Clinical and radiographic outcomes following 120 consecutive patients undergoing prone transpsoas lateral lumbar interbody fusion.

PURPOSE: The prone transpsoas approach is a single-position alternative to traditional lateral lumbar interbody fusion (LLIF). Earlier prone LLIF studies have focused on technique, feasibility, perioperative efficiencies, and immediate postoperative radiographic alignment. This study was undertaken to report longer-term clinical and radiographic outcomes, and to identify learnings from experiential evolution of the prone LLIF procedure. METHODS: All consecutive patients undergoing prone LLIF for any indication at one institution were included (n = 120). Demographic, diagnostic, treatment, and outcomes data were captured via prospective institutional registry. Retrospective analysis identified 31 'pre-proceduralization' and 89 'post-proceduralization' prone LLIF approaches, enabling comparison across early and later cohorts. RESULTS: 187 instrumented LLIF levels were performed. Operative time, retraction time, LLIF blood loss, and hospital stay averaged 150 min, 17 min, 50 ml, and 2.2 days, respectively. 79% of cases were without complication. Postoperative hip flexion weakness was identified in 14%, transient lower extremity weakness in 12%, and sensory deficits in 10%. At last follow-up, back pain, worst-leg pain, Oswestry, and EQ-5D health state improved by 55%, 46%, 48%, and 51%, respectively. 99% improved or maintained sagittal alignment with an average 6.5° segmental lordosis gain at LLIF levels. Only intra-psoas retraction time differed between pre- and post-proceduralization; proceduralization saved an average 3.4 min/level (p = 0.0371). CONCLUSIONS: The largest single-center prone LLIF experience with the longest follow-up to-date shows that it results in few complications, quick recovery, improvements in pain and function, high patient satisfaction, and improved sagittal alignment at an average one year and up to four years postoperatively.

What is the early fate of adjacent segmental lordosis compensation at L3-4 and L5-S1 following a lateral versus transforaminal lumbar Interbody Fusion at L4-5?

INTRODUCTION: Degenerative spondylolisthesis causes translational and angular malalignment, resulting in a loss of segmental lordosis. This leads to compensatory adjustments in adjacent levels to maintain balance. Lateral lumbar interbody fusion (LLIF) and transforaminal lumbar interbody fusion (TLIF) are common techniques at L4-5. This study compares compensatory changes at adjacent L3-4 and L5-S1 levels six months post LLIF versus TLIF for grade 1 degenerative spondylolisthesis at L4-5. METHODS: A retrospective study included patients undergoing L4-5 LLIF or TLIF with posterior pedicle screw instrumentation (no posterior osteotomy) for grade 1 spondylolisthesis. Pre-op and 6-month post-op radiographs measured segmental lordosis (L3-L4, L4-L5, L5-S1), lumbar lordosis (LL), and pelvic incidence (PI), along with PI-LL mismatch. Multiple regressions were used for hypothesis testing. RESULTS: 113 patients (61 LLIF, 52 TLIF) were studied. TLIF showed less change in L4-5 lordosis (mean = 1.04°, SD = 4.34) compared to LLIF (mean = 4.99°, SD = 5.53) (p = 0.003). L4-5 angle changes didn't correlate with L3-4 changes, and no disparity between LLIF and TLIF was found (all p > 0.16). In LLIF, greater L4-5 lordosis change predicted reduced compensatory L5-S1 lordosis (p = 0.04), while no significant relationship was observed in TLIF patients (p = 0.12). CONCLUSION: LLIF at L4-5 increases lordosis at the operated level, with compensatory decrease at L5-S1 but not L3-4. This reciprocal loss at adjacent L5-S1 may explain inconsistent improvement in lumbar lordosis (PI-LL) post L4-5 fusion.

Lateral versus posterior approaches to treat degenerative lumbar pathologies-systematic review and meta-analysis of recent literature.

