Category: Spine

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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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Pars interarticularis screws for posterior cervical fusion – investigating a new trajectory using a CT‑based multiplanar reconstruction: Part I

Acta Neurochirurgica (2024) 166:295

Lateral mass screw fixation is the standard for posterior cervical fusion between C3 and C6. Traditional trajectories stabilize but carry risks, including nerve root and vertebral artery injuries. Minimally invasive spine surgery (MISS) is gaining popularity, but trajectories present anatomical challenges. Research Question. This study proposes a novel pars interarticularis screw trajectory to address these issues and enhance in-line instrumentation with cervical pedicle screws.

Materials and Methods A retrospective analysis of reformatted cervical CT scans included 10 patients. Measurements of the pars interarticularis morphology were performed on 80 segments (C3-C6). Two pars interarticularis screw trajectories were evaluated: Trajectory A (upper outer quadrant entry, horizontal trajectory) and Trajectory B (lower outer quadrant entry, cranially pointed trajectory). These were compared to standard lateral mass and cervical pedicle screw trajectories, assessing screw lengths, angles, and potential risks to the spinal canal and transverse foramen.

Results Trajectory B showed significantly longer pars lengths (15.69 ± 0.65 mm) compared to Trajectory A (12.51 ± 0.24 mm; p < 0.01). Lateral mass screw lengths were comparable to pars interarticularis screw lengths using Trajectory B. Both trajectories provided safe angular ranges, minimizing the risk to delicate structures.

Discussion and Conclusion. Pars interarticularis screws offer a viable alternative to lateral mass screws for posterior cervical fusion, especially in MISS contexts. Trajectory B, in particular, presents a feasible and safe alternative, reducing the risk of vertebral artery and spinal cord injury. Preoperative assessment and intraoperative technologies are essential for successful implementation. Biomechanical validation is needed before clinical application.

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

Operative Neurosurgery 27:14–22, 2024

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

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

RESULTS: A total of 11 patients (65.4 ± 12.5 years, 33.3% female) were retrospectively reviewed. The Kambin, safe, and transfacet corridors were measured bilaterally at the operative level. The mean area (124.1 ± 19.7 mm 2 vs 83.0 ± 11.7 mm2 vs 49.5 ± 11.4 mm2 ) and maximum permissible cannula diameter (9.9 ± 0.7 mm vs 6.8 ± 0.5 mm vs 6.05 ± 0.7 mm) for the transfacet triangles were significantly larger than Kambin and the traditional safe triangles, respectively (P < .001).

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

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Comparing posterior cervical foraminotomy with anterior cervical discectomy and fusion in radiculopathic patients: an analysis from the Quality Outcomes Database

J Neurosurg Spine 41:56–68, 2024

OBJECTIVE The objective of this study was to compare clinical and patient-reported outcomes (PROs) between posterior foraminotomy and anterior cervical discectomy and fusion (ACDF) in patients presenting with cervical radiculopathy.

METHODS The Quality Outcomes Database was queried for patients who had undergone ACDF or posterior foraminotomy for radiculopathy. To create two highly homogeneous groups, optimal individual matching was performed at a 5:1 ratio between the two groups on 29 baseline variables (including demographic characteristics, comorbidities, symptoms, patient-reported scores, underlying pathologies, and levels treated). Outcomes of interest were length of stay, reoperations, patient-reported satisfaction, increase in EQ-5D score, and decrease in Neck Disability Index (NDI) scores for arm and neck pain as long as 1 year after surgery. Noninferiority analysis of achieving patient satisfaction and minimal clinically important difference (MCID) in PROs was performed with an accepted risk difference of 5%.

RESULTS A total of 7805 eligible patients were identified: 216 of these underwent posterior foraminotomy and were matched to 1080 patients who underwent ACDF. The patients who underwent ACDF had more underlying pathologies, lower EQ-5D scores, and higher NDI and neck pain scores at baseline. Posterior foraminotomy was associated with shorter hospitalization (0.5 vs 0.9 days, p < 0.001). Reoperations within 12 months were significantly more common among the posterior foraminotomy group (4.2% vs 1.9%, p = 0.04). The two groups performed similarly in PROs, with posterior foraminotomy being noninferior to ACDF in achieving MCID in EQ-5D and neck pain scores but also having lower rates of maximal satisfaction at 12 months (North American Spine Society score of 1 achieved by 65.2% posterior foraminotomy patients vs 74.6% of ACDF patients, p = 0.02).

CONCLUSIONS The two procedures were found to be offered to different populations, with ACDF being selected for patients with more complicated pathologies and symptoms. After individual matching, posterior foraminotomy was associated with a higher reoperation risk within 1 year after surgery compared to ACDF (4.2% vs 1.9%). In terms of 12-month PROs, posterior foraminotomy was noninferior to ACDF in improving quality of life and neck pain. The two procedures also performed similarly in improving NDI scores and arm pain, but ACDF patients had higher maximal satisfaction rates.

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Treatment of conus medullaris arteriovenous malformation: the role of microsurgical treatment

J Neurosurg Spine 41:115–121, 2024

Conus medullaris arteriovenous malformation (AVM) is rare and challenging to treat. To better define the presentation, prognosis, and optimal treatment of these lesions, the authors present their treatment experiences for conus medullaris AVM.

