Safety Profile, Surgical Technique, and Early Clinical Results for Simultaneous Lateral Lumbar Interbody Fusion and Anterior Lumbar Interbody Fusion in a Lateral Position

Abstract

Study Design:

Description of surgical technique and retrospective review.

Objective:

To describe a novel surgical technique for multilevel lumbar fusion and describe early clinical results.

Summary of Background Data:

Patients with multilevel lumbar spinal stenosis and adult degenerative scoliosis often require multilevel interbody placement to achieve indirect decompression and lordosis. We describe a case series of patients treated with simultaneous lateral lumbar interbody fusion (LLIF) and anterior lumbar interbody fusion (ALIF) at L5–S1.

Methods:

We retrospectively reviewed a consecutive series of patients treated for multilevel lumbar spinal stenosis with simultaneous ALIF and LLIF with at least 3-month follow-up. All patients received supplemental percutaneous bilateral pedicle screw placement as well. We measured on preoperative radiographs their lumbar lordosis, pelvic incidence, and L5–S1 lordosis. Intraoperative factors such as operative time, estimated blood loss, fluids provided, number of levels fused, and whether a trainee was present during the procedure were all recorded.

Results:

There were 15 patients included within our case series (69.5, 4 F). There were no reported intraoperative vascular or neurological complications in 15 cases. The operative time for the cases ranged from 2.7 to 8.4 hours (average=5.2±1.9 h). The average lordosis gained at L5–S1 was 8.6±3.0 degrees and the average lumbar lordosis gained was 14.7±6.4 degrees. The average PI-LL mismatch went from 22.4±13.3 degrees preoperative to 7.8±10.2 degrees postoperative. One patient had a postoperative complication of a sacral fracture requiring placement of a pelvic screw for a L2-pelvis fusion. There were 8 patients with 4+ levels of fusion. For this cohort of patients, the average lumbar lordosis gained was 16.0±7.5 degrees and the average PI-LL mismatch went from 24.7±16.3 degrees preoperative to 8.8±12.9 degrees postoperative. For the patients with 4+ levels of fusion, the average operative time was 5.9±1.8 hours.

Conclusions:

We have described our early positive results with simultaneous LLIF/ALIF surgery for treatment of lumbar degenerative conditions.

Research surrounding efficiency in the operating room is centered on decreasing operative complications, reducing postoperative complications, reducing unnecessary costs/resources while maintaining improved clinical outcomes.¹ For spine surgeons, operating room efficiency is centered on achieving the goals of surgery (ie, fusion and decompression) while decreasing costs/operative time and thereby increasing the value proposition of spine surgery.² Steps to improve efficiency in spine surgery might include synchronizing start times, decreasing turnover time between cases, equipment tray consolidation, and decreasing operating room time overall.³ Research has also focused on advancements in equipment to perform procedures like pedicle screw placement in less time.⁴

One type of spine surgery that takes significant operating room resources is multiposition spinal fusion surgery.⁵ Separately, the lateral lumbar interbody fusion (LLIF) and anterior lumbar interbody fusion (ALIF) allows for indirect decompression of neural elements while providing a broad footprint for spinal fusion.^6,7 In specific situations such as strategies to employ minimally invasive surgical techniques to treat spinal deformity, both an ALIF and LLIF is required.⁸ These operations, however, often take over 6 hours and require significant health care resources.⁸

Given the obvious clinical utility of both an LLIF and ALIF in specific surgical situations, the authors have designed a surgical technique to perform an ALIF and LLIF in a simultaneous manner to improve operating room efficiency. We feel this technique allows us to achieve the goals of surgery (ie, creation of a fusion bed, decompression of neural elements, and at times correction of a spinal deformity) safely and effectively. Within this article we describe the surgical technique for performing this procedure as well as a case series of short-term results for our cohort of patients.

INDICATION FOR SIMULTANEOUS ALIF/LLIF

When evaluating a patient with lumbar pathology we use strict criteria before indicating a simultaneous ALIF/LLIF procedure. Patients with multilevel lumbar foraminal stenosis and/or spondylolisthesis are candidates for indirect decompression/fusion using an ALIF and LLIF.⁹ Careful evaluation is also made for any bony lateral stenosis or substantial central stenosis which may make success of indirect decompression more difficult.¹⁰ If there is any vascular anatomy that would make mobilization of vessels/visceral structures challenging/dangerous using an anterior approach then this is a contraindication for our simultaneous procedure.¹¹ If a patient has a high pelvic incidence and the angle of the L5–S1 disc space is aimed too caudal then this is a contraindication to an ALIF. Patients with unfavorable neurovascular anatomy such as having a lumbar plexus draped over the lateral disc space (ie, “mickey mouse ears”) then this is a contraindication to a LLIF.¹² Obesity or high body mass index was also used as a relative contraindication to a simultaneous ALIF/LLIF.

