Femoral nerve and lumbar plexus injury after minimally invasive lateral retroperitoneal transpsoas approach: electrodiagnostic prognostic indicators and a roadmap to recovery

A prospective case series to evaluate subcostal nerve injury with high-resolution ultrasound in posterior retroperitoneoscopic adrenalectomy

BACKGROUND

Posterior retroperitoneoscopic adrenalectomy has several advantages over transabdominal laparoscopic adrenalectomy regarding operating time, blood loss, postoperative pain, and recovery. However, postoperatively several patients report chronic pain or hypoesthesia. We hypothesized that these symptoms may be the result of damage to the subcostal nerve, because it passes the surgical area.

METHODS

A prospective single-center case series was performed in adult patients without preoperative pain or numbness of the abdominal wall who underwent unilateral posterior retroperitoneoscopic adrenalectomy. Patients received pre- and postoperative questionnaires and a high-resolution ultrasound scan of the subcostal nerve and abdominal wall muscles was performed before and directly after surgery. Clinical evaluation at 6 weeks was performed with repeat questionnaires, physical examination, and high-resolution ultrasound. Long-term recovery was evaluated with questionnaires, and photographs from the patients were examined for abdominal wall asymmetry.

RESULTS

A total of 25 patients were included in the study. There were no surgical complications. Preoperative visualization of the subcostal nerve was possible in all patients. At 6 weeks, ultrasound showed nerve damage in 15 patients, with no significant association between nerve damage and postsurgical pain. However, there was a significant association between nerve damage and hypoesthesia (p = 0.01), sensory (p < 0.001), and motor (p < 0.001) dysfunction on physical examination. After a median follow-up of 18 months, 5 patients still experienced either numbness or muscle weakness, and one patient experienced chronic postsurgical pain.

CONCLUSION

In this exporatory case series the incidence of postoperative damage to the subcostal nerve, both clinically and radiologically, was 60% after posterior retroperitoneoscopic adrenalectomy. There was no association with pain, and the spontaneous recovery rate was high.

Biomechanical Comparison of Unilateral and Bilateral Pedicle Screw Fixation after Multilevel Lumbar Lateral Interbody Fusion

STUDY DESIGN

Human Cadaveric Biomechanical Study.

OBJECTIVES

Lumbar Lateral Interbody Fusion (LLIF) utilizing a wide cage has been reported as having favorable biomechanical characteristics. We examine the biomechanical stability of unilateral pedicle screw and rod fixation after multilevel LLIF utilizing 26 mm wide cages compared to bilateral fixation.

METHODS

Eight human cadaveric specimens of L1-L5 were included. Specimens were attached to a universal testing machine (MTS 30/G). Three-dimensional specimen range of motion (ROM) was recorded using an optical motion-tracking device. Specimens were tested in 3 conditions: 1) intact, 2) L1-L5 LLIF (4 levels) with unilateral rod, 3) L1-L5 LLIF with bilateral rods.

RESULTS

From the intact condition, LLIF with unilateral rod decreased flexion-extension by 77%, lateral bending by 53%, and axial rotation by 26%. In LLIF with bilateral rods, flexion-extension decreased by 83%, lateral bending by 64%, and axial rotation by 34%. Comparing unilateral and bilateral fixation, LLIF with bilateral rods reduced ROM by a further 23% in flexion-extension, 25% in lateral bending, and 11% in axial rotation. The difference was statistically significant in flexion-extension and lateral bending (P < .005).

CONCLUSIONS

Considerable decreases in ROM were observed after multilevel (4-level) LLIF utilizing 26 mm cages supplemented with both unilateral and bilateral pedicle screws and rods. The addition of bilateral fixation provides a 10-25% additional decrease in ROM. These results can inform surgeons of the incremental biomechanical benefit when considering unilateral or bilateral posterior fixation after multilevel LLIF.

Sequential Depth Stimulation Within the Psoas Offers No Benefit for Localization of the Lumbar Plexus During Lateral Lumbar Fusion Surgery

STUDY DESIGN

Prospective cohort study.

OBJECTIVES

In this study we aim to assess the difference in triggered EMG readings throughout different depths in the psoas muscle during the lateral approach to the lumbar spine and their effect on surgeon decision making.

METHODS

Three surgeons, practicing at different institutions, assessed triggered EMG readings during the trans psoas approach at the level of the disc and 5,10 and 15 millimeters into the psoas muscle with sequential dilators. Measurement of distance into the psoas muscle was done with a specially designed instrument. Results of anterior and posterior directed stimulation as well as the delta value between these were recorded and underwent statistical analysis. Patients who had partial readings were excluded from the study.

RESULTS

A total of 40 levels in 35 patients were included in the study. There was no significant difference found between means of anterior or posterior threshold readings along the different distance groups. A significant difference was found (P = .024) in the mean difference between the distance groups with a decrease in the difference between anterior and posterior threshold values found as the distance from the disc space increased. None of the surgeons reported a decision to abort the fusion of a spinal level.

CONCLUSIONS

In the trans-psoas approach to the lumbar spine, the assessment of the location of the femoral nerve using directional neuromonitoring when advancing in the psoas muscle shows no clear benefit as opposed to stimulating solely when adjacent to the disc space.

