Endoscopic lateral transpsoas approach to the lumbar spine

Nerve injury after lateral lumbar interbody fusion: a review of 919 treated levels with identification of risk factors

BACKGROUND CONTEXT

Lateral lumbar interbody fusion (LLIF) has become an increasingly common minimally invasive procedure for selective degenerative deformity correction, reduction of low-grade spondylolisthesis, and indirect foraminal decompression. Concerns remain about the safety of the transpsoas approach to the spine due to proximity of the lumbosacral plexus.

PURPOSE

To address risk factors for iatrogenic nerve injury in a large cohort of patients undergoing LLIF.

STUDY DESIGN

Retrospective analysis of 919 LLIF procedures to identify risk factors for lumbosacral plexus injuries.

METHODS

The medical charts of patients who underwent transpsoas interbody fusion with or without supplemental posterior fusion for degenerative spinal conditions over a 6-year period were retrospectively reviewed. Patients with prior lumbar spine surgery or follow-up of less than 6 months were excluded. Factors that may affect the neurologic outcome were investigated in a subset of patients who underwent stand-alone LLIF.

RESULTS

Four hundred fifty-one patients (males/females: 179/272) met the inclusion criteria and were followed for a mean of 15 months (range, 6-53 months). Average age at the time of surgery was 63 years (range, 24-90 years). Average body mass index was 29 kg/m(2) (range, 17-65 kg/m(2)). A total of 919 levels were treated (mean, 2 levels per patient). Immediately after surgery, 38.5% of the patients reported anterior thigh/groin pain, whereas sensory and motor deficits were recorded in 38% and 23.9% of the patients, respectively. At the last follow-up, 4.8% of the patients reported anterior thigh/groin pain, whereas sensory and motor deficits were recorded in 24.1% and 17.3% of the patients, respectively. When patients with neural deficits present before surgery were excluded, persistent surgery-related sensory and motor deficits were identified in 9.3% and 3.2% of the patients, respectively. Among 87 patients with minimum follow-up of 18 months, persistent surgery-related sensory and motor deficits were recorded in 9.6% and 2.3% of the patients, respectively. Among patients with stand-alone LLIF, the level treated was identified as a risk factor for postoperative lumbosacral plexus injury. The use of recombinant human bone morphogenetic protein 2 was associated with persistent motor deficits.

CONCLUSIONS

Although LLIF is associated with an increased prevalence of anterior thigh/groin pain as well as motor and sensory deficits immediately after surgery, our results support that pain and neurologic deficits decrease over time. The level treated appears to be a risk factor for lumbosacral plexus injury.

The rising psoas sign: an analysis of preoperative imaging characteristics of aborted minimally invasive lateral interbody fusions at L4–5

Minimally invasive lateral interbody fusion for the treatment of degenerative disc disease, spondylolisthesis, or scoliosis is becoming increasingly popular. The approach at L4–5 carries the highest risk of nerve injury given the proximity of the lumbar plexus and femoral nerve. The authors present 3 cases that were aborted during the approach because of pervasive electromyography responses throughout the L4–5 disc space. Preoperative imaging characteristics of psoas muscle anatomy in all 3 cases are analyzed and discussed. In all cases, the psoas muscle on axial views was rising away from the vertebral column as opposed to its typical location lateral to it. Preoperative evaluation of psoas muscle anatomy is important. A rising psoas muscle at L4–5 on axial imaging may complicate a lateral approach.

Technical note: Resolution of spontaneous electromyographic discharge following disk-space distraction during lateral transpsoas interbody fusion

Purpose

The lateral transpsoas interbody fusion (LTIF) is an increasingly popular minimally invasive technique for lumbar interbody fusion. Although a posterior approach to the lumbar spine has traditionally been favored for the treatment of canal stenosis and neural foraminal stenosis, a growing body of evidence suggests that indirect decompression of the spinal canal and neural foramen can be achieved using a lateral transpsoas approach to the lumbar spine. We present 2 cases that may suggest a role for spontaneous electromyography (s-EMG) monitoring in assessing the adequacy of decompression during LTIF.

Methods

The 2 cases presented in this technical note illustrate resolution of s-EMG firing during LTIF, following distraction across the disk space. Removal of the distracting device produced the return of s-EMG firing. Both of these cases were operated at the L2-3 level.

Results

In the first case, s-EMG firing was noted in the bilateral tibialis anterior leads. Resolution of EMG firing may suggest indirect decompression of the canal via ligamentotaxis as the L5 root traverses the L2-3 disk space. In the second case, s-EMG firing was noted in the left abductor hallucis and resolved with distraction of the L2-3 disk space. Again, this may be explained by canal decompression via ligamentotaxis as the S1 root traverses the L2-3 disk space.

Conclusion

In both cases, distraction across the disk space resulted in resolution of s-EMG discharges—this correlated with an improvement in symptoms. These findings may suggest a role for s-EMG as a marker for adequacy of decompression in a select subset of patients undergoing LTIF. Further study is needed to determine if resolution of s-EMG is a useful measure of indirect decompression during LTIF.

Effects on inadvertent endplate fracture following lateral cage placement on range of motion and indirect spine decompression in lumbar spine fusion constructs: A cadaveric study

BACKGROUND

The lateral transpsoas approach to interbody fusion is gaining popularity. Existing literature suggests that perioperative vertebra-related complications include endplate breach owing to aggressive enedplate preparation and poor bone quality. The acute effects of cage subsidence on stabilization and indirect decompression at the affected level are unknown. The purpose of this study was to compare the kinematics and radiographic metrics of indirect decompression in lumbar spines instrumented with laterally placed cages in the presence of inadvertent endplate fracture, which was determined radiographically, to specimens instrumented with lateral cages with intact endplates.

METHODS

Five levels in 5 specimens sustained endplate fracture during lateral cage implantation followed by supplementary fixation (pedicle screw/rod [PSR]: n = 1; anterolateral plate [ALP]: n = 4), as part of a larger laboratory-based study. Range of motion (ROM) in these specimens was compared with 13 instrumented specimens with intact endplates. All specimens were scanned using computed tomography (CT) in the intact, noninstrumented condition and after 2-level cage placement with internal fixation under a 400-N follower load. Changes in disc height, foraminal area, and canal area were measured and compared between specimens with intact endplates and fractured endplates.

RESULTS

Subsidence in the single PSR specimen and 4 ALP specimens was 6.5 mm and 4.3 ± 2.7 mm (range: 2.2-8.3 mm), respectively. ROM was increased in the PSR and ALP specimens with endplate fracture when compared with instrumented specimens with intact endplates. In 3 ALP specimens with endplate fracture, ROM in some motion planes increased relative to the intact, noninstrumented spine. These increases in ROM were paralleled by increase in cage translations during cyclic loading (up to 3.3 mm) and an unpredictable radiographic outcome with increases or decreases in posterior disc height, foraminal area, and canal area when compared with instrumented specimens with intact endplates.

CONCLUSIONS

Endplate fracture and cage subsidence noted radiographically intraoperatively or in the early postoperative period may be indicative of biomechanical instability at the affected level concomitant with a lack of neurologic decompression, which may require revision surgery.

Safe zone for retractor placement to the lumbar spine via the transpsoas approach

PURPOSE

To measure anatomic variations of the lumbar plexus within the psoas in relation to the L2/3, L3/4, and L4/5 disc spaces and to delineate a safe zone to avoid nerve injury during retractor placement via the transpsoas approach.

METHODS

Six male and 6 female cadavers (24 psoas/ lumbar plexuses) aged 35 to 74 years were dissected. The lumbar plexus was isolated bilaterally. The L2, L3, and L4 nerve roots were identified and isolated without disturbing their natural anatomic course. The anteroposterior (AP) diameter of each intervertebral disc at L2/3, L3/4, and L4/5 was used as a reference. Four measurements were made using a caliper: the AP and mediolateral (ML) diameters of the psoas and AP and ML excursions of each nerve root. Percentages were calculated for the 4 measurements using the reference of the AP diameter of the intervertebral disc at each level. Comparison between left and right sides, between males and females, and between excursions of nerve roots were made.

RESULTS

The AP diameter of the psoas increased from L2 to L4, with a mean vertebral body coverage of 80%, 86%, and 85% at L2/3, L3/4, and L4/5, respectively. Both the L2 and L3 nerve roots demonstrated substantial anterior trajectories as they coursed distally in the lumbar spine. No nerve root encroached anteriorly beyond 33% of the intervertebral disc space at L2 to L5.

CONCLUSION

The lumbar plexus area corresponding to the anterior half of the intervertebral disc was the safe zone. Procedures to the lumbar spine via the transpsoas approach should be performed within the safe zone to avoid nerve injury.

