Lateral Interbody Fusion Research Articles

The anatomical positioning change of retroperitoneal organs in prone and lateral position: an assessment for single-prone position lateral lumbar surgery.

There are reports that performing lateral lumbar interbody fusion (LLIF) in a prone, single position (single-prone LLIF) can be done safely in the prone position because the retroperitoneal organs reflect anteriorly with gravity. However, only a few study has investigated the safety of single-prone LLIF and retroperitoneal organ positioning in the prone position. We aimed to investigate the positioning of retroperitoneal organs in the prone position and evaluate the safety of single-prone LLIF surgery. A total of 94 patients were retrospectively reviewed. The anatomical positioning of the retroperitoneal organs was evaluated by CT in the preoperative supine and intraoperative prone position. The distances from the centre line of the intervertebral body to the organs including aorta, inferior vena cava, ascending and descending colons, and bilateral kidneys were measured for the lumbar spine. An "at risk" zone was defined as distance less than 10mm anterior from the centre line of the intervertebral body. Compared to supine preoperative CTs, bilateral kidneys at the L2/3 level as well as the bilateral colons at the L3/4 level had statistically significant ventral shift with prone positioning. The proportion of retroperitoneal organs within the at-risk zone ranged from 29.6 to 88.6% in the prone position. The retroperitoneal organs shifted ventrally with prone positioning. However, the amount of shift was not large enough to avoid risk for organ injuries and substantial proportion of patients had organs within the cage insertion corridor. Careful preoperative planning is warranted when considering single-prone LLIF.

Current Trends in Recombinant Human Bone Morphogenetic Protein 2 (rhBMP2) Usage for Spinal Fusion Surgery.

(1) Background: Since first approved by the FDA, on-label and off-label usage of recombinant human bone morphogenetic protein 2 (rhBMP2) for spinal fusion surgeries has become widespread. While many studies have investigated the safety and efficacy of its use, as well as its economic impact, few have looked at the current trends in its on- and off-label use. The goal of this study is to evaluate the current trends of on- and off-label rhBMP2 use for spinal fusion surgery. (2) Methods: A deidentified survey was created and electronically distributed to members of two international spine societies. Surgeons were asked to report their demographic information, surgical experience, and current usage of rhBMP2. They were then presented with five spinal fusion procedures and asked to report if they use rhBMP2 for these indications in their current practice. Responses were stratified between rhBMP2 users vs. non-users and on-label vs. off-label use. Data were analyzed using chi-square with Fisher's exact test for categorical data. (3) Results: A total of 146 respondents completed the survey with a response rate of 20.5%. There was no difference in overall rhBMP2 usage based on specialty, experience, or number of cases per year. Fellowship-trained surgeons and those who practice in the United States were more likely to use rhBMP2. Surgeons who were trained in the Southeast and Midwest regions reported the highest usage rates. rhBMP2 use was more common among fellowship-trained and US surgeons for ALIFs; non-US surgeons for multilevel anterior cervical discectomy and fusions; and fellowship-trained and orthopedic spine surgeons for lateral lumbar interbody fusions. Non-US surgeons were more likely to use rhBMP2 for off-label indications compared to surgeons from the US. (4) Conclusions: While various demographics of surgeons report different rates of rhBMP2 use, off-label use remains relatively commonplace amongst practicing spine surgeons.

Graft subsidence and reoperation after lateral lumbar interbody fusion: a propensity score-matched and cost analysis of polyetheretherketone versus 3D-printed porous titanium interbodies.

Lumbar interbody cage subsidence has a multifactorial etiology. Cage material, although well studied after transforaminal lumbar interbody fusion, has not been investigated as a contributing factor to subsidence after lateral lumbar interbody fusion (LLIF). In this study the authors compared rates of subsidence and reoperation after LLIF between polyetheretherketone (PEEK) and 3D-printed porous titanium (pTi) in an institutional propensity score-matched and cost analysis. This is a retrospective observational cohort analysis of adult patients who underwent LLIF with pTi versus PEEK between 2016 and 2020. Demographic, clinical, and radiographic characteristics were collected. Propensity scores were calculated and 1:1 matching without replacement of surgically treated levels was performed. The primary outcome of interest was subsidence. The Marchi subsidence grade was determined at the time of last follow-up. Chi-square or Fisher's exact tests were used to compare subsidence and reoperation rates between lumbar levels treated with PEEK versus pTi. Modeling and cost analysis were performed using TreeAge Pro Healthcare. The authors identified a total of 192 patients; 137 underwent LLIF with PEEK (212 levels) and 55 had LLIF with pTi (97 levels). After propensity score matching, a total of 97 lumbar levels remained in each treatment group. After matching, there were no statistically significant differences between groups in baseline characteristics. Levels treated with pTi were significantly less likely to exhibit subsidence (any grade) compared to those treated with PEEK (8% vs 27%, p = 0.001). Five (5.2%) levels treated with PEEK required reoperation for subsidence, but only 1 (1.0%) level treated with pTi required reoperation for subsidence (p = 0.12). Given subsidence and revision rates experienced in the cohorts in this study, the pTi interbody device is economically superior to PEEK in a single-level LLIF as long as its cost is at least $1185.94 lower than that of PEEK. The pTi interbody device was associated with less subsidence, but statistically similar revision rates after LLIF. pTi is potentially a superior economic choice at this study's reported revision rate.