Femoral and obturator neuropathies

The femoral and obturator nerves both arise from the L2, L3, and L4 spinal nerve roots and descend into the pelvis before emerging in the lower limbs. The femoral nerve's primary function is knee extension and hip flexion, along with some sensory innervation to the leg. The obturator nerve's primary function is thigh adduction and sensory innervation to a small area of the medial thigh. Each may be injured by a variety of potential causes, many of them iatrogenic. Here, we review the anatomy of the femoral and obturator nerves and the clinical features and potential etiologies of femoral and obturator neuropathies. Their necessary investigations, including electrodiagnostic studies and imaging, their prognosis, and potential treatments, are discussed in this chapter.

Using Novel Segmentation Technology to Define Safe Corridors for Minimally Invasive Posterior Lumbar Interbody Fusion

BACKGROUND AND OBJECTIVES

There has been a rise in minimally invasive methods to access the intervertebral disk space posteriorly given their decreased tissue destruction, lower blood loss, and earlier return to work. Two such options include the percutaneous lumbar interbody fusion through the Kambin triangle and the endoscopic transfacet approach. However, without accurate preoperative visualization, these approaches carry risks of damaging surrounding structures, especially the nerve roots. Using novel segmentation technology, our goal was to analyze the anatomic borders and relative sizes of the safe triangle, trans-Kambin, and the transfacet corridors to assist surgeons in planning a safe approach and determining cannula diameters.

METHODS

The areas of the safe triangle, Kambin, and transfacet corridors were measured using commercially available software (BrainLab, Munich, Germany). For each approach, the exiting nerve root, traversing nerve roots, theca, disk, and vertebrae were manually segmented on 3-dimensional T2-SPACE magnetic resonance imaging using a region-growing algorithm. The triangles' borders were delineated ensuring no overlap between the area and the nerves.

RESULTS

A total of 11 patients (65.4 ± 12.5 years, 33.3% female) were retrospectively reviewed. The Kambin, safe, and transfacet corridors were measured bilaterally at the operative level. The mean area (124.1 ± 19.7 mm2 vs 83.0 ± 11.7 mm2 vs 49.5 ± 11.4 mm2) and maximum permissible cannula diameter (9.9 ± 0.7 mm vs 6.8 ± 0.5 mm vs 6.05 ± 0.7 mm) for the transfacet triangles were significantly larger than Kambin and the traditional safe triangles, respectively (P < .001).

CONCLUSION

We identified, in 3-dimensional, the borders for the transfacet corridor: the traversing nerve root extending inferiorly until the caudal pedicle, the theca medially, and the exiting nerve root superiorly. These results illustrate the utility of preoperatively segmenting anatomic landmarks, specifically the nerve roots, to help guide decision-making when selecting the optimal operative approach.

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.

Transpsoas Approaches to the Lumbar Spine: Lateral and Prone

The lateral transpsoas approach has become fundamental to minimally invasive spine surgery. The large interbody grafts that can be placed through this approach allow for robust arthrodesis of the anterior column, indirect decompression, and restoration of lordosis without disrupting the posterior musculature or ligamentous structures. The lateral decubitus position has traditionally been used for this approach but the prone position has gained popularity because it can reduce operating times for patients who also require posterior pedicle screw fixation. The transpsoas approach can be effectively performed in either position but surgeons should know the nuances that distinguish them.

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.

Incidence and risk factors of lumbar plexus injury in patients undergoing oblique lumbar interbody fusion surgery

PURPOSE

To investigate the incidence and risk factors of lumbar plexus injury (LPI) after oblique lumbar interbody fusion (OLIF) surgery.

METHODS

A total of 110 patients who underwent OLIF surgery between January 2017 and January 2021 were retrospectively reviewed. Patients were divided into two groups: the group with LPI (LPI group) and the group without LPI (non-LPI group). The baseline demographic data, surgical variables and radiographic parameters were compared and analyzed between these two groups.

RESULTS

Among all participants, 13 (8.5%) had LPI-related symptoms postoperatively (short-term), and 6 (5.5%) did not fully recover after one year (long-term). Statistically, there were no significant differences in the baseline demographic data, surgery duration, intraoperative blood loss, preoperative diagnosis, surgical procedures used and incision length. Compared with the non-LPI group, patients in the LPI group had a narrower OLIF channel space. In LPI group, the anterior edge of left psoas major muscle overpasses the anterior edge of surgical intervertebral disk (IVD) on axial MRI. Logistic regression analysis revealed that narrow OLIF channel space and the anterior edge of left psoas major muscle overpassing the anterior edge of surgical IVD on axial MRI were independently associated with both short-term and long-term LPI.

CONCLUSION

Narrow OLIF channel space and the anterior edge of left psoas major muscle overpassing the anterior edge of surgical IVD are significant risk factors of OLIF surgery-related LPI. Surgeons should use preoperative imaging to adequately assess these risk factors to reduce the occurrence of LPI.

A modified oblique lumbar interbody fusion: A better way to establish an exposure under direct microscopic vision

Study design

This is a retrospective study.

Objective

To demonstrate a modified oblique lumbar interbody fusion (OILF) technique for L1-L5.

Methods

The modified technique splits anterior portion of psoas belly to access the oblique corridor (OC) anteroinferior to psoas, minimizing psoas manipulation and retraction and avoiding nerve injury while offering excellent microscopic visualization. Psoas weakness and neurovascular complication rates in patients treated with traditional OLIF (T-OLIF) or anteroinferior psoas OLIF (AP-OLIF) were retrospectively reviewed. Clinical outcomes were also reviewed.