Current status of adult spinal deformity

Purpose To review the current literature for the nonoperative and operative treatment for adult spinal deformity. Recent Findings With more than 11 million baby boomers joining the population of over 60 years of age in the United States, the incidence of lumbar deformity is greatly increasing. Recent literature suggests that a lack of evidence exists to support the effectiveness of nonoperative treatment for adult scoliosis. In regards to operative treatment, current literature reports a varying range of improved clinical outcomes, curve correction, and complication rates. The extension of fusion to S1 compared with L5 and lower thoracic levels compared with L1 remains a highly controversial topic among literature. Summary Most adult deformity patients never seek nonoperative or operative treatment. Of the few that seek treatment, many can benefit from nonoperative treatment. However, in selected patients who have failed nonoperative treatment and who are candidates for surgical intervention, the literature reflects positive outcomes related to surgical intervention as compared with nonoperative treatment despite varying associated ranges in morbidity and mortality rates. If nonoperative therapy fails in addressing a patient's complaints, then an appropriate surgical procedure that relieves neural compression, corrects excessive sagittal or coronal imbalance, and results in a solidly fused, pain-free spine is warranted.

Postoperative lumbar plexus injury after lumbar retroperitoneal transpsoas minimally invasive lateral interbody fusion

STUDY DESIGN

Retrospective review.

OBJECTIVE

To evaluate the motor and sensory deficit rate after the lumbar retroperitoneal transpsoas minimally invasive lateral interbody fusion (MIS LIF) by reviewing a single surgeon's experience.

SUMMARY OF BACKGROUND DATA

The MIS LIF is an increasingly used alternative to traditional open anterior or posterior operations to treat a host of spinal disorders. It has many advantages, but the potential for immediate postoperative thigh numbness, pain, and potential motor weakness has been reported. Published rates range widely in part because previous studies have based patient outcomes on data from different surgeons using different techniques.

METHODS

An institutional review board-approved, retrospective review of a prospectively collected database was conducted. Seventy-one consecutive patients who underwent this procedure between L1 and L5 during a 3-year period met criteria and were included. Postoperative clinical examinations immediately after surgery and during routine follow-up intervals were examined.

RESULTS

There was a 19.1% (14/71) rate of immediate postoperative ipsilateral thigh numbness during the study period. The annual rates of numbness progressively decreased annually. There was a 26.1% (6/23), 25% (5/20), and 10.7% (3/28) rate for 2008, 2009, and 2010, respectively. All patients with numbness had a fusion construct that involved L4-L5. More than half the patients, 54.9% (39/71), had immediate postoperative ipsilateral iliopsoas or quadriceps weakness. Of these, the vast majority had resolution by 3 months (92.3%), and all had complete resolution by 2 years.

CONCLUSION

The lumbar retroperitoneal transpsoas MIS LIF is a safe alternative to traditional open operations for many spinal conditions. As with most minimally invasive techniques, there is a learning curve to be overcome to minimize the risk of iatrogenic nerve injuries. Our refined technique of the MIS LIF during a 3-year period has led to a significant reduction of the incidence of postoperative numbness of nearly 60% (from 26.1%-10.7%).

Iliac crest osteotomy to enhance exposure of the L4–5 interspace in minimally invasive lateral transpsoas interbody fusion: a cadaveric feasibility study

Object

Minimally invasive lateral transpsoas interbody fusion (LTIF) has emerged as a popular surgical technique in a remarkably short period of time. The authors' experience with this procedure and anecdotal evidence in the literature suggest that the iliac crest may occasionally prevent access to the L4–5 interspace during minimally invasive LTIF. The authors propose that removal of a minimal amount of ilium would allow for successful exposure of the L4–5 interspace in those cases with a “high-riding” iliac crest. Therefore, the objective of this study was to evaluate the feasibility of iliac osteotomy to enhance exposure of the L4–5 interspace for minimally invasive LTIF.

Methods

Twenty L4–5 minimally invasive LTIF procedures were performed on 10 cadavers. The L4–5 minimally invasive LTIFs were successfully completed in 13 of 20 attempts. In the remaining 7 cases, the iliac crest prevented perfect orthogonal access to the L4–5 interspace. An iliac osteotomy was performed until the tubular retractors could be perfectly aligned with the L4–5 interspace and minimally invasive LTIF accomplished. Anteroposterior fluoroscopic images were obtained before and after the osteotomies. The angle between the working instrument and the superior L-5 endplate was measured, as were craniocaudal displacement and the resected iliac area.

Results

Iliac osteotomy enabled completion of L4–5 minimally invasive LTIF in the 7 remaining cases. Iliac resection was minimal; an average of 4.92 cm2 of iliac surface was resected (range 2.08–8.27 cm2) to enable L4–5 access. Adequate working angles were maintained (average 3.3° change after resection) while significant caudal displacement of the tubular system was achieved (average 15.7 mm, range 5.2–27.6 mm).

Conclusions

A significant portion of patients may have a high-riding iliac crest and that may have had an impact on minimally invasive LTIF in this series; L4–5 cases are rare in relation to midlumbar spine cases in most minimally invasive LTIF patient series. Significant caudal displacement of the tubular system was achieved with minimal iliac osteotomy, ensuring access to the L4–5 interspace in all specimens while maintaining the minimally invasive philosophy behind minimally invasive LTIF.

Grade 2 spondylolisthesis at L4-5 treated by XLIF: safety and midterm results in the "worst case scenario"

Spondylolisthesis is one of the most common indications for spinal surgery. However, no one approach has been proven to be more effective in treating spondylolisthesis. Recent advances in minimally invasive spine technology have allowed for different approaches to be applied to this indication, notably extreme lateral interbody fusion (XLIF). The risk, however, of using XLIF in treating grade II spondylolisthesis is the ventral position of the lumbar plexus, particularly at L4-5. Objective. This study reports the safety and midterm clinical and radiographic outcomes of patients with grade II lumbar spondylolisthesis treated with XLIF. Methods. 63 patients with grade II spondylolisthesis and spinal stenosis were treated with XLIF and were available for 12-month followup. Of those, 61 (97%) were treated at L4-5. Clinical (VAS, complications, and reoperation rate) and radiographic (anterolisthesis, disk height, and fusion) parameters were assessed. Study Design. Data were collected via a prospective registry and analyzed retrospectively. Results. Sixty-three patients were available for evaluations at least one year postoperatively. Average pain (visual analog scale) decreased from a score of 8.7 at baseline to 2.2 at 12 months postoperatively. Average anterior slippage was reduced by 73% and was well maintained. Average disk height (4.6 mm pre-op and 9.0 mm post-op) nearly doubled after surgery. Slight settling (average 1.3 mm) occurred over the twelve-month follow-up period. There were no neural injuries and no nonunions noted. Conclusions. XLIF is a safe and effective minimally invasive treatment alternative for grade II spondylolisthesis. Real-time neurological monitoring and attention to technique are mandatory.

A comparison of complication rate between anterior and lateral approaches to the lumbar spine

AIM

The aim of this study was to compare the complication rate of traditional minimally invasive anterior with the new minimally invasive lateral trans-psoatic retroperitoneal approaches to the intervertebral discs at levels T12-L5.

METHODS

A review of all cases of minimally invasive anterior (ALIF) and lateral (XLIF) intervertebral disc surgery at levels T12-L5, treated at the Department of Neurosurgery from January 1996 to September 2011. The ALIF group consisted of 120 and the XLIF group consisted of 88 patients. Preoperative diagnoses were: degenerative disc disease, failed back surgery syndrome, spondylolisthesis, retrolisthesis and posttraumatic disc injury. The surgical steps are described. All surgical intraoperative and postoperative complications directly related to the spinal surgery were prospectively documented. The outcome measure was rate of complications.

RESULTS

In the ALIF group there were no major complications, only 35 minor intra- and postoperative complications in 32 patients (26.6%). The main complication was lumbar post-sympathectomy syndrome in 19 patients (15.8%). In the XLIF group there were 26 complications in 22 patients (25%). One major intraoperative complication was partial and transient injury to the L5 nerve root (1.1%). There were 25 minor postoperative complications in the XLIF group in 21 patients (23.9%), mainly transient pain of the left groin or anterior thigh in 11 patients (12.5%) or numbness in the same dermatomas in 9 patients (10.2%). Statistically there was no difference between the ALIF and XLIF groups in complication rate.

CONCLUSION

Anterolateral and lateral retroperitoneal minimally invasive approaches to levels T12-L5 disc spaces are safe procedures with only minor complications and one exception. The rate of complications was similar in both groups. In the case of ALIF, the particular complication was post-sympathectomy syndrome. The main complication of XLIF was transient nerve root injury in one patient due to underestimation of the procedure in the outset. Intraoperative neuromonitoring during XLIF surgery is fully recommended.

The lateral transpsoas approach to the lumbar and thoracic spine: A review

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.

Case report of an abscess developing at the site of a hematoma following a direct lateral interbody fusion

BACKGROUND CONTEXT

A direct lateral interbody fusion (DLIF) is relatively new, yet commonly performed procedure in spine surgery. This procedure is associated with risk, including damage to nerve or vascular structures. However, to our knowledge, there has not been a case of an abscess developing at the site of a postoperative hematoma after this procedure.