Clinical value and effectiveness profiles of oblique lateral interbody fusion and posterior lumbar interbody fusion in the treatment of lumbar brucellosis spondylitis.

The aim of this study was to assess the clinical efficacy of oblique lateral interbody fusion (OLIF) and posterior lumbar interbody fusion (PLIF) for lumbar brucellosis spondylitis. Between April 2018 and December 2021, 80 cases of lumbar brucellosis spondylitis admitted to our institution were evaluated for eligibility and randomly assigned to either PLIF (group A, lesion removal by posterior approach + interbody fusion + percutaneous pedicle screw internal fixation) or OLIF (group B, lesion removal by anterior approach + interbody fusion + percutaneous pedicle screw internal fixation). The outcome measures included operative time, intraoperative bleeding, hospital stay, preoperative and postoperative visual analogue scale (VAS) ratings, American Spinal Injury Association (ASIA) classification, Cobb angle, and interbody fusion time. PLIF resulted in shorter operative time and hospital stay and less intraoperative bleeding vs. OLIF (p<0.05). All eligible patients showed significantly lower VAS scores, and smaller ESR values and Cobb angles after treatment (p<0.05), but no significant intergroup differences were observed (p>0.05). The two groups showed similar preoperative ASIA (American Spinal Injury Association) classification and interbody fusion time (p>0.05). PLIF was associated with better ASIA classification at three months postoperatively vs. OLIF (p<0.05). Both surgical techniques are efficient at removing the lesion, relieving pain, maintaining spinal stability, promoting implant fusion, and facilitating prognostic inflammation control. PLIF features a shorter surgical duration and hospital stay, less intraoperative bleeding, and greater neurological improvement vs. OLIF. Nevertheless, OLIF outperforms PLIF in the excision of peri-vertebral abscesses. PLIF is indicated for posterior spinal column lesions, particularly those with spinal nerve compression in the spinal canal, whereas OLIF is indicated for structural bone deterioration in the anterior column, particularly for those with perivascular abscesses.

Preoperative Back Pain Severity Influences Postoperative Clinical Outcomes and Trajectory in Patients Undergoing Lateral Lumbar Interbody Fusion