Surgical Technique

Operating Room Setup

The operating room setup for a combined ALIF/LLIF is similar to a traditional LLIF procedure with the exception of fluoroscopy. Whereas in LLIF, fluoroscopy is usually brought in from the patients’ ventral aspect (front), the C-arm is brought in from a dorsal position in these cases. A representative photograph depicting a typical operating room setup is shown in Figure 1. On the basis of relevant anatomy and spinal alignment the surgeon should choose a right-sided or left-sided approach. If in the left lateral decubitus position, the fluoroscopy machine should be placed to the patient’s right side and vice versa if the patient is in the right lateral decubitus position. This will allow enough space for both surgeons to work anteriorly and laterally. If the surgeon prefers to use a microscope during the lateral discectomy (as one of the senior surgeon’s prefers to do), the microscope comes in from the posterior side of the patient. The clamps for the mounted retractor for the ALIF portion of the procedure is placed on the anterior side of the patient. One clamp is placed just below the arm boards and the other clamp can be placed below the level of pubis. The retractor for the LLIF can be connected to a clamp on the proximal and posterior side of the patient.

FIGURE 1.

Operating room setup depicting the position of the patient as well as the position of the fluoroscopy machine posterior to the patient. The patient’s abdomen is prepped low below the umbilicus and distal enough past the pubis to allow access anteriorly to the L5–S1 disc space.

Patient Positioning

The position of the patient on the operating room table must be done with each of the planned procedures in mind. The side that is safest and/or best for a patient’s alignment should dictate whether the patient is in the right/left lateral decubitus position. As with all LLIF procedures, we place the patient’s greater trochanter over the break of the bed and secure the patient with tape over the chest, legs, and pelvis. The bed is angled over the break of the bed in order to create distance between the rib cage and iliac crest. We drape out the entire posterior lower back if bilateral pedicle screws are planned. We also drape out distally to the pubic ramus anteriorly in order to allow access to the L5–S1 disc space.

ALIF Approach—Modifications

Once the patient is positioned, we use a localizing radiograph to identify the angle of the L5–S1 disc space. A 5–6-cm oblique incision is made in the lower abdomen lateral to the rectus muscle, in line with the L5–S1 disk space. This is typically a few centimeters above the pubic ramus. It is important for the surgical team to prep the patient’s abdomen this far caudal in order to gain appropriate access to the L5–S1 disc space. On the posterior side, we recommend prepping the patient as far to the ground as possible (this would mean prepping as much of the right side of the low back as possible if the patient was in the right lateral decubitus position). This is because the trajectory of the screws on the dependent side will require significant medialization and it is best to provide ample room to avoid any contamination of the surgical field. A standard dissection is made through the oblique layers of the abdominal musculature in line with the original skin incision. The anterior rectus sheath can be incised if necessary, but the rectus muscle should be left intact. Once the retroperitoneal space is found, we use blunt dissection in order to achieve access to the L5–S1 disc space. The ureter is mobilized medially along with the retroperitoneal contents. The middle sacral vessels are identified and ligated to allow for mobilization of the iliac vein confluence.

Once the L5–S1 disc space is first exposed we confirm our position with another localizing radiograph. At this point we mobilize all soft tissue in order to have full visualization of the anterior disc space. The authors prefer the use of specialized anterior-lateral self-retaining retractors at this point in the procedure in order maintain exposure of the L5–S1 disc space. Figure 2 shows the typical setup of these specialized anterior retractors designed for a lateral ALIF. Please note how the ALIF retractors have arms that are anchored to clips that are on the anterior side of the patient. These specialized retractors attach to a table mounted retractor anterior side of the patient. This retractor maintains adequate position for full visualization of the disc space. A photograph of this setup is shown in Figure 2. Another picture depicting the L5–S1 “view” is shown in Figure 3. The authors do, however, feel comfortable using a standard Thompson retractor in the lateral position as well. At this point a discectomy and disc preparation can be done by the spine surgeon. It is important to keep one’s orientation when performed the discectomy and ensure that instruments are passed in a direct anterior-posterior direction. A graft is then placed in a standard manner for an ALIF as is shown in Figure 4.

