Tag: Spine

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The Timing of Diskectomy as a Predictor of Outcomes in Patients With Lumbar Disk Herniation

Neurosurgery 98:1051–1062, 2026

This prospective cohort study evaluates how the duration of preoperative symptoms influences outcomes after microdiskectomy for lumbar disk herniation. Outcomes measured include radicular pain, low back pain, disability (ODI), and motor and sensory deficits, with follow-up at 6 weeks, 6, 12, and 24 months in 1,120 analyzed patients.

Key finding: surgical intervention within one month of symptom onset yields faster, more pronounced pain relief and neurological recovery, whereas symptoms persisting beyond two years associate with the highest rates of residual motor and sensory deficits at 24 months.

Objective Evaluate how the preoperative duration of low back pain, disability, radicular leg pain, and motor/sensory deficits relates to postoperative outcomes after microdiskectomy for lumbar disk herniation (LDH).

Design/setting Prospective cohort (April 2015–October 2022) of adults undergoing microdiskectomy for symptomatic LDH with imaging-confirmed herniation consistent with symptoms.

Assessments & follow-up Pain measured by NRS, disability by ODI, motor deficit by MRC grading, sensory deficit as present/absent; assessed pre-op and at 6 weeks, 6, 12, and 24 months post-op.

Cohort size 1222 patients enrolled; 69 recurrences and 33 lost to follow-up excluded, leaving 1120 for statistical analyses.

Symptom-duration grouping Patients categorized by symptom duration thresholds ≤1, ≤6, ≤24, and ≥25 months for LDH-related symptoms (pain/disability/neurologic symptomatology).

Key outcome (timing) Surgery performed within 1 month of symptom onset was associated with more favorable outcomes than longer symptom duration, including faster improvement in neurological deficit and more significant radicular pain relief.

Residual deficits at 2 years Residual motor and sensory deficits at 24 months were least common when preoperative neurological symptoms lasted ≤1 month, and more common when symptoms exceeded 1 month.

Worst outcomes with long duration LDH symptoms persisting beyond 2 years were associated with the least favorable postoperative outcomes, including the highest residual motor and sensory deficits at 2 years.

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Segmental Lordosis After Open Transforaminal Lumbar Interbody Fusion Using Expandable Oblique Versus Static Anterior Banana Cages

Operative Neurosurgery 30:78–89, 2026

This clinical research article compares segmental and lumbar lordosis outcomes after open transforaminal lumbar interbody fusion (TLIF) with posterior column osteotomy using either static anterior “banana” cages or obliquely placed expandable cages. In a single-surgeon retrospective cohort of 210 patients (327 segments), expandable cages produced a significantly greater median change in segmental lordosis (ΔSL) by 2.0° at six months, persisting after multivariate adjustment and propensity matching.

The study also reports inconsistent effects of cage type on overall lumbar lordosis (ΔLL), with subgroup and matched analyses yielding differing results, and found no difference in subsidence or complication rates. Findings emphasize the influence of preoperative segmental lordosis, segment level (notably L5–S1), and construct length on achieved correction, while noting limitations including retrospective design and lack of clinical outcomes.

Expandable Cages: Expandable obliquely placed cages in open transforaminal lumbar interbody fusion (TLIF) with posterior column osteotomy (PCO) produce a significantly greater median increase in segmental lordosis (ΔSL) of 2.0° compared to static anteriorly placed banana cages, representing a 50% increase.

Statistical Robustness: The greater segmental lordosis achieved with expandable cages remained significant after multivariate regression analysis and propensity score matching, confirming the reliability of the finding.

Overall Lumbar Lordosis (ΔLL): No clear advantage was found between cage types regarding the change in overall lumbar lordosis, with results varying depending on the statistical method used.

Surgical Technique Consistency: All surgeries were performed open with a full PCO using a consistent technique, minimizing confounding variables related to surgical approach or technique.

Preoperative Segmental Lordosis Impact: Segments with lower preoperative segmental lordosis (<15°) experienced the greatest increase in lordosis postoperatively, regardless of cage type.

L5-S1 Segment Benefit: Expandable cages were especially favorable at the L5-S1 segment, likely due to anatomical constraints that make insertion of large static cages more challenging at this level.

Complication and Subsidence Rates: No significant differences were observed between cage types in rates of complications, cage subsidence, or spondylolisthesis correction.

Clinical Outcomes Unclear: The study did not assess clinical outcomes, so the impact of the observed radiographic differences on patient-reported outcomes remains unknown.