INTRODUCTION: The lateral lumbar interbody fusion arose as a revolutionary approach to treating several spinal pathologies because the techniques were able to promote indirect decompression and lordosis restoration through a minimally invasive approach allowing for reduced blood loss and early recovery for patients. However, it is still not clear how the technique compares to other established approaches for treating spinal degenerative diseases, such as TLIF, PLIF, and PLF. MATERIAL AND METHODS: This is a systematic review and meta-analysis of articles published in the last 10 years comparing lateral approaches to posterior techniques. The authors included articles that compared the LLIF technique to one or more posterior approaches, treating only degenerative pathologies, and containing at least one of the key outcomes of the study. Exclusion articles that were not original and the ones that the authors could not obtain the full text; also articles without the possibility to calculate the standard deviation or mean were excluded. For count variables, the odds ratio was used, and for continuous variables, the standard means difference (SMD) was used, and the choice between random or fixed-effects model was made depending on the presence or not of significant (p < 0.05) heterogeneity in the sample. RESULTS: Twenty-four articles were included in the quantitative review. As for the intra-/perioperative variables, the lateral approaches showed a significant reduction in blood loss (SMD-1.56, p < 0.001) and similar operative time (SMD = - 0.33, p = 0.24). Moreover, the use of the lateral approaches showed a tendency to lead to reduced hospitalization days (SMD = - 0.15, p = 0.09), with significantly reduced odds ratios of complications (0.53, p = 0.01). As for the clinical outcomes, both approaches showed similar improvement both at improvement as for the last follow-up value, either in ODI or in VAS-BP. Finally, when analyzing the changes in segmental lordosis and lumbar lordosis, the lateral technique promoted significantly higher correction in both outcomes (p < 0.05). CONCLUSION: Lateral approaches can promote significant radiological correction and similar clinical improvement while reducing surgical blood loss and postoperative complications.

Changes in psoas and posterior paraspinal muscle morphology after standalone lateral lumbar interbody fusion: a quantitative MRI-based analysis.

PURPOSE: Standalone lateral lumbar interbody fusion (SA-LLIF) without posterior instrumentation can be an alternative to 360° fusion in selected cases. This study aimed to investigate quantitative changes in psoas and paraspinal muscle morphology that occur on index levels after SA-LLIF. METHODS: Patients undergoing single- or multi-level SA-LLIF at L2/3 to L4/5 who had preoperative and postoperative lumbar MRI scans, the latter performed between 3 and 18 months after surgery for any reason, were retrospectively included. Muscle measurements were performed of the psoas and posterior paraspinal muscles (PPM; erector spinae and multifidus) on index levels using manual segmentation and an automated pixel intensity threshold method to differentiate muscle from fat signal. Changes in the total cross-sectional area (TCSA), the functional cross-sectional area (FCSA), and the percentage of fat infiltration (FI) of these muscles were assessed. RESULTS: A total of 67 patients (55.2% female, age 64.3 ± 10.6 years, BMI 26.9 ± 5.0 kg/m2) with 125 operated levels were included. Follow-up MRI scans were performed after an average of 8.7 ± 4.6 months, primarily for low back pain. Psoas muscle parameters did not change significantly, irrespective of the approach side. Among PPM parameters, the mean TCSA at L4/5 (+ 4.8 ± 12.4%; p = 0.013), and mean FI at L3/4 (+ 3.1 ± 6.5%; p = 0.002) and L4/5 (+ 3.0 ± 7.0%; p = 0.002) significantly increased. CONCLUSION: Our study demonstrated that SA-LLIF did not alter psoas muscle morphology, underlining its minimally invasive nature. However, FI of PPM significantly increased over time despite the lack of direct tissue damage to posterior structures, suggesting a pain-mediated response and/or the result of segmental immobilization.

A retrospective review of single-position prone lateral lumbar interbody fusion cases: early learning curve and perioperative outcomes.

PURPOSE: The objective of this study was to discuss our experience performing LLIF in the prone position and report our complications. METHODS: A retrospective chart review was conducted that included all patients who underwent single- or multi-level single-position pLLIF alone or as part of a concomitant procedure by the same surgeon from May 2019 to November 2022. RESULTS: A total of 155 patients and 250 levels were included in this study. Surgery was most commonly performed at the L4-L5 level (n = 100, 40%). The most common preoperative diagnosis was spondylolisthesis (n = 74, 47.7%). In the first 30 cases, 3 surgeries were aborted to an MIS TLIF. Complications included 3 unintentional ALL ruptures (n = 3/250, 1.2%), and 1 malpositioned implant impinging on the contralateral foramen requiring revision (n = 1/250, 0.4%), which all occurred within the first 30 cases. Out of 147 patients with more than 6-week follow-ups, there were 3 cases of femoral nerve palsy (n = 3/147, 2.0%). Two cases of femoral nerve palsy improved to preoperative strength by the 6th week postoperatively, while one improved to 4/5 preoperative strength by 1 year. There were no cases of bowel perforation or vascular injury. CONCLUSION: Our single-surgeon experience demonstrates the initial learning curve when adopting pLLIF. Thereafter, we experienced reproducibility in our technique and large improvements in our operative times, and complication profile. We experienced no technical complications after the 30th case. Further studies will include long-term clinical and radiographic outcomes to understand the complete utility of this approach.