Background The Visual Analog Scale (VAS) is a frequently used and validated instrument for assessing a patient’s self-perceived lower back and leg pain and is often employed to assess the efficacy of lumbar surgical intervention. Our study seeks to assess how preoperative severity of presenting lumbar back pain may influence postoperative clinical trajectory and patient-reported outcome measures (PROMs) following lateral lumbar interbody fusion (LLIF) Objective To compare perioperative and postoperative mean patient-reported outcome measures and minimum clinical important difference (MCID) achievement following LLIF in patients stratified by preoperative back pain. Methods A prospectively maintained surgical database was retrospectively reviewed for lumbar operations between June 2005 and December 2021. Inclusion criteria was set as primary, elective, single or multi-level LLIF procedures for degenerative lumbar spinal pathology. Patients undergoing a revision procedure, or surgery indicated for infectious, malignant, or traumatic etiologies were excluded. Additionally, patients who did not fill out a preoperative VAS back survey were excluded as well. Patient demographics, perioperative characteristics, and PROMs were collected. PROMs were administered at preoperative and 6-week, 12-week, 6-month, 1-year, and 2-year postoperative time-points and included Patient-Reported Outcomes Measurement Information System- Physical Function (PROMIS-PF), Visual Analogue Scale (VAS) for back and leg pain, Oswestry Disability Index (ODI), and 12-Item Short Form Physical Composite Score (SF-12 PCS). Postoperative complications were collected for each group as well. Patients were grouped into two cohorts, depending on whether a patient had a preoperative VAS back score of &lt; (mild to moderate back pain cohort or VAS back score ≥ 7 (Severe back pain cohort). Demographic and perioperative characteristics were compared among groups using chi-square and Student’s t-test for categorical and continuous variables, respectively. Mean PROM scores were compared between cohorts at each time point utilizing a unpaired Student’s t-test. Postoperative improvement from preoperative baseline within each cohort was assessed with paired samples t-test. Achievement of Minimum Clinical Important Difference (MCID) was determined by comparing ΔPROM scores to previously established threshold values. MCID achievement rates were compared between groups with chi-squared analysis. Results Patient cohort consisted of 199 patients – 84 patients in VAS back preoperative &lt;7 and 115 patients in the VAS back Preoperative ≥ 7 cohort (Table 1). Significant demographic differences between cohorts were noted for hypertensive status with VAS back Preoperative&lt; 7 cohort having significantly higher rates of hypertension (p&lt;0.029) (Table 1). The majority of patient cohort were male (51.8%), Caucasian (80.8%), non-smokers (81.6%), non-diabetic (85.9%) and utilizing private insurance(62.8%). Majority of patients in both cohorts had presenting spinal pathology of Degenerative Spondylolisthesis (50.8%) with concomitant central stenosis(86.9%) (Table 2). A significantly greater proportion of patients in VAS back preoperative &lt; 7 cohort reported central and foraminal stenosis. No significant differences were noted between cohorts for operative duration, estimated blood loss, or postoperative day of discharge. Patients in the severe back pain cohort demonstrated significantly greater mean postoperative length of stay (53.9 hrs vs 40.6 hrs), greater postoperative VAS pain scores on POD0 and 1, and greater postoperative narcotic consumption on POD1 (p&lt;0.049, all) (Table 2). Rate of postoperative complications did not differ between cohorts. Preoperative mean PROM scores were significantly different for all PROMs collected (Table 4). Cohorts demonstrated significant mean postoperative differences for the following PROMs at the following postoperative time points: VAS back at 6-weeks, 12-weeks, 6-months, and 2-years, VAS leg at 6-months, ODI at 6-weeks, 12-weeks. 6-months, and 2-years, SF-12 PCS at 6-months, and PROMIS-PF at 12-weeks, 6-months, and 1-year(p&lt;0.049, all) (Table 4). Preop VAS back &lt;7 patient cohort demonstrated improvement from preoperative baseline to the 2-year time point for all PROMs collected at all individual postoperative timepoints with the exception of VAS leg at 1-year, ODI at 6-weeks, SF-12 PCS at 6-weeks, and PROMIS-PF at 6-weeks. (Table 4). Preop VAS back ≥ 7 patient cohort demonstrated improvement from preoperative baseline to 2-year time point for all PROMs collected at all individual postoperative timepoints (Table 4). Patients in the VAS back ≥ 7 patient cohort demonstrated greater proportion achieving MCID for VAS back at 6-weeks, 12-weeks, 1-year, and overall as well as for VAS leg at 6-weeks (p &lt;0.043, all) (Table 5). Conclusion Patients in both preoperative back pain severity cohorts demonstrated significant long term clinical improvement from their respective preoperative baselines at 2-years postoperatively for back pain, leg pain, physical function, and general disability. Patients with severe preoperative back pain (VAS &gt;7), however, demonstrated significantly inferior short (6weeks-6months) and long term (2-year) mean outcome scores for back pain and general disability. 2-year mean outcome scores for leg pain and physical function were similar between cohorts. Results from our study may be used by surgeons to understand differing postoperative trajectories of patients undergoing LLIF stratified by back pain severity.

CT-based analysis of oblique lateral interbody fusion from L1 to L5: location of incision, feasibility of safe corridor approach, and influencing factors.

The primary aim was to measure the safe corridor (SC), surgical incision anterior margin (AM), and posterior margin (PM) for OLIF bilaterally from L1 to L5. The secondary aim was to determine the feasibility of approach via the SC. The tertiary aim was to analyze the influence of demographic and anthropometric factors on OLIF parameters. We performed a radiographic analysis of 100 subjects who received an abdominal CT. Measurements of the AM, PM, and SC were obtained as well as patient age, sex, height, weight, and BMI. The intraclass correlation coefficient was used to evaluate interrater reliability. To assess associations among variables, Pearson's correlation tests and multivariate linear regression models were constructed. Sex differences were analyzed using Student's t tests. At L1-2, L2-3, L3-4, and L4-5, the PM was 6.6, 8.2, 9.4, and 10.2cm on the left side and 7.2, 7.7, 8.8, and 9.5cm on the right side in relation to the disk space center. The SC was less than 1 cm 1%, 3%,3%, and 18% of the time on the left side, and 15%, 12%,29%, and 60% on the right side. None of the anthropometric factors demonstrated a strong correlation with incision location. SC was larger on the left side. Interrater ICC was .934. This study is the first to provide guidelines on the appropriate location of the incision line during OLIF based on SC from L1 to L5. SC measurements do not vary by sex. OLIF is more feasible via a left-sided approach.