PURPOSE

The objective was to document a case of the delayed presentation of an abscess at the site of a postoperative hematoma after a DLIF.

STUDY DESIGN/SETTING

The study was designed to be a case report and literature review.

METHODS

We present a case of a 63-year-old patient who developed a large retroperitoneal hematoma after an L2-L5 DLIF. The patient developed a postoperative urinary tract infection with cultures positive for Pseudomonas. The infection was treated with oral antibiotics. Eight months after her procedure, the patient was found to have developed an abscess (measuring 11.6 × 8.4 × 10.0 cm) at the site of the prior hematoma.

RESULTS

After radiological-guided aspiration and a 2-week course of oral antibiotics, the abscess resolved and the patient recovered with no sequelae.

CONCLUSION

Direct lateral interbody fusion is a minimally invasive procedure that may result in postoperative hematoma formation. We have reported a case of the development of an abscess at the site of a postoperative hematoma.

Anterior elongation as a minimally invasive alternative for sagittal imbalance-a case series

BACKGROUND

Degenerative and iatrogenic conditions may lead to flat back or even to kyphotic deformity, and sagittal imbalance can cause significant clinical impairment. Minor imbalance cases are usually treated with conservative care. Among currently popular surgical techniques for the correction of sagittal imbalance are posterior-based procedures, which are associated with access-related risks (mostly neurological) and postoperative morbidity risks.

PURPOSE

This study aims to report a minimally invasive lateral approach using hyperlordotic cages in the treatment of mild sagittal imbalance. Radiological correction, clinical improvement, and safety will be analyzed.

METHODS

Eight patients (mean age 71.8 years, SD 7.8; mean BMI 27.5, SD 2.3) with symptomatic sagittal imbalance were retrospectively reviewed. Eight cases were treated by anterior interbody fusion with lordotic cages. A minimally invasive lateral retroperitoneal approach was used in the surgical procedures, with or without percutaneous pedicle screw supplementation.

RESULTS

No major complications occurred and just one case needed revision for direct decompression. Clinical outcomes Visual Analog Scale score changed from 88 at preoperative visit to 51 at 1-week visit, and Oswestry Disability Index score decreased from 82 at preoperative visit to 44 at 6-week visit. The 6-month radiological assessment revealed improvement in spinopelvic parameters: Focal lordosis improved from 2.3° ± 7.7 to 27.1° ± 6.7. Sagittal vertical alignment improved from 11.7 ± 5.3 to 6.2 ± 4.0 cm. Preoperative sacral slope improved from 20.1° ± 5.8 to 29.4° ± 10.3 and preoperative pelvic tilt improved from 35.2° ± 5.2 to 23.8° ± 4.3. Short-term results indicate that the minimally invasive lateral approach can be applied to the treatment of mild sagittal imbalance, with special advantage in elderly patients or those in which posterior approaches are relatively contraindicated.

Complications of the lateral transpsoas approach for lumbar interbody arthrodesis: a case series and literature review

BACKGROUND

The lateral transpsoas approach to the lumbar spine was developed to eliminate the need for an anterior-approach surgeon and retraction of the great vessels and has the potential for shorter operative times. However, the reported complications associated with this approach vary.

QUESTIONS/PURPOSES

We identified the incidence of complications associated with the lateral transpsoas approach to the lumbar spine.

PATIENTS AND METHODS

We retrospectively reviewed 45 patients who underwent a lateral transpsoas approach to the spine for various diagnoses between January 1, 2006, and October 31, 2010. The patients' average age was 63.3 years. Sixteen (35.6%) patients had prior lumbar spinal surgery. Twenty-one patients (46.7%) underwent supplemental posterior instrumentation. Minimum followup was 0 months (mean, 11 months; range, 0-34 months).

RESULTS

Eighteen of the 45 patients (40%) had complications: 10 (22.2%) developed postoperative iliopsoas weakness, three had quadriceps weakness, and one experienced foot drop. Eight patients (17.8%) developed anterior thigh hypoesthesia, which did not fully resolve in seven of the eight patients at an average of 9 months' followup. Three patients had postoperative radiculopathies, one a durotomy, and one died postoperatively from a pulmonary embolism.

CONCLUSIONS

We found a 40% incidence of complications and a nontrivial frequency and severity of postoperative weakness, numbness, and radicular pain in patients who underwent a lateral transpsoas approach to the spine. Given the expanding use of the approach, a thorough understanding of the risks associated with it is essential for patient education, medical decision making, and identifying methods of reducing such complications.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Minimally invasive approaches for the correction of adult spinal deformity

Introduction

Spinal deformity surgery is historically associated with significant blood loss and medical complications. Minimally invasive deformity correction is a promising approach to spinal deformity surgery where deformity correction and fusion can be achieved with less tissue trauma, reduced blood loss and potentially less complications.

Materials and methods

We discuss technical aspects of minimally invasive deformity correction, review the transpsoas and presacral approaches for discectomy and fusion, and review multilevel posterior percutaneous pedicle instrumentation and rod placement for deformity correction. We also review our results using these techniques and review the literature regarding outcomes in this emerging area of spinal surgery.

Conclusions

Minimally invasive deformity correction is a promising method of spinal deformity correction. Early clinical results are similar to open techniques, with reduced blood loss and less complications than traditional approaches. Meticulous technique and careful patient selection are required for good results and to avoid complications.

Minimally invasive lateral lumbar interbody fusion and transpsoas approach–related morbidity

Object

Recently, the minimally invasive, lateral retroperitoneal, transpsoas approach to the thoracolumbar spinal column has been described by various authors. This is known as the minimally invasive lateral lumbar interbody fusion. The purpose of this study is to elucidate the approach-related morbidity associated with the minimally invasive transpsoas approach to the lumbar spine. To date, there have been only a couple of reports regarding the morbidity of the transpsoas muscle approach.

Methods

A nonrandomized, prospective study utilizing a self-reported patient questionnaire was conducted between January 2006 and June 2008 at Northwestern University. Data were collected in 53 patients with a follow-up period ranging from 6 months to 3.5 years. Only 2 patients were lost to follow-up.

Results

Thirty-six percent (19 of 53) of patients reported subjective hip flexor weakness, 25% (13 of 53) anterior thigh numbness, and 23% (12 of 53) anterior thigh pain. However, 84% of the 19 patients reported complete resolution of their subjective hip flexor weakness by 6 months, and most experienced improved strength by 8 weeks. Of those reporting anterior thigh numbness and pain, 69% and 75% improved to their baseline function by the 6-month follow-up evaluations, respectively. All patients with self-reported subjective hip flexor weakness underwent examinations during subsequent clinic visits after surgery; however, these examinations did not confirm a motor deficit less than Grade 5. Subset analysis showed that the L3–4 and L4–5 levels were most often affected.

Conclusions

The minimally invasive, transpsoas muscle approach to the lumbar spine has a number of advantages. The data show that a percentage of the patients undergoing the transpsoas approach will have temporary sensory and motor symptoms related to this approach. The majority of the symptoms are thought to be related to psoas muscle inflammation and/or stretch injury to the genitofemoral nerve due to the surgical corridor traversed during the operation. No major injuries to the lumbar plexus were encountered. It is important to educate patients prior to surgery of the possibility of these largely transient symptoms.

Percutaneous endoscopic lumbar discectomy and interbody fusion with B-Twin expandable spinal spacer

BACKGROUND

Posterior lumbar interbody fusion (PLIF) is biomechanically sound as it ablates the degenerated disc, restores the intervertebral height, relieves foraminal stenosis, and positions the bone graft along the weight-bearing axis. But this conventional procedure also results in significant traction on the dural sac and the cauda equina and is thereby a potential source of neurologic damage. Therefore, we performed a minimally invasive technique: percutaneous endoscopic discectomy and interbody fusion (PEDIF) with B-Twin expandable spinal spacer (B-twin ESS) to treat symptomatic lumbar degenerative disc disease and explored the clinical outcome.

METHODS

From June 2004 to December 2006, 43 consecutive patients with symptomatic lumbar degenerative disc disease were included in this study. There were 28 males and 15 females, with average age of 47 years (range 26-63). Following a routine micro-endoscopic discectomy or percutaneous nucleotomy, endplate curettage was meticulously carried out. The intervertebral space was packed with autograft cancellous bone cut from lumbar delivered through a 5-mm diameter funnel. The B-twin ESS was introduced into the intervertebral space and then expanded. Both stages were monitored by C-arm fluoroscopy.

RESULTS

The mean operative time was 110 ± 36 min (80-150). The mean blood loss was 350 ± 68 ml (210-700). The mean length of hospitalization was 6.6 ± 2.9 days (3-10). All patients were evaluated in follow-up of 12-30 months (mean 18). According to radiological evidence of fusion on dynamic X-ray plain film, 31 cases (72.1%) achieved bone graft fusion after 6 months postoperatively; at the final follow-up, union of the bone graft has been established in all but one patient (97.7%). The subsidence degree of the B-twin ESS was 20-30% in 2 cases and in rest of the cases less than 10%. According to the modified criteria of Chinese Orthopaedic Association, excellent in 31 cases, good in 8 cases, fair in 3 cases, poor in 1 case, and the rate of excellent and good cases was 91%.

