection of any herniated fragments, and increased endplate exposure, improving the preparation of the disc interspace for fusion formation compared to the trephine technique used with the laparo-scopic approach. The mini-open laparotomy is less technically demanding, contributing to a shorter preparation and operative time. The reduced incidence of retrograde ejaculation has also been observed with the mini-open laparotomy [4].

Surgical Technique

Patient Positioning

There are a number of previously published reports describing the details of both the laparoscopic and mini-open techniques [3, 6, 14, 18]. For both approaches the assistance of either a general or vascular surgeon, familiar with laparoscopic techniques when indicated, is advised. This team approach will optimize the speed and safety of the procedure, providing the patient with maximal benefit.

Patient positioning is essentially identical for each approach, however accommodations for the video monitor are required with the laparoscopic exposure. The patient is positioned supine on a radiolucent operative table with a pillow or bolster placed under the patient's hips to accentuate the natural lumbar lordosis and under the knees to avoid hyperextension. The patient is securely strapped to the operative table. This is particularly necessary for the laparoscopic approach due to the steep Trendelenburg position required to allow the abdominal viscera to move rostrally out of the pelvis. Fluoroscopic imaging is used with both techniques during positioning of the implants.

Laparoscopic Technique

The patient is prepared and draped under sterile conditions in the usual fashion. The fluoroscopic equipment is brought into the operative field to confirm the midline prior to any incisions. For the laparoscopic approach, intraabdominal access is obtained through four small incisions in the anterior abdominal wall (fig. 1). The viewing camera is inserted through a curvilinear umbilical incision and two lower paramedian incisions provide portals for the

10-mm trocar (laparoscope)

5- or 10-mm trocar

10-mm trocar (laparoscope)

5- or 10-mm trocar trocar

18-mm trocar n! (working port)

L4/L5 or L5/S1 suprapubic

Fig. 1. Diagram demonstrating the trocar placement for laparoscopic ALIF. The channels for working instruments are provided through two paramedian incisions. The laparoscope is inserted through an umbilical incision and the instrumentation portal through a suprapubic incision.

working instruments. The channel for interbody implant insertion is passed through a midline suprapubic incision and measures approximately 2-4 cm in length (fig. 2).

Harvesting of the bone graft is performed at the beginning of the procedure. During this period the laparoscopic surgeon obtains access and insufflates the abdominal cavity. At this point the operative table is placed in a steep Trendelenburg position to assist in mobilizing the abdominal viscera out of the pelvis inlet.

Adequate exposure of the disc is critical. It is essential to identify the appropriate anatomical landmarks and midline (fig. 3). The sacral promontory is identified by palpation and the midline determined with fluoroscopic imaging. The posterior peritoneum is opened sharply. In an attempt to avoid retrograde ejaculation in male patients the presacral sympathetic plexus is mobilized through blunt dissection and the use of monopolar cautery avoided at the disc interspace. More liberal use of the monopolar cautery is allowed with female patients. The middle sacral artery and vein are then identified, ligated, and divided.

The insertion of interbody implants is performed only after confirmation of the midline is repeated. The implants are inserted through a trephine

Fig. 2. Final placement of abdominal trocars following insufflation of the abdomen. The instrumentation trocar is positioned toward the top and the laparo-scope toward the bottom of the photograph.

Fig. 3. Anterior view of the lumbosacral spine prior to retroperitoneal exposure. The dotted line indicates a possible peritoneal incision to access the retroperitoneum and anterior disc space.

Fig. 4. Lateral view of the instrumentation port positioned within the disc interspace for trephination of the disc material and insertion of implant.

Fig. 3. Anterior view of the lumbosacral spine prior to retroperitoneal exposure. The dotted line indicates a possible peritoneal incision to access the retroperitoneum and anterior disc space.

Fig. 4. Lateral view of the instrumentation port positioned within the disc interspace for trephination of the disc material and insertion of implant.

technique according to the guidelines specific for the implant chosen (fig. 4). Following radiographic confirmation of implant position, the posterior peritoneum is closed using clip ligation. The abdominal incisions are closed with interrupted absorbable sutures and Steri-Strips.

Fig. 5. Typically a transverse incision is used for single level exposure for cosmesis, however a longitudinal incision can be used for obese patients, history of prior abdominal surgery, or if more than one level is addressed. The incision is usually 4-6 cm in length.