Single-Position Prone Lateral Lumbar Interbody Fusion Increases Operative Efficiency and Maintains Safety in Revision Lumbar Spinal Fusion.

Multi-centre retrospective cohort study. To evaluate the feasibility and safety of the single-position prone lateral lumbar interbody fusion (LLIF) technique for revision lumbar fusion surgery. Prone LLIF (P-LLIF) is a novel technique allowing for placement of a lateral interbody in the prone position and allowing posterior decompression and revision of posterior instrumentation without patient repositioning. This study examines perioperative outcomes and complications of single position P-LLIF against traditional Lateral LLIF (L-LLIF) technique with patient repositioning. A multi-centre retrospective cohort study involving patients undergoing 1 to 4 level LLIF surgery was performed at 4 institutions in the US and Australia. Patients were included if their surgery was performed via either: P-LLIF with revision posterior fusion; or L-LLIF with repositioning to prone. Demographics, perioperative outcomes, complications, and radiological outcomes were compared using independent samples t-tests and chi-squared analyses as appropriate with significance set at P <0.05. 101 patients undergoing revision LLIF surgery were included, of which 43 had P-LLIF and 58 had L-LLIF. Age, BMI and CCI were similar between groups. The number of posterior levels fused (2.21 P-LLIF vs. 2.66 L-LLIF, P =0.469) and number of LLIF levels (1.35 vs. 1.39, P =0.668) was similar between groups.Operative time was significantly less in the P-LLIF group (151 vs. 206 min, P =0.004). EBL was similar between groups (150mL P-LLIF vs. 182mL L-LLIF, P =0.31) and there was a trend toward reduced length of stay in the P-LLIF group (2.7 vs. 3.3d, P =0.09). No significant difference was demonstrated in complications between groups. Radiographic analysis demonstrated no significant differences in preoperative or postoperative sagittal alignment measurements. P-LLIF significantly improves operative efficiency when compared to L-LLIF for revision lumbar fusion. No increase in complications was demonstrated by P-LLIF or trade-offs in sagittal alignment restoration. Level 4.

Anatomical Analysis of the Gonadal Veins and Spine in Lateral Lumbar Interbody Fusion.

The current study aimed to investigate the anatomical position of the gonadal veins (GVs) from the viewpoint of spine surgery and the risk factors associated with lateral lumbar interbody fusion (LLIF). This retrospective study included 99 consecutive patients. The GV locations were divided into the ventral (V), dorsal medial (DM), and dorsal lateral (DL) sides based on lumbar disk levels on axial contrast-enhanced computed tomography images. The DM region surrounded by the vertebral body and psoas muscle had the highest risk of GV injury. The GV at each intervertebral disk level was examined in terms of laterality and sex. The patients were divided into group M (which included those with GV in the DM region at any vertebral level) and group O (which included those without GV in the DM region at any vertebral level). Then, the two groups were compared. In the case of lower lumbar levels and in women, the GVs were commonly observed in the DM region. Group M had a higher incidence of degenerative scoliosis than group O and a significantly larger Cobb angle. We should pay close attention to the GV location on the preoperative image when using LLIF, particularly in female patients with degenerative scoliosis.

Comparison of PLIF/TLIF and LLIF for two-level degenerative lumbar spondylolisthesis

IntroductionIn recent years, lateral lumbar interbody fusion (LLIF), performed as extreme lateral interbody fusion (XLIF) and oblique lateral interbody fusion (OLIF), has also become widely used for anterior-posterior corrective fusion. However, there are few detailed reports comparing techniques in the treatment of two-level degenerative spondylolisthesis. We compared the surgical invasiveness and postoperative outcomes between posterior interbody fusion with posterior lumbar interbody fusion (PLIF) or transforaminal lumbar interbody fusion (TLIF) and LLIF for two-level lumbar degenerative spondylolisthesis. MethodsFifteen patients underwent PLIF or TLIF at 2 vertebral intervals (posterior group) and 8 patients received XLIF or OLIF (LLIF group). The following parameters were examined: operative time, blood loss, preoperative %slip, preoperative sagittal parameters, postoperative %slip, postoperative 1-year %slip, postoperative 1-year sagittal parameters, bone fusion rate at 1 year postoperatively, pre- and postoperative visual analog scale scores, pre- and postoperative Japanese Orthopaedic Association (JOA) scores, and complications. ResultsIn the LLIF group, blood loss was significantly lower and operative time was shorter than in the posterior group. There were no significant differences for 1-year postoperative %slip, sagittal vertical axis, or lumbar lordosis, although the frequency of cases with a 1-year postoperative pelvic incidence (PI)-LL ≤ 10 degrees was significantly higher in the LLIF group. In both groups, JOA scores were improved significantly at 1 year postoperatively (both p < 0.01), with no remarkable difference in improvement rate between the groups (p = 0.09). ConclusionsLLIF was less invasive, comparably effective, and more preserving of global spinal balance in correcting two-level degenerative spondylolisthesis than conventional posterior interbody fusion.

