Intraoperative Neuromonitoring During Lateral Lumbar Interbody Fusion

Single Position Prone Lateral Lumbar Interbody Fusion: A Review of the Current Literature

PURPOSE OF REVIEW

Spinal fusion, vital for treating various spinal disorders, has evolved since the introduction of the minimally invasive Lateral Lumbar Interbody Fusion (LLIF) by Pimenta in 2001. Traditionally performed in the lateral decubitus position, LLIF faces challenges such as intraoperative repositioning, neurological complications, and lack of access to lower lumbar levels. These challenges lead to long surgery times, increased rates of perioperative complications, and increased costs. The more recently popularized prone lateral approach mitigates these issues primarily by eliminating patient repositioning, thereby enhancing surgical efficiency, and reducing operative times. This review examines the progression of spinal fusion techniques, focusing on the advantages and recent findings of the prone lateral approach compared to the traditional LLIF.

RECENT FINDINGS

The prone lateral approach has shown improved patient outcomes, including lower blood loss and shorter hospital stays, and has been validated by multiple studies for its safety and efficacy compared to the LLIF approach. Significant enhancements in postoperative metrics, such as the Oswestry Disability Index, Visual Analog Scale, and radiological improvements have been noted. Comparatively, the prone lateral approach offers superior segmental lordosis correction and potentially better subjective outcomes than the lateral decubitus position. Despite these advances, both techniques present similar risks of neurological complications. Overall, the prone lateral approach has emerged as a promising alternative in lumbar interbody fusion, combining efficiency, safety, and improved clinical outcomes.

Feasibility of Saphenous Nerve Somatosensory-Evoked Potential Intraoperative Monitoring During Lumbar Spine Surgery: Early Results

STUDY DESIGN

Retrospective review.

OBJECTIVE

Assess the feasibility of saphenous nerve somatosensory evoked potentials (SN-SSEP) monitoring in lumbar spine surgeries.

BACKGROUND CONTEXT

SN-SSEPs have been proposed for detecting lumbar plexus and femoral nerve injury during lateral lumbar surgery where tibial nerve (TN) SSEPs alone are insufficient. SN-SSEPs may also be useful in other types of lumbar surgery, as stimulation of SN below the knee derives solely from the L4 root and provides a means of L4 monitoring, whereas TN-SSEPs often do not detect single nerve root injury. The feasibility of routine SN-SSEP monitoring has not been established.

METHODS

A total of 563 consecutive cases using both TN-SSEP and SN-SSEP monitoring were included. Anesthesia was at the discretion of the anesthesiologist, using an inhalant in 97.7% of procedures. SN stimulation was performed using 13 mm needle electrodes placed below the knee using 200-400 μsec pulses at 15 to 100 mA. Adjustments to stimulation parameters were made by the neurophysiology technician while obtaining baselines. Data were graded retrospectively for monitorability and cortical response amplitudes were measured by two independent reviewers.

RESULTS

Ninety-eight percent of TN-SSEPs and 92.5% of SN-SSEPs were monitorable at baseline, with a mean response amplitude of 1.35 μV for TN-SSEPs and 0.71 μV for SN-SSEPs. A significant difference between the stimulation parameters used to obtain reproducible TN and SN-SSEPs at baseline was observed, with SN-SSEPs requiring greater stimulation intensities. Body mass index is not associated with baseline monitorability. Out of 20 signal changes observed, 11 involved SN, while TN-SSEPs were unaffected.

CONCLUSION

With adjustments to stimulation parameters, SN-SSEP monitoring is feasible within a large clinical cohort without modifications to the anesthetic plan. Incorporating SN into standard intraoperative neurophysiological monitoring protocols for lumbar spine procedures may expand the role of SSEP monitoring to include detecting injury to the lumbar plexus.

LEVEL OF EVIDENCE

3.

Single-Position Prone Lateral Lumbar Interbody Fusion Technique Guide: Surgical Tips and Tricks

Lateral lumbar interbody fusion (LLIF) is a popular technique as it allows for the placement of a large interbody implant through a retroperitoneal, transpsoas working corridor. Historically, the interbody is placed with the patient in lateral decubitus and then repositioned to prone for the posterior instrumentation. While this has been an effective and successful technique, removing the interoperative flip would improve the efficiency of these cases. This has led to modified LLIF approaches including single-position prone LLIF (pLLIF). This modification has shown to be an efficient and powerful technique; however, learning to navigate the LLIF approach in the prone position has its own challenges. The purpose of this article is to provide a detailed description of our pLLIF technique while simultaneously introducing surgical tips to overcome the challenges of the approach and optimize the implantation of the interbody device.