CONCLUSION

The PEDIF technique provided an option for percutaneous interbody fusion similar to that in open surgery while minimizing destruction to adjacent tissues. This technique was safe and exhibited a trend toward decreased intraoperative blood loss, length of stay and the risk of neurological complications.

Clinical anatomy and 3D virtual reconstruction of the lumbar plexus with respect to lumbar surgery

Background

Exposure of the anterior or lateral lumbar via the retroperitoneal approach easily causes injuries to the lumbar plexus. Lumbar plexus injuries which occur during anterior or transpsoas lumbar spine exposure and placement of instruments have been reported. This study aims is to provide more anatomical data and surgical landmarks in operations concerning the lumbar plexus in order to prevent lumbar plexus injuries and to increase the possibility of safety in anterior approach lumbar surgery.

Methods

To study the applied anatomy related to the lumbar plexus of fifteen formaldehyde-preserved cadavers, Five sets of Virtual Human (VH) data set were prepared and used in the study. Three-dimensional (3D) computerized reconstructions of the lumbar plexus and their adjacent structures were conducted from the VH female data set.

Results

The order of lumbar nerves is regular. From the anterior view, lumbar plexus nerves are arranged from medial at L5 to lateral at L2. From the lateral view, lumbar nerves are arranged from ventral at L2 to dorsal at L5. The angle of each nerve root exiting outward to the corresponding intervertebral foramen increases from L1 to L5. The lumbar plexus nerves are observed to be in close contact with transverse processes (TP). All parts of the lumbar plexus were located by sectional anatomy in the dorsal third of the psoas muscle. Thus, access to the psoas major muscle at the ventral 2/3 region can safely prevent nerve injuries. 3D reconstruction of the lumbar plexus based on VCH data can clearly show the relationships between the lumbar plexus and the blood vessels, vertebral body, kidney, and psoas muscle.

Conclusion

The psoas muscle can be considered as a surgical landmark since incision at the ventral 2/3 of the region can prevent lumbar plexus injuries for procedures requiring exposure of the lateral anterior of the lumbar. The transverse process can be considered as a landmark and reference in surgical operations by its relative position to the lumbar plexus. 3D reconstructions of the lumbar plexus based on VCH data provide a virtual morphological basis for anterior lumbar surgery.

Changes in coronal and sagittal plane alignment following minimally invasive direct lateral interbody fusion for the treatment of degenerative lumbar disease in adults: a radiographic study

OBJECTIVE

The lateral transpsoas approach for lumbar interbody fusion is a minimal access technique that has been used by some to treat lumbar degenerative conditions, including degenerative scoliosis. Few studies, however, have analyzed its effect on coronal and sagittal plane correction, and no study has compared changes in segmental, regional, and global coronal and sagittal alignment after this technique. The object of this study was to determine changes in sagittal and coronal plane alignment occurring after direct lateral interbody fusion (DLIF).

METHODS

The authors performed a review of the radiographic records of 36 patients with lumbar degenerative disease treated with the DLIF technique. Thirty-five patients underwent supplemental posterior fixation to maintain correction. Preoperative and postoperative standing anteroposterior and lateral lumbar radiographs were obtained in all patients for measurement of segmental and regional coronal and sagittal Cobb angles. Standing anteroposterior and lateral 36-in radiographs were also obtained in 23 patients for measurement of global coronal (center sacral vertebral line) and sagittal (C-7 plumb line) balance.

RESULTS

The mean coronal segmental Cobb angle was 4.5° preoperatively, and it was 1.5° postoperatively (p < 0.0001). The mean pre- and postoperative regional lumbar coronal Cobb angles were 7.6° and 3.6°, respectively (p = 0.0001). In 8 patients with degenerative scoliosis, the mean pre- and postoperative regional lumbar coronal Cobb angles were 21.4° and 9.7°, respectively (p = 0.0004). The mean global coronal alignment was 19.1 mm preoperatively, and it was 12.5 mm postoperatively (p < 0.05). In the sagittal plane, the mean segmental Cobb angle measured -5.3° preoperatively and -8.2° postoperatively (p < 0.0001). The mean pre- and postoperative regional lumbar lordoses were 42.1° and 46.2°, respectively (p > 0.05). The mean global sagittal alignment was 41.5 mm preoperatively and 42.4 mm postoperatively (p = 0.7). The average clinical follow-up was 21 months in 21 patients. The mean pre- and postoperative visual analog scale scores were 7.7 and 2.9, respectively (p < 0.0001). The mean pre- and postoperative Oswestry Disability Indices were 43 and 21, respectively (p < 0.0001).

CONCLUSIONS

Direct lateral interbody fusion significantly improves segmental, regional, and global coronal plane alignment in patients with degenerative lumbar disease. Although DLIF increases the segmental sagittal Cobb angle at the level of instrumentation, it does not improve regional lumbar lordosis or global sagittal alignment.

An analysis of postoperative thigh symptoms after minimally invasive transpsoas lumbar interbody fusion

OBJECTIVE

The minimally invasive transpsoas interbody fusion technique requires dissection through the psoas muscle, which contains the nerves of the lumbosacral plexus posteriorly and genitofemoral nerve anteriorly. Retraction of the psoas is becoming recognized as a cause of transient postoperative thigh pain, numbness, paresthesias, and weakness. However, few reports have described the nature of thigh symptoms after this procedure.

METHODS

The authors performed a review of patients who underwent the transpsoas technique for lumbar spondylotic disease, disc degeneration, and spondylolisthesis treated at a single academic medical center. A review of patient charts, including the use of detailed patient-driven pain diagrams performed at equal preoperative and follow-up intervals, investigated the survival of postoperative thigh pain, numbness, paresthesias, and weakness of the iliopsoas and quadriceps muscles in the follow-up period on the ipsilateral side of the surgical approach.

RESULTS

Over a 3.2-year period, 59 patients underwent transpsoas interbody fusion surgery. Of these, 62.7% had thigh symptoms postoperatively. New thigh symptoms at first follow-up visit included the following: burning, aching, stabbing, or other pain (39.0%); numbness (42.4%); paresthesias (11.9%); and weakness (23.7%). At 3 months postoperatively, these percentages decreased to 15.5%, 24.1%, 5.6%, and 11.3%, respectively. Within the patient sample, 44% underwent a 1-level, 41% a 2-level, and 15% a 3-level transpsoas operation. While not statistically significant, thigh pain, numbness, and weakness were most prevalent after L4-5 transpsoas interbody fusion at the first postoperative follow-up. The number of lumbar levels that were surgically treated had no clear association with thigh symptoms but did correlate directly with surgical time, intraoperative blood loss, and length of hospital stay.

CONCLUSIONS

Transpsoas interbody fusion is associated with high rates of immediate postoperative thigh symptoms. While larger, prospective studies are necessary to validate these findings, the authors found that half of the patients had symptom resolution at approximately 3 months postoperatively and more than 90% by 1 year.

Safe working zones using the minimally invasive lateral retroperitoneal transpsoas approach: a morphometric study

PURPOSE

The minimally invasive lateral retroperitoneal transpsoas approach is a recent technique developed for lumbar interbody fusion and discectomy. The proximity of the retroperitoneal vessels and ventral nerve roots to the surgical pathway increases the risk of injury to these anatomical structures. A precise knowledge of the regional anatomy of the lumbar plexus is required for safe passage through the psoas muscle. Preoperative examination of the axial MRI images will allow the surgeon to observe the neural structures at the operative levels and confirm that abdominal vessels do not obstruct the lateral disc space. The objective of this study was to determine the anatomic position of the ventral nerve roots and the retroperitoneal vessels in relation to the vertebral body in the degenerative spine and to delineate a safe working zone using magnetic resonance imaging (MRI).

METHODS

We retrospectively evaluated lumbar spine MRI in 78 patients (from L1-L2 to L4-L5). The total number of lumbar vertebrae measured was 304 levels. Sagittal MRI sections were used to measure disc height (anterior, middle, posterior). Axial MRI sections were used to measure the sagittal and transversal vertebral endplate diameters, the overlap between ventral nerve roots and the posterior border of the lower endplate of the vertebral body, and the overlap between the retroperitoneal vessels and the anterior border of the lower endplate of the vertebral body. The safe zone was subsequently calculated. It was defined as the relative lower endplate vertebral body sagittal diameter that is anterior to the nerve root and is posterior to the retroperitoneal vessels.

