Category: Spine

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Comparison of accuracy, revision, and perioperative outcomes in robot-assisted spine surgeries: systematic review and meta-analysis

J Neurosurg Spine 41:519–531, 2024

Pedicle screw placement guidance is critical in spinal fusions, and spinal surgery robots aim to improve accuracy and reduce complications. Current literature has yet to compare the relative merits of available robotic systems. In this review, the authors aimed to 1) assess the current state of spinal robotics literature; 2) conduct a meta-analysis of robotic performance based on accuracy, speed, and safety; and 3) offer recommendations for robotic system selection.

METHODS Following PRISMA guidelines, the authors conducted a systematic literature review across PubMed, Embase, Cochrane Library, Web of Science, and Scopus as of April 28, 2022, for studies on approved robots for placing lumbar pedicle screws. Three reviewers screened and extracted data relating to the study characteristics, accuracy rate, intraoperative revisions, and reoperations. Secondary performance metrics included operative time, blood loss, and radiation exposure. The authors statistically compared the performance of the robots using a random-effects model to account for variation within and between the studies. Each robot was also compared with performance benchmarks of traditional techniques including freehand, fluoroscopic, and CT-navigated insertion. Finally, we performed a Duval and Tweedie trim-and-fill test to assess for the presence of publication bias.

RESULTS The authors identified 46 studies, describing 4670 patients and 25,054 screws, that evaluated 4 different robotic systems: Mazor X, ROSA, ExcelsiusGPS, and Cirq. The weighted accuracy rates of Gertzbein-Robbins classification grade A or B screws were as follows: ExcelsiusGPS, 98.0%; ROSA, 98.0%; Mazor, 98.2%; and Cirq, 94.2%. No robot was significantly more accurate than the others. However, the accuracy of the ExcelsiusGPS was significantly higher than that of traditional methods, and the accuracies of the Mazor and ROSA were significantly higher than that of fluoroscopy. The intraoperative revision rates were Cirq, 0.55%; ROSA, 0.91%; Mazor, 0.98%; and ExcelsiusGPS, 1.08%. The reoperation rates were Cirq, 0.28%; ExcelsiusGPS, 0.32%; and Mazor, 0.76% (no reoperations were reported for ROSA). Operative times were similar for all robots. Both the ExcelsiusGPS and Mazor were associated with significantly less blood loss than the ROSA. The Cirq had the lowest radiation exposure. Robots tended to be more accurate and generally their use was associated with fewer reoperations and less blood loss than freehand, fluoroscopic, or CT-navigated techniques.

CONCLUSIONS Robotic platforms perform comparably based on key metrics, with high accuracy rates and low intraoperative revision and reoperation rates. The spinal robotics publication rate will continue to accelerate, and choosing a robot will depend on the context of the practice.

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Safe resection of a complex type 3 foramen magnum meningioma with dorsal displacement of the neurovascular bundle

Acta Neurochirurgica (2024) 166:376

We describe techniques for safe resection of a Type 3 foramen magnum meningioma with dorsal displacement of the accessory nerve rootlets and vertebral artery which limits ventral access to the tumor.

Method Partial sectioning of the accessory nerve rootlets may help create larger working space. Topical lidocaine placement on the rootlets of the spinal accessory nerve may mitigate trapezius muscle contraction and facilitates further progress throughout tumor resection.

Conclusion Creating safe working corridors between the lower cranial nerves through mobilization or partial sectioning of rootlets in the case of CN XI facilitates tumor resection through a far lateral approach.

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Comparison of biportal endoscopic and microscopic tubular paraspinal approach for foraminal and extraforaminal lumbar disc herniation

J Neurosurg Spine 41:473–482, 2024

Foraminal and extraforaminal lumbar disc herniation (FELDH) is an important pathological condition that can lead to lumbar radiculopathy. The paraspinal muscle–splitting approach introduced by Reulen and Wiltse is a reasonable surgical technique. Minimally invasive procedures using a tubular retractor system have also been introduced. However, surgical treatment is considered more challenging for FELDH than for central or subarticular lumbar disc herniations (LDHs). Some researchers have proposed uniportal extraforaminal endoscopic lumbar discectomy through a posterolateral approach as an alternative for FELDH, but heterogeneous clinical results have been reported. Recently, the biportal endoscopic (BE) paraspinal approach has been suggested as an alternative. The aim of this study was to compare the clinical outcomes of BE and microscopic tubular (MT) paraspinal approaches for decompressive foraminotomy and lumbar discectomy (paraLD) in patients with FELDH.