Perioperative Predictors in Patients Undergoing Lateral Lumbar Interbody Fusion for Minimum Clinically Important Difference Achievement

To identify perioperative predictors of minimum clinically important difference (MCID) for patients undergoing lateral lumbar interbody fusion (LLIF) for the patient-reported outcome measures (PROMs) of Patient-Reported Outcomes Measurement Information System Physical Function (PROMIS-PF), Visual Analog Scale (VAS) Back, VAS Leg, Oswestry Disability Index (ODI), and Patient Health Questionnaire-9 (PHQ-9). Patients undergoing LLIF were identified through retrospective review of a single-surgeon database. Overall MCID achievement was determined as the number of unique patients achieving ΔPROM thresholds of PROMIS-PF=4.5, VAS Back=2.1, VAS Leg=2.8, ODI=14.9, and PHQ-9=3.0 over a 2-year postoperative time period. Univariate and multivariable logistic regression were utilized to determine perioperative predictors for MCID achievement. Two-hundred and ninety patients were identified. For PROMIS-PF MCID achievement, increased preoperative PROMIS-PF and POD 1 VAS pain were significant negative predictors. For VAS Back, primary fusion with revision decompression was a negative predictor, while increased preoperative VAS Back was a positive predictor of MCID achievement. For VAS Leg, increased preoperative VAS Leg was a positive predictor. For ODI, increased POD 0 VAS pain was a negative predictor, while increased preoperative ODI was a positive predictor. For PHQ-9, increased preoperative PHQ-9 was a positive predictor. In patients undergoing LLIF, perioperative predictors for MCID achievement were highly dependent on PROM. Preoperative PROM was the most consistent perioperative predictor for achieving MCID. Elevated acute postoperative pain and primary fusion after failed index decompression were significant predictors of failing to achieve MCID. Surgeons may use these findings in prognostication and management of postoperative expectations.

BIOMECHANICAL STUDY OF LATERAL LUMBAR INTERBODY FUSION VERSUS A POSTERIOR FIXATION WITH PEDICLE SCREWS AND RODS USING A HUMAN CADAVERIC MODEL

Lateral lumbar interbody fusion (LLIF) has biomechanical advantages due to the preservation of ligamentous structures (ALL/PLL), and optimal cage height afforded by the strength of the apophyseal ring. We compare the biomechanical motion stability of multiple levels LLIF (4 segments) utilising PEEK interbody 26mm cages to stand-alone cage placement and with supplemental posterior fixation with pedicle screw and rods.Six lumbar human cadaver specimens were stripped of the paraspinal musculature while preserving the discs, facet joints, and osteoligamentous structures and potted. Specimens were tested under 5 conditions: intact, posterior bilateral fixation (L1-L5) only, LLIF-only, LLIF with unilateral fixation and LLIF with bilateral fixation. Non-destructive testing was performed on a universal testing machine (MTS Systems Corp) to produce flexion-extension, lateral-bending, and axial rotation using customized jigs and a pulley system to define a non-constraining load follower. Three-dimensional spine motion was recorded using a motion device (Optotrak).Results are reported for the L3-L4 motion segment within the construct to allow comparison with previously published works of shorter constructs (1-2 segments). In all conditions, there was an observed decrease in ROM from intact in flexion/extension (31%-89% decrease), lateral bending (19%-78%), and axial rotation (37%-60%). At flexion/extension, the decreases were statistically significant (p&lt;0.007) except for stand-alone LLIF. LLIF+unilateral had similar decreases in all planes as the LLIF+bilateral condition. The observed ROM within the 4-level construct was similar to previously reported results in 1-2 levels for stand-alone LLIF and LLIF+bilateral.Surgeons may be concerned about the biomechanical stability of an approach utilizing stand-alone multilevel LLIF. Our results show that 4-level multilevel LLIF utilizing 26 mm cages demonstrated ROM comparable to short-segment LLIF. Stand-alone LLIF showed a decrease in ROM from the intact condition. The addition of posterior supplemental fixation resulted in an additional decrease in ROM. The results suggest that unilateral posterior fixation may be sufficient.

Effect of Unintended Tissue Injury on the Development of Thigh Symptoms After Lateral Lumbar Interbody Fusion in Patients With Adult Spinal Deformity: A Retrospective Case Series.