RESULTS

The safe working zone was 75.3% of the lower endplate of the vertebral body sagittal diameter at L1-L2, 59.5% at L2-L3, 51.9% at L3-L4 and 37.8% at L4-L5 levels. This area significantly decreases from L1-L2 to L4-L5 (p < 0.05). Compared with L1-L2, L2-L3 levels, the more anterior position of the nerve root and the more posterior position of the retroperitoneal vessels at the L4-L5 level causes a significant reduction of this area. Compared with the L3-L4 level, we observed that the safe zone decrease was simply secondary to the more anterior position of the nerve roots at the L4-L5 level.

CONCLUSION

Preoperative planning and safe zone delineation are a simple method to assess the relative position of neural and vascular anatomic structures in relation to the surgical area. This method can help spine surgeons to prevent perioperative complications.

Intraoperative and early postoperative complications in extreme lateral interbody fusion: an analysis of 600 cases

STUDY DESIGN

Prospective analysis of 600 extreme lateral interbody fusion (XLIF) approach procedures for intraoperative and perioperative complications.

OBJECTIVE

To delineate and describe complications in a large, prospective series of minimally invasive lateral lumbar fusion procedures (XLIF).

SUMMARY OF BACKGROUND DATA

While some small series of lateral lumbar fusion have discussed complications, no results from large studies have been reported.

METHODS

A total of 600 patients were treated with a lateral approach to fusion (XLIF) for degenerative spinal conditions. Data were collected prospectively on all patients and analyzed for demographic, diagnostic, and hospitalization information to identify operative and early postoperative complications. Documented complication types and rates in this large series were compared with smaller prior reports on lateral approach fusions, as well as other minimally invasive (mini-anterior lumbar interbody fusion and minimally invasive surgical [MIS] transforaminal lumbar interbody fusion) and more traditional fusion approaches (posterior intertransverse fusion, anterior lumbar interbody fusion, posterior lumbar interbody fusion, transforaminal lumbar interbody fusion).

RESULTS

Seven hundred forty-one levels were treated, 80.8% single level, 15.0% 2 level, 4.0% 3 level, 0.2% 4 level; 59.3%, including the L4 to L5 levels. A total of 99.2% included supplemental internal fixation; 83.2% included pedicle screw fixation (predominantly unilateral). Hemoglobin change from pre- to postoperation averaged 1.38. Hospital stay averaged 1.21 days. The overall incidence of perioperative complications (intraoperation and out to 6 weeks postoperation) was 6.2%: 9 (1.5%) in-hospital surgery-related events, 17 (2.8%) in-hospital medical events, 6 (1.0%) out-of-hospital surgery-related events, and 5 (0.8%) out-of-hospital medical events. There were no wound infections, no vascular injuries, no intraoperative visceral injuries, and 4 (0.7%) transient postoperative neurologic deficits. Eleven events (1.8%) resulted in additional procedures/reoperation.

CONCLUSIONS

Compared with traditional open approaches, the MIS lateral approach to fusion by using the XLIF technique resulted in a lower incidence of infection, visceral and neurologic injury, and transfusion as well as markedly shorter hospitalization. Complications in MIS XLIF compare favorably with those from other MIS fusion procedures; duration of hospitalization is shorter than with any previously reported technique.

Dynamically evoked, discrete-threshold electromyography in the extreme lateral interbody fusion approach

OBJECT

because the psoas muscle, which contains nerves of the lumbar plexus, is traversed during the extreme lateral interbody fusion (XLIF) approach, appropriate nerve monitoring is needed to avoid nerve injury during surgery and prevent approach-related neural deficit. This study was performed to assess the effectiveness of dynamically evoked electromyography (EMG) to detect and prevent neural injury during the XLIF approach.

METHODS

one hundred two patients undergoing XLIF at L3-4 and/or L4-5 were enrolled in a prospective, multicenter, nonrandomized clinical study. The EMG threshold values for each of the 3 successive dilators were recorded at the surface of the psoas muscle, mid-psoas, and on the spine. At each location, the dilators were rotated 360°, taking recordings immediately posterior, superior, anterior, and inferior. For each dilator, the authors noted the rotational position (the angle in degrees) at which the lowest threshold was found. Findings of pre- and postoperative neurological examinations were also recorded.

RESULTS

nerves were identified within proximity of the dilators (alert-level EMG feedback) in 55.7% of all cases during the XLIF approach. Although nerves were more commonly identified in the posterior margin (63%), there was significant variability in the location of nerves identified. Despite the fact that the posterior half of the disc space was targeted in 90% of cases, no significant long-lasting neural deficits were identified in any case; 27.5% experienced new iliopsoas/hip flexion weakness and 17.6% experienced new postoperative upper medial thigh sensory loss. Transient motor deficits were identified in 3 patients (2.9%), and all had resolved by the 6-month follow-up visit.

CONCLUSIONS

the ability to identify and report a discrete, real-time EMG threshold during the transpsoas approach helps to avoid nerve injury and is required for the safe performance of the XLIF procedure. Additionally, nerve location is variable, thus reinforcing the need for real-time directional and proximity information.

Minimally invasive surgery: lateral approach interbody fusion: results and review

STUDY DESIGN

A retrospective review of patients treated at 2 institutions with anterior lumbar interbody fusion using a minimally invasive lateral retroperitoneal approach, and review of literature.

OBJECTIVE

To analyze the outcomes from historical literature and from a retrospectively compiled database of patients having undergone anterior interbody fusions performed through a lateral approach.

SUMMARY OF BACKGROUND DATA

A paucity of published literature exists describing outcomes following lateral approach fusion surgery.

METHODS

Patients treated with extreme lateral interbody fusion (XLIF) were identified through retrospective chart review. Treatment variables included operating room (OR) time, estimated blood loss (EBL), length of hospital stay (LOS), complications, and fusion rate. A literature review, using the National Center for Biotechnology Information databases PubMed/MEDLINE and Google Scholar, yielded 14 peer-reviewed articles reporting outcomes scoring, complications, fusion status, long-term follow-up, and radiographic assessments related to XLIF. Published XLIF results were summarized and evaluated with current study data.

RESULTS

A total of 84 XLIF patients were included in the current cohort analysis. OR time, EBL, and length of hospital stay averaged 199 minutes, 155 mL, and 2.6 days, respectively, and perioperative and postoperative complication rates were 2.4% and 6.1%. Mean follow-up was 15.7 months. Sixty-eight patients showed evidence of solid arthrodesis and no subsidence on computed tomography and flexion/extension radiographs. Results were within the ranges of those in the literature. Literature review identified reports of significant improvements in clinical outcomes scores, radiographic measures, and cost effectiveness.

CONCLUSION

Current data corroborates and contributes to the existing body of literature describing XLIF outcomes. Procedures are generally performed with short OR times, minimal EBL, and few complications. Patients recover quickly, requiring minimal hospital stay, although transient hip/thigh pain and/or weakness is common. Long-term outcomes are generally favorable, with maintained improvements in patient-reported pain and function scores as well as radiographic parameters, including high rates of fusion.

Electromyographic monitoring and its anatomical implications in minimally invasive spine surgery

STUDY DESIGN

Literature review.

OBJECTIVE

The objective of this article is to examine current intraoperative electromyography (EMG) neurophysiologic monitoring methods and their application in minimally invasive techniques. We will also discuss the recent application of EMG and its anatomic implications to the minimally invasive lateral transpsoas approach to the spine.

SUMMARY OF BACKGROUND DATA

Minimally invasive techniques require that the same goals of surgery be achieved, with the hope of decreased morbidity to the patient. Unlike standard open procedures, direct visualization of the anatomy is decreased. To increase the safety of minimally invasive spine surgery, neurophysiological monitoring techniques have been developed.

METHODS

Review of the literature was performed using the National Center for Biotechnology Information databases using PUBMED/MEDLINE. All articles in the English language discussing the use of intraoperative EMG monitoring and minimally invasive spine surgery were reviewed. The role of EMG monitoring in special reference to the minimally invasive lateral transpsoas approach is also described.

RESULTS

In total, 76 articles were identified that discussed the role of neuromonitoring in spine surgery. The majority of articles on EMG and spine surgery discuss the use of intraoperative neurophysiological monitoring (IOM) for safe and accurate pedicle screw placement. In general, there is a paucity of literature that pertains to intraoperative EMG neuromonitoring and minimally invasive spine surgery. Recently, EMG has been used during minimally invasive lateral transpsoas approach to the lumbar spine for interbody fusion. The addition of EMG to the lateral approach has contributed to decrease the complication rate from 30% to less than 1%.

CONCLUSION

In minimally invasive approaches to the spine, the use of EMG IOM might provide additional safety, such as percutaneous pedicle screw placement, where visualization is limited compared with conventional open procedures. In addition to knowledge of the anatomy and image guidance, directional EMG IOM is crucial for safe passage through the psoas muscle during the minimally invasive lateral retroperitoneal approach.

