- Department of Neurosurgery, University of Kansas Medical Center, 3901 Rainbow Blvd., Kansas City, KS 66160, USA.
- Traumatic and Reconstructive Spinal Surgery, University of Mississippi Medical Center, 2500 North State St., Jackson MS 39216, USA
Correspondence Address:
Paul M. Arnold
Traumatic and Reconstructive Spinal Surgery, University of Mississippi Medical Center, 2500 North State St., Jackson MS 39216, USA
DOI:10.4103/2152-7806.98583
Copyright: © 2012 Arnold PM. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.How to cite this article: Arnold PM, Anderson KK, McGuire RA. The lateral transpsoas approach to the lumbar and thoracic spine: A review. Surg Neurol Int 17-Jul-2012;3:
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Abstract
Background:In the last several years, the lateral transpsoas approach to the thoracic and lumbar spine, also known as extreme lateral interbody fusion (XLIF) or direct lateral interbody fusion (DLIF), has become an increasingly common method to achieve fusion. Several recent large series describe several advantages to this approach, including less tissue dissection, smaller incisions, decreased operative time, blood loss, shorter hospital stay, reduced postoperative pain, enhanced fusion rates, and the ability to place instrumentation through the same incision. Indications for this approach have expanded and now include degenerative disease, tumor, deformity, and infection.
Methods:A lateral X-ray confirms that the patient is in a truly lateral position. Next, a series of tubes and dilators are used, along with fluoroscopy, to identify the mid-position of the disk to be incised. After continued dilation, the optimal site to enter the disk space is the midpoint of the disk, or a position slightly anterior to the midpoint of the disk. XLIF typically allows for a larger implant to be inserted compared to TLIF or PLIF, and, if necessary, instrumentation can be inserted percutaneously, which would allow for an overall minimally invasive procedure.
Results:Fixation techniques appear to be equal between XLIF and more traditional approaches. Some caution should be exercised because common fusion levels of the lumbar spine, including L4-5 and L4-S1, are often inaccessible. In addition, XLIF has a unique set of complications, including neural injuries, psoas weakness, and thigh numbness.
Conclusion:Additional studies are required to further evaluate and monitor the short and long-term safety, efficacy, outcomes, and complications of XLIF procedures.
Keywords: Lateral transpsoas approach, extreme lateral interbody fusion, direct lateral interbody fusion, lumbar spine, lumbosacral plexus, surgical technique
INTRODUCTION
The minimally invasive lateral transpsoas approach to the lumbar and thoracic spine, also known as extreme lateral interbody fusion (XLIF) or direct lateral interbody fusion (DLIF), was first described in 2001.[
BACKGROUND
Differences between the lateral transpsoas approach, anterior lumbar interbody fusion, posterior lumbar interbody fusion, and transforaminal interbody fusion
The lateral transpsoas procedure differs from traditional anterior lumbar interbody fusion (ALIF), traditional posterior lumbar interbody fusion (PLIF), and transforaminal lumbar interbody fusion (TLIF) in several important ways[
METHODS OF THE LATERAL TRANSPSOAS APPROACH TO THE SPINE
Monitoring and x-ray confirmation of proper positioning
After the patient is properly positioned and the appropriate surgical area is localized, electrodes are placed that correspond to the myotomes L2-L5. Stimulation is then performed to achieve adequate twitch strength, allowing for accurate and reproducible EMG recordings. A lateral X-ray confirms that the patient is in a truly lateral position.
Performing the lateral transpsoas approach utilizing multiple tubes/dilators
Several techniques utilize the XLIF approach to the disk space. A series of tubes and dilators are used, along with fluoroscopy, to identify the mid-position of the disk to be incised. The first dilator is introduced through a small incision, and from a second small posterior incision, the surgeon's index finger directs the dilator through the retroperitoneal space to the psoas muscle.