A retrospective case series. This study aimed to investigate the effects of lateral lumbar interbody fusion (LLIF)-induced unintended tissue damage, including cage subsidence, cage malposition, and hematoma in the psoas major muscle, on the development of thigh symptoms. Thigh symptoms are the most frequent complications after LLIF and are assumed to be caused by lumbar plexus compression and/or direct injury to the psoas major muscle. However, the causes and risk factors of thigh symptoms are yet to be fully understood. Adult patients with spinal deformity who underwent two-stage surgery using LLIF and a posterior open fusion for the first and second stages, respectively, were included. Computed tomography and magnetic resonance imaging were routinely performed after LLIF before posterior surgery to investigate cage subsidence, cage malposition, and hematoma in the psoas muscle. We evaluated the development of thigh symptoms after LLIF and examined the effects of tissue injury on the occurrence of thigh symptoms. The differences in demographics and surgical and tissue damage parameters were compared between the groups with and without thigh symptoms using unpaired t tests and chi-squared tests. Factors associated with the development of thigh symptoms and muscle weakness were also assessed using logistic regression analysis. Overall, 130 patients [17 men and 113 women; mean age, 68.7 (range, 47-84)] were included. Thigh symptoms were observed in 52 (40.0%) patients, including muscle weakness and contralateral side symptoms in 20 (15.4%) and 9 (17.3%) patients, respectively. The factors significantly associated with thigh symptoms identified after multiple logistic regression analysis included hematoma (odds ratio: 2.27, 95% CI, 1.03-5.01) and approach from the right side (odds ratio: 2.64, 95% CI, 1.21-5.75). The presence of cage malposition was the only significant factor associated with muscle weakness (odds ratio: 4.12, 95% CI, 1.37-12.4). We found unintended tissue injury during LLIF was associated with thigh symptoms. We found that hematoma in the psoas major muscle and cage malposition were the factors associated with thigh symptoms and muscle weakness, respectively.

Elimination of Lumbar Plexus Injury by Changing the Entry Point and Traction Direction of the Psoas Major Muscle in Transpsoas Lateral Lumbar Spine Surgery.

Background and Objectives: The lateral approach is commonly used for anterior column reconstruction, indirect decompression, and fusion in patients with lumbar degenerative diseases and spinal deformities. However, intraoperative lumbar plexus injury may occur. This is a retrospective comparative study to investigate and compare neurological complications between the conventional lateral approach and a modified lateral approach at L4/5. Materials and Methods: Patients with a lumbar degenerative disease requiring single-level intervertebral fusion at L4/5 were included and categorized into group X and group A. Patients in group X underwent conventional extreme lateral interbody fusion, while those in group A underwent a modified surgical procedure that included splitting of the anterior third of the psoas muscle, which was dilated by the retractor on the anterior third of the intervertebral disc. The incidence of lumbar plexus injury, defined as a decrease of ≥1 grade on manual muscle testing of hip flexors and knee extensors and sensory impairment of the thigh for ≥3 weeks, on the approach side, was investigated. Results: Each group comprised 50 patients. No significant between-group differences in age, sex, body mass index, and approach side were observed. There was a significant between-group difference in intraoperative neuromonitoring stimulation value (13.1 ± 5.4 mA in group X vs. 18.5 ± 2.3 mA in group A, p < 0.001). The incidence of neurological complications was significantly higher in group X than in group A (10.0% vs. 0.0%, respectively, p < 0.05). Conclusions: In our modified procedure, the anterior third of the psoas muscle was entered and split, and the intervertebral disc could be reached without damaging the lumbar plexus. When performing lumbar surgery using the lateral approach, lumbar plexus injury can be avoided by following surgical indication criteria based on the location of the lumbar plexus with respect to the psoas muscle and changing the transpsoas approach to the intervertebral disc.

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

PurposeThe objective of this study was to discuss our experience performing LLIF in the prone position and report our complications.MethodsA 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.ResultsA 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.ConclusionOur 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.