METHODS Ninety-one consecutive patients with unilateral lumbar radiculopathy and FELDH underwent paraLD. Demographic and perioperative data were collected. Clinical outcomes were evaluated using the visual analog scale (VAS) for back and leg pain, the Oswestry Disability Index (ODI) for spinal disability, and the modified Macnab criteria for patient satisfaction. Postoperative complications and reoperation rates were also evaluated.

RESULTS In total, 76 patients were included in the final analysis. Among them, 43 underwent BE paraLD (group A) and the remaining 33 underwent MT paraLD (group B). The demographic and preoperative data were not statistically different between the groups. All patients showed significant improvements in VAS back, VAS leg, and ODI scores compared with baseline values (p < 0.05). The improvement in VAS back scores was significantly better in group A than in group B on postoperative day 2 (p < 0.001). However, all clinical parameters were comparable between the two groups after postoperative year 1 (p > 0.05). According to the modified Macnab criteria, 86.1% and 72.7% of the patients had excellent or good outcomes in groups A and B, respectively. No intergroup differences were observed (p = 0.367). In addition, there were no differences in the total operation time or amount of surgical drainage. Postoperative complications were not significantly different between the two groups (p = 0.301); however, reoperation rates were significantly higher in group B (p = 0.035).

CONCLUSIONS BE paraLD is an effective treatment for FELDH and is an alternative to MT paraLD. In particular, BE paraLD has advantages of early improvement in postoperative back pain and low reoperation rates.

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Transforaminal lumbar interbody fusion subsidence

J Neurosurg Spine 41:463–472, 2024

The aims of this study were to 1) define the incidence of transforaminal lumbar interbody fusion (TLIF) interbody subsidence; 2) determine the relative importance of preoperative and intraoperative patient- and instrumentation-specific risk factors predictive of postoperative subsidence using CT-based assessment; and 3) determine the impact of TLIF subsidence on postoperative complications and fusion rates.

METHODS All adult patients who underwent one- or two-level TLIF for lumbar degenerative conditions at a multi-institutional academic center between 2017 and 2019 were retrospectively identified. Patients with traumatic injury, infection, malignancy, previous fusion at the index level, combined anterior-posterior procedures, surgery with greater than two TLIF levels, or incomplete follow-up were excluded. Interbody subsidence at the superior and inferior endplates of each TLIF level was directly measured on the endplate-facing surface of both coronal and sagittal CT scans obtained greater than 6 months postoperatively. Patients were grouped based on the maximum subsidence at each operative level classified as mild, moderate, or severe based on previously documented < 2-mm, 2- to 4-mm, and ≥ 4-mm thresholds, respectively. Univariate and regression analyses compared patient demographics, medical comorbidities, preoperative bone quality, surgical factors including interbody cage parameters, and fusion and complication rates across subsidence groups.

RESULTS A total of 67 patients with 85 unique fusion levels met the inclusion and exclusion criteria. Overall, 28% of levels exhibited moderate subsidence and 35% showed severe subsidence after TLIF with no significant difference in the superior and inferior endplate subsidence. Moderate (≥ 2-mm) and severe (≥ 4-mm) subsidence were significantly associated with decreases in cage surface area and Taillard index as well as interbody cages with polyetheretherketone (PEEK) material and sawtooth surface geometry. Severe subsidence was also significantly associated with taller preoperative disc spaces, decreased vertebral Hounsfield units (HU), the absence of bone morphogenetic protein (BMP) use, and smooth cage surfaces. Regression analysis revealed decreases in Taillard index, cage surface area, and HU, and the absence of BMP use predicted subsidence. Severe subsidence was found to be a predictor of pseudarthrosis but was not significantly associated with revision surgery.

CONCLUSIONS Patient-level risk factors for TLIF subsidence included decreased HU and increased preoperative disc height. Intraoperative risk factors for TLIF subsidence were decreased cage surface area, PEEK cage material, bullet cages, posterior cage positioning, smooth cage surfaces, and sawtooth surface designs. Severe subsidence predicted TLIF pseudarthrosis; however, the causality of this relationship remains unclear.

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Accurate placement of thoracolumbar pedicle screws using a handheld iOS-based navigation device

The Spine Journal 24 (2024) 1671−1677

Accurate pedicle screw placement is a challenge with reported misplacement rates of 10% and higher. A handheld navigation device (HND) may provide accuracy equal to CT-based navigation (CT-Nav) but without the cost and complexity.