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The Association of Area Deprivation Index and Spine Surgery Outcomes: A Systematic and Narrative Review

Operative Neurosurgery 29:775–784, 2025

This systematic review examines the relationship between neighborhood-level socioeconomic disadvantage, measured by the Area Deprivation Index (ADI), and outcomes after various spine surgeries. Ten North American observational studies (56,925 patients) indicate higher ADI is associated with increased readmissions, emergency visits, longer lengths of stay, higher costs, and worse patient-reported outcomes for cervical and lumbar procedures.

The review outlines potential mechanisms—limited health literacy, barriers to follow-up, comorbidity control, and access deficits—and proposes targeted interventions across education, income/employment, housing, and household support to mitigate disparities and improve perioperative optimization and outcomes.

Area Deprivation Index (ADI): ADI is a validated, neighborhood-level measure of socioeconomic disadvantage, incorporating 17 variables across education, income/employment, housing, and household characteristics, with scores ranked from 0 (least disadvantaged) to 100 (most disadvantaged).

Association with Spine Surgery Outcomes: High ADI is linked to worse outcomes after spine surgery, including higher rates of postoperative readmissions, complications, emergency room visits, longer hospital stays, and poorer patient-reported outcomes (PROs).

Cervical Spine Surgery: Increased ADI is associated with higher costs of care, increased surgical utilization, and longer hospital length of stay after anterior cervical discectomy and fusion (ACDF); some studies also report increased likelihood of 30-day readmission, though not always statistically significant.

Lumbar Spine Surgery: High ADI predicts worse preoperative pain, function, depression, and anxiety scores; patients with high ADI experience greater rates of complications (e.g., respiratory failure), longer hospital stays, increased emergency visits, higher costs, and are less likely to achieve clinically meaningful improvements postoperatively.

Mechanisms of Disparity: Poor health literacy, reduced access to primary and follow-up care, barriers to transportation, and poor control of comorbidities are key mechanisms by which high ADI leads to worse surgical outcomes.

Potential Interventions: Targeted interventions addressing education (health literacy outreach, transitional care), income/employment (public assistance, nutrition programs), housing (medical-legal partnerships, transitional housing), and household resources (home health, internet access, transportation assistance) may help mitigate disparities for high ADI patients.

Limitations: Evidence is limited by heterogeneity of included studies, moderate risk of bias, small sample sizes for some subgroups, and lack of generalizability across all spine surgery types.

Future Directions: ADI can serve as a prognostic tool for identifying at-risk patients; further research should validate these associations and evaluate the effectiveness of targeted interventions to improve spine surgery outcomes in disadvantaged populations.

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Prone Lateral Transpsoas Approach to the Spine: A Technical Guide for Mastery

Int J Spine Surg 2025, 19 (S1) S19-S27

• The prone lateral transpsoas (PTP) approach offers an alternative to traditional lateral lumbar interbody fusion (LLIF), allowing direct posterior access without repositioning the patient.

• Advantages of PTP include improved segmental lordosis, single-position surgery, and ease of posterior techniques, though it has a distinct learning curve.

• The technical guide aims to shorten the learning curve, optimize surgical workflow, and ensure patient safety through preoperative planning and technical adjustments.

• Preoperative imaging is crucial for assessing anatomical characteristics and guiding surgical approach decisions.

• Patient positioning in PTP involves prone positioning on a radiolucent table, with special attention to stabilizing the pelvis and optimizing working angles.

• Intraoperative monitoring with triggered electromyography (t-EMG) is essential to minimize lumbar plexus injury risk.

• Technical pearls include strategies for retractor positioning, minimizing retraction time, and using intraoperative navigation to enhance safety and efficiency.

• Conclusion: PTP LIF is a viable alternative to traditional methods, offering significant benefits but requiring mastery of its unique technical nuances.

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How Do the True Intraoperative Costs of Endoscopic Diskectomy Compare With Microdiskectomy for Lumbar Disk Herniations?

Operative Neurosurgery 27:690–697, 2024

Endoscopic lumbar diskectomy (ED) is a minimally invasive option for addressing lumbar disk herniations. With the introduction of value-based care systems, assessing the true cost of certain procedures is critical when creating reimbursement models and comparing procedures. Here, we compared the costs of performing a microdiskectomy (MD) and ED using time-driven activity-based costing.