Results

A total of 162 cases treated with T-OLIF (n = 73) and AP-OLIF (n = 89) for degenerative lumbar disease were included. The mean operative time and blood loss were less with AP-OLIF (P < 0.01). Approach related complications were 14 (19.1%) with T-OLIF and 4 (4.5%) with AP-OLIF. Postoperative visual analog scale (VAS) and Oswestry Disability Index (ODI) scores improved in both T-OIF and AP-OIF groups (P < 0.01).

Conclusion

The modified OLIF technique (AP-OLIF) is characterized by an easy exposure of the lumbar spine under direct microscopic vision, resulting in less psoas weakness and neurovascular injury.

L4 Corpectomy: Surgical Approaches and Mitigating the Risk of Femoral Nerve Injuries

OBJECTIVE

Because of the challenging anatomic location, corpectomies are performed less often at the fourth lumbar vertebral body than at other levels. Our objective was to review the literature of L4 corpectomy and anterior column reconstruction.

METHODS

A literature search in the Medline/PubMed database was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines to identify all relevant cases and cases series describing corpectomies of the L4 vertebral body using "lumbar" AND "corpectomy" as search terms. We present an illustrative case to describe the technique.

RESULTS

We identified 18 articles with 30 patients who met the search criteria. Including our case illustration, the most common approach used was the lateral retroperitoneal approach (n = 17, 54.8%), of which 8 (26.7%) were performed via a transpsoas approach. Seven (23%) patients underwent corpectomy through a posterior approach, 4 (12.9%) through an anterior retroperitoneal approach, and 3 (10%) through combined anterior and lateral retroperitoneal. The overall complications rate was 19.3% including 1 case each of femoral nerve injury and iatrogenic lumbar nerve root injury.

CONCLUSIONS

Corpectomies of the L4 vertebral body are challenging. None of the various approaches described clearly demonstrates any superiority in mitigating the risk of neural complications. Decision making about which surgical approach to use should be based on patient-specific characteristics.

What clinicians should consider when performing oblique lumbar interbody fusion in a patient with long vertebral body osteophytes

OBJECTIVE

Oblique lumbar interbody fusion (OLIF) is known as a minimally invasive technique for disc space augmentation. Motor weakness after OLIF has been known to occur in some cases. This study aimed to report the incidence and potential risk factors for motor weakness following OLIF.

MATERIALS AND METHODS

We enrolled 36 patients and 57 segments who underwent OLIF. Computed tomography was performed before and after OLIF. Clinical data, including age, sex, presenting symptoms, bone mineral density, visual analog scale score, operating segments, and postoperative complications, were collected. We divided the patients into groups with and without neurologic deficit. The disc height was measured and compared between the two groups. We also divided the segments into groups with and without neurologic deficit. Foramen height and osteophyte length were measured and compared between the two groups.

RESULTS

The neurologic deficit group included three patients (8%), whereas non-neurologic deficit group included 33 patients (92%). The neurologic deficit group included five segments (4%), whereas the non-neurologic deficit group included 109 segments (96%). The disc and foramen heights did not differ significantly between the groups with and without neurologic deficit; however, the osteophyte lengths were longer in the neurologic deficit group.

CONCLUSION

In our study, vertebral osteophyte length was found to be a potential risk factor for motor weakness after OLIF. For patients with long osteophytes, additional laminectomy following OLIF or another surgical approach for direct decompression should be considered.

Pearls and Pitfalls of Oblique Lateral Interbody Fusion: A Comprehensive Narrative Review

Lumbar degenerative disease is a common problem in an aging society. Oblique lateral interbody fusion (OLIF) is a minimally invasive surgical (MIS) technique that utilizes a retroperitoneal antepsoas corridor to treat lumbar degenerative disease. OLIF has theoretical advantages over other lumbar fusion techniques, such as a lower risk of lumbar plexus injury than direct lateral interbody fusion (DLIF). Previous studies have reported favorable clinical and radiological outcomes of OLIF in various lumbar degenerative diseases. The use of OLIF is increasing, and evidence on OLIF is growing in the literature. The indications for OLIF are also expanding with the help of recent technical developments, including stereotactic navigation systems and robotics. In this review, we present current evidence on OLIF for the treatment of lumbar degenerative disease, focusing on the expansion of surgical indications and recent advancements in the OLIF procedure.

Do evoked potentials matter? Pre-pathologic signal change and clinical outcomes with expandable cages in lateral lumbar interbody fusion surgery

Minimally Invasive Lateral Lumbar Interbody Fusion (MIS LLIF) is a reliable technique for treatment of degenerative disk disease, foraminal stenosis and spinal deformity. The retroperitoneal transpsoas approach risks lumbar plexus injury that may result in anterior thigh pain, sensory loss and weakness. A prospective study of 64 consecutive patients undergoing MIS LLIF with expandable cages (23 standalone, 41 integrated with lateral plate) using multimodal electrophysiological monitoring was performed. We measured sequential retraction times, complications, patient reported outcome scores and electrophysiologic findings with a minimum 12-month follow-up. Incidence of evoked potential and electromyographic signal change was moderate, and rarely resulted in post-operative neurologic deficit. Evoked potential signal changes were frequently resolved by the un-breaking of the surgical table or repositioning of the retractor. Average retraction times were 24 (15-41) minutes for standalone cages and 30 (15-41) minutes for integrated cages. At follow-up, the vast majority (97%) of patients reported significant clinical improvement post-operatively with only 2 patients reporting postoperative neurologic symptoms and subsequent recovery at 12-months. The present study shows that evoked potentials combined with electromyography is a more sensitive measure of pre-pathologic lumbar plexopathy in LLIF compared to electromyography alone, especially at L3/4 and L4/5 levels. Based on our findings, there is limited clinical indication for routine neural monitoring at rostral lumbar levels. The routine inclusion of multimodal electrophysiological monitoring in lateral transpsoas surgery is recommended to minimise the risk of neural injury by enabling optimal patient and retractor positioning and continued surveillance throughout the procedure.