OBJECTIVE: To study the accuracy of a handheld navigation device for pedicle screw placement. STUDY DESIGN: This prospective cross-sectional study with consistently applied reference standard enrolled 20 patients undergoing 92 pedicle screw placements.

PATIENTS: Patients who underwent pedicle screw placement between May 2022 and September 2022.

OUTCOME MEASURES: Pedicle screw placement accuracy per Gertzbein−Robbins.

METHODS: Once the screw pilot hole was established, the proposed trajectory of the HND was compared with that proposed by CT-Nav. Postoperatively, screw accuracy was graded according to Gertzbein−Robbins by a blinded radiologist based on CT scans. Accuracy was compared between the two systems and published control for fluoroscopy assisted and CT-Nav placement using Bayesian posterior distribution.

RESULTS: The trajectory proposed by the HND and CT-Nav were in agreement in 98.9% (95% Exact CI; 94.09%−99.97%). The HND accuracy was 98.9% with 91 screws rated “A” and 1 rated “C”. Noninferiority to fluoroscopic placement was achieved because the one-sided normalapproximation 95% CI Lower Bound (LB) of 95.3% is greater than the Performance Goal (PG) of 83.4%. Posthoc analysis demonstrated that the probability of superiority of the HND relative to the historical accuracy rate of 91.5% for fluoroscopy assisted procedures is >0.999 and that the HND’s accuracy rate is within 4.5% of CT-Nav of 95.5% is >0.999. No adverse events or intra-operative complications associated with HND were observed. There was 1 (1.1%) intra-operative repositioning and no reoperations for any reason.

CONCLUSIONS: The accuracy rate of the HND was 98.9%, and the proposed trajectory matched with CT-Nav in 98.9% of the time. This is superior to the historical published accuracy rate for fluoroscopy-assisted procedures and equivalent to the historical published accuracy rate for CT-Nav.

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Full-endoscopic lumbar discectomy for lumbar disc herniation in young adults: 199 consecutive cases treated by a single surgeon with a mean 3.7-year follow-up

J Neurosurg Spine 41:369–377, 2024

Lumbar disc herniation (LDH) is rare in young adults. The present study aimed to evaluate the clinical outcomes of full-endoscopic lumbar discectomy (FELD) for LDH in young adults and to determine the risk factors that predict unfavorable outcomes of FELD for LDH in young adults.

METHODS A retrospective two-center cohort study was performed between January 2015 and October 2021 at the authors’ institutions. Clinical outcomes were assessed using the visual analog scale (VAS) for low-back pain and leg pain and the Oswestry Disability Index (ODI). The modified Macnab criteria were used to evaluate clinical efficacy at the last follow-up, and the global outcomes were classified into 4 groups, namely excellent, good, fair, and poor. The fair and poor groups were defined as unfavorable outcomes.

RESULTS One hundred ninety-nine patients were analyzed in this study (mean age 18.5 years, mean BMI 25.1 kg/m 2 , male/female sex ratio 2.8). The duration from the onset of symptoms to the operation was in general prolonged with age. The VAS and ODI scores significantly improved after surgery. A total of 17 of 195 single-segment cases had unfavorable outcomes based on the modified Macnab criteria. Lateral disc herniation (OR 3.72, 95% CI 1.14–12.12, p = 0.029) and high preoperative VAS score (OR 1.98, 95% CI 1.13–3.46, p = 0.017) were identified as risk factors for unfavorable outcomes after FELD.

CONCLUSIONS FELD for LDH in young adults is safe and effective. Preoperative VAS score and lateral disc herniation are risk factors of nonfavorable outcomes after surgery and may be a useful index for surgical procedure selection.

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Radiographic Risk Factors for Adjacent Segment Disease Following Anterior Cervical Discectomy and Fusion (ACDF): A Systematic Review and Meta-Analysis

Global Spine Journal 2024, Vol. 14(7) 2183–2200

Study Design: Systematic review and meta-analysis.

Objectives: To assess the radiographic risk factors for adjacent segment disease (ASD) following anterior cervical discectomy and fusion (ACDF) for degenerative cervical spine pathologies.

Methods: PubMed, Embase and the Cochrane Library databases were searched up to December 2023. The primary inclusion criteria were degenerative spinal conditions treated with ACDF, comparing radiological parameters in patients with and without postoperative ASD. The radiographic parameters included intervertebral disc height, cervical sagittal alignment, sagittal segmental alignment, range of motion, segmental height, T1 slope, sagittal vertical axis (SVA), thoracic inlet angle (TIA), and plate to disc distance (PPD). Risk of bias was assessed for all studies. The Cochrane Review Manager was utilized to perform the meta-analysis.