Influence of the preoperative L5S1 disc state on lateral L2 to L5 fusion's outcomes at an average follow-up of 3,5 years (minimum 2 years).

INTRODUCTION: The impact of pre-existing degeneration of a disc underlying a lumbar arthrodesis via lateral approach on long-term clinical outcome has, to our knowledge, not been studied. When performing arthrodesis between L2 and L5, its extension to L5S1 is challenging because it imposes a different surgical approach. Therefore, surgeon's temptation is to not include L5S1 in the fusion even in case of discopathy. Our objective was to study the influence of the preoperative L5S1 status on the clinical outcome of lumbar lateral interbody fusion (LLIF) using a pre-psoatic approach between L2 and L5 with a minimum follow-up of 2 years. MATERIAL AND METHODS: Patients who underwent LLIF from L2 to L5 between 2015 and 2020 were included in our study. We studied VAS, ODI, and global clinical outcome before surgery and at last follow-up. The L5-S1 disc was radiologically studied in preoperative imaging. Patients were included in two groups (A "with" and B :without" L5-S1 disc degeneration) to compare the clinical outcomes at last follow-up. Our primary objective was to evaluate the rate of L5-S1 disc revision surgery at last follow-up. RESULTS: 102 patients were included. 2 required L5-S1 disc surgery following overlying arthrodesis. Our results showed a significant improvement in the patients' clinical outcomes at the last follow-up (p < 0.0001). We did not find any significant difference on clinical criteria between groups A & B. CONCLUSION: A preop L5S1 disc degeneration does not seem to impact the final clinical outcomes after lumbar lateral interbody fusion at a minimal two years F.U. It should not be systematically involved in an overlying fusion.

Biomechanical properties of lumbar vertebral ring apophysis cage under endplate injury: a finite element analysis.

OBJECTIVE: This study aimed to compare the biomechanical properties of lumbar interbody fusion involving two types of cages. The study evaluated the effectiveness of the cage spanning the ring apophysis, regardless of the endplate's integrity. METHODS: A finite element model of the normal spine was established and validated in this study. The validated model was then utilized to simulate Lateral Lumbar Interbody Fusion (LLIF) with posterior pedicle screw fixation without posterior osteotomy. Two models of interbody fusion cage were placed at the L4/5 level, and the destruction of the bony endplate caused by curetting the cartilaginous endplate during surgery was simulated. Four models were established, including Model 1 with an intact endplate and long cage spanning the ring apophysis, Model 2 with endplate decortication and long cage spanning the ring apophysis, Model 3 with an intact endplate and short cage, and Model 4 with endplate decortication and short cage. Analyzed were the ROM of the fixed and adjacent segments, screw rod system stress, interface stress between cage and L5 endplate, trabecular bone stress on the upper surface of L5, and intervertebral disc pressure (IDP) of adjacent segments. RESULTS: There were no significant differences in ROM and IDP between adjacent segments in each postoperative model. In the short cage model, the range of motion (ROM), contact pressure between the cage and endplate, stress in L5 cancellous bone, and stress in the screw-rod system all exhibited an increase ranging from 0.4% to 79.9%, 252.9% to 526.9%, 27.3% to 133.3%, and 11.4% to 107%, respectively. This trend was further amplified when the endplate was damaged, resulting in a maximum increase of 88.6%, 676.1%, 516.6%, and 109.3%, respectively. Regardless of the integrity of the endplate, the long cage provided greater support strength compared to the short cage. CONCLUSIONS: Caution should be exercised during endplate preparation and cage placement to maintain the endplate's integrity. Based on preoperative X-ray evaluation, the selection of a cage that exceeds the width of the pedicle by at least 5 mm (ensuring complete coverage of the vertebral ring) has demonstrated remarkable biomechanical performance in lateral lumbar interbody fusion procedures. By opting for such a cage, we expect a reduced occurrence of complications, including cage subsidence, internal fixation system failure, and rod fracture.