METHODS: Total cost for the intraoperative episode was calculated using time-driven activity-based costing methodology. Individual costs were obtained by direct observation and electronic medical records and through querying multiple departments (business operations, sterile processing, plant operations, and pharmacy). Timestamps for all involved personnel and material resources were documented. A retrospective analysis was performed on 202 patients who underwent lumbar diskectomy through either MD (n = 167) or ED (n = 35) from 2018 to 2022. Personnel cost was calculated by multiplying the cost per unit time for each personnel type by the length of time spent in the operating room. Supply cost was calculated by aggregating the cost of all individual supplies, from medications to consumables to surgical trays, used during the case. Univariate and multivariable regression analyses were performed comparing the costs between these procedures.

RESULTS: The average intraoperative cost per case for ED and MD was $3915 ± $1025 and $3162 ± $954, respectively. Multivariable regression analysis revealed that ED had higher total cost ( β -coefficient: $912 ± $281, P = <.01) and supply cost ( β -coefficient: $474 ± $155, P = <.01) than MD. When accounting for surgeon as a covariate, however, total cost (P = .478) and supply cost (P = .468) differences between ED and MD were negligible.

CONCLUSION: ED has shown to be a better value option in addressing lumbar disk herniations, mostly because of advantages in perioperative care. Here, we show that when correcting for surgeon-level effects, the cost between the two procedures is statistically insignificant, reaffirming the value provided by ED.

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Percutaneous Screw Distraction for Anatomic Restoration: Case Series

Operative Neurosurgery 27:698–706, 2024

Percutaneous pedicle screw fixation with distraction reduces morbidity after traumatic thoracolumbar burst fractures; however, there are substantial limitations, particularly for correction of kyphosis. The use of fixed-angle screws may offer improved anatomic restoration, facilitating greater postdistraction vertebral height restoration and spinal canal fragment reduction. We examined the radiographic results of distraction across fixed-angle screws immediately after surgery and in long-term follow-up.

METHODS: Demographic and clinical characteristics were captured for patients with traumatic thoracolumbar fractures undergoing percutaneous pedicle screw fixation by a single surgeon. Radiographic measurements were collected at predistraction, postdistraction, and long-term follow-up time points. Paired t-tests, Student’s t-tests, Mann–Whitney U tests, and χ 2 tests were used to assess data where appropriate.

RESULTS: The case series included 22 patients (77.3% male; mean age 42.0 ± 18.4 years). Hounsfield density consistent with osteopenia was seen in 13.6% of patients at the time of injury. Sporting injuries and motor vehicle accidents were common (both 31.8%). Most injuries occurred at L1 (45.5%). Upon long-term follow-up, the mean injured-level predistraction cross-sectional area improved from 2.1 to 2.9 cm 2 (P < .01). Compared with the superadjacent level, the injured-level cross-sectional canal area improved by 28.6% (P < .01). Vertebral body index also improved significantly (18.8°mean change, P < .01). The mean bisegmental Cobb angle improved by 6.2°(P = .01), and injured vertebral body compression decreased by 22.4% (P < .01). Significant improvement in correction was achieved with experience, with final technique yielding superior cross-sectional area (P = .04) and compression ratios (P = .03).

CONCLUSION: Distraction across fixed-angle percutaneous screw instrumentation systems stabilizes traumatic thoracolumbar burst fractures, corrects deformity, and decompresses the spinal canal. Further comparative research is necessary to demonstrate whether outcomes are different between percutaneous instrumentation vs open fusion for thoracolumbar trauma.

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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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Postoperative Measurement of the Retropharyngeal Space Predicts the Risk of Dysphagia After Anterior Cervical Diskectomy and Fusion

Neurosurgery 94:1116–1121, 2024

Postoperative dysphagia is a common complication of anterior cervical diskectomy and fusion (ACDF), although its pathophysiology remains poorly understood. Patients with severe dysphagia may suffer from serious complications such as aspiration pneumonia, in addition to difficulty with oral intake or malnutrition; therefore, a prompt indicator for postoperative management would be helpful. We quantitatively evaluated the retropharyngeal space (RS) after ACDF and investigated its association with postoperative dysphagia.

METHODS: This multicenter retrospective study analyzed the clinical data of 82 consecutive patients who underwent ACDF. The anteroposterior distance (APD) of the RS was measured at the C2 level using a lateral radiographic view on postoperative day 1. Postoperative dysphagia was subjectively assessed using the Bazaz-Yoo Dysphagia Severity Scale. We statistically evaluated the association between the APD of the RS and postoperative dysphagia.