Results: From 7044 articles, 13 retrospective studies were included in the final analysis. Three studies had “not serious” bias and the other 10 studies had serious or very serious bias. The total number of patients in the included studies was 1799 patients. Five studies included single-level ACDF, 2 studies included multi-level ACDF, and 6 studies included single or multi-level ACDF. On meta-analysis, the significant risk factors associated with ASD development were reduced postoperative cervical lordosis (mean difference [MD] = 3.35°, P = .002), reduced last-follow-up cervical lordosis (MD = À3.02°, P = .0003), increased preoperative to postoperative cervical sagittal alignment change (MD = À3.68°, P = .03), and the presence of developmental cervical canal stenosis (Odds ratio [OR] = 4.17, P < .001).

Conclusions: Decreased postoperative cervical lordosis, greater change in cervical sagittal alignment and developmental cervical canal stenosis were associated with an increased risk of ASD following ACDF.

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Posterolateral lumbar spine fixation and decompression with navigation interfaced with a robotic exoscope with head mounted display

Acta Neurochirurgica (2024) 166:342

Lumbar spine fixation and fusion is currently performed with intraoperative tools such as intraoperative CT scan integrated to navigation system to provide accurate and safe positioning of the screws. The use of microscopic visualization systems enhances visualization and accuracy during decompression of the spinal canal as well.

Methods We introduce a novel setting in microsurgical decompression and fusion of lumbar spine using an exoscope with robotized arm (RoboticScope) interfaced with navigation and head mounted displays.

Conclusion Spinal canal decompression and fusion can effectively be performed with RoboticScope, with significant advantages especially regarding ergonomics.

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Single-stage correction of severe scoliosis with syringomyelia: performed with traction assistance without prophylactic neurosurgical decompression

J Neurosurg Spine 41:316–324, 2024

There is still controversy about whether it is necessary to perform prophylactic neurosurgical decompression for severe scoliosis (SS) with syringomyelia (SM) to reduce the risk of neurological complications during subsequent spinal correction. This study aimed to explore the safety and effectiveness of using traction-assisted single-stage spinal correction as a treatment for patients who had SS with SM (SS-SM).

METHODS The patients who had SS-SM without previous neurosurgical intervention and who underwent traction-assisted single-stage posterior spinal correction at a single center were included, and the initial, posttraction, and postoperative clinical data were reviewed. Based on preoperative MRI, the included patients were divided into two categories: those with versus those without Chiari malformation type I (CM-I–related SM [CS] vs idiopathic SM [IS]), and those with a moderate syrinx (MS) versus those with a large syrinx (LS). Different groups’ traction and operation contributions were calculated for comparisons (CS vs IS, MS vs LS).

RESULTS A total of 28 patients were included. The initial mean major scoliosis was 101.0° with a mean flexibility of 21.4%. After the operation, the mean total correction rate for scoliosis was 63.9%. The mean traction and operation contributions were 61.5% and 38.5%, respectively. Most of the patients (75%) underwent spinal corrections without 3-column osteotomies, and only 1 patient reported postoperative regional numbness without motor deficits. No differences were found in the mean total correction rates, traction, and operation contributions when comparing CS versus IS and MS versus LS with the comparable initial clinical data (p > 0.05). More than 50% of the total corrections were achieved by preoperative traction in all groups.

CONCLUSIONS Traction-assisted single-stage spinal correction can safely and effectively correct SS-SM without prophylactic neurosurgical decompression under strict patient selection. Additionally, traction can achieve more than half of the final spinal correction, even for patients with varying sizes of SMs.

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Optimal Implant Sizing Using Machine Learning Is Associated With Increased Range of Motion After Cervical Disk Arthroplasty

Neurosurgery 95:627–633, 2024

Cervical disk arthroplasty (CDA) offers the advantage of motion preservation in the treatment of focal cervical pathology. At present, implant sizing is performed using subjective tactile feedback and imaging of trial cages. This study aims to construct interpretable machine learning (IML) models to accurately predict postoperative range of motion (ROM) and identify the optimal implant sizes that maximize ROM in patients undergoing CDA.