Comparison of staged LLIF combined with posterior instrumented fusion with posterior instrumented fusion alone for the treatment of adult degenerative lumbar scoliosis with sagittal imbalance

BackgroundTo retrospectively compare the clinical and radiological outcomes of staged lateral lumbar interbody fusion (LLIF) combined with posterior instrumented fusion(PIF)with PIF alone for the treatment of adult degenerative lumbar scoliosis (ADLS) with sagittal imbalance.MethodsADLS patients with sagittal imbalance underwent corrective surgery were included and divided into staged group (underwent multilevel LLIF in the first-stage and PIF in the second-stage) and control group (PIF alone). The clinical and radiological outcomes were evaluated and compared between the two groups.ResultsForty-five patients with an average age of 69.7±6.3 years were enrolled, including 25 in the staged group and 20 in the control group. Compared with preoperative values, patients in both groups achieved significant improvement in terms of ODI, VAS back, VAS leg and spinopelvic parameters after surgery, which were maintained well during the follow-up period. Compared with control group, total operative time in the staged group was longer, but the amounts of blood loss and blood transfusion were reduced. The average posterior fixation segments were 6.20±1.78 in the staged group and 8.25±1.16 in the control group (P<0.01), respectively. Posterior column osteotomy (PCO) was performed in 9 patients (36%) in the staged group, while PCO and/or pedicle subtraction osteotomy were performed in 15 patients (75%) in the control group (P<0.01). There was no difference in complications between the two groups.ConclusionBoth surgical strategies were effective for the treatment of ADLS with sagittal imbalance. However, staged treatment was less invasive, which reduced the number of posterior fixation segments and osteotomy requirement.

Clinical outcomes, MRI evaluation and predictive factors of indirect decompression with lateral transpsoas approach for lumbar interbody fusion: a multicenter experience.

Evaluating the effects of indirect decompression obtained through lateral lumbar interbody fusion (LLIF) by clinical improvements and radiological parameters on MRI scans. Identifying predictors of better decompression and clinical outcome. From 2016 to 2019, patients who underwent single- or double-level indirect decompression LLIF were consecutively reviewed. Radiological signs of indirect decompression were evaluated in preoperative and follow-up MRI studies and were subsequently correlated to clinical data, expressed as axial/radicular pain (VAS back/leg), index of disability (Oswestry Disability Index) and clinical severity of lumbar stenosis (Swiss Spinal Stenosis Questionnaire). 72 patients were enrolled. The mean follow-up was 24 months. Differences in vertebral canal area (p < 0.001), height of the foramina (p < 0.001), thickness of the yellow ligament (p = 0.001) and anterior height of the interbody space (p = 0.02) were observed. Older age (p = 0.042), presence of spondylolisthesis (p = 0.042), presence of intra-articular facet effusion (p = 0.003) and posterior height of the implanted cage (p = 0.020) positively affected the increase of the canal area. Change in root canal area (p < 0.001), height of the implanted cage (p = 0.020) and younger age (p = 0.035) were predictive factors of root pain relief, while increased vertebral canal area (p = 0.020) and height of the interbody fusion cage (p = 0.023) positively affected the severity of clinical stenosis. LLIF indirect decompression showed both clinical and radiological improvements. Presence and degree of spondylolisthesis, presence of intra-articular facet effusion, age of the patient and height of the cage were predictive factors of major clinical improvements.

184 Clinical Outcomes of the Prone Transpsoas Lateral Lumbar Interbody Fusion for Degenerative Lumbar Spine Disease: A Multicentre Study

INTRODUCTION: The prone transpsoas lateral lumbar interbody fusion (PTP) is a novel technique for degenerative lumbar spine disease. However, there is a paucity of the literature on the clinical outcomes of this procedure, with all the published being of a small sample size. METHODS: A retrospective electronic medical records review was conducted in ten centers for patients who underwent PTP. We collected the intraoperative data (operative time, estimated blood loss [EBL], intraoperative complications [anterior longitudinal ligament (ALL) rupture, cage subsidence, vascular and visceral injuries), postoperative complications, the patient-reported outcome measures (PROMS) such as back pain visual analogue scale (VAS), and hospital stay. RESULTS: A total of 350 patients were included in the study. There was a significant improvement in the mean VAS by 4.4 ± 6.7 (p &lt; 0.001). 2.8% had ALL rupture, 1.2% had cage subsidence, 0.4% had a vascular injury, and none had visceral injuries. The mean operative time was 229.9 ± 144 minutes, the mean EBL was 134.3±210.2 mL, and the mean hospital stay was 2.6 ± 2.2. In regard to postoperative complications, there was 8.9% new sensory symptoms, 6% transient hip flexor weakness, 1.4% wound infection, 1.4% cage subsidence, 0.6% psoas hematoma, 0.3% ureteric injury, 0.3% small bowel obstruction/ischemia, and 1.6% 90-days readmission. CONCLUSIONS: Multicenter consecutive case series show that PTP is well tolerated and has satisfactory clinical outcomes.