FIGURE 2.

The specialized anterior retractors designed for the lateral position allows for full visualization of the L5–S1 disc space while still leaving room for a surgeon to work posteriorly to place an interbody device through a lateral incision.

FIGURE 3.

Self-retaining retractors for the anterior lumbar interbody fusion allow for full visualization of the L5–S1 disc space.

FIGURE 4.

The ALIF self-retaining retractors can be placed further anteriorly to allow for a LLIF approach. Two surgeons can comfortably work on both sides of the operating room table. The arrow within this picture points to a dilator for the LLIF approach. ALIF indicates anterior lumbar interbody fusion; LLIF, lateral lumbar interbody fusion.

While no vascular injuries were encountered in our case series, the surgeons involved in this study have created a plan of treatment in case there is a vascular injury while the patient is in the lateral decubitus position. If there is a controllable injury to an iliac vein then an attempt to fix the vein in the lateral position is performed. If needed the anterior incision is extended as well. In the scenario where a catastrophic injury takes place then the patient is immediately turned into a supine position in order to repair the damaged vessel.

LLIF Approach

When performing a multilevel fusion, the LLIF spinal surgeon begins at the most cephalad level and works downward toward the L5–S1 level. This allows more space between the vascular surgeon anteriorly and the spinal surgeon working laterally. In most cases, 2 levels of an LLIF are completed during the exposure for the ALIF. Once the ALIF exposure is completed the surgeon will stop the LLIF portion of the procedure to perform the cage insertion portion of the ALIF. A standard LLIF approach is used by the surgical team when performing the lateral portion of the procedure. A 1-incision technique is performed in order to gain access to the lateral disc space of the levels cephalad to L5–S1. Once the disc space is prepared and the surgeon is ready for an antero-posterior radiograph, the surgeon performing the anterior portion of the procedure takes a step back to allow room for the collimator to swing anterior to the patient.

Posterior Instrumentation

Posterior instrumentation is used by both senior spine surgeons when performing a multilevel fusion. One of the senior surgeon’s prefers to perform posterior instrumentation during the same procedure as the simultaneous ALIF/LLIF, whereas the other senior surgeon will stage the posterior instrumentation portion of the case. Staging is done when the senior author wants to evaluate correction of radiographic parameters based solely on LLIF cage placement. The protocol is that the patient gets a standing full-length scoliosis radiograph before the second stage of the procedure in order for the author to evaluate the amount of correction gained. If there is insufficient correction the senior author may consider performing a larger deformity correction surgery possibly using open techniques. There is evidence of improved corrections using a staged technique as well.¹³ There are a variety of ways that posterior instrumentation can be placed in the lateral position.^14–16 This includes navigation-assisted, freehand, or robotic-assisted pedicle screw placement. For both navigation-assisted and robotic-assisted technique, the reference marker for instrumentation is placed in the pelvis. The authors would encourage surgeons who prefer to place screws in a prone position to continue to do so. It is surgeon preference and it likely does not significantly impact the time for the overall case to turn a patient back into the prone position.

METHODS

We performed a retrospective review of patients undergoing multilevel lumbar fusions performed by the 2 senior authors on this study after receiving Institutional Review Board approval from our home institution. We included patients that had at least 1 LLIF done simultaneous to an ALIF. Patient’s with revision surgery were included. Both patients with supplemental posterior fixation done at the same time as LLIF/ALIF and those that had their posterior fixation staged were included within our analysis. Relevant demographic information such as age, body mass index, and sex were collected for all patients. The preoperative diagnosis for each patient was also collected.

Intraoperative data collected included relevant operative details such as the length of the procedure, the levels operated upon, whether a trainee was present, blood loss, fluids received intraoperatively and intraoperative complications. If a procedure required multiple visits to the operating room (ie, a staged procedure) the operative times were added. Any intraoperative events were recorded including vascular injuries, neuromonitoring events, or nerve injuries. Postoperative complications such as hardware failure, motor deficits that lasted longer than 4 weeks, infection, fracture, or any event that caused a return to the operating room. Postoperative radiographs were examined and compared with preoperative radiographs. Specifically, the lumbar lordosis and L5–S1 lordosis was recorded from the preoperative and postoperative standing, full-length radiographs. The change in PI-LL mismatch was also calculated for the preoperative and postoperative standing full-length radiographs.

RESULTS

There were 15 patients included within our analysis. Relevant demographic data are presented in Table 1 along with diagnoses for the patients. Of note, all patients had overlapping diagnoses of either lumbar neurogenic claudication, lumbar radiculopathy, and/or degenerative scoliosis.

