Deep learning for automated, interpretable classification of lumbar spinal stenosis and facet arthropathy from axial MRI.

OBJECTIVES: To evaluate a deep learning model for automated and interpretable classification of central canal stenosis, neural foraminal stenosis, and facet arthropathy from lumbar spine MRI. METHODS: T2-weighted axial MRI studies of the lumbar spine acquired between 2008 and 2019 were retrospectively selected (n = 200) and graded for central canal stenosis, neural foraminal stenosis, and facet arthropathy. Studies were partitioned into patient-level train (n = 150), validation (n = 20), and test (n = 30) splits. V-Net models were first trained to segment the dural sac and the intervertebral disk, and localize facet and foramen using geometric rules. Subsequently, Big Transfer (BiT) models were trained for downstream classification tasks. An interpretable model for central canal stenosis was also trained using a decision tree classifier. Evaluation metrics included linearly weighted Cohen's kappa score for multi-grade classification and area under the receiver operator characteristic curve (AUROC) for binarized classification. RESULTS: Segmentation of the dural sac and intervertebral disk achieved Dice scores of 0.93 and 0.94. Localization of foramen and facet achieved intersection over union of 0.72 and 0.83. Multi-class grading of central canal stenosis achieved a kappa score of 0.54. The interpretable decision tree classifier had a kappa score of 0.80. Pairwise agreement between readers (R1, R2), (R1, R3), and (R2, R3) was 0.86, 0.80, and 0.74. Binary classification of neural foraminal stenosis and facet arthropathy achieved AUROCs of 0.92 and 0.93. CONCLUSION: Deep learning systems can be performant as well as interpretable for automated evaluation of lumbar spine MRI including classification of central canal stenosis, neural foraminal stenosis, and facet arthropathy. KEY POINTS: • Interpretable deep-learning systems can be developed for the evaluation of clinical lumbar spine MRI. Multi-grade classification of central canal stenosis with a kappa of 0.80 was comparable to inter-reader agreement scores (0.74, 0.80, 0.86). Binary classification of neural foraminal stenosis and facet arthropathy achieved favorable and accurate AUROCs of 0.92 and 0.93, respectively. • While existing deep-learning systems are opaque, leading to clinical deployment challenges, the proposed system is accurate as well as interpretable, providing valuable information to a radiologist in clinical practice.

Systematic review and meta-analysis of topical tranexamic acid in spine surgery.

OBJECTIVE: Tranexamic acid (TXA) is an antifibrinolytic drug associated with reduced blood loss in a range of surgical specialties, including neurosurgery, orthopedic surgery, and cardiac surgery. Concerns about venous thromboembolism and seizures from intravenous (IV) TXA have led to increased use of topical TXA. Given the relative scarcity of the literature on topical TXA compared with that on IV TXA within neurosurgery, the authors aimed to conduct a systematic review and meta-analysis on the safety, efficacy, and optimal administration of topical TXA in a wide range of spinal procedures and pathologies. METHODS: The PRISMA guidelines, Cochrane risk of bias tool, and Newcastle-Ottawa Scale were used to extract randomized controlled trials and high-quality case-control and cross-sectional/cohort studies (adult studies only) from PubMed, Web of Science, Cochrane Library, and Embase published between 2016 and 2023. Studies were analyzed by two independent reviewers for variables including dosage, TXA administration route, type of spine procedure, blood loss, adverse events including thromboembolism and infection, postoperative hemoglobin level, and hospitalization length. Pooled analysis comparing intraoperative and postoperative blood loss, postoperative hemoglobin levels, and hospitalization length of stay on the basis of route of TXA administration was conducted. RESULTS: Four cohort studies, 1 cross-sectional study, 1 case-control study, and 12 randomized controlled trials, together involving 2045 patients, were included. The most common route of topical TXA administration was via TXA in saline solution. Other routes of topical TXA included retrograde injection and TXA-soaked Gelfoam. In pooled analysis, topical TXA significantly reduced visible blood loss (standardized mean difference [SMD] -0.22, 95% CI -0.45 to -0.00001), postoperative blood loss (SMD -1.63, 95% CI -2.03 to -1.22), and length of hospital stay (SMD -1.02, 95% CI -1.42 to -0.61), as well as higher postoperative hemoglobin (SMD 0.59, 95% CI 0.34-0.83), compared with non-TXA controls. No significant differences in outcomes were found between topical and IV TXA or between combined (topical and IV) and IV TXA. Thromboembolism and infection rates did not significantly differ between any TXA administration group and non-TXA controls. CONCLUSIONS: In pooled analyses, topical TXA was associated with decreased perioperative blood loss in a wide range of scenarios, including cervical spine surgery and thoracolumbar trauma, as well as in patients with a thromboembolic history.

Minimally invasive versus open transforaminal lumbar interbody fusion for grade I lumbar spondylolisthesis: 5-year follow-up from the prospective multicenter Quality Outcomes Database registry.