Prognostic Bone Metastasis-Associated Immune-Related Genes Regulated by Transcription Factors in Mesothelioma

Mesothelioma (MESO) is a mesothelial originate neoplasm with high morbidity and mortality. Despite advancement in technology, early diagnosis still lacks effectivity and is full of pitfalls. Approaches of cancer diagnosis and therapy utilizing immune biomarkers and transcription factors (TFs) have attracted more and more attention. But the molecular mechanism of these features in MESO bone metastasis has not been thoroughly studied. Utilizing high-throughput genome sequencing data and lists of specific gene subsets, we performed several data mining algorithm. Single-sample Gene Set Enrichment Analysis (ssGSEA) was applied to identify downstream immune cells. Potential pathways involved in MESO bone metastasis were identified using Gene Oncology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, Gene Set Variation Analysis (GSVA), Gene Set Enrichment Analysis (GSEA), and Cox regression analysis. Ultimately, a model to help early diagnosis and to predict prognosis was constructed based on differentially expressed immune-related genes between bone metastatic and nonmetastatic MESO groups. In conclusion, immune-related gene SDC2, regulated by TFs TCF7L1 and POLR3D, had an important role on immune cell function and infiltration, providing novel biomarkers and therapeutic targets for metastatic MESO.

Neurologic deficit due to vertebral body osteophytes after oblique lumbar interbody fusion: A case report

RATIONALE

In recent years, oblique lumbar interbody fusion (OLIF), which uses a window between the peritoneum and the iliopsoas muscle to split the muscle to access the lumbar spine, is known as an effective and safe treatment for spinal diseases, such as degenerative disc disease, spondylolisthesis, recurrent disc herniation, and spinal deformity. Despite this fast and useful surgical method, there were often cases of new neurological symptoms or worsening of symptoms after surgery. We analyzed the preoperative risk factors in a patient with neurologic symptoms, such as motor weakness and exacerbation of radiating pain, after OLIF.

PATIENT CONCERNS

A 78-year-old man presented with complaints of numbness in the soles of both feet. L4-5 stenosis was diagnosed on MRI. We performed bilateral L4 laminotomy and L4-5 percutaneous posterior screw fixation after L4-5 OLIF. Postoperatively, his radiating pain improved, and there were no other neurologic symptoms. In the 6th week after surgery, he complained of pain in both ankles, while in the 10th week, the pain progressively worsened, and there was a decrease in motor performance of the right ankle.

DIAGNOSIS

Magnetic resonance imaging findings indicated that L4-5 stenosis was resolved. On the basis of the computed tomography findings, the cage was well inserted, the disc height and foramen height increased, and the alignment was good. However, a nerve root injury due to the protruding osteophyte from the inferior endplate of the L4 body was suspected, necessitating exploration of both L4 nerve roots by focusing on the right side.

INTERVENTIONS

We performed right facetectomy and right foraminotomy. During surgery, it was confirmed that the right L4 nerve root was entrapped by the osteophyte.

OUTCOMES

Postoperatively, his radiating pain improved, and motor performance of his right ankle was restored.

LESSONS

A prominently protruding osteophyte is assessed as a possible risk factor for the development of new neurologic deficits after OLIF. In patients with confirmed osteophytes, surgery should be planned taking into consideration the shape of the osteophytes and their relationship to the nerve root.

Role of Robotics in Adult Spinal Deformity

Robotic-assisted adult deformity surgery has played a rapidly expanding role since its introduction. As robotic spine technologies improve, the potential to limit complications and morbidity is vast. The improvements in instrumentation accuracy combined with the ability to maintain that accuracy in multiple positions allow creative surgical approaches and techniques that can limit operative time, blood loss, and improve outcomes. In the years to come, robotic-assisted spine surgery and navigation will likely play an expanding role that continues to be defined. LEVEL OF EVIDENCE: 5, expert opinion.

Electrodiagnostic Assessment of Plexopathies

Disorders of the brachial and lumbosacral plexus are complex and may occur as a consequence of trauma, compression, inflammatory disorders, malignant infiltration, or delayed effects of radiation therapy. An understanding of plexus anatomy and surrounding structures will allow the electromyographer to facilitate an efficient and comprehensive assessment of the plexus. A careful and thorough electrodiagnostic assessment allows for localization within the plexus and may provide important information about underlying pathology and prognosis.