Management of Refractory Post-operative Osteomyelitis and Discitis: A Case Report

Vertebral osteomyelitis/discitis is a relatively rare disease but is a known potential complication of spinal surgical intervention. In general, the first-line treatment for this condition is targeted antibiotic therapy with surgical intervention only utilized in refractory cases with evidence of extensive damage, structural instability, or abscess formation. However, surgical best practices have not been established for osteomyelitis, including indications for anterior lateral interbody fusion (ALIF), posterior lateral interbody fusion (PLIF), or direct lateral interbody fusion (DLIF). This case provides a discussion of the indications that led to a direct lateral approach in the setting of refractory osteomyelitis/discitis, supporting factors that led to its success, and the efficacy of utilizing intraoperative neuromonitoring in cases of infection.

Female Sex and Supine Proximal Lumbar Lordosis Are Associated With the Size of the LLIF "Safe Zone" at L4-L5

STUDY DESIGN

Retrospective chart review.

OBJECTIVE

Identify demographic and sagittal alignment parameters that are independently associated with femoral nerve position at the L4-L5 disk space.

SUMMARY OF BACKGROUND DATA

Iatrogenic femoral nerve or lumbar plexus injury during lateral lumbar interbody fusion (LLIF) can result in neurological complications. The LLIF "safe zone" is the anterior half to two third of the disk space. However, femoral nerve position varies and is inconsistently identifiable on magnetic resonance imaging. The safe zone is also narrowest at L4-L5.

METHODS

An analysis of patients with symptomatic lumbar spine pathology and magnetic resonance imaging with a visibly identifiable femoral nerve evaluated at a single large academic spine center from January 1, 2017, to January 8, 2020, was performed. Exclusion criteria were transitional anatomy, severe hip osteoarthritis, coronal deformity with cobb >10 degrees, > grade 1 spondylolisthesis at L4-L5 and anterior migration of the psoas.Standing and supine lumbar lordosis (LL) and its proximal (L1-L4) and distal (L4-S1) components were measured. Femoral nerve position on sagittal imaging was then measured as a percentage of the L4 inferior endplate. A stepwise multivariate linear regression of sagittal alignment and LL parameters was then performed. Data are written as estimate, 95% CI.

RESULTS

Mean patient age was 58.2±14.7 years, 25 (34.2%) were female and 26 (35.6%) had a grade 1 spondylolisthesis. Mean femoral nerve position was 26.6±10.3% from the posterior border of L4. Female sex (-6.6, -11.1 to -2.1) and supine proximal lumbar lordosis (0.4, 0.1-0.7) were independently associated with femoral nerve position.

CONCLUSIONS

Patient sex and proximal LL can serve as early indicators of the size of the femoral nerve safe zone during a transpsoas LLIF approach at L4-L5.

Imaging study of the effect of postural changes on the retroperitoneal oblique corridor in degenerative lumbar scoliosis

PURPOSE

To investigate the effect of postural changes on access for the OLIF of L2 to L5 in patients with degenerative lumbar scoliosis.

METHODS

Twenty-one individuals with degenerative lumbar scoliosis were chosen at random, 11 with left-sided convexity and 10 with left-sided concavity. Axial T2-weighted images were used to measure the following variables: (1) the distance between the left psoas major muscle and the abdominal aorta; (2) the angle of the surgical access; (3) the distance between the psoas major muscle attachment point and the vertebral body's transverse axis; (4) the region of the psoas major muscle above the vertebrae; and (5) the width-to-thickness ratio. A statistical analysis of the measured parameters was done.

RESULTS

The L2-5 segment in the supine position had a significantly longer window distance in the left convex and left concave groups than in the right lateral recumbent posture (P < 0.05). In all segments, the left concave group outperformed the left convex group, which was substantially higher in the right lateral recumbent posture than in the supine position (P < 0.05). After the position change, the spanning area was significantly higher compared to the same segment in the supine position. The psoas major muscle's morphology was stretched.

CONCLUSIONS

The right lateral recumbent position limits access to OLIF for degenerative lumbar scoliosis, and the "safety window" for OLIF operation in the parietal region is smaller in the left convex group compared to the left concave group, posing a higher risk of intraoperative vascular and neurological injury.

Prone position lateral interbody fusion-a narrative review

Background and Objective

Lateral access lumbar interbody fusion is an increasingly popular procedure that allows for anterior column support through discectomy, endplate preparation, and interbody insertion. This procedure was initially described and performed with the patient in the lateral decubitus position. This would typically be followed by repositioning the patient to the prone position for pedicle screw fixation. Increasingly common is the lateral access lumbar interbody fusion in the prone position. This narrative review seeks to summarize the available literature on advantages, disadvantages, and unique features of the prone position lateral access lumbar interbody fusion.