OBJECTIVE: Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) has been used to treat degenerative lumbar spondylolisthesis and is associated with expedited recovery, reduced operative blood loss, and shorter hospitalizations compared to those with traditional open TLIF. However, the impact of MI-TLIF on long-term patient-reported outcomes (PROs) is less clear. Here, the authors compare the outcomes of MI-TLIF to those of traditional open TLIF for grade I degenerative lumbar spondylolisthesis at 60 months postoperatively. METHODS: The authors utilized the prospective Quality Outcomes Database registry and queried for patients with grade I degenerative lumbar spondylolisthesis who had undergone single-segment surgery via an MI or open TLIF method. PROs were compared 60 months postoperatively. The primary outcome was the Oswestry Disability Index (ODI). The secondary outcomes included the numeric rating scale (NRS) for back pain (NRS-BP), NRS for leg pain (NRS-LP), EQ-5D, North American Spine Society (NASS) satisfaction, and cumulative reoperation rate. Multivariable models were constructed to assess the impact of MI-TLIF on PROs, adjusting for variables reaching p < 0.20 on univariable analyses and respective baseline PRO values. RESULTS: The study included 297 patients, 72 (24.2%) of whom had undergone MI-TLIF and 225 (75.8%) of whom had undergone open TLIF. The 60-month follow-up rates were similar for the two cohorts (86.1% vs 75.6%, respectively; p = 0.06). Patients did not differ significantly at baseline for ODI, NRS-BP, NRS-LP, or EQ-5D (p > 0.05 for all). Perioperatively, MI-TLIF was associated with less blood loss (108.8 ± 85.6 vs 299.6 ± 242.2 ml, p < 0.001) and longer operations (228.2 ± 111.5 vs 189.6 ± 66.5 minutes, p < 0.001) but had similar lengths of hospitalizations (MI-TLIF 2.9 ± 1.8 vs open TLIF 3.3 ± 1.6 days, p = 0.08). Discharge disposition to home or home health was similar (MI-TLIF 93.1% vs open TLIF 91.1%, p = 0.60). Both cohorts improved significantly from baseline for the 60-month ODI, NRS-BP, NRS-LP, and EQ-5D (p < 0.001 for all comparisons). In adjusted analyses, MI-TLIF, compared to open TLIF, was associated with similar 60-month ODI, ODI change, odds of reaching ODI minimum clinically important difference, NRS-BP, NRS-BP change, NRS-LP, NRS-LP change, EQ-5D, EQ-5D change, and NASS satisfaction (adjusted p > 0.05 for all). The 60-month reoperation rates did not differ significantly (MI-TLIF 5.6% vs open TLIF 11.6%, p = 0.14). CONCLUSIONS: For symptomatic, single-level grade I degenerative lumbar spondylolisthesis, MI-TLIF was associated with decreased blood loss perioperatively, but there was no difference in 60-month outcomes for disability, back pain, leg pain, quality of life, or satisfaction between MI and open TLIF. There was no difference in cumulative reoperation rates between the two procedures. These results suggest that in appropriately selected patients, either procedure may be employed depending on patient and surgeon preferences.

Developing nonlinear k-nearest neighbors classification algorithms to identify patients at high risk of increased length of hospital stay following spine surgery.

OBJECTIVE: Spondylolisthesis is a common operative disease in the United States, but robust predictive models for patient outcomes remain limited. The development of models that accurately predict postoperative outcomes would be useful to help identify patients at risk of complicated postoperative courses and determine appropriate healthcare and resource utilization for patients. As such, the purpose of this study was to develop k-nearest neighbors (KNN) classification algorithms to identify patients at increased risk for extended hospital length of stay (LOS) following neurosurgical intervention for spondylolisthesis. METHODS: The Quality Outcomes Database (QOD) spondylolisthesis data set was queried for patients receiving either decompression alone or decompression plus fusion for degenerative spondylolisthesis. Preoperative and perioperative variables were queried, and Mann-Whitney U-tests were performed to identify which variables would be included in the machine learning models. Two KNN models were implemented (k = 25) with a standard training set of 60%, validation set of 20%, and testing set of 20%, one with arthrodesis status (model 1) and the other without (model 2). Feature scaling was implemented during the preprocessing stage to standardize the independent features. RESULTS: Of 608 enrolled patients, 544 met prespecified inclusion criteria. The mean age of all patients was 61.9 ± 12.1 years (± SD), and 309 (56.8%) patients were female. The model 1 KNN had an overall accuracy of 98.1%, sensitivity of 100%, specificity of 84.6%, positive predictive value (PPV) of 97.9%, and negative predictive value (NPV) of 100%. Additionally, a receiver operating characteristic (ROC) curve was plotted for model 1, showing an overall area under the curve (AUC) of 0.998. Model 2 had an overall accuracy of 99.1%, sensitivity of 100%, specificity of 92.3%, PPV of 99.0%, and NPV of 100%, with the same ROC AUC of 0.998. CONCLUSIONS: Overall, these findings demonstrate that nonlinear KNN machine learning models have incredibly high predictive value for LOS. Important predictor variables include diabetes, osteoporosis, socioeconomic quartile, duration of surgery, estimated blood loss during surgery, patient educational status, American Society of Anesthesiologists grade, BMI, insurance status, smoking status, sex, and age. These models may be considered for external validation by spine surgeons to aid in patient selection and management, resource utilization, and preoperative surgical planning.