Positioning of the dilator and exposure for the lateral transpsoas approach
The surgeon's index finger, now in the retroperitoneal space, guides the dilator from the first incision to the psoas muscle, taking care not to injure the intra-abdominal organs. The fibers of the psoas muscles are separated with the initial dilator, and the neural monitoring system can evaluate how close the dilator is to the lumbar nerve roots, which is a critical step in guarding against neural injury. The closer the tip of the electrode is to a nerve, the greater the current adjacent to the nerve. However, direct vision of the surgical field may reveal nerve tissue that does not respond to customary EMG stimulation. This stimulation usually localizes the lumbosacral plexus to the inferior posterior quadrant of the dilator tube over the lateral disk space. Thus, with continued dilation, the optimal site to enter the disk space is the midpoint of the disk, or a position slightly anterior to the midpoint of the disk.
Application of the retractor for the lateral transpsoas approach
After the second and then third dilators are introduced over the initial dilator, a retractor is inserted over the last dilator and fixed in place to the operating room table. The retractor is then opened to the surgical field over the disk space and neural monitoring is again checked to assure the neural elements are not being stretched across the operative field.
Disk excision utilizing the lateral transpsoas approach
The disk can now be incised and removed. Fluoroscopy is useful to ascertain the depth to which the disk is resected; XLIF typically allows for a larger implant to be inserted compared to either TLIF or PLIF. If instrumentation is necessary, it can be inserted percutaneously, which will allow for an overall minimally invasive procedure. Ozgur et al. provides a comprehensive discussion of the details of XLIF.[
ANATOMY
Definition of “safe” working zones for the lateral transpsoas approach
Because nerve injury during the transpsoas approach is the most common and potentially the most devastating complication of the XLIF procedure,[
Cadaver studies for the lateral transpsoas approach
Several cadaver studies defined the anatomy of the lumbar plexus and proposed an appropriate working space where dilators could be placed at each level of the lumbar spine.[
RESULTS OF XLIF SURGERY
Levels and limitations of XLIF surgery
The most common XLIF procedure involves treatment of one disk level, although four- and five-level disease has been treated with this approach. The L5-S1 disk space is usually inaccessible due to the presence of the sacrum, and nearly half the time the L4-5 interspace is similarly obscured.[
Multiple indications for XLIF surgery
The majority of XLIF procedures are performed for degenerative conditions, including spondylolisthesis, herniated disk, degenerative disk disease, postlaminectomy kyphosis, adjacent segment disease, and degenerative scoliosis. Rarely has the procedure been used to treat osteomyelitis or tumor [
Most common indication for XLIF (degenerative lumbar disease) and outcomes
One of the most common indications for XLIF is degenerative disease of the lumbar and thoracolumbar spine. Ozgur et al., in advancing the technology from endoscopy to the XLIF, published the first feasibility study in 2006.[
Fusion rates and outcomes after XLIF surgery
The bulk of the large series detailing outcomes and complications for XLIF were published in the past few years. Most of these studies were retrospective, and surgical procedures were typically performed at one or two levels accompanied by supplemental fixation (plates or pedicle screws)[
Complications after XLIF surgery
Rodgers et al. further assessed fusion rates and patient outcomes in 66 patients one year after surgery; 96.6% of levels were judged as fused on CT scan, with nearly 90% of patients “satisfied or very satisfied.”[
Ozgur et al. reported a series of 62 patients who had two-year follow-up following XLIF.[
Complication rate for XLIF in obese patients not increased
Rodgers et al. reported on a series of 156 obese patients who underwent XLIF and found that they were no more likely to experience complications than the nonobese patients.[
XLIF surgery with bone morphogenetic protein rhBMP-2 [INFUSE® Bone Graft, (Medtronic Sofamor Danek Inc., Memphis TN, USA)]
Oliveira et al. reported on a series of 15 patients who underwent one-level stand-alone XLIFs supplemented with bone morphogenetic protein (rhBMP-2: INFUSE®).[