Methods

We performed a narrative review of articles published up to 01 November 2022 through a PubMed search. The search terms "prone lateral spine surgery" and "lateral approach spine surgery" AND "prone position" were used. Articles not available in English were excluded. The search result abstracts were independently reviewed by 2 authors and 28 full text articles were reviewed. Both reviewing authors were orthopedic surgery chief residents.

Key Content and Findings

There are several unique advantages as well as disadvantages to the prone position lateral interbody fusion. Some advantages include ease of placing pedicle screws, simultaneous posterior and lateral access, greater ease in achieving segmental lumbar lordosis, and a relatively safer positioning of the psoas muscle, lumbar plexus, and abdominal structures. Disadvantages include more difficulties with exposure and retraction, as well as visualization, positioning and ergonomics of surgery.

Conclusions

Prone position lateral interbody fusion is an increasingly prevalent and useful surgical technique with several advantages and disadvantages when compared to lateral interbody fusion in the lateral decubitus position. There are several surgical indications and goals for which prone lateral interbody fusion may provide significant benefit when compared to other interbody fusion techniques.

Surgical treatment of spondylolisthesis by oblique lumbar interbody fusion and transpedicular screw fixation: Comparison between conventional double position versus navigation-assisted single lateral position

BACKGROUND AND OBJECTIVES

Oblique lumbar interbody fusion (OLIF) procedures involve anterior insertion of interbody cage in lateral position. Following OLIF, insertion of pedicle screws and rod system is performed in a prone position (OLIF-con). The location of the cage is important for restoration of lumbar lordosis and indirect decompression. However, inserting the cage at the desired location is difficult without reduction of spondylolisthesis, and reduction after insertion of interbody cage may limit the amount of reduction. Recent introduction of spinal navigation enabled both surgical procedures in one lateral position (OLIF-one). Therefore, reduction of spondylolisthesis can be performed prior to insertion of interbody cage. The objective of this study was to compare the reduction of spondylolisthesis and the placement of cage between OLIF-one and OLIF-con.

METHODS

We retrospectively reviewed 72 consecutive patients with spondylolisthesis for this study; 30 patients underwent OLIF-one and 42 underwent OLIF-con. Spinal navigation system was used for OLIF-one. In OLIF-one, the interbody cage was inserted after reducing spondylolisthesis, whereas in OLIF-con, the cage was inserted before reduction. The following parameters were measured on X-rays: pre- and postoperative spondylolisthesis slippage, reduction degree, and the location of the cage in the disc space.

RESULTS

Both groups showed significant improvement in back and leg pains (p < .05). Transient motor or sensory changes occurred in three patients after OLIF-con and in two patients after OLIF-one. Pre- and postoperative slips were 26.3±7.7% and 6.6±6.2% in OLIF-one, and 23.1±7.0% and 7.4±5.8% in OLIF-con. The reduction of slippage was 74.4±6.3% after OLIF-one and 65.4±5.7% after OLIF-con, with a significant difference between the two groups (p = .04). The cage was located at 34.2±8.9% after OLIF-one and at 42.8±10.3% after OLIF-con, with a significant difference between the two groups (p = .004).

CONCLUSION

Switching the sequence of surgical procedures with OLIF-one facilitated both the reduction of spondylolisthesis and the placement of the cage at the desired location.

Three-column reconstruction through the posterior approach alone for the treatment of a severe lumbar burst fracture in Korea: a case report

Generally, patients with severe burst fractures, instability, or neurological deficits require surgical treatment. In most cases, circumferential reconstruction is performed. Surgical methods for three-column reconstruction include anterior, lateral, and posterior approaches. In cases involving an anterior or lateral approach, collaboration with general or thoracic surgeons may be necessary because the adjacent anatomical structures are unfamiliar to spinal surgeons. Risks include vascular or lumbar plexus injuries and cage displacement, and in most cases, additional posterior fusion surgery is required. However, the posterior approach is the most common and anatomically familiar approach for surgeons performing spinal surgery. We present a case in which three-column reconstruction was performed using only the posterior approach to treat a patient with a severe lumbar burst fracture.