TABLE 1.

Demographic and Diagnosis Information for Patients Undergoing a Simultaneous ALIF/LLIF

Demographic
Average age (min-max age) (y)	69.5±9.17 (57–84)
Sex	73.3% male (11/15 male)
Diagnoses
Lumbar neurogenic claudication	5 patients (33.3%)
Lumbar radiculopathy	9 patients (60%)
Degenerative scoliosis	6 patients (40%)

ALIF indicates anterior lumbar interbody fusion; LLIF, lateral lumbar interbody fusion; max, maximum; min, minimum.

The mean and SD for estimated blood loss for our cohort of patients was 212.0±171.7mL. The average and SD of fluids provided intraoperatively was 1786.7±1043.1mL. There was 1 case where a unit of packed red blood cells was provided for the patient during their hospital course. This was a case with 600mL of blood loss and involved 7 levels of surgery. Of the 15 cases presented, 11 cases involved a trainee in the procedure whereas the other 4 cases had a physician assistant helping the primary surgeon. Of the 11 cases with a trainee, 6 had a fellow and 5 had a resident.

Radiographic measurements for our cohort of patients is shown in Table 2. Operative levels and times are also outlined in Table 2. The average lordosis gained at L5–S1 was 8.6±3.0 degrees. Patients with more than 4 levels of fusion and those with < 4 levels of fusion were analyzed separately in Table 2 as well. Representative radiographs of preoperative and postoperative radiographs are shown in Figures 5 and 6. Within our cohort of patients there was 1 surgical complication. Approximately 6 months after a 2-level revision L4–S1 fusion the patient developed bilateral sacral insufficiency fractures that was associated with significant pain. He was treated with a revision procedure involving extension of posterior instrumentation to the iliac crest.

TABLE 2.

Radiographic Parameters and Operative Data for all Patients Included Within Our Cohort

Radiographic Parameter	All Patients	Less Than 4 Levels Fused	More Than 4 Levels Fused
Average preoperative lumbar lordosis (min-max) (deg.)	27.7±14.7 (−2.2 to 47.7)	31.1±14.2 (7–46.2)	24.8±15.4 (−2.2 to 47.7)
Average pelvic incidence (min-max) (deg.)	50.2±6.7 (37.0–61.0)	51.1±7.4 (37–59.6)	49.5±6.5 (43.0–61.0)
Average preoperative PI-LL mismatch (min-max) (deg.)	22.5±13.3 (22.8–14.5)	19.9±9.5 (5.2–30)	24.7±16.3 (12.1–57.2)
Average postoperative lumbar lordosis (min-max) (deg.)	42.5±11.0 (19.0–55.0)	44.4±11.9 (27.7–55)	40.8±10.6 (19–54.2)
Average postoperative PI-LL mismatch (min-max) (deg.)	7.8±10.3 (7.4–11.2)	6.5±7.1 (−3.4 to 15.6)	8.8±12.9 (−3.2 to 36.0)
Average change in lumbar lordosis preoperative to postoperative (deg.)	14.7±6.3	13.3±4.8	16.0±7.5
Operative data
Median number of levels fused (min-max)	3 (2–7) levels	3 (2–3) levels	5 (4–7) levels
Average operative time (min-max) (h)	5.2±1.9 (2.5–8.5)	4.3±1.72 (2.5–6.5)	5.9±1.79 (3.5–8.4)

Max indicates maximum; min, minimum.

FIGURE 5.

Preoperative radiographs (A, B) and postoperative radiographs (C, D) for a patient that underwent a simultaneous 2-level ALIF/LLIF procedure. ALIF indicates anterior lumbar interbody fusion; LLIF, lateral lumbar interbody fusion.

FIGURE 6.

Preoperative (A, B) and postoperative (C, D) standing EOS films of a patient treated with a multilevel simultaneous ALIF/ LLIF procedure. ALIF indicates anterior lumbar interbody fusion;LLIF, lateral lumbar interbody fusion.

DISCUSSION

With innovations in spine surgery it is imperative to ensure that procedures can be performed safely and reproducibly to get positive clinical outcomes.¹⁷ Our study describes a safe and reproducible surgical technique in order to perform a simultaneous ALIF/LLIF procedure. Early clinical results show significant improvement in sagittal parameters after the simultaneous procedure as well as a low complication rate. No vascular or neurological injuries were associated with the 15 cases presented within our study.

