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

Variations of the extrapsoas course of the lumbar plexus with implications for the lateral transpsoas approach to the lumbar spine: a cadaveric study

BACKGROUND

Together with an increased interest in minimally invasive lateral transpsoas approach to the lumbar spine goes a demand for detailed anatomical descriptions of the lumbar plexus. Although definitions of safe zones and essential descriptions of topographical anatomy have been presented in several studies, the existing literature expects standard appearance of the neural structures. Therefore, the aim of this study was to investigate the variability of the extrapsoas portion of the lumbar plexus in regard to the lateral transpsoas approach.

METHODS

A total of 260 lumbar regions from embalmed cadavers were utilized in this study. The specimens were dissected as per protocol and all nerves from the lumbar plexus were morphologically evaluated.

RESULTS

The most common variation of the iliohypogastric and ilioinguinal nerves was fusion of these two nerves (9.6%). Nearly in the half of the cases (48.1%) the genitofemoral nerve left the psoas major muscle already divided into the femoral and genital branches. The lateral femoral cutaneous nerve was the least variable one as it resembled its normal morphology in 95.0% of cases. Regarding the variant origins of the femoral nerve, there was a low formation outside the psoas major muscle in 3.8% of cases. The obturator nerve was not variable at its emergence point but frequently branched (40.4%) before entering the obturator canal. In addition to the proper femoral and obturator nerves, accessory nerves were present in 12.3% and 9.2% of cases, respectively.

CONCLUSION

Nerves of the lumbar plexus frequently show atypical anatomy outside the psoas major muscle. The presented study provides a compendious information source of the possibly encountered neural variations during retroperitoneal access to different segments of the lumbar spine.

Accuracy of the Cage Placement in Oblique Lumbar Interbody Fusion and its Effects on the Radiological Outcome in Lumbar Degenerative Disease

STUDY DESIGN

A retrospective study.

OBJECTIVES

This study aimed to check how accurately cages were inserted and how they affected the radiological results in oblique lumbar interbody fusion (OLIF) at L2-L5.

METHODS

A total of 137 patients diagnosed with lumbar degenerative disease, 184 intervertebral discs were included. We used a new cage deviation classification system on magnetic resonance imaging (MRI) to determine cage insertion accuracy. Cage deviation angles (CDA) were classified into four groups based on the angle formed by the long axis of the cage and the horizontal axis of the vertebral body. Other radiological parameters on plain radiographs and MRI were compared based on this classification.

RESULTS

Among 183 cages, 19 were in zone Ⅰ-Ⅱ (10.32%), 163 were in zone II-III (88.59%), and two were in zone III-IV (1.09%). The median cage deviation was 4.97°. No significant differences (H = 2.479, P = .290 > .05) of CDA were found among different segments. Posterior cage deviation accounted 94.57%. The minimal, mild, moderate, and severe cage deviation was 89 (48.4%), 51 (27.7%), 30 (16.3%), and 14 (7.6%) respectively. No differences in radiological parameter changes were noted among different cage obliquity categories.

CONCLUSIONS

Approximately 98.91% of cages were placed in zones I-II and II-III. Most cages deviated posteriorly with CDA ranging minimal to moderate. Minimal to moderate cage deviation did not impact radiological outcomes significantly in OLIF at L2-L5. However, avoiding severe cage deviation is crucial to prevent contralateral traversing nerve root injuries.

Da Vinci Robotic Assistance for Anterolateral Lumbar Arthrodesis: Results of a French Multicentric Study

BACKGROUND

The da Vinci robot (DVR) is the most widely used robot in abdominal, urological, and gynecological surgery. Due to its minimally invasive approach, the DVR has demonstrated its effectiveness and improved safety in these different disciplines. The aim of our study was to report its use in an anterior approach of complex lumbar surgery.

METHODS

In a retrospective multicenter observational study, 10 robotic-assisted procedures were performed from March 2021 to May 2022. Six oblique lumbar interbody fusion procedures and 4 lumbar corpectomies were performed by anterolateral approach assisted by the DVR. The characteristics of the patients and the intraoperative and postoperative data were recorded.

RESULTS

Six men and 4 women underwent surgery (mean age 50.5 years; body mass index 28.6 kg/m2). No vascular injuries were reported, and no procedures required conversion to open surgery. Mean surgical time were 219 minutes for 1-level oblique lumbar interbody fusion (3 patients), 286 minutes for 2-level oblique lumbar interbody fusion (3 patients), and 390 minutes for corpectomy (4 patients). Four patients experienced nonserious adverse events due to lumbar plexus nerve damage. One patient had a vertebral body plate fracture requiring posterior revision surgery, and 1 patient had a psoas hematoma requiring transfusion. No abdominal wall complications or surgical site infection were found. Seven patients were reviewed at 12 months, none had complications, and all showed radiological evidence of fusion.

CONCLUSIONS

The use of the DVR in lumbar surgery allows a safe minimally invasive transperitoneal approach, but to date, only hybrid procedures have been performed.

Lateral lumbar interbody fusion at L4-L5 has a low rate of complications in appropriately selected patients when using a standardized surgical technique

Aims

The aim of this study was to reassess the rate of neurological, psoas-related, and abdominal complications associated with L4-L5 lateral lumbar interbody fusion (LLIF) undertaken using a standardized preoperative assessment and surgical technique.

Methods

This was a multicentre retrospective study involving consecutively enrolled patients who underwent L4-L5 LLIF by seven surgeons at seven institutions in three countries over a five-year period. The demographic details of the patients and the details of the surgery, reoperations and complications, including femoral and non-femoral neuropraxia, thigh pain, weakness of hip flexion, and abdominal complications, were analyzed. Neurological and psoas-related complications attributed to LLIF or posterior instrumentation and persistent symptoms were recorded at one year postoperatively.

Results

A total of 517 patients were included in the study. Their mean age was 65.0 years (SD 10.3) and their mean BMI was 29.2 kg/m2 (SD 5.5). A mean of 1.2 levels (SD 0.6) were fused with LLIF, and a mean of 1.6 (SD 0.9) posterior levels were fused. Femoral neuropraxia occurred in six patients (1.2%), of which four (0.8%) were LLIF-related and two (0.4%) had persistent symptoms one year postoperatively. Non-femoral neuropraxia occurred in nine patients (1.8%), one (0.2%) was LLIF-related and five (1.0%) were persistent at one year. All LLIF-related neuropraxias resolved by one year. A total of 32 patients (6.2%) had thigh pain, 31 (6.0%) were LLIF-related and three (0.6%) were persistent at one year. Weakness of hip flexion occurred in 14 patients (2.7%), of which eight (1.6%) were LLIF-related and three (0.6%) were persistent at one year. No patients had bowel injury, three (0.6%) had an intraoperative vascular injury (not LLIF-related), and five (1.0%) had ileus. Reoperations occurred in five patients (1.0%) within 30 days, 37 (7.2%) within 90 days, and 41 (7.9%) within one year postoperatively.

Conclusion

LLIF involving the L4-L5 disc level has a low rate of persistent neurological, psoas-related, and abdominal complications in patients with the appropriate indications and using a standardized surgical technique.

An Expanded Surgical Corridor of Oblique Lateral Interbody Fusion at L4-5: A Magnetic Resonance Imaging Study

OBJECTIVE

We introduced a new preoperative method, the "expanded surgical corridor," to evaluate the actual safety corridor, which may expand the possibility of performing oblique lateral interbody fusion (OLIF).

METHODS

Axial T2-weighted magnetic resonance images at the L4-5 disc level of 511 lumbar degenerative disease patients was evaluated. The distance between the medial edge of the left-sided psoas muscle and the major artery was measured as the conventional surgical corridor (CSc). The distance between the major vein and lumbar plexus was measured as the expanded surgical corridor (ESc).

RESULTS

The mean CSc and ESc were 13.9 ± 8.20 and 37.43 ± 10.1 mm, respectively. No surgical corridor was found in 7.05% of CSc and 1.76% of ESc, small corridor ( ≤ 1 cm) was found in 27.40% of CSc and 0.59% of ESc, moderate corridor (1-2 cm) was found in 42.07% of CSc and 1.96% of ESc, and large corridor ( > 2 cm) was found in 23.48% of CSc and 95.69% of ESc. A total of 33.83% (45 of 133) of whom were preoperatively categorized as having a limited surgical corridor by conventional measurement, underwent OLIF L4-5 successfully.

CONCLUSION

By using the ESc, only 2.35% were categorized as having a limited surgical corridor. The other 97.65% of the patients had an approachable corridor that could be successfully operated by experienced spine surgeons who employ meticulous surgical dissection and thorough understanding of the anatomical structures. The ESc may represent true accessibility to the disc space for OLIF, particularly at the L4-5 level.

Position of lumbar plexus nerves in the psoas major: Application to transpsoas approaches to the lumbar spine

Far lateral interbody fusion is a minimally invasive operating technique. However, the incidence of postoperative neurological complications is high, and some scholars question its safety. This study describes the neuroanatomical features and spatial orientation within the psoas major. Ten embalmed male cadavers were selected and the left psoas major was dissected. Subsequently, the area between the anterior and the posterior edges of the vertebral body was divided into three equal zones. The nerves' distribution, number, and spatial orientation of the L1/2 to L4/5 intervertebral discs were examined. A caliper was used to measure the diameter of the nerve. The safety zone of the L1/2 intervertebral disc level is located in zone I and II, the relative safe zones of the L2/3 and L4/5 intervertebral discs are located in zone II, and the safety zone of the L3/4 intervertebral disc level is located in the caudal side of zone II. The genitofemoral nerve exits the psoas major in a co-trunk or two-branch pattern, and its exit point was distributed between the L3 and L4 vertebral bodies, mainly at the L3/4 intervertebral disc level. The sympathetic ganglia in the psoas major appeared only in zone I at the L2/3 intervertebral disc level. This is a systematic anatomical study that describes the nerves of the psoas major. Spine surgeons can use this study-which consists of important clinical implications-for preoperative planning, and thus, reduce the risk of nerve injury during surgery.