Migrated XLIF cage: case report and discussion of surgical technique

Extreme lateral interbody fusion (XLIF; NuVasive, Inc, San Diego, California) is a minimally invasive technique developed to avoid complications associated with traditional or minimally invasive anterior or posterior approaches to lumbar interbody fusion. It uses a direct lateral, retroperitoneal, transpsoas approach for placement of an interbody cage. To date, no reports of cage-related complications or procedures for revising an XLIF have been published. This article describes a case of a complication unique to this procedure and the surgical technique used to treat it. A 49-year-old woman underwent XLIF at L3-4 with supplemental posterior pedicle fixation for treatment of a pseudarthrosis of a previous fusion performed for junctional degeneration below an old scoliosis construct. One month postoperatively, she reported increasing leg pain, and imaging studies demonstrated the cage to have extruded laterally. The cage was revised using a mini-open lateral approach. The presence of neurologic symptoms (leg pain) necessitated the cage to first be reimpacted before it could be safely extracted. A new cage was placed with the addition of a lateral plate. The patient's leg pain resolved shortly after the revision, and at 1-year follow-up, she appeared to have a solid fusion with no further complications. If required, XLIF may be safely and effectively revised through a minimally invasive or mini-open lateral approach. Use of a lateral plate as a buttress should be considered in cases associated with significant coronal deformity or lateral listhesis, even when planning use of supplemental posterior instrumentation.

Incidence and prevention of intervertebral cage overhang with minimally invasive lateral approach fusions

STUDY DESIGN

Radiographic review.

OBJECTIVE

To evaluate the incidence and degree of cage overhang in minimally invasive spinal (MIS) fusions, when using either the direct lateral interbody fusion (DLIF) or extreme lateral interbody fusion (XLIF) techniques.

SUMMARY OF BACKGROUND DATA

Among the difficulties surgeons face during a MIS lateral interbody fusion is to assess the proper placement of the cage without the use of direct visualization. Determining the proper length of the cage using AP view fluoroscopy can be misleading. As the axial profile of the vertebral body is oval, inserting the cage anterior or posterior to the maximal width point requires adjustment of the cage's length.

METHODS

The incidence and degree of cage overhang were measured using magnetic resonance imaging (MRI) and computed tomography (CT) studies from patients that underwent a MIS lateral interbody fusion. To determine the adjustment needed when the cage is inserted at various sagittal sites, the coronal spans of normal vertebral endplates were measured.

RESULTS

Forty-five percent of the cages were placed in the central portion, 34% were located in the anterior 1/3, and 7% were located in the posterior 1/3 of the disc space. Of the anterior positioned cages, 45% were found to be overhanging outside of the boundaries of the intervertebral disc space. The average measured lateral protrusion was 7.8 +/- 3.6 mm, and anterior protrusion was 9.8 +/- 3.3 mm. The vertebral body width measured 41.7 +/- 6 mm at the anterior 1/3, 50 +/- 4 mm at the mid, and 49 +/- 1 mm at the posterior 1/3. Compared with the midvertebral width, the vertebral body width at the anterior 1/3 was decreased by 16.5% +/- 0.9% (P < 0.05).

CONCLUSION

The risk of placing an excessively long cage, when the insertion site is located in the anterior 1/3 of the disc, is relatively high, when performing MIS lateral approach interbody fusions. When using an anterior entry point for the insertion of the cage, choosing a 15% shorter cage length compared with that measured on the AP should prevent anterolateral protrusion of the cage.

Fusion after minimally disruptive anterior lumbar interbody fusion: Analysis of extreme lateral interbody fusion by computed tomography

BACKGROUND

Less invasive fusion approaches, such as extreme lateral interbody fusion (XLIF), have proliferated, but few reports have critically assessed fusion rates. To date, no studies have reported computed tomography (CT) documented fusion rates following XLIF.

METHODS

An institutional review board-approved prospective radiographic and CT assessment of minimally disruptive anterior lumbar interbody fusion (mini-ALIF) fusions performed through the XLIF approach. Sixty-six patients (88 operative levels) were examined 12 months after XLIF to determine the rate and quality of anterior lumbar fusion.

RESULTS

Eighty five of the 88 levels (96.6%) were judged fused by CT. Sixty-four of the 66 patients (97.0%) were judged fused by CT. Patient satisfaction at 12 months after surgery was high, with 89.4% reportedly "satisfied or very satisfied" with their results. No revisions were necessary for pseudarthrosis.

CONCLUSION

Mini-ALIF using an XLIF approach reliably results in anterior lumbar fusion.

Presacral retroperitoneal approach to axial lumbar interbody fusion: a new, minimally invasive technique at L5-S1: Clinical outcomes, complications, and fusion rates in 50 patients at 1-year follow-up

BACKGROUND

The presacral retroperitoneal approach to an axial lumbar interbody fusion (ALIF) is a percutaneous, minimally invasive technique for interbody fusion at L5-S1 that has not been extensively studied, particularly with respect to long-term outcomes.

OBJECTIVE

The authors describe clinical and radiographic outcomes at 1-year follow-up for 50 consecutive patients who underwent the presacral ALIF.

METHODS

Our patients included 24 males and 26 females who underwent the presacral ALIF procedure for interbody fusion at L5-S1. Indications included mechanical back pain and radiculopathy. Thirty-seven patients had disc degeneration at L5-S1, 7 had previously undergone a discectomy, and 6 had spondylolisthesis. A 2-level L4-S1 fusion was performed with a transforaminal lumbar interbody fusion at L4-5 in 15 patients. AxiaLIF was performed as a stand-alone procedure in 5 patients and supplemented with pedicle screws in 45 patients. Pre- and postoperative visual analog scale (VAS) and Oswestry Disability Index (ODI) scores were evaluated and complications were tracked. Fusion was evaluated by an independent neuro-radiologist.

RESULTS

At 1-year follow-up, VAS and ODI scores had significantly improved by 49% and 50%, respectively, versus preoperative scores. By high-resolution computer tomography (CT) scans, fusion was achieved in 44 (88%) patients, developing bone occurred in 5 (10%), and 1 (2%) patient had pseudoarthrosis. One patient suffered a major operative complication-a bowel perforation with a pre-sacral abscess that resolved with treatment.

CONCLUSION

Our initial 50 patients who underwent presacral ALIF showed clinical improvement and fusion rates comparable with other interbody fusion techniques; its safety was reflected by low complication rates. Its efficacy in future patients will continue to be monitored, and will be reported in a 2-year follow-up study of fusion.

Minimally invasive surgery for thoracolumbar spinal deformity: initial clinical experience with clinical and radiographic outcomes

Object

Adult degenerative scoliosis can be a cause of intractable pain, decreased mobility, and reduced quality of life. Surgical correction of this problem frequently leads to substantial clinical improvement, but advanced age, medical comorbidities, osteoporosis, and the rigidity of the spine result in high surgical complication rates. Minimally invasive surgery is being applied to this patient population in an effort to reduce the high complication rates associated with adult deformity surgery.

Methods

A retrospective study of 23 patients was undertaken to assess the clinical and radiographic results with minimally invasive surgery for adult thoracolumbar deformity surgery. All patients underwent a lateral interbody fusion followed by posterior percutaneous screw fixation and possible minimally invasive surgical transforaminal lumbar interbody fusion if fusion near the lumbosacral junction was necessary. A mean of 3.7 intersegmental levels were treated (range 2–7 levels). The mean follow-up was 13.4 months.

Results

The mean preoperative Cobb angle was 31.4°, and it was corrected to 11.5° at follow-up. The mean blood loss was 477 ml, and the operative time was 401 minutes. The mean visual analog scale score improvement for axial pain was 3.96. Clear evidence of fusion was seen on radiographs at 84 of 86 treated levels, with no interbody pseudarthroses. Complications included 2 returns to the operating room, one for CSF leakage and the other for hardware pullout. There were no wound infections, pneumonia, deep venous thrombosis, or new neurological deficits. However, of all patients, 30.4% experienced new thigh numbness, dysesthesias, pain, or weakness, and in one patient these new symptoms were persistent.

Conclusions

The minimally invasive surgical treatment of adult deformities is a promising method for reducing surgical morbidity. Numerous challenges exist, as the surgical technique does not yet allow for all correction maneuvers used in open surgery. However, as the techniques are advanced, the applicability of minimally invasive surgery for this population will likely be expanded and will afford the opportunity for reduced complications.

Early outcomes and safety of the minimally invasive, lateral retroperitoneal transpsoas approach for adult degenerative scoliosis

Object

The object of this study was to evaluate an alternative surgical approach to degenerative thoracolumbar deformity in adults. The authors present their early experience with the minimally invasive, lateral retroperitoneal transpsoas approach for placing interbody grafts and providing anterior column support for adult degenerative deformity.

Methods

The authors retrospectively reviewed a prospectively acquired database of all patients with adult thoracolumbar degenerative deformity treated with the minimally invasive, lateral retroperitoneal transpsoas approach at our institution. All patient data were recorded including demographics, preoperative evaluation, procedure used, postoperative follow-up, operative time, blood loss, length of hospital stay, and complications. The Oswestry Disability Index and visual analog scale (for pain) were also administered pre- and postoperatively as early outcome measures. All patients were scheduled for follow-up postoperatively at weeks 2, 6, 12, and 24, and at 1 year.