Three-level ACDF versus 3-level laminectomy and fusion: are there differences in outcomes? An analysis of the Quality Outcomes Database cervical spondylotic myelopathy cohort.

OBJECTIVE: The authors sought to compare 3-level anterior with posterior fusion surgical procedures for the treatment of multilevel cervical spondylotic myelopathy (CSM). METHODS: The authors analyzed prospective data from the 14 highest enrolling sites of the Quality Outcomes Database CSM module. They compared 3-level anterior cervical discectomy and fusion (ACDF) and posterior cervical laminectomy and fusion (PCF) surgical procedures, excluding surgical procedures crossing the cervicothoracic junction. Rates of reaching the minimal clinically important difference (MCID) in patient-reported outcomes (PROs) were compared at 24 months postoperatively. Multivariable analyses adjusted for potential confounders elucidated in univariable analysis. RESULTS: Overall, 199 patients met the inclusion criteria: 123 ACDF (61.8%) and 76 PCF (38.2%) patients. The 24-month follow-up rates were similar (ACDF 90.2% vs PCF 92.1%, p = 0.67). Preoperatively, ACDF patients were younger (60.8 ± 10.2 vs 65.0 ± 10.3 years, p < 0.01), and greater proportions were privately insured (56.1% vs 36.8%, p = 0.02), actively employed (39.8% vs 22.8%, p = 0.04), and independently ambulatory (14.6% vs 31.6%, p < 0.01). Otherwise, the cohorts had equivalent baseline modified Japanese Orthopaedic Association (mJOA), Neck Disability Index (NDI), numeric rating scale (NRS)-arm pain, NRS-neck pain, and EQ-5D scores (p > 0.05). ACDF patients had reduced hospitalization length (1.6 vs 3.9 days, p < 0.01) and a greater proportion had nonroutine discharge (7.3% vs 22.8%, p < 0.01), but they had a higher rate of postoperative dysphagia (13.5% vs 3.5%, p = 0.049). Compared with baseline values, both groups demonstrated improvements in all outcomes at 24 months (p < 0.05). In multivariable analyses, after controlling for age, insurance payor, employment status, ambulation status, and other potential clinically relevant confounders, ACDF was associated with a greater proportion of patients with maximum satisfaction on the North American Spine Society Patient Satisfaction Index (NASS) (NASS score of 1) at 24 months (69.4% vs 53.7%, OR 2.44, 95% CI 1.17-5.09, adjusted p = 0.02). Otherwise, the cohorts shared similar 24-month outcomes in terms of reaching the MCID for mJOA, NDI, NRS-arm pain, NRS-neck pain, and EQ-5D score (adjusted p > 0.05). There were no differences in the 3-month readmission (ACDF 4.1% vs PCF 3.9%, p = 0.97) and 24-month reoperation (ACDF 13.5% vs PCF 18.6%, p = 0.36) rates. CONCLUSIONS: In a cohort limited to 3-level fusion surgical procedures, ACDF was associated with reduced blood loss, shorter hospitalization length, and higher routine home discharge rates; however, PCF resulted in lower rates of postoperative dysphagia. The procedures yielded comparably significant improvements in functional status (mJOA score), neck and arm pain, neck pain-related disability, and quality of life at 3, 12, and 24 months. ACDF patients had significantly higher odds of maximum satisfaction (NASS score 1). Given comparable outcomes, patients should be counseled on each approach's complication profile to aid in surgical decision-making.

Which supervised machine learning algorithm can best predict achievement of minimum clinically important difference in neck pain after surgery in patients with cervical myelopathy? A QOD study.

OBJECTIVE: The purpose of this study was to evaluate the performance of different supervised machine learning algorithms to predict achievement of minimum clinically important difference (MCID) in neck pain after surgery in patients with cervical spondylotic myelopathy (CSM). METHODS: This was a retrospective analysis of the prospective Quality Outcomes Database CSM cohort. The data set was divided into an 80% training and a 20% test set. Various supervised learning algorithms (including logistic regression, support vector machine, decision tree, random forest, extra trees, gaussian naïve Bayes, k-nearest neighbors, multilayer perceptron, and extreme gradient boosted trees) were evaluated on their performance to predict achievement of MCID in neck pain at 3 and 24 months after surgery, given a set of predicting baseline features. Model performance was assessed with accuracy, F1 score, area under the receiver operating characteristic curve, precision, recall/sensitivity, and specificity. RESULTS: In total, 535 patients (46.9%) achieved MCID for neck pain at 3 months and 569 patients (49.9%) achieved it at 24 months. In each follow-up cohort, 501 patients (93.6%) were satisfied at 3 months after surgery and 569 patients (100%) were satisfied at 24 months after surgery. Of the supervised machine learning algorithms tested, logistic regression demonstrated the best accuracy (3 months: 0.76 ± 0.031, 24 months: 0.773 ± 0.044), followed by F1 score (3 months: 0.759 ± 0.019, 24 months: 0.777 ± 0.039) and area under the receiver operating characteristic curve (3 months: 0.762 ± 0.027, 24 months: 0.773 ± 0.043) at predicting achievement of MCID for neck pain at both follow-up time points, with fair performance. The best precision was also demonstrated by logistic regression at 3 (0.724 ± 0.058) and 24 (0.780 ± 0.097) months. The best recall/sensitivity was demonstrated by multilayer perceptron at 3 months (0.841 ± 0.094) and by extra trees at 24 months (0.817 ± 0.115). Highest specificity was shown by support vector machine at 3 months (0.952 ± 0.013) and by logistic regression at 24 months (0.747 ± 0.18). CONCLUSIONS: Appropriate selection of models for studies should be based on the strengths of each model and the aims of the studies. For maximally predicting true achievement of MCID in neck pain, of all the predictions in this balanced data set the appropriate metric for the authors' study was precision. For both short- and long-term follow-ups, logistic regression demonstrated the highest precision of all models tested. Logistic regression performed consistently the best of all models tested and remains a powerful model for clinical classification tasks.