RESULTS: The mean APD of the RS in all 82 patients was 3.6 mm preoperatively and significantly increased to 8.2 mm postoperatively (P < .0001). Twenty-two patients (26.8%) had postoperative dysphagia. Multivariable analysis revealed that the postoperative APD was associated with postoperative dysphagia (odds ratio 1.27, 95% CI 1.10-1.50, P = .0007). The receiver operating characteristic curve (area under the curve 0.70, 95% CI 0.58-0.83) demonstrated that the postoperative APD of the RS cutoff value was 6.1 mm, with a sensitivity of 100% and a specificity of 35%. With this cutoff value, the positive and negative predictive values for postoperative dysphagia were 36% and 100%, respectively.

CONCLUSION: Our data demonstrate that a value of 6.1 mm for the APD of the RS is an effective indicator for dysphagia after ACDF, which contributes to optimizing the patient management in the acute postoperative period.

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Pain alleviation and functional improvement: ultra-early patient-reported outcome measures after full endoscopic spine surgery

J Neurosurg Spine 40:465–474, 2024

Questions regarding anticipated pain improvement and functional recovery postsurgery are frequently posed in preoperative consultations. However, a lack of data characterizing outcomes for the first postoperative days only allows for anecdotal answers. Hence, the assessment of ultra-early patient-reported outcome measures (PROMs) is essential for patient-provider communication and patient satisfaction. The aim of this study was to elucidate this research gap by assessing and characterizing PROMs for the first days after full endoscopic spine surgery (FESS).

METHODS This multicenter study included patients undergoing lumbar FESS from March 2021 to July 2023. After informed consent was provided, data were collected prospectively through a smartphone application. Patients underwent either discectomy or decompression. Analyzed parameters included demographics, surgical details, visual analog scale scores for both back and leg pain, and the Oswestry Disability Index (ODI) score. Data were acquired daily for the 1st postoperative week, as well as after 2 weeks, 3 months, and 6 months.

RESULTS A total of 182 patients were included, of whom 102 underwent FESS discectomy and 80 underwent FESS decompression. Significant differences between the discectomy and decompression groups were found for age (mean 50.45 ± 15.28 years and 63.85 ± 13.25 years, p < 0.001; respectively), sex (p = 0.007), and surgery duration (73.45 ± 45.23 minutes vs 98.05 ± 46.47 minutes, p < 0.001; respectively). Patients in both groups reported a significant amelioration of leg pain on the 1st postoperative day (discectomy group VAS score: 6.2 ± 2.6 vs 2.4 ± 2.9, p < 0.001; decompression group: 5.3 ± 2.8 vs 1.9 ± 2.2, p < 0.001) and of back pain within the 1st postoperative week (discectomy group VAS score: 5.5 ± 2.8 vs 2.8 ± 2.2, p < 0.001; decompression group: 5.2 ± 2.7 vs 3.1 ± 2.4, p < 0.001). ODI score improvement was most pronounced at the 3-month time point (discectomy group: 21.7 ± 9.1 vs 9.3 ± 9.1, p < 0.001; decompression group: 19.3 ± 7.8 vs 9.9 ± 8.3, p < 0.001). For both groups, pain improvement within the 1st week after surgery was highly predictive of later benefits.

CONCLUSIONS Ultra-early PROMs reveal an immediate pain improvement after FESS. While the benefits in pain reduction plateaued within the 1st postoperative week for both groups, functional improvements developed over a more extended period. These results illustrate a biphasic rehabilitation process wherein initial pain alleviation transitions into functional improvement over time.

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Hospital cost differences between open and endoscopic lumbar spine decompression surgery

J Neurosurg Spine 40:77–83, 2024

In recent years, fully endoscopic decompression surgery for degenerative spine disease has become increasingly popular in the US. Although an endoscopic approach has demonstrated some benefits compared with open procedures in randomized controlled trials, the cost of advanced technologies remains contested. The authors evaluated the differences in costs and cost drivers between open and endoscopic decompression surgical procedures performed at a single institution.

METHODS Using associated Current Procedural Terminology codes, the authors identified all open and endoscopic decompression lumbar surgical procedures performed from January 1, 2016, through December 31, 2022. Preoperative comorbidities, surgical characteristics, and postoperative outcomes were captured. The costs of index surgery–related readmission for revision, washout, or other complications were included in the index surgery expenses. Associated inhospital costs were collected; these were reported in comparative percentages with open surgical procedures as the baseline because of an institutional agreement. Univariate and multivariate analyses were performed.