The ALIF procedure has a unique complication profile and the authors acknowledge that all surgeons involved in the ALIF/LLIF case must be comfortable with working with a patient in the lateral decubitus position. Although estimates vary, Garg et al¹⁸ report a 6.1% rate of vascular injury with the traditional supine ALIF approach with a mean blood loss of 143mL. Another study by Mobbs et al¹⁹ described the rate of vascular injury to be 6.6%. It is important to note, however 1 risk factor for a vascular injury during the ALIF is a multilevel procedure. By approaching disc spaces cephalad to L5–S1 laterally, this risk factor is somewhat lowered. The authors acknowledge that the vascular or approach surgeon must be comfortable with the slightly altered anatomy over the abdomen when a patient is in the lateral decubitus position.²⁰

Our ALIF/LLIF technique has distinct differences to a traditional oblique lumbar interbody fusion (OLIF). The OLIF procedure utilizes the plane between the aorta and the psoas muscle.²¹ Although this approach does hold the advantage of sparing the psoas muscle from the dissection required during a LLIF approach, the working corridor to get to the L5–S1 disc space can be small and in some instances nonexistent.²¹ At the level of L5–S1 the OLIF exposure is essentially the same as the traditional ALIF exposure as a result. When considering multilevel OLIF procedures versus our proposed technique for simultaneous ALIF/LLIF it is important to consider that while an OLIF is designed to spare the psoas muscle, there is still a significant risk of transient psoas weakness, thigh numbness when performing an OLIF.²² Second, our technique allows for improved operating room efficiency by allowing 2 surgeons to work simultaneously and avoiding redocking over more cephalad vertebral levels during the multilevel OLIF surgery. Performing this type of anterior lumbar exposure in the lateral position for either technique, however, can be somewhat disorienting and the authors acknowledge that this approach may be difficult for some surgeons more accustomed to the traditional ALIF approach in a supine position.

Minimally invasive spine surgery offers unique advantages for treatment of adult spinal deformity. Park et al²³ demonstrated that utilization of the LLIF procedure allows for significant correction of sagittal alignment for deformity patients. Mundis et al²⁴ also reported on significant improvements in patient reported outcome measurements with the incorporation of the lateral approach for treatment of deformity. The authors consider the ALIF procedure to also be a relative minimally invasive procedure in terms of muscle injury and studies have indicated the significant correction that can be achieved by an ALIF for deformity patients.²⁵ Both the ALIF and LLIF also provide large interbody support for bone growth/fusion to occur.^26,27 Combining these approaches for our patient did allow us to achieve significant correction of PI-LL mismatch especially when treating patients with multilevel fusions.

Staging in lengthy spine procedures such as a multilevel ALIF/LLIF surgery has risks and benefits. Within our cohort of patients, one of the senior authors elected to stage their posterior fixation for 3 cases, whereas the other senior author routinely placed posterior fixation on the same day as the ALIF/LLIF surgery. Procedures requiring multiple approaches are associated with increased morbidity/mortality.⁵ One study by Passias et al²⁸ analyzing a Nationwide Inpatient Sample also showed no benefit of staging in terms of mortality for procedures requiring multiple approaches. Contrastingly, a study by Hassanzadeh et al²⁹ showed that staging anterior/posterior surgeries did help decrease the need for blood transfusions. Another study by Gum et al³⁰ showed that planned staging of posterior-only vertebral column reconstructions did not increase perioperative complications. Clearly, data are not definitive regarding when staging for lengthy spine procedures is necessary. The authors recommend surgeons use their own discretion when deciding whether or not to stage the posterior fixation portion of simultaneous ALIF/LLIF.

There are clearly significant limitations to this retrospective review. We are describing the experience of 2 surgeons for this study. This is also a small patient cohort of 15 people and more procedures are likely required to be able to draw definitive conclusions regarding clinical efficacy of the simultaneous ALIF/LLIF. Given the fact that the minimum follow-up of our patients was 3 months, longer term follow-up is required to determine the possible complications related to the procedure. It is encouraging, however, that there were no approach-related complications for this first 15 patient cohort.

In conclusion, the simultaneous ALIF/LLIF procedure represents an efficient technique to place interbody fixation at L5–S1 and cephalad levels. Multilevel fusions using this technique are also associated with significant improvement in sagittal parameters. Further research is required to determine the complete safety profile of this technique, but early results are promising. With the appropriate team, this surgery can be done safely and efficiently to achieve sagittal realignment, lumbar indirect decompression, and fusion.