METHODS: Adult patients who underwent CDA for single-level disease from 2012 to 2020 were identified. Patient demographics, comorbidities, and outcomes were collected, including symptoms, examination findings, subsidence, and reoperation. Affected disk height, healthy rostral disk height, and implant height were collected at sequential time points. Linear regression and IML models, including bagged regression tree, bagged multivariate adaptive regression spline, and k-nearest neighbors, were used to predict ROM change. Model performance was assessed by calculating the root mean square error (RMSE) between predicted and actual changes in ROM in the validation cohort. Variable importance was assessed using RMSE loss. Area under the curve analyses were performed to identify the ideal implant size cutoffs in predicting improved ROM.

RESULTS: Forty-seven patients were included. The average RMSE between predicted and actual ROM was 7.6°(range: 5.8-10.1) in the k-nearest neighbors model, 7.8°(range: 6.5-10.0) in the bagged regression tree model, 7.8°(range: 6.210.0) in the bagged multivariate adaptive regression spline model, and 15.8°(range: 14.3-17.5°) in a linear regression model. In the highest-performing IML model, graft size was the most important predictor with RMSE loss of 6.2, followed by age (RMSE loss = 5.9) and preoperative caudal disk height (RMSE loss = 5.8). Implant size at 110% of the normal adjacent disk height was the optimal cutoff associated with improved ROM.

CONCLUSION: IML models can reliably predict change in ROM after CDA within an average of 7.6 degrees of error. Implants sized comparably with the healthy adjacent disk may maximize ROM.

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What is the Marginal Cost of Using Robot Assistance or Navigation for Transforaminal Lumbar Interbody Fusion? A Time-Driven Activity-Based Cost Analysis

Neurosurgery 95:556–565, 2024

Our primary objective was to compare the marginal intraoperative cost of 3 different methods for pedicle screw placement as part of transforaminal lumbar interbody fusions (TLIFs). Specifically, we used time-driven activity-based costing to compare costs between robot-assisted TLIF (RA-TLIF), TLIF with intraoperative navigation (ION-TLIF), and freehand (non-navigated, nonrobotic) TLIF.

METHODS: Total cost was divided into direct and indirect costs. We identified all instances of RA-TLIF (n = 20), ION-TLIF (n = 59), and freehand TLIF (n = 233) from 2020 to 2022 at our institution. Software was developed to automate the extraction of all intraoperatively used personnel and material resources from the electronic medical record. Total costs were determined through a combination of direct observation, electronic medical record extraction, and interdepartmental collaboration (business operations, sterile processing, pharmacy, and plant operation departments). Multivariable linear regression analysis was performed to compare costs between TLIF modalities, accounting for patient-specific factors as well as number of levels fused, surgeon, and hospital site.

RESULTS: The average total intraoperative cost per case for the RA-TLIF, ION-TLIF, and freehand TLIF cohorts was $24 838 ± $10 748, $15 991 ± $6254, and $14 498 ± $6580, respectively. Regression analysis revealed that RA-TLIF had significantly higher intraoperative cost compared with both ION-TLIF ( β -coefficient: $7383 ± $1575, P < .001) and freehand TLIF ( β -coefficient: $8182 ± $1523, P < .001). These cost differences were primarily driven by supply cost. However, there were no significant differences in intraoperative cost between ION-TLIF and freehand TLIF (P = .32).

CONCLUSION: We demonstrate a novel use of time-driven activity-based costing methodology to compare different modalities for executing the same type of lumbar fusion procedure. RA-TLIF entails significantly higher supply cost when compared with other modalities, which explains its association with higher total intraoperative cost. The use of ION, however, does not add extra expense compared with freehand TLIF when accounting for confounders. This might have implications as surgeons and hospitals move toward bundled payments.

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Efficacy of Biportal Endoscopic Decompression for Lumbar Spinal Stenosis: A Meta-Analysis With Single-Arm Analysis and Comparative Analysis With Microscopic Decompression and Uniportal Endoscopic Decompression

Operative Neurosurgery 27:158–173, 2024

Biportal endoscopic decompression is a minimally invasive surgical technique for lumbar spinal stenosis (LSS). This meta-analysis aimed to evaluate the efficacy and safety of biportal endoscopic decompression through both a single-arm analysis and a comparative analysis.

METHODS: A comprehensive literature search was conducted to identify eligible studies reporting the outcomes of biportal endoscopic decompression for LSS. Single-arm analysis and comparisons with microscopic and uniportal endoscopic decompression were performed. Evaluated outcomes included visual analog scale (VAS) scores for back pain and leg pain, Oswestry Disability Index (ODI) scores, operation time, estimated blood loss, duration of hospital stay, and adverse events.