RESULTS The retrospective search identified 633 open surgical procedures and 195 endoscopic surgical procedures for inclusion. The two patient cohorts were similar, with clinically nonrelevant but statistically significant differences in mean age (open 55.7 years vs endoscopic 59.4 years, p = 0.01) and mean American Society of Anesthesiologists physical status class (open 2.3 vs endoscopic 2.4, p = 0.03). Postoperatively, patients who underwent open surgical procedures had significantly longer mean hospital stays (open 1.4 days vs endoscopic 0.7, p < 0.01) and more perioperative complications (open 7.9% of patients vs endoscopic 3.1%, p = 0.02), and they required washout surgical procedures in some cases (open 1.3% vs endoscopic 0%, p = 0.12). The largest cost difference between open and endoscopic surgical procedures was the significantly greater cost of disposable supplies for endoscopic cases (10.1% vs 31.7% of the total cost of open procedures, p < 0.01), and open surgical procedures were generally less costly in total (100.0% vs 115.1%, p < 0.01). In multivariate linear regression, endoscopic surgery was independently associated with greater total costs (standardized beta 15.9%, p < 0.01), although length of hospital stay (standardized beta 34.0%) and readmissions (standardized beta 30.0%, p < 0.01) had larger effects on cost.

CONCLUSIONS The endoscopic approach was associated with greater total in-hospital costs compared with open procedures. The findings of further cost evaluations, including those of patient-reported outcomes, social cost, and capital costs per procedure type, need to be included in operational and clinical decisions.

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Midline lumbar interbody fusion: a review of the surgical technique and outcomes

J Neurosurg Spine 39:462–470, 2023

Midline lumbar interbody fusion (MidLIF) is a mini-open posterior interbody fusion technique defined by a cortical screw trajectory wherein screws are placed from a more medial to lateral trajectory compared with traditional pedicle screws. This enables the surgeon to perform a smaller muscle dissection with the benefits of improved blood loss, less muscle retraction, decreased operative time, shorter length of stay, and improved back pain outcomes compared with the traditional posterior lumbar interbody fusion techniques utilizing pedicle screw fixation.

Importantly, MidLIF offers comparable clinical outcomes and radiographic outcomes to other posterior lumbar interbody fusion techniques.

In the current review, the authors aimed to educate readers about the MidLIF surgical technique, as well as surgical, clinical, radiographic, cost effectiveness, and biomechanical outcomes, when compared with both open and minimally invasive posterior lumbar interbody fusion techniques with pedicle screw fixation.

Readers will be able to utilize this information to determine how the MidLIF procedure compares as an alternative to traditional techniques.

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Spinal Intradural Arachnoid Cysts in Adults

Neurosurgery 92:450–463, 2023

Adult spinal intradural arachnoid cysts are rare pathologic entities with an unclear etiopathogenesis. These lesions can be dichotomized into primary (idiopathic) or secondary (related to inflammation, intradural surgery, or trauma) etiologies. Limited series have depicted optimal management strategies and clinical outcomes.

OBJECTIVE: To illustrate our experience with spinal intradural arachnoid cysts and to present a literature review of surgically treated cysts to elucidate the clinical and anatomic differences between etiologies.

METHODS: Institutional review revealed 29 patients. Various data were extracted from the medical record. Initial and follow-up symptomatologies of the surgical cohort were compared. The literature review included case series describing cysts managed surgically.

RESULTS: From patients treated surgically at our institution (22), there was a significant reduction in thoracic back pain postoperatively (P = .034). A literature review yielded 271 additional cases. Overall, primary and secondary lesions accounted for 254 and 39 cases, respectively. Cysts of secondary origin were more likely localized ventral to the spinal cord (P = .013). The rate of symptomatic improvement after surgical intervention for primary cysts was more than double than that of secondary cysts (P < .001). Compared with primary etiologies, the rates of radiographic progression (P = .032) and repeat surgery (P = .041) were each more than double for secondary cysts.

CONCLUSION: Surgical intervention for spinal intradural arachnoid cysts improves thoracic back pain. The literature supports surgical intervention for symptomatic primary spinal intradural arachnoid cysts with improved clinical outcomes. Surgery should be cautiously considered for secondary cysts given worse outcomes.

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Do the newly proposed realignment targets for C2 and T1 slope bridge the gap between radiographic and clinical success in corrective surgery for adult cervical deformity?

J Neurosurg Spine 37:368–375, 2022

Surgical correction of cervical deformity (CD) has been associated with superior alignment and functional outcomes. It has not yet been determined whether baseline or postoperative T1 slope (T1S) and C2 slope (C2S) correlate with health-related quality-of-life (HRQoL) metrics and radiographic complications, such as distal junctional kyphosis (DJK) and distal junctional failure (DJF). The objective of this study was to determine the impact of T1S and C2S deformity severity on HRQoL metrics and DJF development in patients with CD who underwent a cervical fusion procedure.