Role of electrodiagnosis in nerve transfers for focal neuropathies and brachial plexopathies

Over the past 2 decades, the surgical treatment of brachial plexus and peripheral nerve injuries has advanced considerably. Nerve transfers have become an important surgical tool in addition to nerve repair and grafting. Electrodiagnosis has traditionally played a role in the diagnosis and localization of peripheral nervous system injuries, but a different approach is needed for surgical decision-making and monitoring recovery. When patients have complete or severe injuries they should be referred to surgical colleagues early after injury, as outcomes are best when nerve transfers are performed within the first 3 to 6 mo after onset. Patients with minimal recovery of voluntary activity are particularly challenging, and the presence of a few motor unit action potentials in these individuals should be interpreted on the basis of timing and evidence of ongoing reinnervation. Evaluation of potential recipient and donor muscles, as well as redundant muscles, for nerve transfers requires an individualized approach to optimize the chances of a successful surgical intervention. Anomalous innervation takes on new importance in these patients. Communication between surgeons and electrodiagnostic medicine specialists (EMSs) is best facilitated by a joint collaborative clinic. Ongoing monitoring of recovery post-operatively is critical to allow for decision making for continued surgical and rehabilitation treatments. Different electrodiagnostic findings are expected with resolution of neurapraxia, distal axon sprouting, and axonal regrowth. As new surgical techniques become available, EMSs will play an important role in the assessment and treatment of these patients with severe nerve injuries.

Clinical results and complications associated with oblique lumbar interbody fusion technique

Background

Oblique lumbar interbody fusion (OLIF) is a minimally invasive technique performed through the antero-oblique trajectory to address a wide range of lumbar pathologies. However, it can lead to complications. We reviewed the results of OLIF and discussed the effective methods to avoid such complications.

Methods

Seventy-nine consecutive patients who underwent OLIF between May 2016 and July 2019 were retrospectively analyzed. They were divided into three groups: stand-alone, posterior, and lateral fixation, according to whether they were followed up with auxiliary internal fixation as well as the fixation methods. Preoperative and last follow-up visual analog scale (VAS) and Oswestry Disability Index (ODI) scores were used to assess the improvement in the lower back and leg pain as well as neurological conditions. We analyzed intervertebral disc height (DH), segmental lumbar lordotic angle (SLL), lumbar lordotic angle (LL), pelvic tilt (PT), pelvic incidence-lumbar lordosis (PI-LL) mismatch, and the cross-section area (CSA) on axial magnetic resonance imaging (MRI) image in different groups. Complications, including thigh symptoms, cage subsidence, neurological injury, and vascular injury, were also noted.

Results

Seventy-nine patients were followed up postoperatively for 23.2±11.5 (range, 12-48) months. Forty-eight (61%) patients underwent stand-alone surgery (without fixation), 15 (19%) patients underwent supplemental percutaneous pedicle screw fixation (posterior fixation), and 16 (20%) patients underwent lateral vertebral instrumentation (lateral fixation). In all three groups, the VAS score and the ODI score had significantly decreased at the final follow-up compared to pre-operation. The DH, SLL, LL, CSA, PT, and PI-LL mismatch had also improved by final follow-up. The most common approach-related complication was thigh symptoms. Of the 79 patients, ipsilateral transient psoas paresis occurred in 9 (11.4%), ipsilateral transient quadriceps weakness in 2 (2.5%), and groin/thigh numbness and pain in 17 (21.5%). Cage subsidence occurred in 8 (10.1%) patients, including five cases of grade 0, one of grade I, and two of grade II. Three (3.8%) patients in this study had a vascular injury.

Conclusions

OLIF is a minimally invasive and effective technique for dealing with degenerative lumbar diseases. However, it should also be noted that this approach carries risks of complications.

State of the art advances in minimally invasive surgery for adult spinal deformity

Adult spinal deformity (ASD) can be associated with substantial suffering due to pain and disability. Surgical intervention for achieving neural decompression and restoring physiological spinal alignment has shown to result in significant improvement in pain and disability through patient-reported outcomes. Traditional open approaches involving posterior osteotomy techniques and instrumentation are effective based on clinical outcomes but associated with high complication rates, even in the hands of the most experienced surgeons. Minimally invasive techniques may offer benefit while decreasing associated morbidity. Minimally invasive surgery (MIS) for ASD has evolved over the past 20 years, driven by improved understanding of open procedures along with novel technique development and technologic advancements. Early efforts were hindered due to suboptimal outcomes resulting from high pseudarthrosis, inadequate correction, and fixation failure rates. To address this, multi-center collaborative groups have been established to study large numbers of ASD patients which have been vital to understanding optimal patient selection and individualized management strategies. Different MIS decision-making algorithms have been described to better define appropriate candidates and interbody selection approaches in ASD. The purpose of this state of the review is to describe the evolution of MIS surgery for adult deformity with emphasis on landmark papers, and to discuss specific MIS technology for ASD, including percutaneous pedicle screw instrumentation, hyperlordotic grafts, three-dimensional navigation, and robotics.

Lateral Lumbar Interbody Fusion: Review of Surgical Technique and Postoperative Multimodality Imaging Findings

The lateral lumbar interbody fusion (LLIF) approach is a minimally invasive surgery that can be used as an alternative to traditional lumbar interbody fusion techniques. LLIF accesses the intervertebral disk through the retroperitoneum and psoas muscle to avoid major vessels and visceral organs. The exposure of retroperitoneal structures during LLIF leads to unique complications compared with other surgical approaches. An understanding of the surgical technique and its associated potential complications is necessary for radiologists who interpret imaging before and after LLIF. Preoperative imaging must carefully assess the location of anatomic structures, including major retroperitoneal vasculature, lumbar nerve roots, lumbosacral plexus, and the genitofemoral nerve, relative to the psoas muscle. Multiple imaging modalities can be used in postoperative assessment including radiographs, CT, CT myelography, and MRI. Of these, CT is the preferred modality, because it can assess a range of complications relating to both the retroperitoneal exposure and the spinal instrumentation, as well as bone integrity and fusion status. This article describes surgical approaches for lumbar interbody fusion, comparing the approaches' indications, contraindications, advantages, and disadvantages; reviews the surgical technique of LLIF and relevant anatomic considerations; and illustrates for interpreting radiologists the normal postoperative findings and potential postsurgical complications of LLIF.