RESULTS: Single-arm analysis demonstrated significant improvements in VAS back pain, VAS leg pain, and ODI scores after biportal endoscopic decompression at postoperative 1-day to 36-month follow-up (all P < .001), compared with preoperative levels. The pooled mean single-level operation time was 71.44 min, and the pooled mean hospital stay was 3.63 days. The overall adverse event rate was 4.0%, with dural tear being the most common complication (3.0%). Compared with microscopic decompression, biportal endoscopic decompression showed significantly lower VAS back pain at 1-month (P < .001) and 6-month (P < .001) follow-up; lower VAS leg pain at 1-month (P = .045) follow-up; lower ODI scores at 3-month (P < .001), 12-month (P = .017), and >12-month (P = .007) follow-up; lower estimated blood loss (P = .003); and shorter hospital stay (P < .001). Adverse event rates did not differ between the techniques. No significant differences were observed between biportal endoscopic and uniportal endoscopic decompression groups for most efficacy and safety outcomes.

CONCLUSION: Biportal endoscopic decompression emerges as a safe and effective alternative for LSS, presenting potential advantages over the microscopic technique and comparable efficacy with the uniportal endoscopic technique.

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The Safety and Efficacy of Dorsal Root Entry Zone Lesioning for Pain Management in Patients With Brachial Plexus Avulsion

Neurosurgery 95:259–274, 2024

Persistent neuropathic pain after brachial plexus avulsion (BPA) is common and generally nonresponsive to medical management. Dorsal root entry zone (DREZ) lesioning is the last resort for pain management in patients with BPA. This study aims to investigate and compare the outcomes and complications of DREZ procedures.

METHODS: A systematic literature search was conducted to identify all related studies. Comparisons were based on the number of patients with preoperative pain vs postoperative pain, with the effect size calculated using the risk ratio. Mean visual analog scale (VAS) scores were extracted and analyzed between interventions. A meta-regression analysis was performed to identify risk factors for final outcomes. The rates of complications were also assessed and analyzed between interventions.

RESULTS: A total of 30 studies with 917 patients (90.0% male and 10.0% female, mean age: 42.9 ± 16.6) were included in this systematic review. Of the 917 patients who underwent surgery, 655 (71.4%) patients had significant pain reduction at the last follow-up (P < .05). The weighted mean preoperative VAS score was 8.3 ± 1.3, compared with postoperative VAS scores (1.9 ± 2.2); a significant improvement was observed (P < .05). The subgroup analysis showed that microsurgical DREZotomy (MDT) is associated with better outcomes in terms of VAS score improvements compared with radiofrequency (RF)-assisted DREZ lesioning (P < .05). Meta-analysis showed that the relative risk of motor deficits was significantly lower in the MDT group, compared with the RF-assisted group (P < .05). Meta-regression showed that older age is correlated with an elevated risk of postoperative motor deficits compared with the incidence of sensory loss.

CONCLUSION: DREZ lesioning is effective for intractable pain alleviation after BPA. Compared with RF-assisted DREZ lesioning, MDT is associated with better VAS score improvements and a lower rate of postoperative motor weakness.

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A retrospective analysis of perioperative complications of lateral approach lumbar interbody fusion in patients with prior abdominal surgery or a history of colonic inflammatory disease

The Spine Journal 24 (2024) 1451−1458

Lateral approaches for lumbar interbody fusion (LIF) allow for access to the lumbar spine and disc space by passing through a retroperitoneal corridor either preor trans-psoas. A contraindication for this approach is the presence of retroperitoneal scarring that may occur from prior surgical intervention in the retroperitoneal space or from inflammatory conditions with fibrotic changes and pose challenges for the mobilization and visualization needed in this approach. However, there is a paucity of evidence on the prevalence of surgical complications following lateral fusion surgery in patients with a history of abdominal surgery.

PURPOSE: The primary aim of this study is to describe the association between surgical complications following lateral interbody fusion surgery and prior abdominal surgical.

STUDY DESIGN: Retrospective study.

PATIENT SAMPLE: Patients over the age of 18 who underwent lateral lumbar interbody fusion at a large, tertiary care center between 2011 and 2019 were included in the study.

OUTCOME MEASURES: The primary outcome included medical, surgical, and thigh-related complications either in the intraoperative or 90-day postoperative periods. Additional outcome metrics included readmission rates, length of stay, and operative duration.

METHODS: The electronic health records of 250 patients were reviewed for demographic information, surgical data, complications, and readmission following surgery. The association of patient and surgical factors to complication rate was analyzed using multivariable logistic regression. Statistical analysis was performed using R statistical software (R, Vienna, Austria).