Long-Term Motor versus Sensory Lumbar Plexopathy After Lateral Lumbar Interbody Fusion: Single-Center Experience, Intraoperative Neuromonitoring Results, and Multivariate Analysis of Patient-Level Predictors

BACKGROUND

Although lateral lumbar interbody fusion (LLIF) is an effective surgical option for lumbar arthrodesis, postoperative plexopathies are a common complication. We characterized post-LLIF plexopathies in a large cohort and analyzed potential risk factors for each.

METHODS

A single-institutional cohort who underwent LLIF between May 2015 and December 2019 was retrospectively reviewed for postoperative lumbar plexopathies. Plexopathies were divided based on sensory and motor symptoms and duration, as well as by laterality relative to the surgical approach. We assessed these subgroups for associations with patient and surgical characteristics as well as psoas dimensions. We then evaluated risk of developing plexopathies after intraoperative neuromonitoring observations.

RESULTS

A total of 127 patients were included. The overall rate of LLIF-induced sensory or motor lumbar plexopathy was 37.8% (48/127). Of all cases, 42 were ipsilateral to the surgical approach (33.1%); conversely, 6 patients developed contralateral plexopathies (4.7%). Most (31/48; 64.6%) resolved with a follow-up interval of 402 days in the plexopathy group. Of ipsilateral cases, 24 patients experienced persistent (>90 days) postoperative sensory symptoms (18.9%), whereas 20 experienced persistent weakness (15.7%). More levels fused predicted persistent sensory symptoms (odds ratio, 1.714 [1.246-2.359]; P = 0.0085), whereas surgical duration predicted persistent weakness (odds ratio, 1.004 [1.002-1.006]; P = 0.0382). Psoas anatomic variables were not significantly associated with plexopathy. Nonresolution of intraoperative evoked motor potential alerts was a significant risk factor for developing plexopathies (relative risk, 2.29 [1.17-4.45]).

CONCLUSIONS

Post-LLIF plexopathies are common but usually resolve. Surgical complexity and unresolved neuromonitoring alerts are possible risk factors for persistent plexopathy.

The Prone Lateral Approach for Lumbar Fusion-A Review of the Literature and Case Series

Lateral lumbar interbody fusion is an evolving procedure in spine surgery allowing for the placement of large interbody devices to achieve indirect decompression of segmental stenosis, deformity correction and high fusion rates through a minimally invasive approach. Traditionally, this technique has been performed in the lateral decubitus position. Many surgeons have adopted simultaneous posterior instrumentation in the lateral position to avoid patient repositioning; however, this technique presents several challenges and limitations. Recently, lateral interbody fusion in the prone position has been gaining in popularity due to the surgeon's ability to perform simultaneous posterior instrumentation as well as decompression procedures and corrective osteotomies. Furthermore, the prone position allows improved correction of sagittal plane imbalance due to increased lumbar lordosis when prone on most operative tables used for spinal surgery. In this paper, we describe the evolution of the prone lateral approach for interbody fusion and present our experience with this technique. Case examples are included for illustration.

Impact of preoperative symptom duration in patients undergoing lateral lumbar interbody fusion

BACKGROUND

Few studies have examined the influence of preoperative symptom duration on clinical outcomes in patients undergoing lateral lumbar interbody fusion (LLIF) for degenerative conditions.

METHODS

Patients undergoing LLIF presenting with radiculopathy and/or neurogenic claudication were separated into two groups: preoperative symptom duration < 1-year (shorter duration) versus duration ≥ 1-year (longer duration). Patients undergoing surgery for trauma/malignancy/infection were excluded. Patient-reported outcome measures (PROMs) of Patient-Reported Outcomes Measurement Information System-Physical Function (PROMIS-PF), 12-Item Short Form Physical/Mental Component Score (SF-12 PCS/MCS), Patient Health Questionnaire-9 (PHQ-9), visual analog scale (VAS) back/leg, and Oswestry Disability Index (ODI) were collected at preoperative and postoperative time points.

RESULTS

Eighty-two total patients, with 34 shorter-duration patients, were identified after propensity score matching for demographics. Longer-duration patients had higher estimated blood loss. All patients reported significant improvement in physical function, mental function, pain, and disability in at least one postoperative time point, except for SF-12 MCS in the shorter duration cohort. The longer duration cohort had higher MCID achievement in 12-week VAS back.

CONCLUSION

Patients undergoing LLIF demonstrated significant postoperative improvement in physical function, mental function, pain, and disability outcomes independent of preoperative symptom duration. Both cohorts, when compared by preoperative symptom duration, demonstrated similar postoperative PROM scores. Patients with longer preoperative symptom duration had higher 12-week leg pain MCID achievement. These findings suggest that delayed time to surgery may not lead to inferior clinical outcomes in patients undergoing LLIF for degenerative conditions.