Greater improvement in Neck Disability Index scores in women after surgery for cervical myelopathy: an analysis of the Quality Outcomes Database.

OBJECTIVE: There is a high prevalence of cervical myelopathy that requires surgery; as such, it is important to identify how different groups benefit from surgery. The American Association of Neurological Surgeons launched the Quality Outcomes Database (QOD), a prospective longitudinal registry, that includes demographic, clinical, and patient-reported outcome data to measure the safety and quality of neurosurgical procedures. In this study, the authors assessed the impact of gender on patient-reported outcomes in patients who underwent surgery for cervical myelopathy. METHODS: The authors analyzed 1152 patients who underwent surgery for cervical myelopathy and were included in the QOD cervical module. Univariate comparison of baseline patient characteristics between males and females who underwent surgery for cervical spondylotic myelopathy was performed. Baseline characteristics that significantly differed between males and females were included in a multivariate generalized linear model comparing baseline and 1-year postoperative Neck Disability Index (NDI) scores. RESULTS: This study included 546 females and 604 males. Females demonstrated significantly greater improvement in NDI score 1 year after surgery (p = 0.036). In addition to gender, the presence of axial neck pain and insurance status were also significantly predictive of improvement in NDI score after surgery (p = 0.0013 and p = 0.0058, respectively). CONCLUSIONS: Females were more likely to benefit from surgery for cervical myelopathy compared with males. It is important to identify gender differences in postoperative outcomes after surgery in order to deliver more personalized and patient-centric care.

Single-cell transcriptome profiling reveals intra-tumoral heterogeneity in human chordomas.

Chordoma is a rare and aggressive bone tumor. An accurate investigation of tumor heterogeneity is necessary for the development of effective therapeutic strategies. This study aims to assess the poorly understood tumor heterogeneity of chordomas and identify potential therapeutic targets. Single-cell RNA sequencing was performed to delineate the transcriptomic landscape of chordomas. Six tumor samples of chordomas were obtained, and 33,737 cells passed the quality control test and were analyzed. The main cellular populations identified with specific markers were as follows: chordoma cells (16,052 [47.6%]), fibroblasts (6945 [20.6%]), mononuclear phagocytes (4734 [14.0%]), and T/natural killer (NK) cells (3944 [11.7%]). Downstream analysis of each cell type was performed. Six subclusters of chordomas exhibited properties of an epithelial-like extracellular matrix, stem cells, and immunosuppressive activity. Although few immune checkpoints were detected on cytotoxic immune cells such as T and NK cells, a strong immunosuppressive effect was exerted on the Tregs and M2 macrophages. In addition, the cellular interactions were indicative of enhancement of the TGF-ß signaling pathway being the main mechanism for tumor progression, invasion, and immunosuppression. These findings, especially from the analysis of molecular targeted therapy and tumor immune microenvironment, may help in the identification of therapeutic targets in chordomas.

Awake spinal surgery: simplifying the learning curve with a patient selection algorithm.

OBJECTIVE: There is a learning curve for surgeons performing "awake" spinal surgery. No comprehensive guidelines have been proposed for the selection of ideal candidates for awake spinal fusion or decompression. The authors sought to formulate an algorithm to aid in patient selection for surgeons who are in the startup phase of awake spinal surgery. METHODS: The authors developed an algorithm for selecting patients appropriate for awake spinal fusion or decompression using spinal anesthesia supplemented with mild sedation and local analgesia. The anesthetic protocol that was used has previously been reported in the literature. This algorithm was formulated based on a multidisciplinary team meeting and used in the first 15 patients who underwent awake lumbar surgery at a single institution. RESULTS: A total of 15 patients who underwent decompression or lumbar fusion using the awake protocol were reviewed. The mean patient age was 61 ± 12 years, with a median BMI of 25.3 (IQR 2.7) and a mean Charlson Comorbidity Index of 2.1 ± 1.7; 7 patients (47%) were female. Key patient inclusion criteria were no history of anxiety, 1 to 2 levels of lumbar pathology, moderate stenosis and/or grade I spondylolisthesis, and no prior lumbar surgery at the level where the needle is introduced for anesthesia. Key exclusion criteria included severe and critical central canal stenosis or patients who did not meet the inclusion criteria. Using the novel algorithm, 14 patients (93%) successfully underwent awake spinal surgery without conversion to general anesthesia. One patient (7%) was converted to general anesthesia due to insufficient analgesia from spinal anesthesia. Overall, 93% (n = 14) of the patients were assessed as American Society of Anesthesiologists class II, with 1 patient (7%) as class III. The mean operative time was 115 minutes (± 60 minutes) with a mean estimated blood loss of 46 ± 39 mL. The median hospital length of stay was 1.3 days (IQR 0.1 days). No patients developed postoperative complications and only 1 patient (7%) required reoperation. The mean Oswestry Disability Index score decreased following operative intervention by 5.1 ± 10.8. CONCLUSIONS: The authors propose an easy-to-use patient selection algorithm with the aim of assisting surgeons with patient selection for awake spinal surgery while considering BMI, patient anxiety, levels of surgery, and the extent of stenosis. The algorithm is specifically intended to assist surgeons who are in the learning curve of their first awake spinal surgery cases.