Antepsoas Approaches to the Lumbar Spine

Lumbar interbody fusion (LIF) is a well-established approach in treating spinal deformity and degenerative conditions of the spine. Since its inception in the 20th century, LIF has continued to evolve, allowing for minimally invasive approaches, high fusion rates, and improving disability scores with favorable complication rates. The anterior to the psoas (ATP) approach utilizes a retroperitoneal pathway medial to the psoas muscle to access the L1-S1intervertebral disc spaces. In contrast to the transpsoas arppoach, its primary advantage is avoiding transgressing the psoas muscle and the contained lumbar plexus, which potentially decreases the risk of injury to the lumbar plexus. Avoiding transgression of the psoas may minimize the risk of transient or permanent neurological deficits secondary to lumbar plexus injury. Indications for ATP approaches may expand as it is shown to be a safe and effective method of achieving spinal arthrodesis.

Psoas Major Swelling Grade Affects the Clinical Outcomes after OLIF: A Retrospective Study of 89 Patients

OBJECTS

Oblique lumbar interbody fusion (OLIF) has gained increasing popularity recently. However, complications resulting from intraoperative retraction of psoas major (PM) sometimes occur. The aim of this study is to evaluate the degree of PM swelling by developing a scoring system called the Psoas Major Swelling Grade (PMSG), and to investigate the correlation between the PMSG and clinical outcomes after OLIF.

METHODS

Patients who underwent L4-5 OLIF at our hospital from May 2019 to May 2021 were reviewed and all data were recorded. The extent of postoperative PM swelling was determined by calculating the percentage of change in the PM area before and after surgery on MRI and divided into three grades subsequently. Swelling within the range of 0% to 25% was defined as grade I, 25%-50% was grade II, and more than 50% was grade III. All patients were grouped into the new grade system and followed up for at least 1 year, during which the visual analog scale (VAS) and Oswestry disability index (ODI) scores were recorded. Categorical data were analyzed using chi-square and Fisher's exact tests, while continuous variables were assessed with one-way ANOVA and paired t-tests.

RESULTS

Eighty-nine consecutive patients were enrolled in this study, with a mean follow-up duration of 16.9 months. The proportion of female patients in the PMSG I, II, and III groups was 57.1%, 58.3%, and 84.1%, respectively (p = 0.024).  Furthermore, the total complication rate was 43.2% in the PMSG III group, significantly higher than 9.5% and 20.8% in the PMSG I and II groups (p = 0.012). The incidence of thigh paraesthesia was also considerably higher in the PMSG III group at 34.1% (p = 0.015), compared to 9.5% and 8.3% in the PMSG I and II groups. Among the patients, 12.4% exhibited a teardrop-shaped PM, with the majority (90.9%) belonging to the PMSG III group (p = 0.012). Additionally, the PMSG III group demonstrated a higher estimated blood loss (p = 0.007) and significantly worse clinical scores at the 1-week follow-up assessment (p < 0.001).

CONCLUSION

PM swelling adversely affects the OLIF prognosis. Female patients with teardrop-shaped PM are more likely to develop swelling after OLIF. A higher PMSG is associated with a higher complication rate of thigh pain or numbness and worse short-term clinical outcomes.

Lateral interbody fusion without intraoperative neuromonitoring in addition to posterior instrumented fusion in geriatric patients: A single center consecutive series of 108 surgeries

Introduction

Lateral lumbar interbody fusion (LLIF) and lateral thoracic interbody fusion (LTIF), supported by intraoperative neuromonitoring (IONM), gained popularity as a mini-invasive alternatives for standard interbody fusion. The objective of this study was to investigate the clinical outcome in a large elderly patient cohort who underwent LTIF/LLIF without IONM.

Methods

This retrospective, single-center study enrolled elderly patients (≥70 years old) operated during the period from 2010 to 2016. Anterior lumbar interbody fusion (ALIF) in the L5/S1 segment was excluded from the analysis.

Results

The study enrolled 108 patients (63 males, 58.3%) with a mean age of 76.5 ​y/o. The mean follow-up was 14.4 ​± ​11.3 months. The mean time of the surgery was 92 ​± ​34.2 ​min. The mean blood loss was 62.2 ​ml. There were no vascular or visceral surgical complications. 39 medical complications were encountered in 24 (22%) patients. Less than 5% of patients presented with a new onset of motor weakness and less than 2% of the patients developed a new sensory deficit at the discharge. 46% of patients were lost in follow-up at 12 months.

Conclusions

IONM is not mandatory for LLIF/LTIF surgery in geriatric patients and has a low frequency of approach-related complications as well as neurological deterioration. Our results are comparable to the available literature. Regardless of the utilization of these mini-invasive, anterior approaches, in patients of advanced aged, the risk for major medical complications is high and is responsible for contributing to prolonged hospitalization.

Lateral lumbar interbody fusion - clinical outcomes, fusion rates and complications with recombinant human bone morphogenetic protein-2

BACKGROUND

The authors report an Australian experience of lateral lumbar interbody fusion (LLIF) with respect to clinical outcomes, fusion rates, and complications, with recombinant human bone morphogenetic protein-2 (rhBMP-2) and other graft materials.

METHODS

Retrospective cohort study of LLIF patients 2011-2021. LLIFs performed lateral decubitus by four experienced surgeons past their learning curve. Graft materials classified rhBMP-2 or non-rhBMP-2. Patient-reported outcomes assessed by VAS, ODI, and SF-12 preoperatively and postoperatively. Fusion rates assessed by CT postoperatively at 6 and 12 months. Complications classified minor or major. Clinical outcomes and complications analysed and compared between rhBMP-2 and non-rhBMP-2 groups.

RESULTS

A cohort of 343 patients underwent 437 levels of LLIF. Mean age 67 ± 11 years (range 29-89) with a female preponderance (65%). Mean BMI 29kg/m2 (18-56). Most common operated levels L3/4 (36%) and L4/5 (35%). VAS, ODI and SF-12 improved significantly from baseline. Total complication rate 15% (53/343) with minor 11% (39/343) and major 4% (14/343). Ten patients returned to OR (2-wound infection, 8-further instrumentation and decompression). Most patients (264, 77%) received rhBMP-2, the remainder a non-rhBMP-2 graft material. No significant differences between groups at baseline. No increase in minor or major complications in the rhBMP-2 group compared to the non-rhBMP-2 group respectively; (10.6% vs 13.9% [p = 0.42], 2.7% vs 8.9% [p < 0.01]). Fusion rates significantly higher in the rhBMP-2 group at 6 and 12 months (63% vs 40%, [p < 0.01], 92% vs 80%, [p < 0.02]).

CONCLUSION

LLIF is a safe and efficacious procedure. rhBMP-2 in LLIF produced earlier and higher fusion rates compared to available non-rhBMP-2 graft substitutes.

Multimodality Intraoperative Neuromonitoring in Lateral Lumbar Interbody Fusion: A Review of Alerts in 628 Patients

STUDY DESIGN

Retrospective review of private neuromonitoring databases.

OBJECTIVES

To review neuromonitoring alerts in a large series of patients undergoing lateral lumbar interbody fusion (LLIF) and determine whether alerts occurred more frequently when more lumbar levels were accessed or more frequently at particular lumbar levels.

METHODS

Intraoperative neuromonitoring (IONM) databases were reviewed and patients were identified undergoing LLIF between L1 and L5. All cases in which at least one IONM modality was used (motor evoked potentials (MEP), somatosensory evoked potentials (SSEP), evoked electromyography (EMG)) were included in this study. The type of IONM used and incidence of alerts were collected from each IONM report and analyzed. The incidence of alerts for each IONM modality based on number of levels at which at LLIF was performed and the specific level an LLIF was performed were compared.

RESULTS

A total of 628 patients undergoing LLIF across 934 levels were reviewed. EMG was used in 611 (97%) cases, SSEP in 561 (89%), MEP in 144 (23%). The frequency of IONM alerts for EMG, SSEP and MEPs did not significantly increase as the number of LLIF levels accessed increased. No EMG, SSEP, or MEP alerts occurred at L1-L2. EMG alerts occurred in 2-5% of patients at L2-L3, L3-L4, and L4-L5 and did not significantly vary by level (P = .34). SSEP and MEP alerts occurred more frequently at L4-L5 versus L2-L3 and L3-L4 (P < .03).

CONCLUSIONS

IONM may provide the greatest utility at L4-L5, particularly MEPs, and may not be necessary for more cephalad LLIF procedures such as at L1-L2.

Multilevel tandem spondylolisthesis associated with a reduced "safe zone" for a transpsoas lateral lumbar interbody fusion at L4-5

OBJECTIVE

The aim of this study was to investigate the effect of degenerative spondylolisthesis (DS) on psoas anatomy and the L4-5 safe zone during lateral lumbar interbody fusion (LLIF).

METHODS

In this retrospective, single-institution analysis, patients managed for low-back pain between 2016 and 2021 were identified. Inclusion criteria were adequate lumbar MR images and radiographs. Exclusion criteria were spine trauma, infection, metastases, transitional anatomy, or prior surgery. There were three age and sex propensity-matched cohorts: 1) controls without DS; 2) patients with single-level DS (SLDS); and 3) patients with multilevel, tandem DS (TDS). Axial T2-weighted MRI was used to measure the apical (ventral) and central positions of the psoas relative to the posterior tangent line at the L4-5 disc. Lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and PI-LL mismatch were measured on lumbar radiographs. The primary outcomes were apical and central psoas positions at L4-5, which were calculated using stepwise multivariate linear regression including demographics, spinopelvic parameters, and degree of DS. Secondary outcomes were associations between single- and multilevel DS and spinopelvic parameters, which were calculated using one-way ANOVA with Bonferroni correction for between-group comparisons.