Preoperative predictors of prolonged hospitalization in patients undergoing lateral lumbar interbody fusion.

PURPOSE: We aim to examine the preoperative factors associated with increased postoperative length of stay in patients undergoing LLIF in the hospital setting. METHODS: Patient demographics, perioperative characteristics, and patient-reported outcome measures (PROMs) were collected from a single-surgeon database. Patients undergoing LLIF in the hospital setting were separated into postoperative LOS <48 h (H) and LOS ≥ 48H. Univariate analysis for preoperative characteristics was utilized to determine covariates for multivariable logistic regression. Multivariable logistic regression was then utilized to determine significant predictors of extended postoperative length of stay. Secondary univariate analysis of inpatient complications, operative, and postoperative characteristics were calculated to determine postoperative factors associated with prolonged hospitalization. RESULTS: Two-hundred and forty patients were identified with 115 patients' LOS ≥ 48H. Univariate analysis identified age/Charlson Comorbidity Index (CCI) score/gender/insurance type/number of contiguous fused levels/preoperative PROMs of Visual Analog Scale (VAS) back/VAS leg/Patient-Reported Outcomes Measurement Information System (PROMIS-PF)/Oswestry Disability Index (ODI)/degenerative spondylolisthesis diagnoses/foraminal stenosis/central stenosis for multivariable logistic regression. Multivariable logistic regression calculated significant positive predictors of LOS ≥ 48H to be age/3-level fusion/preoperative ODI scores. Negative predictors of LOS ≥ 48H were the diagnosis of foraminal stenosis/preoperative PROMIS-PF/male gender. The secondary analysis determined that patients with longer operative time/estimated blood loss/transfusion/postoperative day 0 and 1 pain and narcotic consumption/complications of altered mental status/postoperative anemia/fever/ileus/urinary retention were associated with prolonged hospitalization. CONCLUSION: Older patients undergoing LLIF with greater preoperative disability and 3-level fusion were more likely to require prolonged hospitalization. Male patients with higher preoperative physical function and who were diagnosed with foraminal stenosis were less likely to require prolonged hospitalization.

Postoperative clinical outcomes in patients undergoing MIS-TLIF versus LLIF for adjacent segment disease.

PURPOSE: Few studies examine the clinical outcomes in patients undergoing minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) versus lateral lumbar interbody fusion (LLIF) for adjacent segment disease (ASD). We aim to compare the postoperative clinical trajectory through patient-reported outcome measures (PROMs) and minimum clinically important difference (MCID) in patients undergoing MIS-TLIF versus LLIF for ASD. METHODS: Patients were stratified into two cohorts based on surgical technique for ASD: MIS-TLIF versus LLIF. PROMs of 12-Item Short Form Physical Component Score (SF-12 PCS), visual analog scale (VAS) back, VAS leg, and Oswestry Disability Index (ODI) were collected at preoperative and postoperative 6-week/12-week/6-month/1-year time points. MCID attainment was calculated through comparison to established thresholds. Cohorts were compared through nonparametric inferential statistics. RESULTS: Fifty-four patients were identified, with 22 patients undergoing MIS-TLIF after propensity score matching. Patients undergoing MIS-TLIF for ASD demonstrated significant postoperative improvement up to 1-year VAS back, up to 1-year VAS leg, and 6-month through 1-year ODI (p ≤ 0.035, all). Patients undergoing LLIF demonstrated significant postoperative improvement in 6-month SF-12 PCS, 6-month through 1-year VAS back, 12-week through 6-month VAS leg, and 6-month to 1-year ODI (p ≤ 0.035, all). No significant differences were calculated between surgical techniques for PROMs or MCID achievement rates. CONCLUSION: Patients undergoing either MIS-TLIF or LLIF for adjacent segment disease demonstrated significant postoperative improvement in pain and disability outcomes. Additionally, patients undergoing LLIF reported significant improvement in physical function. Both MIS-TLIF and LLIF are effective for the treatment of adjacent segment disease.

Ureter position and risk of ureteral injury during lateral lumbar interbody fusion.