Dramatic increase in use of rhBMP-2 (INFUSE®) in the last decade
The use of rhBMP-2 in spinal fusion surgeries increased dramatically in the last decade. The results of preliminary human trials of rhBMP-2 in lumbar fusion were published in 2000 and 2002, and neither study reported any adverse events directly related to rhBMP-2.[
Safety concerns regarding rhBMP-2 (INFUSE®) since 2002
As early as 2002, however, safety concerns regarding the use of rhBMP-2 in spine fusions were reported.[
Intense scrutiny of rhBMP-2 (INFUSE®) since 2006 by United States Food and Drug Administration
In 2006, the first of a series of studies describing serious complications associated with the use of rhBMP-2 was published.[
In 2009, Cahill et al. conducted a retrospective cohort study of 328,468 patients who underwent spinal fusion procedures, including 17,623 patients in whom rhBMP-2 was used. The authors found that rhBMP-2 use in thoracic and lumbar fusions was not associated with any increased frequency of postoperative inpatient complications. (Notably, delayed outpatient complications were not analyzed.)[
XLIF indirect decompression of nerve roots in patients with degenerative disk disease and stenosis
Oliveira et al. also looked at the ability of XLIF procedures to indirectly decompress nerve roots in a small series of patients with degenerative disk disease and stenosis.[
Youssef et al. reported minimal complications, good fusion rates, and good patient outcomes with XLIF in their series of 84 patients with an average follow-up of 16 months.[
A variety of complications of XLIF
In the last year, several additional series have reported a variety of complications attributed to the XLIF procedure.[
Complications of XLIF: transient neurological deficits and requirement for reoperations
Rodgers et al. reported on the largest series of XLIF procedures, and found a 6.2% complication rate in the early (six weeks) postoperative period in 600 procedures.[
Advantages of the XLIF approach with total disk replacement
Pimenta et al. concluded that the XLIF was safer and less invasive than the anterior approach (ALIF), demonstrated minimal morbidity (maintaining pain relief and functional improvement), avoided mobilization of the great vessels, preserved the anterior longitudinal ligament (ALL), resulted in biomechanical stability, and offered broader revision options.[
Neurological complications of the XLIF approach with total disk replacement
Nevertheless, in the Pimenta et al. study, significant neurological complications were observed following XLIF for TDR. For instance, five patients had new psoas weakness and three had new anterior thigh numbness; fortunately, both conditions resolved within 2 postoperative weeks. However, one patient had leg weakness ipsilateral to the approach side which required 6 months to resolve, while another patient had quadriceps hypertrophy contralateral to the approach side which required 12 months to resolve. In two cases, removal of the TDR device and revision to fusion were required for pain that failed to resolve within 2 postoperative years.
Outcomes and complications of XLIF utilized to address scoliosis, tumors, prior fusions, thoracic disks, and discitis/osteomyelitis
Karikari et al. evaluated clinical, radiographic, operative, postoperative, and functional outcomes of 22 patients (mean age 64.6 years) treated with XLIF for various conditions including degenerative scoliosis, pathological fractures from tumors, adjacent level disease from prior fusions, thoracic disk herniations, and discitis/osteomyelitis.[
Results of minimally invasive interbody fusion (XLIF, TLIF) in the elderly
In a companion study published the same year involving minimally invasive interbody fusions (41 cases of XLIF and 27 cases of TLIF), Karikari et al. evaluated the rate of perioperative and postoperative complications in the elderly.[
Complications of minimally invasive thoracolumbar XLIF instrumented fusions
Le et al. investigated hardware-associated complications in 101 patients who underwent minimally invasive lateral interbody thoracolumbar fusions using lateral plates for multilevel fusions or deformity correction.[
Clinical outcomes and complications of XLIF
Berjano et al. reported on the clinical outcomes and complications in 97 consecutive XLIF cases with a minimum 6-month follow-up (mean 12 months).[
Degenerative scoliosis: another indication for XLIF