RESULTS

A total of 230 patients (92 without DS, 92 with SLDS, and 46 with TDS) were included. The mean age was 68.0 ± 8.9 years, and 185 patients (80.4%) were female. The mean BMI was 31.0 ± 7.1, and the mean age-adjusted Charlson Comorbidity Index (aCCI) was 4.2 ± 1.8. Age, BMI, sex, and aCCI were similar between the groups. Each increased grade of DS (no DS to SLDS to TDS) was associated with significantly increased PI (p < 0.05 for all relationships). PT, PI-LL mismatch, center psoas, and apical position were all significantly greater in the TDS group than in the no-DS and SLDS groups (p < 0.05). DS severity was independently associated with 2.4-mm (95% CI 1.1-3.8 mm) center and 2.6-mm (95% CI 1.2-3.9 mm) apical psoas anterior displacement per increased grade (increasing from no DS to SLDS to TDS).

CONCLUSIONS

TDS represents more severe sagittal malalignment (PI-LL mismatch), pelvic compensation (PT), and changes in the psoas major muscle compared with no DS, and SLDS and is a risk factor for lumbar plexus injury during L4-5 LLIF due to a smaller safe zone.

Lumbar plexus safe working zones with lateral lumbar interbody fusion: a systematic review and meta-analysis

PURPOSE

Significant risk of injury to the lumbar plexus and its departing motor and sensory nerves exists with lateral lumbar interbody fusion (LLIF). Several cadaveric and imaging studies have investigated the lumbar plexus position with respect to the vertebral body anteroposterior plane. To date, no systematic review and meta-analysis of the lumbar plexus safe working zones for LLIF has been performed.

METHODS

This systematic review was conducted according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Relevant studies reporting on the position of the lumbar plexus with relation to the vertebral body in the anteroposterior plane were identified from a PubMed database query. Quantitative analysis was performed using Welch's t test.

RESULTS

Eighteen studies were included, encompassing 1005 subjects and 2472 intervertebral levels. Eleven studies used supine magnetic resonance imaging (MRI) with in vivo subjects. Seven studies used cadavers, five of which performed dissection in the left lateral decubitus position. A significant correlation (p < 0.001) existed between anterior lumbar plexus displacement and evaluation with in vivo MRI at all levels between L1-L5 compared with cadaveric measurement. Supine position was also associated with significant (p < 0.001) anterior shift of the lumbar plexus at all levels between L1-L5.

CONCLUSIONS

This is the first comprehensive systematic review and meta-analysis of the lumbar neural components and safe working zones for LLIF. Our analysis suggests that the lumbar plexus is significantly displaced ventrally with the supine compared to lateral decubitus position, and that MRI may overestimate ventral encroachment of lumbar plexus.

Equipoise for Lateral Access Surgery

OBJECTIVE

To investigate the use of lateral access surgery among surgeons from the Asia-Pacific region to determine equipoise for areas of contentious use.

METHODS

A questionnaire was distributed to members of the Asia Pacific Spine Society. Surgeons were asked about their past experiences with lateral access surgery, including their advantages and disadvantages, specific surgical strategies, choices in implant-related factors, order of levels to operate on in multilevel reconstruction surgery, and postoperative complications.

RESULTS

A total of 69 of 102 surgeons (67.6%) had performed lateral access surgery previously. In total, 56 participating surgeons (54.9%) agreed that anterior column reconstruction via lateral access is most of time superior to transforaminal lumbar interbody fusion and other techniques. Surgeons would consider laminectomy instead of indirect decompression in the presence of severe central or lateral recess stenosis, thickened ligamentum flavum, and facet joint hypertrophy. For the order of levels to operate on in multiple level reconstruction for deformity, where 1 stands for L3-L4 or higher, 2 stands for L4-L5, and 3 stands for L5-S1, 2-1-3 (28/95, 29.5%) was most common, followed by 1-2-3 (26/95, 27.4%), and 3-2-1 (21/95, 22.1%).

CONCLUSIONS

Lateral access surgery is seeing greater use in the Asia-Pacific region, especially in upper middle- to high-income countries, whereas keenness of surgeons who practice in lower middle- to low-income countries can be improved by more training, resources, and reasonable cost. A high percentage of surgeons do not consider indirect decompression for spinal stenosis. There was no consensus on the order of levels in multiple level reconstruction for deformity.

Single-position anterior and lateral lumbar fusion in the supine position: a novel technique for multi-level arthrodesis

OBJECTIVE

Anterior lumbar interbody fusion (ALIF) and lateral lumbar interbody fusion (LLIF) are common techniques that typically require staged procedures when performed in combination. Interest is emerging in single-position surgery to increase operative efficiency. We report a novel surgical technique, supine extended reach (SupER) lateral fusion, to perform ALIF and LLIF with the patient in a single supine position.

METHODS

A man in his fifties presented with degenerative levoscoliosis, spondylolisthesis, sagittal-plane deformity, and progressive low back pain. He was offered L3-S1 anterolateral fusion.

RESULTS

With the patient supine, a left abdominal paramedian incision was performed to gain anterior retroperitoneal access, and standard L5-S1 and L4-5 ALIFs were performed. The anterior incision was used for direct visualization, retraction, and bimanual dissection. A left lateral incision was then made to perform an L3-4 LLIF. The patient subsequently underwent a second-stage L3-S1 posterior percutaneous fixation. The patient tolerated the procedures well, without complications. Postoperative radiograph findings confirmed acceptable implant positioning. The patient was discharged home in stable condition and was doing well at follow-up.

CONCLUSION

This case description is the first report of the SupER technique, which allows incorporation of anterior and lateral fusion constructs at adjacent levels without changing patient positioning. Many surgeons believe the ALIF to be the most powerful technique for achieving lordosis, and this technique enables concomitant lateral access in a supine position. It can also be used as an alternative strategy when anterior access to the disc space is unobtainable. Further clinical investigation of this technique is warranted.

Minimally invasive lateral retroperitoneal transpsoas approach for lumbar corpectomy and fusion with posterior instrumentation

In this video, the authors highlight the operative treatment of a 55-year-old man with chronic osteomyelitis discitis. The operation entailed a minimally invasive lateral retroperitoneal transpsoas approach for L3 and L4 corpectomies, L2–5 interbody fusion, and L2–5 minimally invasive posterior instrumentation. The operation proceeded in two stages, beginning in the lateral position with corpectomy of the L3 and L4 vertebral bodies and placement of a corpectomy cage. After closure of this access wound, the patient was turned to a prone position for the posterior element of the operation. Posterior instrumentation was placed with pedicle screws at L2 and L5.

The video can be found here: https://stream.cadmore.media/r10.3171/2022.3.FOCVID2210

Anatomical positional changes in the lateral lumbar interbody fusion

INTRODUCTION

ALIFs and LLIFs are now becoming more utilized for adult spinal disease. As technologies advance, so do surgical techniques, with surgeons now modifying traditional supine-ALIF and lateral-LLIF to lateral-ALIF and prone-LLIF approaches to allow for more efficient surgeries. The objective of this study is to characterize the anatomical changes in the surgical corridor that occur with changes in patient positioning.

METHODS

MRIs of ten healthy volunteers were evaluated in five positions: supine, prone with hips flexed, prone with hips extended, lateral with hips flexed, and lateral with hips extended. All lateral scans were in the left lateral decubitus position. The anatomical changes of the psoas muscles, inferior vena cava, aorta, iliac vessels were assessed with relation to fixed landmarks on the disc spaces from L1 to S1.

RESULTS

The most anteriorly elongated ipsilateral to approach psoas when compared to supine was seen in lateral-flexed position (- 5.82 mm, p < 0.001), followed by lateral-extended (- 2.23 mm, p < 0.001), then prone-flexed (- 1.40 mm, p = 0.014), and finally supine and prone-extended (- 0.21 mm, p = 0.643). The most laterally extending or "thickest" psoas was seen in prone-flexed (- 1.40 mm, p = 0.004) and prone-extended (- 1.17 mm, p = 0.002). The psoas was "thinnest" in lateral-extended (2.03 mm, p < 0.001) followed by lateral-flexed (1.11 mm, p = 0.239). The contralateral psoas did not move as anteriorly as the ipsilateral. 3D volumetric analysis showed that the greatest changes in the psoas occur at its proximal and distal poles near T12-L1 and L4-S1. In lateral-flexed compared to prone-extended, the IVC moves medially to the left (p < 0.001). The aorta moves laterally to the left (p = 0.005). The venous structures appeared more full and open in the lateral positions and flattened in the supine and prone positions. The arteries remain in full calibre.

CONCLUSION

The MRI anatomical evaluation shows that the psoas, and therefore lumbar plexus, and vasculature move significantly with changes in positioning. This is important for preoperative planning for proper intraoperative execution from preoperative supine MRI. Understanding that the psoas and vessels move the most anteriorly in the lateral-flexed position and to a least degree in the prone-extended is essential for safe and efficient utilization of techniques such as the traditional LLIF, traditional ALIF, prone-LLIF.

Oblique Lumbar Interbody Fusion Using a Stand-Alone Construct for the Treatment of Adjacent-Segment Lumbar Degenerative Disease

Objective

Adjacent-segment disease (ASD) is common in patients undergone previous lumbar fusion. A typical revision treatment from posterior approach requires management of postoperative scar tissue and previously implanted instrumentation. An oblique lumbar interbody fusion (OLIF) approach allows surgeon to reduce the potential risk of posterior approach. This study aimed to analyze the clinical and radiographic efficacy of stand-alone OLIF for the treatment of lumbar adjacent-segment disease.