An analysis of tumor-related potential spinal column instability (Spine Instability Neoplastic Scores 7-12) eventually requiring surgery with a 1-year follow-up.

OBJECTIVE: Within the Spine Instability Neoplastic Score (SINS) classification, tumor-related potential spinal instability (SINS 7-12) may not have a clear treatment approach. The authors aimed to examine the proportion of patients in this indeterminate zone who later required surgical stabilization after initial nonoperative management. By studying this patient population, they sought to determine if a clear SINS cutoff existed whereby the spine is potentially unstable due to a lesion and would be more likely to require stabilization. METHODS: Records from patients treated at the University of California, San Francisco, for metastatic spine disease from 2005 to 2019 were retrospectively reviewed. Seventy-five patients with tumor-related potential spinal instability (SINS 7-12) who were initially treated nonoperatively were included. All patients had at least a 1-year follow-up with complete medical records. A univariate chi-square test and Student t-test were used to compare categorical and continuous outcomes, respectively, between patients who ultimately underwent surgery and those who did not. A backward likelihood multivariate binary logistic regression model was used to investigate the relationship between clinical characteristics and surgical intervention. Recursive partitioning analysis (RPA) and single-variable logistic regression were performed as a function of SINS. RESULTS: Seventy-five patients with a total of 292 spinal metastatic sites were included in this study; 26 (34.7%) patients underwent surgical intervention, and 49 (65.3%) did not. There was no difference in age, sex, comorbidities, or lesion location between the groups. However, there were more patients with a SINS of 12 in the surgery group (55.2%) than in the no surgery group (44.8%) (p = 0.003). On multivariate analysis, SINS > 11 (OR 8.09, CI 1.96-33.4, p = 0.004) and Karnofsky Performance Scale (KPS) score < 60 (OR 0.94, CI 0.89-0.98, p = 0.008) were associated with an increased risk of surgery. KPS score was not correlated with SINS (p = 0.4). RPA by each spinal lesion identified an optimal cutoff value of SINS > 10, which were associated with an increased risk of surgical intervention. Patients with a surgical intervention had a higher incidence of complications on multivariable analysis (OR 2.96, CI 1.01-8.71, p = 0.048). CONCLUSIONS: Patients with a mean SINS of 11 or greater may be at increased risk of mechanical instability requiring surgery after initial nonoperative management. RPA showed that patients with a KPS score of 60 or lower and a SINS of greater than 10 had increased surgery rates.

Single versus dual operative spine fractures in ankylosing spondylitis.

OBJECTIVE: Ankylosing spondylitis, the most common spondyloarthritis, fuses individual spinal vertebrae into long segments. The unique biomechanics of the ankylosed spine places patients at unusually high risk for unstable fractures secondary to low-impact mechanisms. These injuries are unique within the spine trauma population and necessitate thoughtful management. Therefore, the authors aimed to present a richly annotated data set of operative AS spine fractures with a significant portion of patients with simultaneous dual noncontiguous fractures. METHODS: Patients with ankylosing spondylitis with acute fractures who received operative management between 2012 and 2020 were reviewed. Demographic, admission, surgical, and outcome parameters were retrospectively collected and reviewed. RESULTS: In total, 29 patients were identified across 30 different admissions. At admission, the mean age was 71.7 ± 11.8 years. The mechanism of injury in 77% of the admissions was a ground-level fall; 30% also presented with polytrauma. Of admissions, 50% were patient transfers from outside hospitals, whereas the other half presented primarily to our emergency departments. Fifty percent of patients sustained a spinal cord injury, and 35 operative fractures were identified and treated in 32 surgeries. The majority of fractures clustered around the cervicothoracic (C4-T1, 48.6%) and thoracolumbar (T8-L3, 37.11%) junctions. Five patients (17.2%) had simultaneous dual noncontiguous operative fractures; these patients were more likely to have presented with a higher-energy mechanism of injury such as a bicycle or motor vehicle accident compared with patients with a single operative fracture (60% vs 8%, p = 0.024). On preoperative MRI, 56.3% of the fractures had epidural hematomas (EDHs); 25% were compressive of the underlying neural elements, which dictated the number of laminectomy levels performed (no EDH, 2.1 ± 2.36; noncompressive EDH, 2.1 ± 1.85; and compressive EDH, 7.4 ± 4 [p = 0.003]). The mean difference in instrumented levels was 8.7 ± 2.6 with a mean estimated blood loss (EBL) of 1183 ± 1779.5 mL. Patients on a regimen of antiplatelet therapy had a significantly higher EBL (2635.7 mL vs 759.4 mL, p = 0.015). Overall, patients had a mean hospital length of stay of 15.2 ± 18.5 days; 5 patients died during the same admission or after transfer to an outside hospital. Nine of 29 patients (31%) had died by the last follow-up (the mean follow-up was 596.3 ± 878.9 days). CONCLUSIONS: Patients with AS who have been found to have unstable spine fractures warrant a thorough diagnostic evaluation to identify secondary fractures as well as compressive EDHs. These patients experienced prolonged inpatient hospitalizations with significant morbidity and mortality.