BACKGROUND: Ureteral injury during lateral lumbar interbody fusion (LLIF) is uncommon. However, it is a serious complication that may require additional surgery should it occur. The objective of this study was to evaluate whether there was any change in the position of the left ureter between preoperative biphasic contrast-enhanced CT scanned in the supine position and intraoperative scanning in the right lateral decubitus position after stent placement, to assess the risk of ureteral injury in the actual surgical position. METHODS: The position of the left ureter scanned with the O-arm navigation system with the patient in the right lateral decubitus position and its position on preoperative biphasic contrast-enhanced CT images scanned with the patient in the supine position were investigated comparing their positions at the L2/3, L3/4, and L4/5 levels. RESULTS: The ureter was located along the interbody cage insertion trajectory in 25 of 44 disc levels (56.8%) in the supine position, but in only 4 (9.5%) in the lateral decubitus position. The proportion of patients in whom the left ureter was located lateral to the vertebral body (along the LLIF cage insertion trajectory) at each level was 80% in the supine position and 15.4% in the lateral decubitus position at the L2/3 level, 53.3% in the supine position and 6.7% in the lateral decubitus position at the L3/4 level, and 33.3% in the supine position and 6.7% in the lateral decubitus position at the L4/5 level. CONCLUSION: The proportion of patients in whom the left ureter was located on the lateral surface of the vertebral body when the patient was in the actual surgical position (lateral decubitus position) was 15.4% at the L2/3 level, 6.7% at the L3/4 level, and 6.7% at the L4/5 level, suggesting that caution is required during LLIF surgery.

Approach-related anatomical differences in patients with lumbo-sacral transitional vertebrae undergoing lumbar fusion surgery at level L4/5.

INTRODUCTION: Lumbo-sacral transitional vertebrae (LSTV) are accompanied by changes in soft tissue anatomy. The aim of our retrospective study was to evaluate the effects of LSTV as well as the number of free lumbar vertebrae on surgical approaches of ALIF, OLIF and LLIF at level L4/5. MATERIAL AND METHODS: We assessed the CTs of 819 patients. Of these, 53 had LSTV from which 11 had six (6LV) and 9 four free lumbar vertebrae (4LV). We matched them for sex and age to a control group. RESULTS: Patients with LSTV had a higher iliac crest and vena cava bifurcation, a greater distance between the common iliac veins and an anterior translation of the psoas muscle at level L4/5. In contrast, patients with 6LV had a lower iliac crest and aortic bifurcation, no differences in vena cava bifurcation and distance between the iliac veins compared to the control group. CONCLUSIONS: For patients with LSTV and five or four free lumbar vertebrae, the LLIF approach at L4/5 may be hindered due to a high riding iliac crest as well as anterior shift of the psoas muscle. Whereas less mobilization and retraction of the iliac veins may reduce the risk of vascular injury at this segment by ALIF and OLIF. For patients with 6LV, a lower relative height of the iliac crest facilitates lateral approach during LLIF. For ALIF and OLIF, a stronger vessel retraction due to the deeper-seated vascular bifurcation is necessary during ALIF and is therefore potentially at higher risk for vascular injury.

Complication rates following stand-alone lateral interbody fusion: a single institution series after 10 years of experience.

PURPOSE: This retrospective single institution study's goal was to analyze and report the complications from stand-alone lateral lumbar interbody fusions (LLIF). METHODS: This research was approved by the institutional review board (STUDY2021000113). We retrospectively reviewed the database of patients with adult degenerative spine deformity treated via LLIF at our institution between January 2016 and December 2020. RESULTS: Stand-alone LLIF was performed in 158 patients (145 XLIF, 13 OLIF; mean age 65 y.; 88 f., 70 m.). Mean surgical time was 85 min (± 24 min). Mean follow-up was 14 months (± 5 m). Surgical blood loss averaged 120 mL (± 187 mL) and the mean number of fused levels was 1.2 (± 0.4 levels). Overall complication rate was 19.6% (31 total; 23 approach-related, 8 secondary complications). CONCLUSION: Lateral interbody fusion appears to be a safe surgical intervention with relatively low complication- and revision rates.

Incidence of major and minor vascular injuries during lateral access lumbar interbody fusion procedures: a retrospective comparative study and systematic literature review.