Results

The authors identified 25 patients with adult degenerative deformity who were treated using the minimally invasive, lateral retroperitoneal transpsoas approach. All patients underwent discectomy and lateral interbody graft placement for anterior column support and interbody fusion. The mean total blood loss was 53 ml per level. The average length of stay in the hospital was 6.2 days. Mean follow-up was 11 months (range 3–20 months). A mean improvement of 5.7 points on visual analog scale scores and 23.7% on the Oswestry Disability Index was observed. Perioperative complications include 1 patient with rhabdomyolysis requiring temporary hemodialysis, 1 patient with subsidence, and 1 patient with hardware failure. Three patients (12%) experienced transient postoperative anterior thigh numbness, ipsilateral to the side of approach. In this series, 20 patients (80%) were identified who had more than 6 months of follow-up and radiographic evidence of fusion. The minimally invasive, lateral retroperitoneal transpsoas approach, without the use of osteotomies, did not correct the sagittal balance in approximately one-third of the patients.

Conclusions

Degenerative scoliosis of the adult spine is secondary to asymmetrical degeneration of the discs. Surgical decompression and correction of the deformity can be performed from an anterior, posterior, or combined approach. These procedures are often associated with long operative times and a high incidence of complications. The authors' experience with the minimally invasive, lateral retroperitoneal transpsoas approach for placement of a large interbody graft for anterior column support, restoration of disc height, arthrodesis, and realignment is a feasible alternative to these procedures.

Direct lateral lumbar interbody fusion for degenerative conditions: early complication profile

STUDY DESIGN/SETTING

A community hospital prospective, nonrandomized chart review. March 2004 to December 2006, 58 patients were treated. Adverse events: new complaints and increasing length of stay limit early mobilization and require consultation with other physicians or reoperation. These formed the focus of the study.

OBJECTIVE

Assess patient demographics and adverse events related to direct lateral lumbar approach.

SUMMARY OF BACKGROUND DATA

Clinicians advocate anterior column support for lumbar conditions. Minimally invasive stabilization of lumbar spine via direct lateral approach gained popularity owing to perceived decrease in patient morbidity.

METHODS

Mild or major adverse events during hospital stay or within 6 weeks of discharge were considered early complications and designated as medical, approach, or implant related. A historical cohort of open posterior spinal fusion patients was used for comparison.

RESULTS

Forty-three female and 15 male patients with a mean age of 61 years formed the study group. Surgery performed included 38 single level, 19 2-level, and 1 3-level case. Adverse events occurred in 13 patients (22.4%); 8 events were approach, 3 medical, and 1 implant bone interface related. Major complications occurred in 5 patients (8.6%). Two patients (3.4%) with L4 nerve injury showed residual motor effects, at 1 year postoperatively. Significant differences were noted between single and 2-level cases; Estimated blood loss (EBL) and operative time. Open posterior fusion patients experienced greater operative time and increased EBL compared with minimally invasive cases.

CONCLUSIONS

Major adverse events approximated 8.6% with approach-related complaints of nerve irritation nearing 3.4%. Mild complications occurred in 13.7% of patients. Meralgia paresthetica was a primary approach-related complaint. Most complaints significantly reduced by first postoperative visit. One patient (1.7%) had symptoms lasting over a year that did not adversely affect function. Significant finding related to exposure, that is, 1-versus 2-level cases. Overall morbidity reduction noted by EBL is considerably less compared with the historical cohort. Direct lateral lumbar interbody fusion has proven to be of value.

Thoracolumbar spinal deformity: Part II. Developments from 1990 to today: historical vignette

In the first part of this 2-part historical review, the authors outlined the early diagnostic and therapeutic strategies used in the management of spinal deformity. In this second part, they expand upon those early innovations and further detail the advances from 1990 to the modern era.

Thoracoscopy for minimally invasive thoracic spine surgery

Thoracoscopy has been used worldwide for many years by thoracic surgeons. Despite a long learning curve and technical demands of the procedure, thoracoscopy has several advantages, including better cosmesis, adequate exposure to all levels of the thoracic spine from T2 to L 1, better illumination and magnification at the site of surgery, less damage to the tissue adjacent to the surgical field, less morbidity when compared with standard thoracotomy in terms of respiratory problems, pain, blood loss, muscle and chest wall damages, consequent shorter recovery time, less postoperative pulmonary function impairment, and shorter hospitalization. Good results at short- and medium-term follow-up need to be confirmed at long-term follow-up.

Morphometric analysis of the ventral nerve roots and retroperitoneal vessels with respect to the minimally invasive lateral approach in normal and deformed spines

STUDY DESIGN

A morphometric analysis, using magnetic resonance imaging (MRI) studies of the lumbar spine.

OBJECTIVE

To identify the anatomic position of the ventral root and the retroperitoneal vessels in relation to the vertebral body in normally aligned and deformed spines.

SUMMARY OF BACKGROUND DATA

The lateral approach to the lumbar spine is a relatively new method for performing interbody fusions. In contrast to the standard open anterior approach with direct vision of the operative field, the lateral approach uses expandable retractors that are positioned under fluoroscopic guidance. Risks of this technique include injury to the exiting nerve root and retroperitoneal vessels.

METHODS

One hundred lumbar spine MRI studies were reviewed from patients treated for various spinal pathologies. The measured intervertebral segments were divided into 3 groups: group 1 (n = 247), normally aligned vertebrae and disc spaces; group 2 (n = 18), degenerative spondylolisthetic segments; and group 3 (n = 19), segments from the apex of degenerative lumbar scoliosis. Axial MR images were used to measure: the vertebral endplate anterior-posterior (AP) diameter, the overlap between the ventral root and the posterior margin of the vertebra, and the overlap between the retroperitoneal large vessels and the anterior edge of the vertebra.

RESULTS

The overlap between the adjacent neuro-vascular structures and the vertebral body endplate gradually increased from L1-L2 to L4-L5. The maximal overlap, at the L4-L5 level reached 87% resulting in a relatively narrow corridor for performing the operative procedure. Alteration in the anatomic location of the nerve root and the retroperitoneal vessels, in Group 3 (scoliosis) further decreased the safe corridor.

CONCLUSION

The safe corridor for performing the discectomy and inserting the intervertebral cage narrows from L1-L2 to the L4-L5 level. This corridor is further narrowed with rotatory deformity of the spine. Using the preoperative MRI to assess the relative position of the adjacent neuro-vascular structures in relation to the lower vertebra's endplate at each level is recommended.

An anatomical study of the lumbosacral plexus as related to the minimally invasive transpsoas approach to the lumbar spine

OBJECT

Minimally invasive anterolateral approaches to the lumbar spine are options for the treatment of a number of adult degenerative spinal disorders. Nerve injuries during these surgeries, although rare, can be devastating complications. With an increasing number of spine surgeons utilizing minimal access retroperitoneal surgery to treat lumbar problems, the frequency of complications associated with this approach will likely increase. The authors sought to better understand the location of the lumbar contribution of the lumbosacral plexus relative to the disc spaces encountered when performing the minimally invasive transpsoas approach, also known as extreme lateral interbody fusion or direct lateral interbody fusion.

METHODS

Three fresh cadavers were placed lateral, and a total of 3 dissections of the lumbar contribution of the lumbosacral plexus were performed. Radiopaque soldering wire was then laid along the anterior margin of the nerve fibers and the exiting femoral nerve. Markers were placed at the disc spaces and lateral fluoroscopy was used to measure the location of the lumbar plexus along each respective disc space in the lumbar spine (L1-2, L2-3, L3-4, and L4-5).

RESULTS

The lumbosacral plexus was found lying within the substance of the psoas muscle between the junction of the transverse process and vertebral body and exited along the medial edge of the psoas distally. The lumbosacral plexus was most dorsally positioned at the posterior endplate of L1-2. A general trend of progressive ventral migration of the plexus on the disc space was noted at L2-3, L3-4, and L4-5. Average ratios were calculated at each level (location of the plexus from the dorsal endplate to total disc length) and were 0 (L1-2), 0.11 (L2-3), 0.18 (L3-4), and 0.28 (L4-5).

CONCLUSIONS

This anatomical study suggests that positioning the dilator and/or retractor in a posterior position of the disc space may result in nerve injury to the lumbosacral plexus, especially at the L4-5 level. The risk of injuring inherent nerve branches directed to the psoas muscle as well as injury to the genitofemoral nerve do still exist.

MINIMALLY INVASIVE POSTERIOR FIXATION

SIGNIFICANT ADVANCES HAVE been made in the contemporary management of thoracolumbar spinal deformities, including improved segmental bony fixation, techniques for osteotomy, and mechanically powerful reduction maneuvers, which now allow the spinal surgeon to correct severe, complex, and rigid spinal deformities. However, one of the major limitations of surgical intervention has been the high complication rates associated with these surgical endeavors. Much of the morbidity associated with posterior deformity surgery relates to the extensive soft tissue destruction necessary to gain access to multiple segments of the axial skeleton. The open exposures for long-segment fixation result in additional blood loss, increased rates of infection, and prolonged immobilization caused by postoperative pain. Minimally invasive techniques attempt to overcome these drawbacks of the open exposures, and this report reviews preliminary experience in treating spinal deformities with long-segment minimally invasive internal fixation.