Methods

A total of 13 consecutive patients who underwent stand-alone OLIF for the treatment of adjacent-segment disease from December 2016 to January 2019 were reviewed. Visual analog scale (VAS) of back pain and leg pain and the Oswestry Disability Index (ODI) before surgery and at last postoperative clinic visits were obtained. Radiography, CT and MRI before and at last follow-up after surgery was evaluated in all patients.

Results

During the study period, 13 cases were successfully treated with stand-alone OLIF. The mean follow-up was 17.7 ± 8.3 months. The back pain VAS improved from 6.2 ± 1.0 to 2.0 ± 1.1 (P < 0.01), and the leg pain VAS improved from 7.0 ± 1.9 to 1.0 ± 0.9 (P < 0.01). ODI improved from 28.0 ± 7.5 to 10.8 ± 4.0 (P < 0.01). The disc height (DH) increased from 9 ± 2 to 12 ± 2 mm (P < 0.01), the cross-sectional area (CSA) of spinal canal increased from 85 ± 26 to 132 ± 24 mm² (P < 0.01), the foraminal height increased from 17 ± 2 to 21 ± 3 mm (P < 0.01) and the CSA of foramen increased from 95 ± 25 to 155 ± 36 mm² (P < 0.01). Cage subsidence was observed in 2 cases.

Conclusions

Stand-alone OLIF provides a safe and effective alternative way to treat ASD.

Anterior column reconstruction of the lumbar spine in the lateral decubitus position: anatomical and patient-related considerations for ALIF, anterior-to-psoas, and transpsoas LLIF approaches

PURPOSE

Circumferential (AP) lumbar fusion surgery is an effective treatment for degenerative and deformity conditions of the spine. The lateral decubitus position allows for simultaneous access to the anterior and posterior aspects of the spine, enabling instrumentation of both columns without the need for patient repositioning. This paper seeks to outline the anatomical and patient-related considerations in anterior column reconstruction of the lumbar spine from L1-S1 in the lateral decubitus position.

METHODS

We detail the anatomic considerations of the lateral ALIF, transpsoas, and anterior-to-psoas surgical approaches from surgeon experience and comprehensive literature review.

RESULTS

Single-position AP surgery allows simultaneous access to the anterior and posterior column and may combine ALIF, LLIF, and minimally invasive posterior instrumentation techniques from L1-S1 without patient repositioning. Careful history, physical examination, and imaging review optimize safety and efficacy of lateral ALIF or LLIF surgery. An excellent understanding of patient spinal and abdominal anatomy is necessary. Each approach has relative advantages and disadvantages according to the disc level, skeletal, vascular, and psoas anatomy.

CONCLUSIONS

A development of a framework to analyze these factors will result in improved patient outcomes and a reduction in complications for lateral ALIF, transpsoas, and anterior-to-psoas surgeries.

Lateral Lumbar Interbody Fusion at the L5-S1 Vertebral Level: A Unique Anatomical Case Report

A 57-year-old female presented with L4-L5 and L5-S1 mobile spondylolisthesis and associated stenosis with radiculopathy who failed conservative treatment. This patient underwent lateral lumbar interbody fusion (LLIF) of L4-L5 and L5-S1, and posterior spinal fusion (PSF) with instrumentation.

LLIF is a minimally invasive procedure to treat degenerative diseases of the lumbar spine. LLIF at the L5-S1 vertebral level is a relative contraindication secondary to increased risk of injury to the lumbar plexus and access issues at this level during the approach. With the help of imaging, careful preoperative planning can make this a feasible procedure in select patients.

A Crucial But Neglected Anatomical Factor Underneath Psoas Muscle and Its Clinical Value in Lateral Lumbar Interbody Fusion-The Cleft of Psoas Major (CPM)

Objective

To describe the anatomical feature positioned beneath the psoas muscle at the lateral aspect of the lower lumbar, and to create a new location system to identify the risk factors of lateral lumbar interbody fusion.

Methods

Six cadavers were dissected and analyzed. The anatomy and neurovascular distribution beneath the psoas major from L₃ to S₁ was observed and recorded, with particular focus on the L_4/5 disc and below. The psoas major surface was divided homogeneously into four parts, from the anterior border of psoas major to the transverse process. The cranial‐to‐caudal division was from the lower edge of the psoas muscle attachment on the L₄ vertebrae to the upper part of the S₁ vertebrae, and was divided into five segments. Then a grid system was used to create 20 grids on the psoas major surface, from the anterior border of the muscle to the transverse process and from L₄ to superior S₁, which was used to determine the anatomical structures' distribution and relationship beneath the psoas major.

Results

A cleft was identified beneath the psoas major, from the level of L_4/5 downwards. It was filled with loose connective tissue and neurovascular structures. We termed it the cleft of psoas major (CPM). The sympathetic trunk, ascending lumbar vein, iliolumbar vessels, obturator nerve, femoral nerve and occasionally the great vessels are contained within the CPM, although there is significant interpersonal variation. The grid system on the psoas major surface helped to identify the anatomical structures in CPM. There was a considerably lower frequency of occurrence of neurovascular structures in the grids of I/II at the L_4/5 level where can be considered the “safe zones” for the lateral lumbar interbody fusion. In contrast, the distribution of neurovascular structures at the L₅S₁ level is dense, where the operation risk is high.

Conclusion

The CPM exists lateral to the vertebral surface from L₄ and below. Although the occurrence and distribution of neurovascular structures within the CPM is complex and varies greatly, it can provide a potential cavity for visualization during lateral lumbar interbody fusion. Using psoas major as a reference, this novel grid system can be used to identify the risk factors in CPM and thus identify a safe entry point for surgery.

Supine lateral lumbar interbody fusion: cadaveric proof of principle for simultaneous anterior and lateral approaches

BACKGROUND

Anterior lumbar interbody fusion (ALIF) and lateral lumbar interbody fusion (LLIF) are commonly performed in separate stages with a change in patient positioning to provide arthrodesis in the lumbar spine. Interest has recently emerged in performing these approaches as a single-stage surgery with the patient in the lateral decubitus position. The objective of this study was to evaluate the technical feasibility of performing minimally invasive anterolateral fixation in a single supine position.

METHODS

Two fresh-frozen cadavers were used and placed supine. Standard minimally invasive anterior access was obtained by the approach surgeon. An ALIF was performed at L5-S1 using standard techniques. A lateral incision was marked over the L4-5 disc space using fluoroscopy. Direct palpation and bimanual dissection were achieved through the same anterior incision, allowing access to the retroperitoneal space. Dilator and retractor docking was performed under fluoroscopic guidance. Direct visualization of the docking hardware through the anterior incision was used to ensure the safety of peritoneal contents and vasculature. The LLIF was then performed using standard techniques at L4-5.

RESULTS

Plain radiographs confirmed acceptable positioning of both the ALIF and LLIF grafts. No injury to the cadaveric peritoneum, vasculature, or lumbar plexus was observed. A slightly enlarged anterior incision also permitted retroperitoneal access and visualization of the L3-4 disc space.

CONCLUSION

This cadaver feasibility study demonstrates that combined minimally invasive ALIF and LLIF procedures may be performed as a single-stage with the patient in the supine position. Clinical consideration and study of this approach are warranted.

Intraoperative Neuromonitoring During Lateral Lumbar Interbody Fusion

Objective

To review the evidence for the use of electromyography (EMG), motor-evoked potentials (MEPs), and somatosensory-evoked potentials (SSEPs) intraoperative neuromonitoring (IONM) strategies during lateral lumbar interbody fusion (LLIF), as well as discuss the limitations associated with each technique.

Methods

A comprehensive review of the literature and compilation of findings relating to clinical studies investigating the efficacy of EMG, MEP, SSEP, or combined IONM strategies during LLIF.

Results

The evidence for the use of EMG is mixed with some studies demonstrating the efficacy of EMG in preventing postoperative neurologic injuries and other studies demonstrating a high rate of postoperative neurologic deficits with EMG monitoring. Multimodal IONM strategies utilizing MEPs or saphenous SSEPs to monitor the lumbar plexus may be promising strategies based on results from a limited number of studies.

Conclusion

The use of traditional EMG during LLIF remains without consensus. There is a growing body of evidence utilizing multimodal IONM with MEPs or saphenous SSEPs demonstrating a possible decrease in postoperative neurologic injuries after LLIF. Future prospective studies, with clear definitions of neurologic injury, that evaluate different multimodal IONM strategies are needed to better assess the efficacy of IONM during LLIF.

Effects of Total Psoas Area Index on Surgical Outcomes of Single-Level Lateral Lumbar Interbody Fusion

OBJECTIVE

We evaluated the effect of the total psoas area index (TPAI = total psoas muscle area [cm²]/height squared [m²]) on neurological complications and clinical outcomes after lateral lumbar interbody fusion and identified the appropriate TPAI to achieve a substantial clinical benefit (SCB).

METHODS

A consecutive series of 123 patients who had undergone single-level lateral lumbar interbody fusion at a single center with ≥2 years of follow-up were retrospectively reviewed. The patient characteristics and operative data were evaluated. The neurological complications were classified as transient and persistent symptoms. The visual analog scale score for back pain was assessed preoperatively and at 1 and 2 years postoperatively.

RESULTS

The present study included 31 men and 92 women. The mean TPAI was 8.97 cm²/m² for the men and 5.04 cm²/m² for the women. The mean TPAI was not significantly different between the patients with and without perioperative neurological complications. Multiple logistic regression analysis showed that solid interbody fusion was the most significant factor for achieving an SCB regarding back pain in men (odds ratio [OR], 2.453; P = 0.019) and women (OR, 2.906; P = 0.042). The TPAI was one of the predictors for achieving an SCB in men (OR, 1.251; P = 0.038) and women (OR, 1.795; P = 0.023). The optimal cutoff point of the TPAI for an SCB was 8.18 cm²/m² for the men and 4.43 cm²/m² for the women.

CONCLUSIONS

The TPAI had little effect on the incidence of perioperative neurological complications. However, the TPAI was identified as one of the predictors for achieving an SCB regarding back pain.