METHODS All operative CD patients with upper instrumented vertebra above C7 and preoperative (baseline) and up to 2-year postoperative radiographic and HRQoL data were included. CD was defined as meeting at least one of the following radiographic parameters: C2–7 lordosis < −15°, TS1–cervical lordosis mismatch > 35°, segmental cervical kyphosis > 15° across any 3 vertebrae between C2 and T1, C2–7 sagittal vertical axis > 4 cm, McGregor’s slope > 20°, or chin-brow vertical angle > 25°. Spearman’s rank-order correlation and linear regression analysis assessed the impact of T1S and C2S on HRQoL metrics (Neck Disability Index [NDI], modified Japanese Orthopaedic Association [mJOA] scale, EuroQOL 5-Dimension Questionnaire [EQ-5D] visual analog scale [VAS] score, and numeric rating scale [NRS]–neck) and complications (DJK, DJF, reoperation). Logistic regression and a conditional inference tree (CIT) were used to determine radiographic thresholds for achieving optimal clinical outcome, defined as meeting good clinical outcome criteria (≥ 2 of the following: NDI < 20 or meeting minimal clinically important difference, mild myelopathy [mJOA score ≥ 14], and NRS-neck ≤ 5 or improved by ≥ 2 points), not undergoing reoperation, or developing DJF or mechanical complication by 2 years.

RESULTS One hundred five patients with CD met inclusion criteria. By surgical approach, 14.7% underwent an anterioronly approach, 46.1% a posterior-only approach, and 39.2% combined anterior and posterior approaches. The mean baseline radiographic parameters were T1S 28.3° ± 14.5° and C2S 25.9° ± 17.5°. Significant associations were found between 3-month C2S and mJOA score (r = −0.248, p = 0.034), NDI (r = 0.399, p = 0.001), EQ-5D VAS (r = −0.532, p < 0.001), NRS-neck (r = 0.239, p = 0.040), and NRS-back (r = 0.264, p = 0.021), while significant correlation was also found between 3-month T1S and mJOA score (r = −0.314, p = 0.026), NDI (r = 0.445, p = 0.001), EQ-5D VAS (r = −0.347, p = 0.018), and NRS-neck (r = 0.269, p = 0.049). A significant correlation was also found between development of DJF and 3-month C2S (odds ratio [OR] 1.1, 95% confidence interval [CI] 1.01–1.1, p = 0.015) as well as for T1S (OR 1.1, 95% CI 1.01–1.1, p = 0.023). Logistic regression with CIT identified thresholds for optimal outcome by 2 years: optimal 3-month T1S < 26° (OR 5.6) and C2S < 10° (OR 10.4), severe 3-month T1S < 45.5° (OR 0.2) and C2S < 38.0° (no patient above this threshold achieved optimal outcome; all p < 0.05). Patients below both optimal thresholds achieved rates of 0% for DJK and DJF, and 100% met optimal outcome.

CONCLUSIONS The severity of CD, defined by T1S and C2S at baseline and especially at 3 months, can be predictive of postoperative functional improvement and occurrence of worrisome complications in patients with CD, necessitating the use of thresholds in surgical planning to achieve optimal outcomes.

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3D printing applications in spine surgery: an evidence‑based assessment toward personalized patient care

European Spine Journal (2022) 31:1682–1690

Spine surgery entails a wide spectrum of complicated pathologies. Over the years, numerous assistive tools have been introduced to the modern neurosurgeon’s armamentarium including neuronavigation and visualization technologies. In this review, we aimed to summarize the available data on 3D printing applications in spine surgery as well as an assessment of the future implications of 3D printing.

Methods We performed a comprehensive review of the literature on 3D printing applications in spine surgery.

Results Over the past decade, 3D printing and additive manufacturing applications, which allow for increased precision and customizability, have gained significant traction, particularly spine surgery. 3D printing applications in spine surgery were initially limited to preoperative visualization, as 3D printing had been primarily used to produce preoperative models of patient-specific deformities or spinal tumors. More recently, 3D printing has been used intraoperatively in the form of 3D customizable implants and personalized screw guides.

Conclusions Despite promising preliminary results, the applications of 3D printing are so recent that the available data regarding these new technologies in spine surgery remains scarce, especially data related to long-term outcomes.

 

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Hounsfield Unit as a Predictor of Adjacent-Level Disease in Lumbar Interbody Fusion Surgery

Neurosurgery 91:146–149, 2022

Bone density has been associated with a successful fusion rate in spine surgery. Hounsfield units (HUs) have more recently been evaluated as an indirect representation of bone density. Low preoperative HUs may be an early indicator of global disease and chronic process and, therefore, indicative of the need for future reoperation.