494 Comparison of Disc Height Restoration and Subsidence Rates Between Static Versus Expandable Titanium Cages for Lateral Lumbar Interbody Fusion

INTRODUCTION: It has been shown that expandable cages for transforaminal lumbar interbody fusion (TLIF) are associated with increased rates of subsidence. However, as lateral lumbar interbody fusion (LLIF) cages offer substantially larger footprints, this may offset the risks. METHODS: A retrospective review was performed of a consecutive adult patients undergoing LLIF with either static or expandable cages from 2013-2021. Demographics and surgical details were collected. Posterior disc height (PDH), subsidence, and fusions status were compared between patients with static and expandable cages. Follow-up were reported at minimum 6-months and 1-year. RESULTS: A total of 120 patients had 173 cages implanted: 96 patients with 143 static cages vs. 24 patients with 30 expandable cages. Mean age was 63.4 and 62.4% were male. There were no significant differences in age, gender, BMI, smoking, or osteoporosis. Overall, PDH was significantly increased following LLIF (4.1 v 7.4 mm, p &lt; 0.001). Static and expandable cage types had similar magnitude (3.7 v 3.3 mm, p = 0.311) and percentage (89.0% v 121.5%, p = 0.127) change in PDH, respectively. Overall incidence of cage subsidence at 6-months and 1-year was 6.9% and 10.4% respectively. There was no significant difference in subsidence rates between cage types at 6 months (7.0% v 6.7%, p = 0.949) and 1-year (11.2 v 6.7%, p = 0.461). Radiographic evidence of fusion was present in 92.7% of cases at 1-year, and both cage types achieved similar fusion rates as well (92.2% v 95.6%, p = 0.555). CONCLUSIONS: LLIF static and expandable cages offer similar PDH restoration depending on surgical goals. Expandable cages seem to be less prone to subsidence than smaller TLIF cage counterparts and offer similar fusion rates to static cages. Larger cohort studies are warranted to further validate these findings which are ongoing.

489 Complications Associated With Single Position Prone Lateral Lumbar Interbody Fusion: A Systematic Review and Meta-Analysis

INTRODUCTION: Lateral lumbar interbody fusion (LLIF) is a workhorse surgical approach for lumbar arthrodesis. There is now emerging interest in performing single position surgery in which both LLIF and pedicle screw fixation are performed in the prone position. To date, most studies of prone LLIF are of poor quality and without long-term follow up; and as such, the complication profile related to this novel approach is not well known. METHODS: A systematic review of the literature and a meta-analysis were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. All studies reporting prone LLIF were assessed for inclusion. Studies not reporting complication rates were excluded. RESULTS: A total of 10 studies met inclusion criteria and were included in the analysis. Overall, 286 patients were treated with prone LLIF across these studies with an average of 1.3 (0.2) levels per patient. There were 18 reported intra-operative complications including cage subsidence (3.8%), rupture of the anterior longitudinal ligament (ALL) (2.3%), cage repositioning (2.1%), aborted prone interbody placement (0.82%), and durotomy (0.6%). There were no reported major vascular or peritoneal injuries. A total of 68 post-operative complications occurred. These included thigh/groin sensory symptoms (13.3%), hip flexor weakness (17.8%), wound infection (1.9%), psoas hematoma (1.3%), motor neural injury (1.2%), and revision surgery (3.8%). CONCLUSIONS: Single position LLIF in the prone position appears to be a safe surgical approach with a low complication profile. Longer term follow up and prospective studies are needed in order to better characterize long-term complication rates related to this approach.

The Analysis of Preoperative Roussouly Classification on Pain Scores and Radiological Data in Lateral Lumbar Interbody Fusion for Patients with Lumbar Degenerative Disease

A retrospective observational study. The type of sagittal profile defined by Roussouly has affected spinal degeneration and surgical outcome. This study aimed to investigate the effect of preoperative Roussouly classification on pain intensity and radiological data of patients with lumbar degenerative disease who underwent indirect decompression with lateral lumbar interbody fusion (LLIF). We retrospectively investigated 102 patients who underwent LLIF without direct decompression. Patients were subdivided into 4 groups according to the Roussouly classification determined from preoperative full-length and lateral spine X-rays, and classified according to Roussouly types I, II, and IV in the nonstandard group and Roussouly type III in the standard group. The nonstandard group showed improved sagittal vertical axis and lumbar lordosis after LLIF surgery, but the midsagittal canal diameter and axial central canal area of the thecal sac using T2-weighted sagittal and axial magnetic resonance imaging were smaller than those in the standard group. On the other hand, each numeric rating scale score 1year after surgery improved in all patients. Changes in numeric rating scale scores in low back pain, leg pain, and numbness were not statistically significant between Roussouly classification types. These results suggest that the nonstandard group may have less indirect decompression effect from LLIF than the standard group. In the short term, we show for the first time after LLIF surgery that preoperative sagittal spinal alignment and the pelvic position may not significantly impact pain improvement.