Localization of the Lumbar Plexus in the Psoas Muscle: Considerations for Avoiding Lumbar Plexus Injury during the Transpsoas Approach

Introduction

Transpsoas lumbar spine surgery is minimally invasive and has very good corrective effects. However, approach-side nerve complications delay post-operative rehabilitation. We anatomically investigated the localization of the lumbar plexus running in the psoas muscle.

Methods

We examined 27 formalin-fixed cadavers. The left-sided psoas muscle was extracted and cut parallel to the intervertebral disc at the L2/3, L3/4, and L4/5 disc levels. Using digitized photographs, we calculated the ratio of the distance from the front edge of the psoas muscle to the center of the lumbar plexus in the anteroposterior diameter of the psoas muscle (%). Then, we calculated the ratio of the distance from the lateral edge of the psoas muscle to the center of the lumbar plexus in the lateral diameter of the psoas muscle (%).

Results

The anterior-posterior lumbar plexus localization was 74.5 at L2/3, 74.7 at L3/4, and 81.2 at L4/5. There was a significant difference between L2/3 and L4/5 and between L3/4 and L4/5, but not between L2/3 and L3/4 (P=0.02, 0.01, and 0.94, respectively). The lateral and medial lumbar plexus localization was 85.4 at L2/3, 83.9 at L3/4, and 77.7 at L4/5. There was a significant difference between L2/3 and L4/5 and between L3/4 and L4/5, but not between L2/3 and L3/4 (P=0.01, 0.04, and 0.41, respectively).

Conclusions

The lumbar plexus was localized in the posterior one-third and medial one-third of the psoas muscle and moved to a posterolateral location at L4/5. To avoid neuropathy, consider the psoas muscle's position relative to that of the intervertebral disc. It is essential to understand lumbar plexus localization in the psoas muscle when looking directly at this muscle to enter the pricking point or route with a lower risk of nerve damage.

Brachial and lumbosacral plexopathies: A review

Diseases of the brachial and lumbosacral plexus are uncommon and complex. The diagnosis of plexopathies is often challenging for the clinician, both in terms of localizing a patient's symptoms to the plexus as well as determining the etiology. The non-specific clinical features and similar presentations to other root, nerve, and non-neurologic disorders emphasize the importance of a high clinical index of suspicion for a plexopathy and comprehensive clinical evaluation. Various diagnostic tests, including electrodiagnostic (EDX) studies, neuroimaging (including ultrasound, MRI, or PET), serologic studies, and genetic testing, may be used to confirm a plexopathy and assist in identifying the underlying etiology. EDX testing plays an important role in confirming a plexopathy defining the localization, pathophysiology, chronicity, severity, and prognosis. Given the complexity of the plexus anatomy, multiple common and uncommon NCS and an extensive needle examination is often required, and a comprehensive, individualized approach to each patient is necessary. Treatment of plexopathies often focuses on symptomatic management although, depending on the etiology, specific targeted treatments may improve outcome. This article reviews the clinical features, EDX approaches, and evaluation and treatment of brachial and lumbosacral plexopathies.

Variability in the size of the retroperitoneal oblique corridor: A magnetic resonance imaging-based analysis

Background:

A minimally invasive approach to the L2-S1 disc spaces through a single, left-sided, retroperitoneal oblique corridor has been previously described. However, the size of this corridor varies, limiting access to the disc space in certain patients. Here, the authors retrospectively reviewed lumbar spine magnetic resonance imaging (MRI) in 300 patients to better define the size and variability of the retroperitoneal oblique corridor.

Methods:

Lumbar spine MRI from 300 patients was reviewed. The size of the retroperitoneal oblique corridor from L2-S1 was measured. It was defined as the (1) distance between the medial aspect of the aorta and the lateral aspect of the psoas muscle from L2-L5 and (2) the distance between the midpoint of the L5-S1 disc and the medial aspect of the nearest major vessel on the left at L5-S1. In addition, the rostral-caudal location of the iliac bifurcation was measured.

Results:

The size of the retroperitoneal oblique corridor at L2/3, L3/4, L4/5, and L5/S1 was, respectively, 17.3 ± 6.4 mm, 16.2 ± 6.3 mm, 14.8 ± 7.8 cm, and 13.0 ± 8.3 mm. The incidence of corridor size <1 cm at L2/3, L3/4, L4/5, and L5/S1 was 10.3%, 16.0%, 30.0%, and 39.3%, respectively. The iliac bifurcation was most commonly found behind the L4 vertebral body (n = 158, 52.67%) followed by the L4/5 disc space (n = 74, 24.67%).

Conclusion:

The size of the retroperitoneal oblique corridor diminishes in a rostral-caudal direction, often limiting access to the L4/5 and L5/S1 disc spaces.

Many Intraoperative Monitoring Modalities Have Been Developed To Limit Injury During Extreme Lateral Interbody Fusion (XLIF/MIS XLIF): Does That Mean XLIF/MIS XLIF Are Unsafe?