During lateral lumbar fusion, the trajectory of implant insertion approaches the great vessels anteriorly and the segmental arteries posteriorly, which carries the risk of vascular complications. We aimed to analyze vascular injuries for potential differences between oblique lateral interbody fusion (OLIF) and lateral lumbar interbody fusion (LLIF) procedures at our institution. This was coupled with a systematic literature review of vascular complications associated with lateral lumbar fusions. A retrospective chart review was completed to identify consecutive patients who underwent lateral access fusions. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were used for the systematic review with the search terms "vascular injury" and "lateral lumbar surgery." Of 260 procedures performed at our institution, 211 (81.2%) patients underwent an LLIF and 49 (18.8%) underwent an OLIF. There were no major vascular complications in either group in this comparative study, but there were four (1.5%) minor vascular injuries (2 LLIF, 0.95%; 2 OLIF, 4.1%). Patients who experienced vascular injury experienced a greater amount of blood loss than those who did not (227.5 ± 147.28 vs. 59.32 ± 68.30 ml) (p = 0.11). In our systematic review of 63 articles, major vascular injury occurred in 0-15.4% and minor vascular injury occurred in 0-6% of lateral lumbar fusions. The systematic review and comparative study demonstrate an increased rate of vascular injury in OLIF when compared to LLIF. However, vascular injuries in either procedure are rare, and this study aids previous literature to support the safety of both approaches.

Single-position circumferential lumbar spinal fusion: an overview of terminology, concepts, rationale and the current evidence base.

PURPOSE: To provide definitions and a conceptual framework for single position surgery (SPS) applied to circumferential fusion of the lumbar spine. METHODS: Narrative literature review and experts' opinion. RESULTS: Two major limitations of lateral lumbar interbody fusion (LLIF) have been (a) a perceived need to reposition the patient to the prone position for posterior fixation, and (b) the lack of a robust solution for fusion at the L5/S1 level. Recently, two strategies for performing single-position circumferential lumbar spinal fusion have been described. The combination of anterior lumbar interbody fusion (ALIF) in the lateral decubitus position (LALIF), LLIF and percutaneous pedicle screw fixation (pPSF) in the lateral decubitus position is known as lateral single-position surgery (LSPS). Prone LLIF (PLLIF) involves transpsoas LLIF done in the prone position that is more familiar for surgeons to then implant pedicle screw fixation. This can be referred to as prone single-position surgery (PSPS). In this review, we describe the evolution of and rationale for single-position spinal surgery. Pertinent studies validating LSPS and PSPS are reviewed and future questions regarding the future of these techniques are posed. Lastly, we present an algorithm for single-position surgery that describes the utility of LALIF, LLIF and PLLIF in the treatment of patients requiring AP lumbar fusions. CONCLUSIONS: Single position surgery in circumferential fusion of the lumbar spine includes posterior fixation in association with any of the following: lateral position LLIF, prone position LLIF, lateral position ALIF, and their combination (lateral position LLIF+ALIF). Preliminary studies have validated these methods.

Development of a decision-making pathway for utilizing standalone lateral lumbar interbody fusion.

PURPOSE: To develop a decision-making pathway for primary SA-LLIF. Furthermore, we analyzed the agreement of this pathway and compared outcomes of patients undergoing either SA-LLIF or 360-LLIF. METHOD: A decision-making pathway for SA-LLIF was created based on the results of interviews/surveys of senior spine surgeons with over 10 years of experience. Internal validity was retrospectively evaluated using consecutive patients undergoing either SA-LLIF or 360-LLIF between 01/2018 and 07/2020 with 3D-printed Titanium cages. An outcome assessment looking primarily at revision surgery and secondary at cage subsidence, changes in disk and foraminal height, global and segmental lumbar lordosis, duration of surgery, estimated blood loss, and length of stay was carried out. RESULTS: 78 patients with 124 treated levels (37 SA-LLIF, 41 360-LLIF) were retrospectively analyzed. The pathway showed a direct agreement (SA-LLIF) of 100.0% and an indirect agreement (360-LLIF) of 95.1%. Clinical follow-up averaged 13.5 ± 6.5 months including 4 revision surgeries in the 360-LLIF group and none in the SA-LLIF group (p = 0.117). Radiographic follow-up averaged 9.5 ± 4.3 months, with no statistically significant difference in cage subsidence rate between the groups (p = 0.440). Compared to preoperative images, patients in both groups showed statistically significant changes in disk height (p < 0.001), foraminal height (p < 0.001), as well as restoration of segmental lordosis (p < 0.001 and p = 0.018). The SA-LLIF group showed shorter duration of surgery, less estimated blood loss and shorter LOS (p < 0.001). CONCLUSION: The proposed decision-making pathway provides a guide to adequately select patients for SA-LLIF. Further studies are needed to assess the external applicability and validity. LEVEL OF EVIDENCE III: Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Saphenous somatosensory-evoked potentials monitoring of femoral nerve health during prone transpsoas lateral lumbar interbody fusion.