Saphenous Nerve Somatosensory-Evoked Potentials Monitoring During Lateral Interbody Fusion

STUDY DESIGN.

Retrospective cohort study.

OBJECTIVES

To clinically evaluate saphenous nerve somatosensory-evoked potentials (SSEPs) as a reliable and predictable way to detect upper lumbar plexus injury intraoperatively during lateral lumbar trans-psoas interbody fusion (LLIF).

METHODS

Saphenous nerve SSEPs were obtained by stimulation of inferior medial thigh with needle electrodes and recording from transcranial potentials. The primary outcome was measured by testing reproducibility of SSEPs at baseline, changes during the procedure, and relevance to standard modalities. Significant SSEP changes were compared with actual postoperative nerve complications. The sensitivity and specificity of saphenous SSEPs to detect postoperative lumbar plexus nerve injury was calculated.

RESULTS

A total of 62 patients were included in the study. Reliable saphenous SSEPs were recorded on the LLIF approach side in 52/62 patients. Persistent saphenous SSEP reduction of amplitude of >50% in 6 cases was observed during expansion of the tubular retractor or during the procedure. Two of 6 patients postoperatively had femoral nerve sensory deficits, and 5 of 6 patients had mild femoral nerve motor weakness, all of which resolved at an average of 12 weeks postoperatively (range 2-24 weeks). One patient had saphenous SSEP changes but demonstrated intraoperative recovery and had no postoperative clinical deficits. Saphenous SSEPs demonstrated 52% to 100% sensitivity and 90% to 100% specificity for detecting postoperative femoral nerve complications.

CONCLUSION

Saphenous SSEPs can be used to detect electrophysiological changes to prevent femoral nerve injury during LLIF. Intraoperative SSEP recovery after amplitude reduction or loss may be a prognostic factor for final clinical outcome.

Intraoperative Radiographs in Single-level Lateral Lumbar Interbody Fusion Can Predict Radiographic and Clinical Outcomes of Follow-up 2 Years After Surgery

MINI

Some of the improvements in DH, FH, and SLL achieved intraoperatively during lateral lumbar interbody fusion surgery were lost by the postoperative 1-week follow-up. An intraoperative radiograph can predict radiographic and clinical outcomes of the 2-year follow-up. The difference between preoperative DH and intraoperative DH should be >4.18 mm.

Intraoperative Computed Tomography-Based Navigation with Augmented Reality for Lateral Approaches to the Spine

Background. Lateral approaches to the spine have gained increased popularity due to enabling minimally invasive access to the spine, less blood loss, decreased operative time, and less postoperative pain. The objective of the study was to analyze the use of intraoperative computed tomography with navigation and the implementation of augmented reality in facilitating a lateral approach to the spine. Methods. We prospectively analyzed all patients who underwent surgery with a lateral approach to the spine from September 2016 to January 2021 using intraoperative CT applying a 32-slice movable CT scanner, which was used for automatic navigation registration. Sixteen patients, with a median age of 64.3 years, were operated on using a lateral approach to the thoracic and lumbar spine and using intraoperative CT with navigation. Indications included a herniated disc (six patients), tumors (seven), instability following the fracture of the thoracic or lumbar vertebra (two), and spondylodiscitis (one). Results. Automatic registration, applying intraoperative CT, resulted in high accuracy (target registration error: 0.84 ± 0.10 mm). The effective radiation dose of the registration CT scans was 6.16 ± 3.91 mSv. In seven patients, a control iCT scan was performed for resection and implant control, with an ED of 4.51 ± 2.48 mSv. Augmented reality (AR) was used to support surgery in 11 cases, by visualizing the tumor outline, pedicle screws, herniated discs, and surrounding structures. Of the 16 patients, corpectomy was performed in six patients with the implantation of an expandable cage, and one patient underwent discectomy using the XLIF technique. One patient experienced perioperative complications. One patient died in the early postoperative course due to severe cardiorespiratory failure. Ten patients had improved and five had unchanged neurological status at the 3-month follow up. Conclusions. Intraoperative computed tomography with navigation facilitates the application of lateral approaches to the spine for a variety of indications, including fusion procedures, tumor resection, and herniated disc surgery.

Psoas Major Muscle Volume Does Not Affect the Postoperative Thigh Symptoms in XLIF Surgery

Background: Extreme lateral interbody fusion (XLIF) is a minimally invasive surgery that accesses the lumbar spine through the psoas muscle. This study aimed to evaluate the correlation between the psoas major muscle volume and anterior thigh symptoms after XLIF. Methods: Eighty-one patients (mean age 63 years) with degenerative spine diseases underwent XLIF (total = 94 levels). Thirty-eight patients were female (46.9%), and 24 patients (29.6%) had a history of lumbar surgery. Supplemental pedicle screws were used in 48 patients, and lateral plates were used in 28 patients. Neuromonitoring devices were used in all cases. The patients were classified into two groups (presence of thigh symptoms and no thigh symptoms after the surgery). The psoas major volumes were measured and calculated by CT (computed tomography) scan and compared between the two patient groups. Results: In the first 24 h after surgery, 32 patients (39.5%) had thigh symptoms (20 reported pain, 9 reported numbness, and 18 reported weakness). At one year postoperatively, only 3 of 32 patients (9.4%) had persistent symptoms. Conclusions: As a final observation, no statistically significant difference in the mean psoas major volume was found between the group of patients with new postoperative anterior thigh symptoms and those with no thigh symptoms. Preoperative psoas major muscle volume seems not to correlate with postoperative anterior thigh symptoms after XLIF.

Transpsoas Lumbar Interbody Fusion Without Psoas Stimulated Electromyography

STUDY DESIGN

This is a retrospective case review.

OBJECTIVE

The objective of this study was to present an anatomic approach to transpsoas interbody fusion without psoas stimulated electromyography (sEMG) and to evaluate the rate of neurological and approach-related complications.

BACKGROUND

The transpsoas approaches have become commonly utilized for lumbar interbody fusion and may have certain advantages compared with other methods of interbody stabilization. Traditionally, transpsoas approaches have been performed utilizing sEMG as it has been purported to reduce the risk of injury to the lumbar plexus; however, an anatomic approach to transpsoas surgery is also possible as cadaveric studies have demonstrated the anatomy of the psoas muscle and lumbar plexus.

METHODS

Patients who underwent transpsoas interbody fusion using an anatomic approach without psoas sEMG between 2005 and 2018 were enrolled in this study. The preoperative and postoperative medical records for this cohort were carefully reviewed to identify any new or persistent radicular symptoms, neurological deficits or approach-related complications.

RESULTS

A total of 133 patients (48 males, 85 females) underwent transpsoas interbody fusion at 222 levels in this cohort-which had a mean age of 63 (61, 65) years and body mass index of 28.8 (27.8, 29.9). New neurological complications were seen in 5 patients (3.8%) and 5 patients (3.8%) were found to have new postoperative radicular pain, up to 3 months postoperatively. The total number of perioperative, approach-related complications was 7 (5.3%) for the entire cohort.

CONCLUSION

An anatomic transpsoas approach to the interbody space without psoas sEMG demonstrated a rate of neurological and approach-related complications that was comparable or superior to the rate of complications reported using the traditional transpsoas approach with sEMG.

Clinical experience of extreme lateral interbody fusion in the treatment of lumbar spondylodiscitis

Introduction

Up to now, there were few studies on extreme lateral interbody fusion (XLIF) surgery for lumbar spondylodiscitis. This study was aimed to evaluate clinical effectiveness and provide more information for XLIF in the treatment of lumbar spondylodiscitis.

Methods

We retrospectively collected cases of XLIF for the treatment of lumbar spondylodiscitis from September 2017 to February 2020. There were 8 cases of non-specific infection of lumbar spine, 4 cases of lumbar tuberculosis, and 1 case of lumbar brucellosis. Basic information, antibiotic application, and inflammatory index were collected before and after surgery. Clinical effectiveness was evaluated at baseline and in 3, 6, and 12 months after the surgery with visual analog scale (VAS) and Oswestry disability index (ODI). The comparison of the indicators before and after the operation was performed by repeated measures analysis of variance.

Results

The average intraoperative blood loss and operation time was 70mL and 99.23 min, respectively. The study consisted of 13 cases with single segment operation. The average follow-up time was 16.54 months. No sign of recurrence of spondylodiscitis occurred at last follow-up. Postoperative VAS and ODI were significantly decreased after the operation. No major blood vessels, nerves, or organ damage occurred during the perioperative period.

Conclusion

XLIF has shown good clinical effectiveness in the treatment of lumbar spondylodiscitis with advantages of less bleeding and less tissue damage in the present study. More multi-center prospective comparative studies are needed to further verify the clinical effectiveness of this procedure in lumbar spondylodiscitis.

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.

Lateral Interbody Fusion at L4/5: Management of the Transitional Psoas

OBJECTIVE

Managing retraction of the lumbar plexus is critical to safely perform lateral lumbar interbody fusion (LLIF) via the transpsoas approach. Occasionally, a transitional psoas is encountered at L4/5 and has been postulated to be a contraindication to transpsoas LLIF. A case series of patients with transitional psoas who underwent L4/5 LLIFs is presented.

METHODS

This retrospective review assessed 79 consecutive patients who underwent L4/5 LLIF during a 24-month period. Preoperative imaging was reviewed, and patients were classified into 2 groups: normal psoas or transitional psoas. Intraoperative features and outcomes were compared between groups.

RESULTS

Seventy-nine patients underwent L4/5 LLIFs, of whom 23 had transitional psoas anatomy and 56 had normal psoas anatomy. Among patients with transitional psoas, the center of the psoas was a mean (range) of 11.2 (5.2-26.6) mm in front of the center of the vertebral body compared with 2.0 (0-4) mm in the normal psoas group. The mean (range) retraction time was similar between groups (10.8 [6.7-14.9] minutes in the transitional psoas group vs. 11.0 [7.8-15.0] minutes in the normal psoas group). No permanent motor injuries occurred in either group, and no differences in length of stay or preoperative or postoperative Oswestry Disability Index scores were found between the groups. The protocol for L4/5 LLIF in patients with transitional psoas anatomy is described.