Background:

Extreme lateral interbody fusions (XLIF) and Minimally Invasive (MIS) XLIF pose significant risks of neural injury to the; lumbar plexus, ilioinguinal, iliohypogastric, genitofemoral, lateral femoral cutaneous, and subcostal nerves. To limit these injuries, many intraoperative neural monitoring (IONM) modalities have been proposed.

Methods:

Multiple studies document various frequencies of neural injuries occurring during MIS XLIF/XLIF: plexus injuries (13.28%); sensory deficits (0-75%; permanent 62.5%); motor deficits (0.7-33.6%; most typically iliopsoas weakness (14.3%-31%)), and anterior thigh/groin pain (12.5-25%.-34%). To avoid/limit these injuries, multiple IONM techniques have been proposed. These include; using finger electrodes during operative dissection, employing motor evoked potentials (MEP), eliminating (no) muscle relaxants (NMR), and using “triggered” EMGs.

Results:

In one study, finger electrodes for XLIF at L4-L5 level for degenerative spondylolisthesis reduced transient postoperative neurological symptoms from 7 [38%] of 18 cases (e.g. without IONM) to 5 [14%] of 36 cases (with IONM). Two series showed that motor evoked potential monitoring (MEP) for XLIF reduced postoperative motor deficits; they, therefore, recommended their routine use for XLIF. Another study demonstrated that eliminating muscle relaxants during XLIF markedly reduced postoperative neurological deficits/thigh pain by allowing for better continuous EMG monitoring (e.g. NMR no muscle relaxants). Finally, a “triggered” EMG study” reduced postoperative motor neuropraxia, largely by limiting retraction time.

Conclusion:

Multiple studies have offered different IONM techniques to avert neurological injuries following MIS XLIF/XLIF. Does this mean that these procedures (e.g. XLIF/MIS XLIF) are unsafe?

Association Between Surgical Level and Early Postoperative Thigh Symptoms Among Patients Undergoing Standalone Lateral Lumbar Interbody Fusion

BACKGROUND

Lateral lumbar interbody fusion (LLIF) has often been associated with postoperative lumbar plexus symptoms, including pain, paresthesia, and motor deficits in the lower extremities, especially the anterior thigh regions. Previous studies have suggested that LLIF procedures at L4-L5 will be associated with a greater motor deficit rate than other levels. However, it is unclear which level has the greatest risk of pain and paresthesia. The purpose of the present retrospective observational study was to investigate the difference in the incidence of early postoperative thigh symptoms (pain and paresthesia) stratified by procedure level among patients who had undergone standalone LLIF.

METHODS

We reviewed the data from consecutive patients who had undergone LLIF at a single academic institution. A total of 285 standalone LLIF cases without preoperative motor deficits were identified. The incidence of postoperative thigh pain and paresthesia at the 6-week postoperative follow-up examination was assessed at all levels from T12-L1 to L4-L5.

RESULTS

A total of 81 patients (28.4%) had anterior thigh pain and 62 (21.8%) had anterior thigh paresthesia. The presence of ≥3 levels fused (odds ratio [OR], 2.96; P = 0.004) and surgery at L2-L3 (OR, 2.59; P = 0.001) were significant risk factors for postoperative anterior thigh paresthesia on univariate analysis but were not associated with anterior thigh pain. Multivariate analyses demonstrated that only surgery L2-L3 was an independent risk factor for anterior thigh paresthesia (OR, 2.09; P = 0.049).

CONCLUSIONS

Our results have demonstrated that standalone LLIF at the L2-L3 was significantly associated with a greater incidence of postoperative anterior thigh paresthesia but that the incidence of postoperative thigh pain showed no significant association with any operative level.

Transient pelvic limb neuropathy following proximal metatarsal and tarsal magnetic resonance imaging in seven horses

BACKGROUND

Pelvic limb neuropathy is a rare post-anaesthetic complication. In the authors' experiences, the incidence of post-anaesthesia neuropathy is increased following MRI of the proximal metatarsus and tarsal regions when compared with previously reported incidences of post-anaesthetic neuropathy.

OBJECTIVES

This study reports the incidence, diagnosis, treatment and outcome of seven horses with post-anaesthesia neuropathy following proximal metatarsal and tarsal MRI.

STUDY DESIGN

Retrospective case series.

METHODS

Case record review of horses receiving general anaesthesia for MRI between 1 January 2012 and 31 December 2017.

RESULTS

A total of 1134 MRI procedures were performed and reviewed for analysis. Eight cases of neuropathy were identified in 1088 limb scans (0.74%). Of these cases, one was subsequent to thoracic limb imaging (1/834; 0.12%) and seven were subsequent to imaging of proximal metatarsal and/or tarsal structures (7/181; 3.9%). Following proximal metatarsal and/or tarsal MRI, transient nondependent limb femoral neuropathy developed in six of the seven affected horses, with one additional horse developing peroneal neuropathy of the dependent limb. Recovery of pelvic limb function occurred within 72 h and 9 days in six and one horse, respectively.

MAIN LIMITATIONS

Anaesthetic protocol and neuropathy treatment for the affected horses were not standardised.

CONCLUSIONS

Though an uncommon complication in horses, transient neuropathy may occur more frequently following MRI of the proximal metatarsal and tarsal structures when compared with other MRI scans. This may be due to patient positioning and the requirement for limb traction for MRI of more proximal regions. Supportive care facilitates rapid return to function.

Clinical and Radiographic Evaluation of Multilevel Lateral Lumbar Interbody Fusion in Adult Degenerative Scoliosis

STUDY DESIGN

Retrospective review of prospective data.