METHODS Eleven patients with AVM of the conus medullaris were identified between March 2013 and December 2021. Among these patients, 7 who underwent microsurgical treatment were included. Patient data, including age, sex, symptoms at presentation, neurological status, radiological findings, nidus depth (mainly pial lesion vs intramedullary lesion), type of treatment, and recurrence at follow-up, were collected. Postoperative angiography was performed in all patients. Spinal cord function was evaluated using the Frankel grade at the time of admission and 1 year after surgery.

RESULTS All 7 patients presenting with myeloradiculopathy were treated surgically. Four patients (57.1%) underwent endovascular embolization, followed by resection. The other 3 patients underwent microsurgery only. Complete occlusion was confirmed with postoperative angiography in all patients. Of the 3 patients who were nonambulatory before surgery (Frankel grade C), 2 were able to walk after surgery (Frankel grade D) and 1 remained nonambulatory (Frankel grade C) at 1-year follow-up.

CONCLUSIONS Based on the authors’ clinical experiences, the results of multimodal treatment for conus medullaris AVM are good, with microsurgical treatment playing an important role. The microsurgical strategy can differ depending on the location of the nidus, and when possible, good results can be expected through microsurgical resection.

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Development and validation of an artificial intelligence model to accurately predict spinopelvic parameters

J Neurosurg Spine 41:88–96, 2024

Achieving appropriate spinopelvic alignment has been shown to be associated with improved clinical symptoms. However, measurement of spinopelvic radiographic parameters is time-intensive and interobserver reliability is a concern. Automated measurement tools have the promise of rapid and consistent measurements, but existing tools are still limited to some degree by manual user-entry requirements. This study presents a novel artificial intelligence (AI) tool called SpinePose that automatically predicts spinopelvic parameters with high accuracy without the need for manual entry.

METHODS SpinePose was trained and validated on 761 sagittal whole-spine radiographs to predict the sagittal vertical axis (SVA), pelvic tilt (PT), pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL), T1 pelvic angle (T1PA), and L1 pelvic angle (L1PA). A separate test set of 40 radiographs was labeled by four reviewers, including fellowship-trained spine surgeons and a fellowship-trained radiologist with neuroradiology subspecialty certification. Median errors relative to the most senior reviewer were calculated to determine model accuracy on test images. Intraclass correlation coefficients (ICCs) were used to assess interrater reliability.

RESULTS SpinePose exhibited the following median (interquartile range) parameter errors: SVA 2.2 mm (2.3 mm) (p = 0.93), PT 1.3° (1.2°) (p = 0.48), SS 1.7° (2.2°) (p = 0.64), PI 2.2° (2.1°) (p = 0.24), LL 2.6° (4.0°) (p = 0.89), T1PA 1.1° (0.9°) (p = 0.42), and L1PA 1.4° (1.6°) (p = 0.49). Model predictions also exhibited excellent reliability at all parameters (ICC 0.91–1.0).

CONCLUSIONS SpinePose accurately predicted spinopelvic parameters with excellent reliability comparable to that of fellowship-trained spine surgeons and neuroradiologists. Utilization of predictive AI tools in spinal imaging can substantially aid in patient selection and surgical planning.

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Risk factors for vascular injuries in anterior lumbar interbody fusion

J Neurosurg Spine 41:17–23, 2024

Vascular injuries in anterior lumbar interbody fusion (ALIF) occur due to the vascular manipulation needed to achieve optimal disc space exposure. In this study, the authors aimed to evaluate intraoperative vascular injuries in patients undergoing single- and multilevel ALIF at a large tertiary academic center.

METHODS Prospectively collected data specifically addressing postoperative complications in patients who underwent ALIF by neurosurgery spine faculty working with a specialized vascular surgeon were retrospectively reviewed. Demographic characteristics and intraoperative data were collected. Patients were split into vascular injury and non–vascular injury groups. Outcome comparisons were conducted using the chi-square exact and Wilcoxon rank-sum tests for categorical and continuous data, respectively. Logistic regression was used to investigate associations with vascular injury, with univariate analysis first conducted to identify candidate associations. Based on these results, variables demonstrating a between-groups test statistic of p < 0.10 were included in the multivariate analysis to determine the independent predictors of vascular injuries.

RESULTS In total, 323 patients who underwent ALIF procedures were identified: 51% were male (n = 166) and 49% were female (n = 157). The mean age was 57.1 years, with 56% (n = 182) having undergone prior lumbar surgery. Vascular injuries were encountered intraoperatively in 7.1% (n = 23) of patients, and the majority (91% [n = 21]) involved the left common iliac vein. Patients with vascular injuries were statistically older (mean 63.6 vs 56.6 years), had greater incidence rates of coronary artery disease, opioid use, multilevel ALIF surgery involving the L2–3 level, and surgery involving multiple disc spaces, had more multilevel anterior instrumentation, and experienced greater blood loss during surgery and longer length of stay (all p < 0.05). Overall, there was 1 death (0.3%) secondary to aortic artery injury. Multivariate analysis identified opioid use, multilevel ALIF involving L2–3, and multiple interbodies as statistically independent predictors of vascular injury (all p < 0.05).

CONCLUSIONS Identifying patient risk factors can reduce the risk of vascular injuries in ALIF. Opioid use, multilevel ALIF involving L2–3, and multiple interbodies were independent predictors of vascular injuries in ALIF.

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