PURPOSE: To assess whether saphenous somatosensory-evoked potentials (saphSSEP) monitoring may provide predictive information of femoral nerve health during prone lateral interbody fusion (LIF) procedures. METHODS: Intraoperative details were captured prospectively in consecutive prone LIF surgeries at a single institution. Triggered electromyography was used during the approach; saphSSEP was monitored throughout using a novel system that enables acquisition of difficult signals and real-time actionable feedback facilitating intraoperative intervention. Postoperative neural function was correlated with intraoperative findings. RESULTS: Fifty-nine patients (58% female, mean age 64, mean BMI 32) underwent LIF at 95 total levels, inclusive of L4-5 in 76%, fixated via percutaneous pedicle screws (81%) or lateral plate, with direct decompression in 39%. Total operative time averaged 149 min. Psoas retraction time averaged 16 min/level. Baseline SSEPs were unreliable in 3 due to comorbidities in 2 and anesthesia in 1; one of those resulted in transient quadriceps weakness, fully recovered at 6 weeks. In 25/56, no saphSSEP changes occurred, and none had postoperative femoral nerve deficits. In 24/31 with saphSSEP changes, responses recovered intraoperatively following intervention, with normal postoperative function in all but one with delayed quadriceps weakness, improved at 4 months and recovered at 9 months, and a second with transient isolated anterior thigh numbness. In the remaining 7/31, saphSSEP changes persisted to close, and resulted in 2 transient isolated anterior thigh numbness and 2 combined sensory and motor femoral nerve deficits, both resolved at between 4 and 8 months. CONCLUSIONS: SaphSSEP was reliably monitored in most cases and provided actionable feedback that was highly predictive of neurological events during LIF. LEVEL OF EVIDENCE: Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Setting for single position surgery: survey from expert spinal surgeons.

PURPOSE: To describe a comprehensive setting of the different alternatives for performing a single position fusion surgery based on the opinion of leading surgeons in the field. METHODS: Between April and May of 2021, a specifically designed two round survey was distributed by mail to a group of leaders in the field of Single Position Surgery (SPS). The questionnaire included a variety of domains which were focused on highlighting tips and recommendations regarding improving the efficiency of the performance of SPS. This includes operation room setting, positioning, use of technology, approach, retractors specific details, intraoperative neuromonitoring and tips for inserting percutaneous pedicle screws in the lateral position. It asked questions focused on Lateral Single Position Surgery (LSPS), Lateral ALIF (LA) and Prone Lateral Surgery (PLS). Strong agreement was defined as an agreement of more than 80% of surgeons for each specific question. The number of surgeries performed in SPS by each surgeon was used as an indirect element to aid in exhibiting the expertise of the surgeons being surveyed. RESULTS: Twenty-four surgeons completed both rounds of the questionnaire. Moderate or strong agreement was found for more than 50% of the items. A definition for Single Position Surgery and a step-by-step recommendation workflow was built to create a better understanding of surgeons who are starting the learning curve in this technique. CONCLUSION: A recommendation of the setting for performing single position fusion surgery procedure (LSPS, LA and PLS) was developed based on a survey of leaders in the field.

Spinal exposure for anterior lumbar interbody fusion (ALIF) in the lateral decubitus position: anatomical and technical considerations.

PURPOSE: Single position surgery has demonstrated to reduce hospital length of stay, operative times, blood loss, postoperative pain, ileus, and complications. ALIF and LLIF surgeries offer advantages of placing large interbody devices under direct compression and can be performed by a minimally invasive approach in the lateral position. Furthermore, simultaneous access to the anterior and posterior column is possible in the lateral position without the need for patient repositioning. The purpose of this study is to outline the anatomical and technical considerations for performing anterior lumbar interbody fusion (ALIF) in the lateral decubitus position. METHODS: Surgical technique and technical considerations for reconstruction of the anterior column in the lateral position by ALIF at the L4-5 and L5-S1 levels. RESULTS: Topics outlined in this review include: Operating room layout and patient positioning; surgical anatomy and approach; vessel mobilization and retractor placement for L4-5 and L5-S1 lateral ALIF exposure, in addition to comparative technique of disc space preparation, trialing and implant placement compared to the supine ALIF procedure. CONCLUSIONS: Anterior exposure performed in the lateral decubitus position allows safe-, minimally invasive access and implant placement in ALIF. The approach requires less peritoneal and vessel retraction than in a supine position, in addition to allowing simultaneous access to the anterior and posterior columns when performing 360° Anterior-Posterior fusion.