Mini-Open Technique

Excluding the equipment required for a laparoscopic approach, the operative setup is identical. The level of incision is determined with fluoroscopic imaging, with a bias toward the caudal border of the level of arthrodesis. This bias will provide a more tangent approach into the disc space and avoid excessive reaming into the inferior vertebral body. A longitudinal or transverse incision approximately 4-6 cm in length is made in the suprapubic region. A longitudinal incision is reserved for two-level ALIF procedures or for obese patients (fig. 5). After the skin incision is made, monopolar cautery is used to dissect down to the rectus abdominus muscle that is split in a longitudinal fashion parallel to the muscle fiber plane. The posterior rectus sheath and transversalis fascia are divided to expose the underlying peritoneum. The peritoneum is incised and the abdominal contents packed superiorly held in position with a table-mounted retractor (fig. 6). Although the anterior lumbar spine can be approached through either a transperitoneal or retroperitoneal exposure, our preference has been the transperitoneal route since a more direct anterior trajectory is obtained.

The posterior peritoneum overlying the disc interspace is identified and sharply divided. Exposure of the L5/S1 interspace is usually easier due to the more rostral bifurcation of the great vessels. In order to expose L4/5 interspace the left iliac artery and vein are mobilized. It is imperative that the iliolumbar vein be identified and ligated. Transection of this vein without adequate control can

Fig. 6. A table-mounted retractor system is placed to optimize exposure and retract the abdominal contents rostrally.
Fig. 7. Once the retractor blades are positioned and the posterior peritoneum opened the anterior surface of the disc is easily identified.

lead to catastrophic blood loss. Mobilizing the presacral sympathetic plexus in male patients is performed with blunt dissection, avoiding the use of monopolar cautery. In females monopolar cautery may be used more liberally to expose the anterior surface of the vertebral bodies and disc space (fig. 7). Midline identification is made through direct visualization and fluoroscopic imaging.

Fig. 8. Intraoperative photograph demonstrated the generous discectomy, with preservation of the lateral annulus, required for adequate endplate exposure prior to implant insertion.

Fig. 9. Intraoperative view of the double-barrel channel in position for implant insertion.

A complete removal of the disc is performed and the entire endplate prepared for graft insertion (fig. 8). The interbody implant is then inserted according to manufacturers' guidelines along with additional autologous bone (fig. 9). Once the appropriate implant position is verified with intraoperative fluoroscopic images, the posterior peritoneum is primarily closed with a running absorbable suture. The anterior peritoneum, transversalis fascia, and rectus sheath are closed with interrupted absorbable sutures and the skin closed with staples.

Postoperative Care

The postoperative course for both the laparoscopic and mini-open groups is essentially identical. Mobilization occurs early, typically on the first postoperative day, and their diet advanced with the initiation of bowel sounds. Patients are generally discharged once they are able to tolerate an oral diet, able to ambulate, and voiding without difficulty. Occasionally this may be as early as the 2nd day following surgery. Radiographic images, to determine implant position, are obtained prior to discharge and during scheduled follow-up visits, at approximately 6 weeks, 3, 6, 9, 12 and 24 months postoperatively.

Laparoscopic versus Mini-Open ALIF

There have been few studies that directly compared the mini-open laparot-omy to the laparoscopic ALIF. Regan et al. [19] compared their experience of 65 laparoscopic fusions to a large number of both anterior and posterior open interbody fusions. The mean operative time was significantly shorter for the mini-open ALIF compared to the laparoscopic approach, 149 compared to 207 min. The average blood loss during the mini-open procedure was 224 ml (range 20-2,000 ml) and for the laparoscopic approach 176 ml (range 10-2,200 ml). The trend for decreased blood loss with the laparoscopic approach did not prove statistically significant. The mean length of hospitalization was essentially the same for both groups, approximately 3.9 days for the laparoscopic group and 4.0 days following the mini-open approach. There were several technical complications associated with the laparoscopic approach that occurred early in the surgeon's operative experience. Nine attempts at a laparoscopic fusion were aborted and converted to an open approach, 3 secondary to laceration of the iliac vein. In 2 cases a herniated disc was noted to impinge upon a nerve root requiring a second operation for removal of the herniated fragment.

More recently Zdeblick and David [5] presented their experience with both the mini-open and laparoscopic approaches. Over a 3-year period data was prospectively collected on 50 patients who underwent an ALIF involving the L4/5 disc interspace, with an equal number of laparoscopic and mini-open laparotomy procedures. The authors found no statistical difference in operating time, intraoperative blood loss, or length of hospital stay between the two groups. When two-level procedures were considered separately, a significant increase in the mean operative time was noted with the laparoscopic approach, 185 versus 160 min. The laparoscopic group demonstrated a significantly higher complication rate, 20 versus 4%. Based on these observations, the authors concluded that the laparoscopic approach offered no advantage over the mini-open laparotomy when performing an ALIF involving the L4/5 level.

Table 1. Comparison of operative variables for all ALIF procedures

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