CONCLUSIONS

Transitional psoas anatomy is frequently encountered in surgical candidates for L4/5 LLIF. Through careful identification of the lumbar plexus and judicious retraction, the transpsoas LLIF can safely be performed in these patients.

Defining a safe working zone for lateral lumbar interbody fusion: a radiographic, cross-sectional study

PURPOSE

To present a radiographic analysis of the anatomy of the lumbar plexus and retroperitoneal blood vessels with respect to psoas morphology and safe working zones (SWZ) for LLIF.

METHODS

A retrospective radiographic analysis of 158 MRI scans was performed. Selected morphometric measurements were performed at L1-L2, L2-L3, L3-L4 and L4-L5 levels: disc anteroposterior distance, psoas anteroposterior distance, lumbar plexus-anterior disc distance, lumbar plexus-anterior psoas distance, vena cava-anterior disc distance and calculation of SWZ in psoas on both left and right sides. The morphometric measurements were analysed for differences with sex and the level.

RESULTS

All the morphometric parameters differed significantly at all levels between males and females. The SWZ was significantly wider on the left side compared to the right-at L2-L3, L3-L4 and L4-L5 levels in females and at L3-L4 and L4-L5 levels in males. The SWZ at L4-L5 was narrowest on both left and right sides-and significantly reduced compared to other levels. 6.9% patients had a SWZ > 20 mm on the left side, and 44.9% patients had SWZ < 20 mm on the right side. With caudal progression of levels, the lumbar plexus and psoas muscle migrated anteriorly and the vena cava/right iliac vein migrated posteriorly.

CONCLUSION

A detailed study of preoperative MRI scans should be carried out in patients planned for LLIF-particularly, at L4-L5 level and in females. A left-sided trans-psoas approach is safer to perform compared to the right side-a right-sided approach should be avoided at L4-L5 considering the narrow SWZ at that level.

Complications associated with L4-5 anterior retroperitoneal trans-psoas interbody fusion: a single institution series

Background

Lateral lumbar interbody fusion (LLIF), first described in the literature in 2006 by Ozgur et al., involves direct access to the lateral disc space via a retroperitoneal trans-psoas tubular approach. Neuromonitoring is vital during this approach since the surgical corridor traverses the psoas muscle where the lumbar plexus lies, risking injury to the lumbosacral plexus that could result in sensory or motor deficits. The risk of neurologic injury is especially higher at L4-5 due to the anatomy of the plexus at this level. Here we report our single-center clinical experience with L4-5 LLIF.

Methods

A retrospective chart review of all patients who underwent an L4-5 LLIF between May 2016 and March 2019 was performed. Baseline demographics and clinical characteristics, such as body mass index (BMI), medical comorbidities, surgical history, tobacco status, operative time and blood loss, length of stay (LOS), and post-op complications were recorded.

Results

A total of 220 (58% female and 42% male) cases were reviewed. The most common presenting pathology was spondylolisthesis. The average age, BMI, operative time, blood loss, and LOS were 64.6 years, 29 kg/m², 214 min, 75 cc, and 2.5 days respectively. A review of post-operative neurologic deficits revealed 31.4% transient hip flexor weakness and 4.5% quadricep weakness on the approach side. At 3-week follow-up, 9.1% of patients experienced mild hip flexor weakness (4 or 4+/5), 0.9% reported mild quadricep weakness, and 9.5% reported anterior thigh dysesthesias; 93.2% of patients were discharged home and 2.3% were readmitted within the first 30 days post discharge. Female sex, higher BMI and longer operative time were associated with hip flexor weakness.

Conclusions

LLIF at L4-5 is a safe, feasible, and versatile approach to the lumbar spine with an acceptable approach-related sensory and motor neurologic complication rates.

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.

Changes in the Operative Corridor in Oblique Lumbar Interbody Fusion Between Preoperative Magnetic Resonance Imaging and Intraoperative Cone-Beam Computed Tomography Using Morphometric Analysis

Background

The oblique lumbar interbody fusion or anterior-to-psoas (OLIF/ATP) technique relies on a corridor anterior to the psoas and posterior to the vasculature for lumbar interbody fusion. This is evaluated preoperatively with CT and/or MRI. To date, there have been no studies examining how intraoperative, lateral decubitus positioning may change the dimensions of this corridor when compared to preoperative imaging.

Objective

Our objective was to evaluate changes in the intraoperative corridor in the supine and lateral positions utilizing preoperative and intraoperative imaging.

Methods

We performed a retrospective analysis among patients who have undergone an OLIF/ATP approach at two tertiary care centers from 2016 to 2018 by measuring the distance between the left lateral border of the aorta or iliac vessels and anteromedial border of the psoas muscle from L1-L2 through L4-5 disc spaces. We compared this corridor between supine, preoperative MRI axial and intraoperative CT acquired in the right lateral decubitus position.

Results

Thirty-three patients, 15 of whom were female, were included in our study. The average age of the patients was 65.4 years and the average BMI was 31 kg/m². The results revealed a statistically significant increase (p<.05) in the intraoperative corridor from supine to lateral decubitus positioning at all levels. However, age, BMI, and gender had no statistically significant impact on the preoperative versus intraoperative corridor.

Conclusion

This is the first study to provide objective evidence that lateral decubitus positioning increases the intraoperative corridor for OLIF/ATP. Our study demonstrates that lateral decubitus positioning provides a more favorable corridor for the OLIF/ATP technique from L1-L5 disc levels.

Minimally Invasive Anterior Longitudinal Ligament Release for Anterior Column Realignment

STUDY DESIGN

Review of the literature.

OBJECTIVES

Anterior column realignment (ACR) is a powerful but relatively new minimally invasive technique for deformity correction. The purpose of this study is to provide a literature review of the ACR surgical technique, reported outcomes, and future directions.

METHODS

A review of the literature was performed regarding the ACR technique. A review of patients at our single center who underwent ACR was performed, with illustrative cases selected to demonstrate basic and nuanced aspects of the technique.

RESULTS

Clinical and cadaveric studies report increases in segmental lordosis in the lumbar spine by 73%, approximately 10° to 33°, depending on the degree of posterior osteotomy and lordosis of the hyperlordosis interbody spacer. These corrections have been found to be associated with a similar risk profile compared with traditional surgical options, including a 30% to 43% risk of proximal junctional kyphosis in early studies.

CONCLUSIONS

ACR represents a powerful technique in the minimally invasive spinal surgeon's toolbox for treatment of complex adult spinal deformity. The technique is capable of significant sagittal plane correction; however, future research is necessary to ascertain the safety profile and long-term durability of ACR.

Novel Implementation of Extreme Lateral Interbody Fusion to Avoid Intraoperative Lumbar Plexus Injury: Technical Note and Preliminary Results

BACKGROUND

This study modified the traditional extreme lateral lumbar interbody fusion (XLIF) surgery and was intended to reduce the approach related to lumbar plexus injury.

METHODS

The patients receiving a new modified XLIF for treatment of lumbar degenerative diseases since September 2017 in our hospital were retrospectively collected. Postoperative additional symptoms of leg numbness, pain, or weakness were recorded as lumbar plexus nerve injury. Intraoperative electromyographic monitoring was recorded during surgery to evaluate the safety of the modified entry point. The visual analog scale and Oswestry Disability Index were adopted to evaluate the postoperative clinical efficacy. Modified MacNab criteria were introduced to evaluate the patients' satisfaction 12 months after surgery. The preoperative and postoperative intervertebral height, foraminal height, and lumbar lordotic angle were measured. Repeated measurement variance analysis was used for comparison of clinical and imaging indexes in various periods. P < 0.05 indicated statistical difference.

RESULTS

Fifty-nine patients were finally included in the retrospective study. The intraoperative average blood loss and operation time were 70 mL (40-130 mL) and 77.90 ± 13.65 minutes. The average follow-up time was 18 months. Postoperative visual analog scale and Oswestry Disability Index were significantly decreased compared with those before the operation. The intervertebral height and foraminal height were dramatically higher than those before surgery. No lumbar plexus injury occurred.

CONCLUSIONS

The initial result was optimistic in reducing lumbar plexus injury and obtaining good clinical efficacy. We need to further expand the sample size and carry out a comparative study to observe the advantages and disadvantages of modified XLIF.

The effect of vascular approach surgeons on perioperative complications in lateral transpsoas lumbar interbody fusions

BACKGROUND CONTEXT

Lateral lumbar interbody fusion (LLIF) is a popular technique used in spine surgery. It is minimally invasive, provides indirect decompression, and allows for coronal plane deformity correction. Despite these benefits, the approach to LLIF has been linked to complications associated with the lumbosacral plexus and vascular anatomy. As a result, vascular surgeons may be recruited for the exposure portion of the procedure.

PURPOSE

The purpose of this study was to compare exposure-related complication and postoperative (postop) neuropraxia rates between exposure (EXP) and spine surgeon only (SSO) groups while performing the approach for LLIF.

STUDY DESIGN/SETTING

Retrospective analysis of patients treated at a single institution.

PATIENT SAMPLE

Patients undergoing LLIF procedures between 2012 and 2018.

OUTCOME MEASURES

Operative time, estimated blood loss, fluoroscopy, length of stay (LOS), intra- and postoperative complications, and physiologic measures including pre- and postoperative motor examinations and unresolved neuropraxia.