OBJECTIVE: To assess preoperative HUs and their association with future adjacent segment disease requiring surgical intervention through retrospective study.

METHODS: Patients who underwent lumbar interbody fusion at a single institution between 2007 and 2016 were retrospectively reviewed. Hounsfield unit values were measured from preoperative computed tomography (CT) using sagittal images, encircling cancellous portion of the vertebral body. Patient charts were reviewed for follow-up data and adjacent-level disease development.

RESULTS: A total of 793 patients (age: 56.1 ± 13.7 years, 54.4% female) were included in this study. Twenty-two patients required surgical intervention for adjacent segment disease. Patients who underwent lumbar interbody fusion and did not subsequently require surgical intervention for adjacent-level disease were found to have a higher mean preoperative HU than patients who did require reoperation (180.7 ± 70.0 vs 148.4 ± 8.1, P = .032). Preoperative CT HU was a significant independent predictor for the requirement of adjacent-level surgery after spinal arthrodesis (odds ratio = 0.891 [0.883-0.899], P = .029).

CONCLUSION: Patients who underwent lumbar interbody fusion that did not require reoperation for adjacent-level degeneration were found to have a higher mean preoperative HU than patients who did require surgical intervention. Lower preoperative CT HU was a significant independent predictor for the requirement of adjacent-level surgery after spinal arthrodesis.

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Influence of Time of Discharge and Length of Stay on 30-Day Outcomes After Elective Anterior Cervical Spine Surgery

Neurosurgery 90:734–742, 2022

Encouraging early time of discharge (TOD) for medical inpatients is commonplace and may potentially improve patient throughput. It is unclear, however, whether early TOD after elective spine surgery achieves this goal without a consequent increase in re-presentations to the hospital.

OBJECTIVE: To evaluate whether early TOD results in increased rates of hospital read- mission or return to the emergency department after elective anterior cervical spine surgery.

METHODS: We analyzed 686 patients who underwent elective uncomplicated anterior cervical spine surgery at a single institution. Logistic regression was used to evaluate the relationship between sociodemographic, procedural, and discharge characteristics, and the outcomes of readmission or return to the emergency department and TOD.

RESULTS: In multiple logistic regression, TOD was not associated with increased risk of readmission or return to the emergency department within 30 days of surgery. Weekend discharge (odds ratio [OR] 0.33, 95% CI 0.21-0.53), physical therapy evaluation (OR 0.44, 95% CI 0.28-0.71), and occupational therapy evaluation (OR 0.32, 95% CI 0.17-0.63) were all significantly associated with decreased odds of discharge before noon. Disadvantaged status, as measured by area of deprivation index, was associated with increased odds of readmission or re-presentation (OR 1.86, 95% CI 0.95-3.66), although this result did not achieve statistical significance.

CONCLUSION: There does not appear to be an association between readmission or return to the emergency department and early TOD after elective spine surgery. Overuse of inpatient physical and occupational therapy consultations may contribute to decreased patient throughput in surgical admissions.

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Spinal Arachnoid Webs

Neurosurgery 89:917–927, 2021

Spinal arachnoid webs are rarely described bands of thickened arachnoid tissue in the dorsal thoracic spine. Much is unknown regarding their origins, risk factors, natural history, and outcomes.

OBJECTIVE: To present the single largest case series, detailing presenting symptoms and outcomes amongst operative and nonoperative patients, to better understand the role of intervention.

METHODS: This retrospective chart review identified 38 patients with arachnoid webs. Patient demographics, radiologic signs, symptoms, and surgical history data were extracted from the electronic medical record. Symptoms were divided by location and character. 28 patients were successfully contacted for follow up outcome surveys.

RESULTS: 26 patients (68%) underwent surgical intervention, 12 (32%) were managed non-operatively. 15 (39%) patients had undergone a previous unsuccessful surgery at a different site for their symptoms prior to arachnoid web diagnosis. Commonly presenting symptoms included myelopathy (68%), focal thoracic back pain (68%), lower extremity weakness (45%), numbness and sensory changes (58%), and lower extremity radicular pain (42%), upper extremity weakness (24%), and radicular pain (37%). Focal thoracic pain was associated with thoracic level (P < .02). Myelopathic symptoms were less common in postoperative patients. Postoperative patients described significantly more upper extremity (P < .01) and thoracic (P < .01) numbness and paresthesias. Surveyed nonoperative patients universally described their symptoms as either stable orworsening.