Lateral decubitus single position anterior-posterior (AP) fusion shows equivalent results to minimally invasive transforaminal lumbar interbody fusion at one-year follow-up.

PURPOSE: This study compares perioperative and 1-year outcomes of lateral decubitus single position circumferential fusion (L-SPS) versus minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) for degenerative pathologies. METHODS: Multicenter retrospective chart review of patients undergoing AP fusion with L-SPS or MIS TLIF. Demographics and clinical and radiographic outcomes were compared using independent samples t tests and chi-squared analyses with significance set at p < 0.05. RESULTS: A total of 445 patients were included: 353 L-SPS, 92 MIS TLIF. The L-SPS cohort was significantly older with fewer diabetics and more levels fused. The L-SPS cohort had significantly shorter operative time, blood loss, radiation dosage, and length of stay compared to MIS TLIF. 1-year follow-up showed that the L-SPS cohort had higher rates of fusion (97.87% vs. 81.11%; p = 0.006) and lower rates of subsidence (6.38% vs. 38.46%; p < 0.001) compared with MIS TLIF. There were significantly fewer returns to the OR within 1 year for early mechanical failures with L-SPS (0.0% vs. 5.4%; p < 0.001). 1-year radiographic outcomes revealed that the L-SPS cohort had a greater LL (56.6 ± 12.5 vs. 51.1 ± 15.9; p = 0.004), smaller PI-LL mismatch (0.2 ± 13.0 vs. 5.5 ± 10.5; p = 0.004). There were no significant differences in amount of change in VAS scores between cohorts. Similar results were seen after propensity-matched analysis and sub-analysis of cases including L5-S1. CONCLUSIONS: L-SPS improves perioperative outcomes and does not compromise clinical or radiographic results at 1-year follow-up compared with MIS TLIF. There may be decreased rates of early mechanical failure with L-SPS.

Usefulness of Lateral Lumbar Interbody Fusion Combined with Indirect Decompression for Degenerative Lumbar Spondylolisthesis: A Systematic Review.

Background and Objective: The aim of this review was to analyze the existing literature and investigate the outcomes or complications of lateral lumbar interbody fusion (LLIF) combined with indirect decompression for degenerative lumbar spondylolisthesis (DS). Materials and Methods: A database search algorithm was used to query MEDLINE, COCHRANE, and EMBASE to identify the literature reporting LLIF with indirect decompression for DS between January 2010 and December 2021. Improvements in outcome measures and complication rates were pooled and tested for significance. Results: A total of 412 publications were assessed, and 12 studies satisfied the inclusion criteria after full review. The pooled data available in the included studies showed that 438 patients with lumbar spondylolisthesis (mean age 65.2 years; mean body mass index (BMI) 38.1 kg/m2) underwent LLIF. A total of 546 disc spaces were operated on. The most frequently treated levels were L4-L5 and L3-L4. Clinically, the average improvement was 32.5% in ODI, 46.3 mm in low back pain, and 48.3 mm in leg pain estimated from the studies included. SF-36 PCS improved by 51.5% and MCS improved by 19.5%. For radiological outcomes, a reduction in slippage was seen in 6.3%. Disc height increased by 55%, foraminal height increased by 21.1%, the foraminal area on the approach side increased by 21.9%, and on the opposite side it increased by 26.1%. The cross-sectional spinal canal area increased by 20.6% after surgery. Post-operative complications occurred in 5-40% of patients with thigh symptoms, such as anterior thigh numbness, dysesthesia, discomfort, pain, and sensory deficits. Conclusions: Indirect decompression by LLIF for DS is an effective method for improving pain and dysfunction with less surgical invasion. In addition, it has the effect of significantly improving disc height, foraminal height and area, and segmental lordosis on radiological outcomes compared to the posterior approach.