Feasibility of achieving planned surgical margins in primary spine tumor: a PTRON study.

OBJECTIVE: Oncological resection of primary spine tumors is associated with lower recurrence rates. However, even in the most experienced hands, the execution of a meticulously drafted plan sometimes fails. The objectives of this study were to determine how successful surgical teams are at achieving planned surgical margins and how successful surgeons are in intraoperatively assessing tumor margins. The secondary objective was to identify factors associated with successful execution of planned resection. METHODS: The Primary Tumor Research and Outcomes Network (PTRON) is a multicenter international prospective registry for the management of primary tumors of the spine. Using this registry, the authors compared 1) the planned surgical margin and 2) the intraoperative assessment of the margin by the surgeon with the postoperative assessment of the margin by the pathologist. Univariate analysis was used to assess whether factors such as histology, size, location, previous radiotherapy, and revision surgery were associated with successful execution of the planned margins. RESULTS: Three hundred patients were included. The surgical plan was successfully achieved in 224 (74.7%) patients. The surgeon correctly assessed the intraoperative margins, as reported in the final assessment by the pathologist, in 239 (79.7%) patients. On univariate analysis, no factor had a statistically significant influence on successful achievement of planned margins. CONCLUSIONS: In high-volume cancer centers around the world, planned surgical margins can be achieved in approximately 75% of cases. The morbidity of the proposed intervention must be balanced with the expected success rate in order to optimize patient management and surgical decision-making.

The association between lower Hounsfield units on computed tomography and cage subsidence after lateral lumbar interbody fusion.

OBJECTIVE: One vexing problem after lateral lumbar interbody fusion (LLIF) surgery is cage subsidence. Low bone mineral density (BMD) may contribute to subsidence, and BMD is correlated with Hounsfield units (HUs) on CT. The authors investigated if lower HU values correlated with subsidence after LLIF. METHODS: A retrospective study of patients undergoing single-level LLIF with pedicle screw fixation for degenerative conditions at the University of California, San Francisco, by 6 spine surgeons was performed. Data on demographics, cage parameters, preoperative HUs on CT, and postoperative subsidence were collected. Thirty-six-inch standing radiographs were used to measure segmental lordosis, disc space height, and subsidence; data were collected immediately postoperatively and at 1 year. Subsidence was graded using a published grade of disc height loss: grade 0, 0%-24%; grade I, 25%-49%; grade II, 50%-74%; and grade III, 75%-100%. HU values were measured on preoperative CT from L1 to L5, and each lumbar vertebral body HU was measured 4 separate times. RESULTS: After identifying 138 patients who underwent LLIF, 68 met the study inclusion criteria. All patients had single-level LLIF with pedicle screw fixation. The mean follow-up duration was 25.3 ± 10.4 months. There were 40 patients who had grade 0 subsidence, 15 grade I, 9 grade II, and 4 grade III. There were no significant differences in age, sex, BMI, or smoking. There were no significant differences in cage sizes, cage lordosis, and preoperative disc height. The mean segmental HU (the average HU value of the two vertebrae above and below the LLIF) was 169.5 ± 45 for grade 0, 130.3 ± 56.2 for grade I, 100.7 ± 30.2 for grade II, and 119.9 ± 52.9 for grade III (p < 0.001). After using a receiver operating characteristic curve to establish separation criteria between mild and severe subsidence, the most appropriate threshold of HU value was 135.02 between mild and severe subsidence (sensitivity 60%, specificity 92.3%). After univariate and multivariate analysis, preoperative segmental HU value was an independent risk factor for severe cage subsidence (p = 0.017, OR 15.694, 95% CI 1.621-151.961). CONCLUSIONS: Lower HU values on preoperative CT are associated with cage subsidence after LLIF. Measurement of preoperative HU values on CT may be useful when planning LLIF surgery.

The association between lower Hounsfield units of the upper instrumented vertebra and proximal junctional kyphosis in adult spinal deformity surgery with a minimum 2-year follow-up.