METHODS

Patients who underwent LLIF were separated into EXP and SSO groups based on the presence or absence of vascular/general surgeon during the approach. The entire clinical history of patients with a decrease in pre- and postop motor examination was reviewed for the presence of neuropraxia. All other intra- and postop exposure-related complications were recorded for comparison. Propensity score matching (PSM) was performed to account for age, Charlson Comorbidity Index (CCI) percentage of LLIFs including L4-L5, and number of levels fused. Independent t test and chi-square analyses were used to identify significant differences between EXP and SSO groups. Statistical significance was set at p<.05.

RESULTS

Two hundred and seventy-five patients underwent LLIF procedures, 155 SSO and 120 EXP. Postoperatively, 26 patients (11.1%) experienced a drop in any Medical Research Council (MRC) score, and two patients (0.7%) experienced unresolved quadriceps palsies. The mean recovery time for MRC scores was 84.4 days. Other complications included 2 pneumothoraces (0.7%), 1 iliac vein injury (0.4%), 14 cases of ileus (5.1%), 3 pulmonary emboli (1.1%), 2 deep vein thrombosis (0.7%), 3 cases of abdominal wall paresis (1.1%), and one abdominal hematoma (0.4%). After PSM, demographics including age, gender, body mass index, CCI, levels fused, and operative time were similar between cohorts. Twenty patients had changes in pre- to postop motor scores (SSO 9.4%, EXP 12.4%, p>.05). Iliopsoas motor scores decreased at the highest rate (EXP 12.4%, SSO 8.2%, p>.05) followed by quadriceps (EXP 5.2%, SSO 4.7%, p>.05). One SSO patient's postop course was complicated by a foot drop but returned to baseline within 1 year. One patient in EXP group developed an unresolved quadriceps palsy (EXP 1.0%, SSO 0.0%, p>.05). Intraoperative exposure complications included one pneumothorax (EXP 1.0%, SSO 0.0%, p>.05). There were no differences in PE/DVT, Ileus, or LOS. In the EXP cohort, three patients experienced abdominal wall paresis (EXP 2.9%, SSO 0.00%, p=.246).

CONCLUSIONS

Comparing the LLIF exposures performed by EXP and SSO, we found no significant difference in the rates of complications. Additional research is needed to determine the etiology of the abdominal wall complications. In conclusion, neuropraxia- and approach-related complications are similarly low between exposure and spine surgeons.

The Navigated Oblique Lumbar Interbody Fusion: Accuracy Rate, Effect on Surgical Time, and Complications

Objective

The oblique lumbar interbody fusion (OLIF) can be done with either fluoroscopy or navigation. However, it is unclear how navigation affects the overall flow of the procedure. We wished to report on the accuracy of this technique using navigation and on how navigation affects surgical time and complications.

Methods

A retrospective review was undertaken to evaluate patients who underwent OLIF using spinal navigation at University of California San Francisco. Data collected were demographic variables, perioperative variables, and radiographic images. Postoperative lateral radiographs were analyzed for accuracy of cage placement. The disc space was divided into 4 quadrants from anterior to posterior, zone 1 being anterior, and zone 4 being posterior. The accuracy of cage placement was assessed by placement.

Results

There were 214 patients who met the inclusion criteria. A total of 350 levels were instrumented from L1 to L5 using navigation. The mean follow-up time was 17.42 months. The mean surgical time was 211 minutes, and the average surgical time per level was 129.01 minutes. After radiographic analysis, 94.86% of cages were placed within quartiles 1 to 3. One patient (0.47%) underwent revision surgery because of suboptimal cage placement. For approach-related complications, transient neurological symptoms were 10.28%, there was no vascular injury.

Conclusion

The use of navigation to perform OLIF from L1 to L5 resulted in a cage placement accuracy rate of 94.86% in 214 patients.

Minimally Invasive Lateral Retroperitoneal Approach for Resection of Extraforaminal Lumbar Plexus Schwannomas: Operative Techniques and Literature Review

BACKGROUND

Traditional approaches for retroperitoneal lumbar plexus schwannomas involve anterior open or laparoscopic resection. For select tumors, the lateral retroperitoneal approach provides a minimally invasive alternative.

OBJECTIVE

To describe a minimally invasive lateral transpsoas approach for the resection of retroperitoneal schwannomas.

METHODS

A lateral retroperitoneal transpsoas approach was used to resect a 3.1 × 2.7 × 4.1 cm schwannoma embedded within the psoas muscle. A minimally invasive retractor system allows for appropriate visualization and complete resection with the aid of the microscope. The patient tolerated the procedure without complication and was discharged on postoperative day 2 in good condition at her neurological baseline.

RESULTS

The lateral retroperitoneal approach provides a minimally invasive alternative for select retroperitoneal schwannomas. In theory, this procedure allows for faster recovery and less blood loss compared to traditional open anterior approaches. For a subset of tumors, anterior laparoscopy may provide better access, but the lateral approach is well known to most neurosurgeons who perform lateral interbody fusions and can be easily tailored to extraforaminal tumor resection.

CONCLUSION

Retroperitoneal schwannomas pose a challenge due to their deep location. The lateral retroperitoneal approach provides a useful alternative for resection of a subset of retroperitoneal schwannomas.

Minimally invasive anterior and lateral transpsoas approaches for closed reduction of grade II spondylolisthesis: initial clinical and radiographic experience

OBJECTIVE Minimally invasive anterior and lateral approaches to the lumbar spine are increasingly used to treat and reduce grade I spondylolisthesis, but concerns still exist for their usage in the management of higher-grade lesions. The authors report their experience with this strategy for grade II spondylolisthesis in a single-surgeon case series and provide early clinical and radiographic outcomes. METHODS A retrospective review of a single surgeon's cases between 2012 and 2016 identified all patients with a Meyerding grade II lumbar spondylolisthesis who underwent minimally invasive lateral lumbar interbody fusion (LLIF) or anterior lumbar interbody fusion (ALIF) targeting the slipped level. Demographic, clinical, and radiographic data were collected and analyzed. Changes in radiographic measurements, Oswestry Disability Index (ODI), and visual analog scale (VAS) scores were compared using the paired t-test and Wilcoxon signed rank test for continuous and ordinal variables, respectively. RESULTS The average operative time was 199.1 minutes (with 60.6 ml of estimated blood loss) for LLIFs and 282.1 minutes (with 106.3 ml of estimated blood loss), for ALIFs. Three LLIF patients had transient unilateral anterior thigh numbness during the 1st week after surgery, and 1 ALIF patient had transient dorsiflexion weakness, which was resolved at postoperative week 1. The mean follow-up time was 17.6 months (SD 12.5 months) for LLIF patients and 10 months (SD 3.1 months) for ALIF patients. Complete reduction of the spondylolisthesis was achieved in 12 LLIF patients (75.0%) and 7 ALIF patients (87.5%). Across both procedures, there was an increase in both the segmental lordosis (LLIF 5.6°, p = 0.002; ALIF 15.0°, p = 0.002) and overall lumbar lordosis (LLIF 2.9°, p = 0.151; ALIF 5.1°, p = 0.006) after surgery. Statistically significant decreases in the mean VAS and the mean ODI measurements were seen in both treatment groups. The VAS and ODI scores fell by a mean value of 3.9 (p = 0.002) and 19.8 (p = 0.001), respectively, for LLIF patients and 3.8 (p = 0.02) and 21.0 (p = 0.03), respectively, for ALIF patients at last follow-up. CONCLUSIONS Early clinical and radiographic results from using minimally invasive LLIF and ALIF approaches to treat grade II spondylolisthesis appear to be good, with low operative blood loss and no neurological deficits. Complete reduction of the spondylolisthesis is frequently possible with a statistically significant reduction in pain scores.

Short-term outcomes of lateral lumbar interbody fusion without decompression for the treatment of symptomatic degenerative spondylolisthesis at L4-5

OBJECTIVE Recently, authors have called into question the utility and complication index of the lateral lumbar interbody fusion procedure at the L4-5 level. Furthermore, the need for direct decompression has also been debated. Here, the authors report the clinical and radiographic outcomes of transpsoas lumbar interbody fusion, relying only on indirect decompression to treat patients with neurogenic claudication secondary to Grade 1 and 2 spondylolisthesis at the L4-5 level. METHODS The authors conducted a retrospective evaluation of 18 consecutive patients with Grade 1 or 2 spondylolisthesis from a prospectively maintained database. All patients underwent a transpsoas approach, followed by posterior percutaneous instrumentation without decompression. The Oswestry Disability Index (ODI) and SF-12 were administered during the clinical evaluations. Radiographic evaluation was also performed. The mean follow-up was 6.2 months. RESULTS Fifteen patients with Grade 1 and 3 patients with Grade 2 spondylolisthesis were identified and underwent fusion at a total of 20 levels. The mean operative time was 165 minutes for the combined anterior and posterior phases of the operation. The estimated blood loss was 113 ml. The most common cage width in the anteroposterior dimension was 22 mm (78%). Anterior thigh dysesthesia was identified on detailed sensory evaluation in 6 of 18 patients (33%); all patients experienced resolution within 6 months postoperatively. No patient had lasting sensory loss or motor deficit. The average ODI score improved 26 points by the 6-month follow-up. At the 6-month follow-up, the SF-12 mean Physical and Mental Component Summary scores improved by 11.9% and 9.6%, respectively. No patient required additional decompression postoperatively. CONCLUSIONS This study offers clinical results to establish lateral lumbar interbody fusion as an effective technique for the treatment of Grade 1 or 2 degenerative spondylolisthesis at L4-5. The use of this surgical approach provides a minimally invasive solution that offers excellent arthrodesis rates as well as favorable clinical and radiological outcomes, with low rates of postoperative complications. However, adhering to the techniques of transpsoas lateral surgery, such as minimal table break, an initial look-and-see approach to the psoas, clear identification of the plexus, minimal cranial caudal expansion of the retractor, mobilization of any traversing sensory nerves, and total psoas dilation times less than 20 minutes, ensures the lowest possible complication profile for both visceral and neural injuries even in the narrow safe zones when accessing the L4-5 disc space in patients with degenerative spondylolisthesis.