OBJECTIVE

The objective of this study was to describe the clinical, radiographic, and complication-related outcomes through ≥1-year of 27 patients who underwent lateral lumbar interbody fusion (LLIF) with posterior instrumentation to treat ≥3 contiguous levels of degenerative lumbar scoliosis.

SUMMARY OF BACKGROUND DATA

Multilevel disease has traditionally been treated with open posterior fusion. Literature on multilevel LLIF is limited. We present our experience with utilizing LLIF to treat multilevel degenerative scoliosis.

METHODS

Clinical outcomes were evaluated using VAS, SF-12, and ODI. Radiographic outcomes included pelvic tilt, pelvic incidence, lumbar lordosis, pelvic incidence-lumbar lordosis mismatch, Cobb angle, and cage subsidence. Perioperative and long-term complications through the ≥1-year final-postoperative visit were reviewed; transient neurological disturbances were assessed independently. Demographic, comorbidity, operative, and recovery variables, including opioid use, were explored for association with primary outcomes.

RESULTS

Mean time to final-postoperative visit was 22.5 months; levels treated with LLIF per patient, 3.7; age, 66 years; and lateral operative time, 203 minutes. EBL was ≤100 mL in 74% of cases. Clinical outcomes remained significantly improved at ≥1-year. Cobb angle was corrected from 21.1 to 7.9 degrees (P<0.001), lordosis from 47.3 to 52.6 degrees (P<0.001), and mismatch from 11.4 to 6.4 degrees (P=0.003). High-grade subsidence occurred in 3 patients. Subsidence did not significantly impact primary outcomes. In total, 11.1% returned to the operating room for complication-related intervention over nearly 2-years; 37% experienced complications. Experiencing a complication was associated with having an open-posterior portion (P=0.048), but not with number of LLIF levels treated, or with clinical or radiographic outcomes. No patients experienced protracted neurological deficits; psoas weakness was associated with increased lateral operative time (P=0.049) and decreased surgeon experience (P=0.028).

CONCLUSIONS

Patients who underwent multilevel LLIF with adjunctive posterior surgery had significant clinical and radiographic improvements. Complication rates were similar compared to literature on single-level LLIF. LLIF is a viable treatment for multilevel degenerative scoliosis.

Lateral and Oblique Lumbar Interbody Fusion-Current Concepts and a Review of Recent Literature

PURPOSE

To review the relevant recent literature regarding minimally invasive, lateral, and oblique approaches to the anterior lumbar spine, with a particular focus on the operative and postoperative complications.

METHODS

A literature search was performed on Pubmed and Web of Science using combinations of the following keywords and their acronyms: lateral lumbar interbody fusion (LLIF), oblique lateral interbody fusion (OLIF), anterior-to-psoas approach (ATP), direct lateral interbody fusion (DLIF), extreme lateral interbody fusion (XLIF), and minimally invasive surgery (MIS). All results from January 2016 through January 2019 were evaluated and all studies evaluating complications and/or outcomes were included in the review.

RECENT FINDINGS

Transient neurological deficit, particularly sensorimotor symptoms of the ipsilateral thigh, remains the most common complication seen in LLIF. Best available current literature demonstrates that approximately 30-40% of patients have postoperative deficits, primarily of the proximal leg. Permanent symptoms are less common, affecting 4-5% of cases. Newer techniques to reduce this rate include different retractors, direct visualization of the nerves, and intraoperative neuromonitoring. OLIF may have lower deficit rates, but the available literature is limited. Subsidence rates in both LLIF and OLIF are comparable to ALIF (anterior lumbar interbody fusion), but further study is required. Supplemental posterior fixation is an active area of investigation that shows favorable biomechanical results, but additional clinical studies are needed. Minimally invasive lumbar interbody fusion techniques continue to advance rapidly. As these techniques continue to mature, evidence-based risk-stratification systems are required to better guide both the patient and clinician in the joint decision-making process for the optimal surgical approach.

Minimally invasive surgery procedure in isthmic spondylolisthesis

PURPOSE

The aim of the study was to evaluate the efficacy and safety of the direct lateral approach to the lumbar spine in the treatment of painful isthmic spondylolisthesis in adults.

METHODS

Twenty-one patients affected by isthmic spondylolisthesis and treated with extreme lateral interbody fusion and posterior percutaneous pedicle screw fixation were enrolled. All included patients were clinically evaluated with Oswestry Disability Index, SF36 and Visual Scale Anatomy (VAS) for back pain at 1, 3 months and at 1 year.

RESULTS

The mean correction of vertebral slippage measured on lateral lumbar X-ray was 56.3% (p = 0.002). The average preoperative VAS score was 7.1, at 1 year decreasing to 2.2 (p = 0.001). The patients had an average preoperative "Oswestry Disability Index" of 36.8 and 24.1% after 1 year (p = 0.02). The preoperative Short-Form 36 Physical Health was equal to 33.8, 72.1% after 1 month, to 76.3% after 3 months and to 83.2% (p = 0.001) after 1 year of follow-up. There were no signs of implant loosening at 1-year CT scan examination in any of the patients.

CONCLUSION

The study showed that the extreme lateral approach to the lumbar spine in case of isthmic spondylolisthesis is a reliable and safe option to the most common open procedures. In the authors' opinion, XLIF procedures allow a good correction of the listhesis associated with good clinical and radiographic results. These slides can be retrieved under Electronic supplementary material.