OBJECTIVE: Patients undergoing long-segment fusions from the lower thoracic (LT) spine to the sacrum for adult spinal deformity (ASD) correction are at risk for proximal junctional kyphosis (PJK). One mechanism of PJK is fracture of the upper instrumented vertebra (UIV) or higher (UIV+1), which may be related to bone mineral density (BMD). Because Hounsfield units (HUs) on CT correlate with BMD, the authors evaluated whether HU values were correlated with PJK after long fusions for ASD. METHODS: The authors performed a retrospective study of patients older than 50 years who had undergone ASD correction from the LT spine to the sacrum in the period from October 2007 to January 2018 and had a minimum 2-year follow-up. Demographic and spinopelvic parameters were measured. HU values were measured on preoperative CT at the UIV, UIV+1, and UIV+2 (2 levels above the UIV) levels and were assessed for correlations with PJK. RESULTS: The records of 127 patients were reviewed. Fifty-four patients (19 males and 35 females) with a mean age of 64.91 years and mean follow-up of 3.19 years met the study inclusion criteria; there were 29 patients with PJK and 25 patients without. There was no statistically significant difference in demographics or follow-up between these two groups. Neither was there a difference between the groups with regard to postoperative pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL), PI minus LL (PI-LL), thoracic kyphosis (TK), or sagittal vertical axis (SVA; all p > 0.05). Postoperative pelvic tilt (p = 0.003) and T1 pelvic angle (p = 0.014) were significantly higher in patients with PJK than in those without. Preoperative HUs at UIV, UIV+1, and UIV+2 were 120.41, 124.52, and 129.28 in the patients with PJK, respectively, and 152.80, 155.96, and 160.00 in the patients without PJK, respectively (p = 0.011, 0.02, and 0.018). Three receiver operating characteristic (ROC) curves for preoperative HU values at the UIV, UIV+1, and UIV+2 as a predictor for PJK were established, with areas under the ROC curve of 0.710 (95% CI 0.574-0.847), 0.679 (95% CI 0.536-0.821), and 0.681 (95% CI 0.539-0.824), respectively. The optimal HU value by Youden index was 104 HU at the UIV (sensitivity 0.840, specificity 0.517), 113 HU at the UIV+1 (sensitivity 0.720, specificity 0.517), and 110 HU at the UIV+2 (sensitivity 0.880, specificity 0.448). CONCLUSIONS: In patients undergoing long-segment fusions from the LT spine to the sacrum for ASD, PJK was associated with lower HU values on CT at the UIV, UIV+1, and UIV+2. The measurement of HU values on preoperative CTs may be a useful adjunct for ASD surgery planning.

Clamshell thoracotomy for en bloc resection of a 3-level thoracic chordoma: technical note and operative video.

The clamshell thoracotomy is often used to access both hemithoraxes and the mediastinum simultaneously for cardiothoracic pathology, but this technique is rarely used for the excision of spinal tumors. We describe the use of a clamshell thoracotomy for en bloc excision of a 3-level upper thoracic chordoma in a 20-year-old patient. The lesion involved T2, T3, and T4, and it invaded both chest cavities and indented the mediastinum. After 2 biopsies to confirm the diagnosis, the patient underwent a posterior spinal fusion followed by bilateral clamshell thoracotomy for 3-level en bloc resection with simultaneous access to both chest cavities and the mediastinum. To demonstrate how the clamshell thoracotomy was used to facilitate the tumor resection, an operative video and illustrations are provided, which show in detail how the clamshell thoracotomy can be used to access both hemithoraxes and the mediastinum.

The effect of anterior lumbar interbody fusion staging order on perioperative complications in circumferential lumbar fusions performed within the same hospital admission.

OBJECTIVE: Anterior lumbar interbody fusion (ALIF) is a powerful technique that provides wide access to the disc space and allows for large lordotic grafts. When used with posterior spinal fusion (PSF), the procedures are often staged within the same hospital admission. There are limited data on the perioperative risk profile of ALIF-first versus PSF-first circumferential fusions performed within the same hospital admission. In an effort to understand whether these procedures are associated with different perioperative complication profiles, the authors performed a retrospective review of their institutional experience in adult patients who had undergone circumferential lumbar fusions. METHODS: The electronic medicals records of patients who had undergone ALIF and PSF on separate days within the same hospital admission at a single academic center were retrospectively analyzed. Patients carrying a diagnosis of tumor, infection, or traumatic fracture were excluded. Demographics, surgical characteristics, and perioperative complications were collected and assessed. RESULTS: A total of 373 patients, 217 of them women (58.2%), met the inclusion criteria. The mean age of the study cohort was 60 years. Surgical indications were as follows: degenerative disease or spondylolisthesis, 171 (45.8%); adult deformity, 168 (45.0%); and pseudarthrosis, 34 (9.1%). The majority of patients underwent ALIF first (321 [86.1%]) with a mean time of 2.5 days between stages. The mean number of levels fused was 2.1 for ALIF and 6.8 for PSF. In a comparison of ALIF-first to PSF-first cases, there were no major differences in demographics or surgical characteristics. Rates of intraoperative complications including venous injury were not significantly different between the two groups. The rates of postoperative ileus (11.8% vs 5.8%, p = 0.194) and ALIF-related wound complications (9.0% vs 3.8%, p = 0.283) were slightly higher in the ALIF-first group, although the differences did not reach statistical significance. Rates of other perioperative complications were no different. CONCLUSIONS: In patients undergoing staged circumferential fusion with ALIF and PSF, there was no statistically significant difference in the rate of perioperative complications when comparing ALIF-first to PSF-first surgeries.