RESULTS: Of 250 lateral interbody fusion patients, 62.8% had a prior abdominal surgery and 13.8% had a history of colonic disease. The most common perioperative complication was transient thigh or groin pain/sensory changes (n=62, 24.8%). A multivariable logistic regression considering prior abdominal surgery, age, BMI, history of colonic disease, multilevel surgery, and the approach relative to psoas found no significant association between surgical complication rates and colonic disease (OR 0.40, 95% CI 0.02−2.22) or a history of prior abdominal surgeries (OR 0.56, 95% CI 0.20−1.55). Further, the invasiveness of prior abdominal surgeries showed no association with overall spine complication rate, lateral-specific complications, or readmission rates (p>.05).

CONCLUSION: Though retroperitoneal scarring is an important consideration for lateral approaches to the lumbar spine, this study found no association between lateral lumbar approach complication rates and prior abdominal surgery. Further study is needed to determine the impact of inflammatory colonic disease on lateral approach spine surgery.

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Completely Minimally Invasive Implant Removal and Transforaminal Lumbar Interbody Fusion for Adjacent Segment Disease: Case Series and Operative Video

Operative Neurosurgery 27:322–328, 2024

Adjacent segment disease is a relatively common late complication after lumbar fusion. If symptomatic, certain patients require fusion of the degenerated adjacent segment. Currently, there are no posterior completely minimally invasive techniques described for fusion of the adjacent segment above or below a previous fusion. We describe here a novel minimally invasive technique for both implant removal (MIS-IR) and adjacent level transforaminal lumbar interbody fusion (MIS-TLIF) for lumbar stenosis.

METHODS: Demographic, surgical, and radiographic outcome data were collected for patients with lumbar stenosis and previous lumbar fusion, who were treated with MIS-IR and MIS-TLIF through the same incision. Radiographic outcomes were assessed postoperatively and complications were assessed at the primary end point of 3 months.

RESULTS: A total of 14 patients (7 female and 7 male), with average age 64.6 years (SD 13.4), were included in this case series. Nine patients had single-level MIS-IR with single-level MIS-TLIF. Three patients had 2-level MIS-IR with single-level MIS-TLIF. Two patients had single-level MIS-IR with 2-level MIS-TLIF. Only 1 patient had a postoperative complication hematoma requiring same-day evacuation. There were no other complications at the primary end point and no fusion failure at the hardware removal levels to date (average follow-up, 11 months). Average increases in posterior disk height and foraminal height after MIS-TLIF were 4.44, and 2.18 mm, respectively.

CONCLUSION: Minimally invasive spinal IR can be successfully completed along with adjacent level TLIF through the same incisions, via an all-posterior approach.

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Interbody cages versus structural bone grafts in lumbar arthrodesis: a systematic review and meta-analysis

J Neurosurg Spine 41:188–198, 2024

The role of interbodies in lumbar arthrodesis has been insufficiently supported by evidence, impacting clinical decision-making and occasionally insurance coverage. This study aimed to compare clinical and radiological outcomes between lumbar arthrodesis with a synthetic interbody spacer (cage) versus structural bone graft alone (autograft or allograft) in patients with degenerative spine disease.

METHODS A systematic review of the literature was performed to identify studies directly comparing outcomes of lumbar interbody arthrodesis with and without interbody cage use. The outcomes of individual studies were synthesized in meta-analyses using random-effects models.

RESULTS Twenty studies with 1508 patients (769 with an interbody cage and 739 without an interbody cage) were included. Interbody cage placement was associated with a significantly greater increase in disc height after surgery (4.0 mm vs 3.4 mm, p < 0.01). There was a significantly greater reduction of back pain (visual analog scale [VAS] score) in cases in which an interbody cage was used (5.4 vs 4.7, p = 0.03). Fusion rates were 5.5% higher in the cage group (96.3% vs 90.8%) and reached statistical significance (p = 0.03). No statistically significant differences were identified between the two groups regarding all-cause reoperation rates, complication rates, or improvement in Oswestry Disability Index score or leg pain (VAS score).

CONCLUSIONS These results suggest that implantation of an interbody cage is associated with higher rates of fusion, more effective maintenance of disc height, and greater improvement of back pain. This study underlines the clinical value of interbody cages in lumbar arthrodesis for patients with degenerative spine disease.

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

Acta Neurochirurgica (2024) 166:319

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.

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Do expandable cage size and number of cages matter in transforaminal lumbar interbody fusion at L5–S1?