The Anatomic Characteristics of the Retroperitoneal Oblique Corridor to the L1-S1 Intervertebral Disc Spaces

STUDY DESIGN

This is a cross-sectional study.

OBJECTIVE

To investigate the oblique corridor to the L1-S1 intervertebral disc space between the psoas muscle and the great vessels in cadaveric specimens bilaterally and the location of genitofemoral nerve and the diaphragmatic crura relative to the oblique corridor.

SUMMARY OF BACKGROUND DATA

Although use of oblique lumbar interbody fusion is rapidly expanding, the morphometric data related to the procedure are limited.

METHODS

Twelve fresh-frozen full-torso cadaveric specimens were dissected to examine the oblique corridor to access the L1-S1 space in a static state and with mild retraction of the psoas. The level at which the genitofemoral nerve pierces from the psoas major and the diaphragmatic crura originate from the lumbar vertebral body was also investigated.

RESULTS

The mean width of oblique corridor in the static state and with mild psoas retraction, respectively, were as follows: on the right side: (L1-2) 13.33 and 16.75 mm; (L2-3) 15.42 and 21.42 mm; (L3-4) 16.58 and 22.67 mm; (L4-5) 12.75 and 21.17 mm; (L5-S1) 5.92 and 12.00 mm; on the left side: (L1-2) 16.75 and 19.67 mm; (L2-3) 18.50 and 25.33 mm; (L3-4) 20.58 and 28.00 mm; (L4-5) 18.17 and 26.08 mm; and (L5-S1) 5.83 and 12.00 mm. The level at which the genitofemoral nerve pierces from the psoas major was between L2 and L4. The diaphragmatic crura originates from L1 to L3.

CONCLUSION

The oblique corridor allows access to the L1-L5 discs from both sides, but it is larger on the left side. The corridor between the iliac vessels and the psoas for L5-S1 is difficult to be applied clinically. Mild psoas retraction can moderately enlarge the oblique corridor. The genitofemoral nerve and diaphragmatic crura may be encountered in this approach and should be carefully observed.

LEVEL OF EVIDENCE

5.

Anatomic Considerations in the Lateral Transpsoas Interbody Fusion: The Impact of Age, Sex, BMI, and Scoliosis

STUDY DESIGN

This is a retrospective case series.

OBJECTIVE

Define the anatomic variations and the risk factors for such within the operative corridor of the transpsoas lateral interbody fusion.

SUMMARY OF BACKGROUND DATA

The lateral interbody fusion approach has recently been associated with devastating complications such as injury to the lumbosacral plexus, surrounding vasculature, and bowel. A more comprehensive understanding of anatomic structures in relation to this approach using preoperative imaging would help surgeons identify high-risk patients potentially minimizing these complications.

MATERIALS AND METHODS

Age-sex distributed, naive lumbar spine magnetic resonance imagings (n=180) were used to identify the corridor for the lateral lumbar interbody approach using axial images. Bilateral measurements were taken from L1-S1 to determine the locations of critical vascular, intraperitoneal, and muscular structures. In addition, a subcohort of scoliosis patients (n=39) with a Cobb angle >10 degrees were identified and compared.

RESULTS

Right-sided vascular anatomy was significantly more variant than left (9.9% vs. 5.7%; P=0.001). There were 9 instances of "at-risk" vasculature on the right side compared with 0 on the left (P=0.004). Age increased vascular anatomy variance bilaterally, particularly in the more caudal levels (P≤0.001). A "rising-psoas sign" was observed in 26.1% of patients. Bowel was identified within the corridor in 30.5% of patients and correlated positively with body mass index (P<0.001). Scoliosis increased variant anatomy of left-sided vasculature at L2-3/L3-4. Nearly all variant anatomy in this group was found on the convex side of the curvature (94.2%).

CONCLUSIONS

Given the risks and complications associated with this approach, careful planning must be taken with an understanding of vulnerable anatomic structures. Our analysis suggests that approaching the intervertebral space from the patient's left may reduce the risk of encountering critical vascular structures. Similarly, in the setting of scoliosis, an approach toward the concave side may have a more predictable course for surrounding anatomy.

LEVEL OF EVIDENCE

Level 3-study.

Lateral lumbar interbody fusion without intraoperative neuromonitoring: a single-center consecutive series of 157 surgeries

OBJECTIVE

Lateral lumbar interbody fusion (LLIF) is frequently used for anterior column stabilization. Many authors have reported that intraoperative neuromonitoring (IONM) of the lumbar plexus nerves is mandatory for this approach. However, even with IONM, the reported motor and sensory deficits are still considerably high. Thus, the authors' approach was to focus on the indication, trajectory, and technique instead of relying on IONM findings per se. The objective of this study therefore was to analyze the outcome of our large cohort of patients who underwent LLIF without IONM.

METHODS

The authors report on 157 patients included from 2010 to 2016 who underwent LLIF as an additional stabilizing procedure following dorsal instrumentation. LLIF-related complications as well as clinical outcomes were evaluated.

RESULTS

The mean follow-up was 15.9 ± 12.0 months. For 90.0% of patients, cage implantation by LLIF was the first retroperitoneal surgery. There were no cases of surgery-related hematoma, vascular injury, CSF leak, or any other visceral injury. Between 1 and 4 cages were implanted per surgery, most commonly at L2-3 and L3-4. The mean length of surgery was 92.7 ± 35 minutes, and blood loss was 63.8 ± 57 ml. At discharge, 3.8% of patients presented with a new onset of motor weakness, a new sensory deficit, or the deterioration of leg pain due to LLIF surgery. Three months after surgery, 3.5% of the followed patients still reported surgery-related motor weakness, 3.6% leg pain, and 9.6% a persistent sensory deficit due to LLIF surgery.

CONCLUSIONS

The results of this series demonstrate that the complication rates for LLIF without IONM are comparable, if not superior, to those in previously reported series using IONM. Hence, the authors conclude that IONM is not mandatory for LLIF procedures if the surgical approach is tailored to the respective level and if the visualization of nerves is performed.

Lumbar Interbody Fusions for Degenerative Spondylolisthesis: Review of Techniques, Indications, and Outcomes

STUDY DESIGN

Broad narrative review.

OBJECTIVES

To review and summarize the current literature on the outcomes, techniques, and indications of lumbar interbody fusion in degenerative spondylolisthesis.

METHODS

A thorough review of peer-reviewed literature was performed on the outcomes, techniques, and indications of lumbar interbody fusions in degenerative spondylolisthesis.

RESULTS

A number of studies have found similar results between interbody fusions and posterolateral fusion in the setting of degenerative spondylolisthesis. There is some evidence that suggests that interbody fusion may be a useful adjunct in the setting of unstable degenerative spondylolisthesis. The number of options for interbody fusions has quickly expanded. Initially, interbody fusions were accomplished via an anterior approach. Posterior and transforaminal interbody fusions are 2 options that accomplish an interbody fusion without the morbidity of an anterior approach. Over the past decade, minimally invasive options including extreme lateral, oblique, and minimally invasive transforaminal interbody fusions have gained popularity.

CONCLUSIONS

Lumbar interbody fusion can be a useful tool in the setting of unstable degenerative spondylolisthesis. A number of technique options, both open and minimally invasive, are available to accomplish an interbody fusion. The literature to this date does not support a clear benefit of one technique over others in the setting of degenerative spondylolisthesis.

Acute Paraparesis Due to Protrusion of a Disc Following Lateral Interbody Fusion for Degenerative Kyphoscoliosis: A Case Report

CASE

A 74-year-old woman presented with severe trunk deformity. Radiographs revealed severe sagittal and coronal imbalance with spinal canal stenosis at L4 to L5. Anterior cages were placed at L2 to L3, L3 to L4, and L4 to L5. Three days later, posterior correction surgery from T5 to the ilium with decompression at L4 to L5 was performed. At 30 minutes after surgery, leg muscle strength severely deteriorated. Emergency surgery revealed disc fragments protruding into the spinal canal at L2 to L3.

CONCLUSION

Because posteriorly placed extreme lateral interbody fusion (XLIF) cages can be a risk factor for disc protrusion into the spinal canal, computed tomographic evaluation or prophylactic posterior decompression should be considered before the correction procedure.

Anatomic Relationship Between Ureter and Oblique Lateral Interbody Fusion Access: Analysis Based on Contrast-Enhanced Computed Tomographic Urography

OBJECTIVE

To investigate the anatomic relationship between ureter and oblique lateral interbody fusion access by using contrast-enhanced computed tomographic urography.

METHODS

Contrast-enhanced computed tomographic urography data of 234 patients were retrospectively analyzed. The angle of inclination (∠α) of bilateral ureters, the angle between bilateral surgical accesses (∠β), the insertion angle of surgical access (∠γ), and the angle between ureter and outer margin of ipsilateral surgical access (∠ε) at L2/3, L3/4, and L4/5 levels were measured and analyzed.

RESULTS

∠α gradually increased from L2/3 to L4/5. ∠β gradually decreased from L2/3 to L4/5, and at each level the left-sided ∠β was larger than right-sided ∠β. ∠ε were positive at L2/3 and left-sided L3/4. The right-sided ∠ε at L3/4 and the bilateral sided ∠ε at L4/5 were negative, and the right-sided ∠ε at L4/5 had the largest absolute value.

CONCLUSIONS

The bilateral ureters gradually descents from the lateral margin to the anteromedial margin on the surface of psoas major muscle. The range of bilateral surgical accesses for oblique lateral interbody fusion gradually decreases from L2/3 to L4/5, and the left-sided access is larger than the right-sided when at the same level. Ureters at the right-sided L3/4 level and bilateral L4/5 levels are at high risk of being injured. In particular, the right ureter at the L4/5 level is most likely to be injured.