MINIMALLY INVASIVE ANTEROLATERAL APPROACHES FOR THE TREATMENT OF BACK PAIN AND ADULT DEGENERATIVE DEFORMITY

MINIMALLY INVASIVE AND interbody and instrumented fusion techniques are increasingly being used for the treatment of adult degenerative disc disease, stenosis, and deformity of the lumbar spine. Advocates of minimal access spinal approaches list certain advantages over open procedures, including decreased postoperative pain and narcotic requirements, shorter hospital stays, less blood loss, and smaller incisions. The minimally invasive anterolateral approach allows access to the lumbar spine through the retroperitoneal space. We report on the short-term clinical and radiographic outcomes in four patients with mid to high lumbar coronal deformities treated at our institution with the anterolateral transpsoas minimally invasive approach. The primary presentation of these patients was back and leg pain. All patients showed improvement in their preoperative symptoms and solid arthrodesis at 6 months. Independent nonbiased patient pain analysis was also performed. Mean follow-up was 10 months (standard deviation, 1.4 mo), and mean hospital stay was 3.5 days (standard deviation, 1.9 d). One patient had additional posterior segmental instrumentation placed. Mean Cobb angles in the coronal plane were 28.5 degrees preoperatively and 18.3 degrees postoperatively (P &lt; 0.05). We also present a historical perspective on retroperitoneal spine surgery, a regional anatomic description of the lumbosacral plexus and surrounding structures, and a description of the surgical technique as related to treatment of lumbar deformity.

Technique and clinical results of minimally invasive reconstruction and stabilization of the thoracic and thoracolumbar spine with expandable cages and ventrolateral plate fixation

OBJECTIVE

To evaluate the techniques of minimally invasive single- and multilevel corpectomy and reconstruction of the thoracic and thoracolumbar spine using expandable vertebral body replacement (VBR) cages and ventrolateral plate fixation (VPF) via anterolateral retropleural (ALRA) and combined thoracoabdominal approaches.

METHODS

38 patients with spondylitis, traumatic or metastatic lesions of thoracic or thoracolumbar vertebrae T4 to L2 underwent spinal decompression and ventral column reconstruction with correction of spinal deformity by VBR and VPF via ALRA or a combined lateral extrapleural/extraperitoneal (extracoelomic) thoracolumbar approach (CLETA). Overall clinical and neurological outcome, operative time, blood loss, reduction of deformity, and postoperative pain were assessed during a mean follow-up period of 22.8 months.

RESULTS

VBR and VPF were carried out successfully without conversion to conventional approaches in all patients. Mean operative time (ALRA, 163 +/- 33 min; CLETA, 175 +/- 39 min), mean blood loss (ALRA, 280 +/- 160 ml; CLETA, 420 +/- 250 ml), average correction (19.3 degrees), loss of correction of sagittal deformity (0.9 degrees), and clinical outcome compare favorably to the results reported for open and endoscopic techniques. Postoperative pain levels (mean visual analog scale score at 24 h, 2.7 +/- 0.9) and the incidence of postoperative pulmonary dysfunction (three out of 38 patients) were low. The average length of stay was 7.4 days. ALRA and CLETA obviate routine chest tube insertion, thus allowing for early postoperative ambulation (average, 1.1 d).

CONCLUSION

Minimally invasive VBR and VPF conducted via minimally invasive approaches (ALRA or CLETA) yields favorable clinical results at least equal to conventional open surgery, with significant reductions in perioperative morbidity and pain, expedited ambulation, and early discharge from the hospital.

Minimally invasive techniques for lumbar interbody fusions

Lumbar spinal fusions have been performed for nearly a century for a variety of spinal conditions and include posterior/posterolateral and anterior lumbar interbody fusions. Traditionally, the ability to achieve adequate exposure to perform these procedures required an open surgical approach; however, the advent of newer techniques and technology, combined with an improved understanding of surgical anatomy, has resulted in newer minimally invasive techniques. Posterior approaches include posterior and transforaminal lumbar interbody fusions, whereas anterior techniques include retroperitoneal and transperitoneal anterior lumbar interbody fusion approaches. More recently, the extreme lateral interbody fusion and axial lumbar interbody fusion have been described. This article provides a general review of the history, indications, brief overview, and description of the more common minimally invasive spine surgery techniques used for achieving a lumbar interbody fusion.

Minimally invasive lumbar spinal fusion

Minimally invasive techniques for lumbar spine fusion have been developed in an attempt to decrease the complications related to traditional open exposures (eg, infection, wound healing problems). Anterior minimally invasive procedures include laparoscopic and mini-open anterior lumbar interbody fusion as well as the lateral transpsoas and percutaneous presacral approaches. Posterior techniques typically use a tubular retractor system that avoids the muscle stripping associated with open procedures. These techniques can be applied to both posterior and transforaminal lumbar interbody fusion procedures. Many initial reports have shown similar clinical results in terms of spinal fusion rates for both traditional open and minimally invasive posterior approaches. However, the anterior minimally invasive procedures are often associated with significantly greater incidence of complications and technical difficulty than their associated open approaches. There is a steep learning curve associated with minimally invasive techniques, and surgeons should not expect to master them in the first several cases.

Access strategies for revision or explantation of the Charité lumbar artificial disc replacement

BACKGROUND

Several lumbar disc prostheses are being developed with the goal of preserving mobility in patients with degenerative disc disease. The disadvantage of lumbar artificial disc replacement (ADR) compared with anterior interbody fusion (ALIF) is the increased potential for displacement or component failure. Revision or removal of the device is complicated by adherence of the aorta, iliac vessels, and the ureter to the operative site. Because of these risks of anterior lumbar procedures, vascular surgeons usually provide access to the spine. We report our experience with secondary exposure of the lumbar spine for revision or explantation of the Charité disc prosthesis.

METHODS

Between January 2001 and May 2006, 19 patients with prior implantation of Charité Artificial Discs required 21 operations for repositioning or removal of the device. Two patients had staged removal of prostheses at two levels. One patient had simultaneous explantation at two levels. The mean age was 49 years (range, 31 to 69 years; 56% men, 42% women). The initial ADR was performed at our institution in 14 patients (74%). The mean time from implantation to reoperation was 7 months (range, 9 days to 4 years). The levels of failure were L3-4 in one, L4-5 in nine, and L5-S1 in 12.

RESULTS

The ADR was successfully removed or revised in all patients that underwent reoperation. Three of the 12 procedures at L5-S1 were performed through the same retroperitoneal approach as the initial access. One of these three, performed after a 3-week interval, was converted to a transperitoneal approach because of adhesions. The rest of the L5-S1 prostheses were exposed from a contralateral retroperitoneal approach. Four of the L4-5 prostheses were accessed from the original approach and five from a lateral, transpsoas exposure (four left, one right). The only explantation at L3-4 was from a left lateral transpsoas approach. Nineteen of the 22 ADR were converted to ALIF. Two revisions at L5-S1 involved replacement of the entire prosthesis. One revision at L4-5 required only repositioning of an endplate. Access-related complications included, in one patient each, iliac vein injury, temporary retrograde ejaculation, small-bowel obstruction requiring lysis, and symptomatic, large retroperitoneal lymphocele. There were no permanent neurologic deficits, deep vein thromboses, or deaths.

CONCLUSIONS

Owing to vascular and ureteral fixation, anterior exposure of the lumbar spine for revision or explantation of the Charité disc replacement should be performed through an alternative approach unless the procedure is performed < or = 2 weeks of the index procedure. The L5-S1 level can be accessed through the contralateral retroperitoneum. Reoperation at L3-4 and L4-5 usually requires explantation and fusion that is best accomplished by way of a lateral transpsoas exposure.

Extreme Lateral Interbody Fusion (XLIF): a novel surgical technique for anterior lumbar interbody fusion

BACKGROUND

Minimally disruptive approaches to the anterior lumbar spine continue to evolve in a quest to reduce approach-related morbidity. A lateral retroperitoneal, trans-psoas approach to the anterior disc space allows for complete discectomy, distraction, and interbody fusion without the need for an approach surgeon.

PURPOSE

To demonstrate the feasibility of a minimally disruptive lateral retroperitoneal approach and the advantages to patient recovery.

METHODS/RESULTS

The extreme lateral approach (Extreme Lateral Interbody Fusion [XLIF]) is described in a step-wise manner. There have been no complications thus far in the author's first 13 patients.

CONCLUSIONS

The XLIF approach allows for anterior access to the disc space without an approach surgeon or the complications of an anterior intra-abdominal procedure. Longer-term follow-up and data analysis are under way, but initial findings are encouraging.