J Neurosurg Spine 41:209–215, 2024

Expandable transforaminal lumbar interbody fusion (TLIF) cages were designed to address the limitations of static cages. Bilateral cage insertion can potentially enhance stability, fusion rates, and segmental lordosis. However, the benefits of unilateral versus bilateral expandable cages with varying sizes in TLIF remain unclear. This study used a validated finite element spine model to compare the biomechanical properties of L5–S1 TLIF by using differently sized expandable cages inserted unilaterally or bilaterally.

METHODS A finite element model of X-PAC expandable lumbar cages was created and used at the L5–S1 level. This model had cage dimensions of 9 mm in height, 15° in lordosis, and varying widths and lengths. Various placements (unilateral vs bilateral) and sizes were examined under pure moment loading to evaluate range of motion, adjacent-segment motion, and endplate stress.

RESULTS Stability at the L5–S1 level decreased when smaller cages were used in both the unilateral and bilateral cage models. In the unilateral model, cage 1 (the smallest cage) resulted in 47.9% more motion at the L5–S1 level compared to cage 5 (the largest cage) in flexion, as well as 64.8% more motion in extension. Similarly, in the bilateral TLIF model, bilateral cage 1 led to 49.4% more motion at the L5–S1 level in flexion and 73.4% more motion in extension compared to bilateral cage 5. Unilateral insertion of cage 5 provided superior stability in flexion and surpassed cages 1–3 in extension when compared to cages inserted either unilaterally or bilaterally. Reduced motion at L5–S1 correlated with increased adjacent-segment motion at L4–5. Bilateral TLIF resulted in greater adjacent-segment motion compared to unilateral TLIF with the same-size cages. Inferior endplates experienced higher stress during flexion and extension than superior endplates, with this difference being more pronounced in the bilateral model. In bilateral cage placement, stress differences ranged from 46.3% to 60.0%, while they ranged from 1.1% to 9.6% in unilateral cages. Qualitative analysis revealed increased focal stress in unilateral cages versus bilateral cages.

CONCLUSIONS The authors’ study shows that using a large unilateral TLIF cage may offer better stability than the bilateral insertion of smaller cages. While large bilateral cages increase adjacent-segment motion, they also provide a uniform stress distribution on the endplates. These findings deepen our understanding of the biomechanics of the available expandable TLIF cages.

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Vertebral Bone Quality Score as a Predictor of Adjacent Segment Disease After Lumbar Interbody Fusion

Neurosurgery 95:284–296, 2024

With lumbar spine fusion being one of the most commonly performed spinal surgeries, investigating common complications such as adjacent segment disease (ASD) is a high priority. To the authors’ knowledge, there are no previous studies investigating the utility of the preoperative magnetic resonance imaging based vertebral bone quality (VBQ) score in predicting radiographic and surgical ASD after lumbar spine fusion. We aimed to investigate the predictive factors for radiographic and surgical ASD, focusing on the predictive potential of the VBQ score.

METHODS: A single-center retrospective analysis was conducted of all patients who underwent 1–3 level lumbar or lumbosacral interbody fusion for lumbar spine degenerative disease between 2014 and 2021 with a minimum 12 months of clinical and radiographic follow-up. Demographic data were collected, along with patient medical, and surgical data. Preoperative MRI was assessed in the included patients using the VBQ scoring system to identify whether radiographic ASD or surgical ASD could be predicted.

RESULTS: A total of 417 patients were identified (mean age, 59.8 ± 12.4 years; women, 54.0%). Eighty-two (19.7%) patients developed radiographic ASD, and 58 (13.9%) developed surgical ASD. A higher VBQ score was a significant predictor of radiographic ASD in univariate analysis (2.4 ± 0.5 vs 3.3 ± 0.4; P < .001) and multivariate analysis (odds ratio, 1.601; 95% CI, 1.453-1.763; P < .001). For surgical ASD, a significantly higher VBQ score was seen in univariate analysis (2.3 ± 0.5 vs 3.3 ± 0.4; P < .001) and served as an independent risk factor in multivariate analysis (odds ratio, 1.509; 95% CI, 1.324-1.720; P < .001). We also identified preoperative disk bulge and preoperative existence of adjacent segment disk degeneration to be significant predictors of both radiographic and surgical ASD. Furthermore, 3-level fusion was also a significant predictor for surgical ASD.

CONCLUSION: The VBQ scoring system might be a useful adjunct for predicting radiographic and surgical ASD.

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