In the last few years, surgeons have expanded the indications for XLIF to include degenerative scoliosis. Due to the nature of this disease, deformity procedures tend to involve several levels of fixation. Anand et al. published a feasibility study in 2008, reporting on their first 12 scoliotic patients; surgical procedures involved an average of 3.64 segments and an average 13° correction per patient.[
Similarly, Dakwar et al. reported on a series of 25 patients who underwent XLIF for thoracolumbar degenerative deformity.[
Comparison of outcomes/morbidity of XLIF and TLIF for scoliosis
In a small study, Tormenti et al. compared the surgical treatment of adult scoliosis utilizing the XLIF approach (eight patients) vs. standard posterior-only TLIF (four patients).[
Morbidity of XLIF for deformity/scoliosis
Neural decompression and fusion in patients with adult degenerative scoliosis presents a surgical challenge. Recent studies on surgical treatment of adult scoliotic deformity have found that the lateral transpsoas approach, when compared to traditional open approaches, results in less blood loss, shorter lengths of stay, and earlier mobilization, along with lower rates of infection and fewer transfusions.[
XLIF resulted in excellent deformity correction for scoliosis
Acosta et al. analyzed changes in coronal and sagittal plane alignment following XLIF for degenerative scoliosis and noted excellent results for deformity correction in both planes.[
Perioperative complications for XLIF with degenerative scoliosis
Isaacs et al. reported on perioperative complications in a prospective series of 107 patients treated for an average 4.4 level degenerative scoliosis.[
XLIF with total disk arthroplasty
Pimenta et al. extended the XLIF indications when they published a series of 36 patients who underwent this procedure for total disk replacement rather than for fusion.[
XLIF for osteomyelitis or tumor
In three earlier mentioned series,[
XLIF and asymptomatic pseudarthrosis
When Youssef et al. evaluated outcomes of 84 patients who underwent XLIF for various degenerative and deformity conditions, including one patient treated for tumor, the overall complication rate was 6.1%.[
Results of XLIF with supplemental posterior instrumentation
Rodgers et al. were the first to delineate complications in the early postoperative period (within the first six weeks) in 600 XLIF cases, 511 of whom underwent supplemental posterior instrumentation.[
Perioperative morbidities for thoracic and thoracolumbar disease
Karikari et al. reported on perioperative morbidities and initial clinical, radiographic, operative, and functional outcomes in 22 patients who underwent XLIF for isolated thoracic and thoracolumbar diseases.[
COMPLICATIONS OF XLIF
Although the most common complications following XLIF include thigh numbness, lower extremity radiculopathy with weakness, and pseudarthrosis, other unusual complications have been reported in smaller series or case reports[
Contralateral femoral nerve compression following XLIF
Out of 14 patients who underwent XLIF, Papanastassiou et al. reported on two patients who developed the unusual complication of contralateral femoral nerve compression.[
Ipsilateral nerve root injury during transpsoas approach for XLIF
Houten et al. described two patients who developed ipsilateral nerve root injuries during the transpsoas approach.[
Failures and reoperations following XLIF with lateral fixation
XLIF has some significant technical shortcomings as indicated by the necessity for early reoperation to address chronic CSF leakage due to dural tears, infection, or displaced implants and/or instrumentation.[
CONCLUSIONS
Popularity and high fusion rates of XLIF
The XLIF procedure has gained significant popularity in the last decade and is likely to become even more popular in the next several years. Indications for its use have increased, and some traumatic lesions may soon be treated with this approach as well. XLIF has a similar fusion rate and outcome profile when compared with more invasive procedures, and, as technology advances, the XLIF may even surpass them. In addition, XLIF appears to be as equally cost-effective as standard interbody fusion procedures.
Unique complications of XLIF
XLIF has its own set of unique complications, and surgeons who continue to utilize this technique must remain vigilant to observe, record, and avoid potential pitfalls. As is true of any new surgical procedure, successful XLIF is based on thorough knowledge of the anatomy, proper patient selection, attention to detail regarding surgical technique, and appropriate preoperative planning.
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