Does state malpractice environment affect outcomes following spinal fusions? A robust statistical and machine learning analysis of 549,775 discharges following spinal fusion surgery in the United States.

OBJECTIVE: Spine surgery is especially susceptible to malpractice claims. Critics of the US medical liability system argue that it drives up costs, whereas proponents argue it deters negligence. Here, the authors study the relationship between malpractice claim density and outcomes. METHODS: The following methods were used: 1) the National Practitioner Data Bank was used to determine the number of malpractice claims per 100 physicians, by state, between 2005 and 2010; 2) the Nationwide Inpatient Sample was queried for spinal fusion patients; and 3) the Area Resource File was queried to determine the density of physicians, by state. States were categorized into 4 quartiles regarding the frequency of malpractice claims per 100 physicians. To evaluate the association between malpractice claims and death, discharge disposition, length of stay (LOS), and total costs, an inverse-probability-weighted regression-adjustment estimator was used. The authors controlled for patient and hospital characteristics. Covariates were used to train machine learning models to predict death, discharge disposition not to home, LOS, and total costs. RESULTS: Overall, 549,775 discharges following spinal fusions were identified, with 495,640 yielding state-level information about medical malpractice claim frequency per 100 physicians. Of these, 124,425 (25.1%), 132,613 (26.8%), 130,929 (26.4%), and 107,673 (21.7%) were from the lowest, second-lowest, second-highest, and highest quartile states, respectively, for malpractice claims per 100 physicians. Compared to the states with the fewest claims (lowest quartile), surgeries in states with the most claims (highest quartile) showed a statistically significantly higher odds of a nonhome discharge (OR 1.169, 95% CI 1.139-1.200), longer LOS (mean difference 0.304, 95% CI 0.256-0.352), and higher total charges (mean difference [log scale] 0.288, 95% CI 0.281-0.295) with no significant associations for mortality. For the machine learning models-which included medical malpractice claim density as a covariate-the areas under the curve for death and discharge disposition were 0.94 and 0.87, and the R2 values for LOS and total charge were 0.55 and 0.60, respectively. CONCLUSIONS: Spinal fusion procedures from states with a higher frequency of malpractice claims were associated with an increased odds of nonhome discharge, longer LOS, and higher total charges. This suggests that medicolegal climate may potentially alter practice patterns for a given spine surgeon and may have important implications for medical liability reform. Machine learning models that included medical malpractice claim density as a feature were satisfactory in prediction and may be helpful for patients, surgeons, hospitals, and payers.

Perioperative Gabapentin Does Not Reduce Postoperative Delirium in Older Surgical Patients: A Randomized Clinical Trial.

BACKGROUND: Postoperative pain and opioid use are associated with postoperative delirium. We designed a single-center, randomized, placebo-controlled, parallel-arm, double-blinded trial to determine whether perioperative administration of gabapentin reduced postoperative delirium after noncardiac surgery. METHODS: Patients were randomly assigned to receive placebo (N = 347) or gabapentin 900 mg (N = 350) administered preoperatively and for the first 3 postoperative days. The primary outcome was postoperative delirium as measured by the Confusion Assessment Method. Secondary outcomes were postoperative pain, opioid use, and length of hospital stay. RESULTS: Data for 697 patients were included, with a mean ± SD age of 72 ± 6 yr. The overall incidence of postoperative delirium in any of the first 3 days was 22.4% (24.0% in the gabapentin and 20.8% in the placebo groups; the difference was 3.20%; 95% CI, 3.22% to 9.72%; P = 0.30). The incidence of delirium did not differ between the two groups when stratified by surgery type, anesthesia type, or preoperative risk status. Gabapentin was shown to be opioid sparing, with lower doses for the intervention group versus the control group. For example, the morphine equivalents for the gabapentin-treated group, median 6.7 mg (25th, 75th quartiles: 1.3, 20.0 mg), versus control group, median 6.7 mg (25th, 75th quartiles: 2.7, 24.8 mg), differed on the first postoperative day (P = 0.04). CONCLUSIONS: Although postoperative opioid use was reduced, perioperative administration of gabapentin did not result in a reduction of postoperative delirium or hospital length of stay.

Stereotactic navigation for the prepsoas oblique lateral lumbar interbody fusion: technical note and case series.

The prepsoas retroperitoneal approach is a minimally invasive technique used for anterior lumbar interbody fusion. The approach may have a more favorable risk profile than the transpsoas approach, decreasing the risks that come with dissecting through the psoas muscle. However, the oblique angle of the spine in the prepsoas approach can be disorienting and challenging. This technical report provides an overview of the use of navigation in prepsoas oblique lateral lumbar interbody fusion in a series of 49 patients.