CONCLUSION: Spinal arachnoid webs present with thoracic myelopathy and back pain but can also present with upper extremity symptoms. Surgical intervention stabilizes or improves symptoms and is well received. Nonoperative patients do not spontaneously improve.

 

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Tear-drop technique in iliac screw placement: a technical analysis

Acta Neurochirurgica (2021) 163:1577–1581

Instrumentation of the lumbosacral region is one of the more challenging regions due to the complex anatomical structures and biomechanical forces. Screw insertion can be done both navigated and based on X-ray verification. In this study, we demonstrate a fast and reliable open, low exposure X-ray-guided technique of iliac screw placement.

Methods Between October 2016 and August 2019, 48 patients underwent sacropelvic fixation in tear-drop technique. Screw insertion was performed in open technique by using an X-ray converter angulated 25-30° in coronal and sagittal view. The anatomical insertion point was the posterior superior iliac spine. Verification of correct screw placement was done by intraoperative 3D scan.

Results In total, 95 iliac screws were placed in tear-drop technique with a correct placement in 98.1%.

Conclusions The tear-drop technique showed a proper screw position in the intraoperative 3D scan and therefore may be considered an alternative technique to the navigated screw placement.

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The Oblique Corridor at L4-L5

SPINE Volume 45, Number 10, pp E552–E559

Study Design. Cross-sectional radioanatomical study.

Objective. The aim of this study was to analyze the prevalence, size, and location of the oblique corridor (OC), and the morphology of the psoas muscle at the L4-L5 disc level.

Summary of Background Data. Lateral lumbar interbody fusion via the OC has the advantage of avoiding injury to the psoas muscle and lumbar plexus. However, the varying anatomy of major vascular structures and the iliopsoas may preclude a safe oblique access to the L4-L5 level.

Methods. Five hundred axial magnetic resonance images of the L4-L5 disc level were shortlisted. OCs were categorized into four grades: Grade 0 ¼ no corridor, Grade 1 ¼ small corridor (1 cm), Grade 2 ¼ moderate corridor (1–2 cm) and Grade 3 ¼ large corridor (>2 cm). OC location was labeled as anterooblique, oblique, or oblique-lateral. Psoas morphology was categorized based on a modified Moro’s classification, where the anterior section was further subdivided into types AI-AIV. Oblique approach was considered nonviable either when there was no corridor due to vascular obstruction (Grade 0) or when the psoas was high-rising (Types AII-AIV).

Results. 10.5% of the selected 449 patients had no measurable OC (grade 0) at the L4-L5 level. There were 35% and 37.2% patients with a grade 1and 2 OC, respectively. The location of the OC was anterior oblique, oblique, and oblique lateral in 3.7%, 89.6%, and 6.7%, respectively. According to the modified Moro’s classification, 19.4% had a high-rising psoas. Predominantly, psoas was either in line with the disc (Type I; 30.7%) or low-rising (Type AI; 47.4%).

Conclusion. Twenty-five percent of the patients did not have an accessible OC either due to obstruction by vascular structures or due to a high-rising psoas. Hence, proper evaluation of the relevant anatomy preoperatively is recommended for early adopters of this technique, as varying anatomy precludes universal suitability of oblique lateral interbody fusion for the L4-L5 level.

Level of Evidence: 3

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Kambin’s triangle: definition and new classification schema

J Neurosurg Spine 32:390–398, 2020

Kambin’s triangle is an anatomical corridor used to access critical structures in a variety of spinal procedures. It is considered a safe space because it is devoid of vascular and neural structures of importance. Nonetheless, there is currently significant variation in the literature regarding the exact dimensions and anatomical borders of Kambin’s triangle. This confusion was originally caused by leaving the superior articular process (SAP) unassigned in the description of the working triangle, despite Kambin identifying that structure in his original report. The SAP is the most relevant structure to consider when accessing the transforaminal corridor. Leaving the SAP unassigned has led to an open-handed application of the term “Kambin’s triangle.” That single eponym currently has two potential meanings, one meaning for endoscopic surgeons working through a corridor in the intact spine and a second meaning for surgeons accessing the disc space after a complete or partial facetectomy. Nevertheless, an anatomical corridor should have one consistent definition to clearly communicate techniques and use of instrumentation performed through that space. As such, the authors propose a new surgically relevant classification of this corridor. Assigning the SAP a border requires adding another dimension to the triangle, thereby transforming it into a prism. The term “Kambin’s prism” indicates the assignment of a border to all relevant anatomical structures, allowing for a uniform definition of the 3D space. From there, the classification scheme considers the expansion of the corridor and the extent of bone removal, with a particular focus on the SAP.

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