Surgical Approaches to Tumors of the Occipito-Cervical, Subaxial Cervical, and Cervicothoracic Spine: An Algorithm for Standard versus Extended Anterior Cervical Access.

OBJECTIVE: To propose a surgical approach algorithm for the tumors of the cervicothoracic spine. METHODS: All patients operated for vertebral column tumors involving the occipito-cervicothoracic spine were reviewed. Oncologic characteristics and surgical approach were gathered. Approach was classified by the use of staging and trajectory (posterior, transnasal, transoral, transmandibular, transcervical, transsternal). Angle of attack was defined for the occipitocervical junction tumor as the angle inscribed by the inferior mandibular plane and line connecting the superior tumor pole and mandibular angle. For lesions extending below the thoracic inlet, angle of attack was that inscribed by the plane of the thoracic inlet and the line connecting the jugular notch and inferior tumor pole. RESULTS: In total, 115 patients were included (mean age 56.7 years, 64 [56%] male, average size 26.5 cm3, 39 [34%] primary tumors). Sixty-nine (60%) of patients had single-stage procedures (57 [49.6%] posterior-only, 12 [10.4%] anterior-only), 35 (30.4%) had 2-stage procedures, and 11 (9.6%) had 3- or 4-stage approaches. Lesions requiring a combined transmandibular-transcervical approach all involved the C2 and C3 levels and had a significantly steeper angle of attack (42.5 ± 9.5 vs. 6.1 ± 13.3°; P = 0.01) and greater superior tumor extent above the inferior plane of the mandible (3.69 ± 2.18 vs. 0.33 ± 0.78; P = 0.002). Lateral tumor extent, tumor size, nor inferior angle of attack differed significantly between approach groups. CONCLUSIONS: Here, we present a preliminary decision-making algorithm for the management of vertebral column tumors of the cervicothoracic spine. Based on this single-center experience, we suggest which patients, assessed via a combination of tumor histology and regional anatomy, may benefit from extended anterior surgical access.

Surgical Decompression for Cervical Spondylotic Myelopathy in Patients with Associated Hypertension: A Single-Center Retrospective Cohort and Systematic Review of the Literature.

OBJECTIVE: To explore the relationship between spinal cord compression and hypertension through analysis of blood pressure (BP) variations in a cervical spondylotic myelopathy (CSM) cohort after surgical decompression, along with a review of the literature. METHODS: A single-institution retrospective review of patients with CSM who underwent cervical decompression between 2016 and 2017 was conducted. Baseline clinical and imaging characteristics, preoperative and postoperative BP readings, heart rate, functional status, and pain scores were collected. In addition, a PRISMA guidelines-based systematic review was performed. RESULTS: We identified 264 patients with CSM treated surgically; 149 (56.4%) of these had hypertension. The degree of spinal canal compromise and spinal cord compression, preoperative neurologic examination, and the presence of T2-signal hyperintensity on magnetic resonance imaging were associated with hypertension. Overall mean arterial pressure (MAP) decreased significantly at 1 and 12 months after surgery. Patients without T2-signal hyperintensity on imaging showed a MAP reduction at 12 months postoperatively, whereas those with T2-signal hyperintensity showed a transient MAP reduction at 1 month postoperatively before returning to preoperative values. At 12 months after surgery, 24 of 97 patients (24.7%) with initially uncontrolled hypertension had controlled BP values with significant reduction of MAP, systolic BP, and diastolic BP. Including the present study, 5 articles were eligible for systematic review, with all reporting a BP decrease in patients with CSM after decompression. CONCLUSIONS: Analysis of our retrospective cohort and a systematic review suggest that cervical surgical decompression reduces BP in some patients with CSM. However, this improvement is less apparent in patients with preoperative spinal cord T2-signal hyperintensity.

Posterior Vertebral Column Subtraction Osteotomy for Recurrent Tethered Cord Syndrome: A Multicenter, Retrospective Analysis.

BACKGROUND: Few have explored the safety and efficacy of posterior vertebral column subtraction osteotomy (PVCSO) to treat tethered cord syndrome (TCS). OBJECTIVE: To evaluate surgical outcomes after PVCSO in adults with TCS caused by lipomyelomeningocele, who had undergone a previous detethering procedure(s) that ultimately failed. METHODS: This is a multicenter, retrospective analysis of a prospectively collected cohort. Patients were prospectively enrolled and treated with PVCSO at 2 institutions between January 1, 2011 and December 31, 2018. Inclusion criteria were age ≥18 yr, TCS caused by lipomyelomeningocele, previous detethering surgery, and recurrent symptom progression of less than 2-yr duration. All patients undergoing surgery with a 1-yr minimum follow-up were evaluated. RESULTS: A total of 20 patients (mean age: 36 yr; sex: 15F/5M) met inclusion criteria and were evaluated. At follow-up (mean: 23.3 ± 7.4 mo), symptomatic improvement/resolution was seen in 93% of patients with leg pain, 84% in back pain, 80% in sensory abnormalities, 80% in motor deficits, 55% in bowel incontinence, and 50% in urinary incontinence. Oswestry Disability Index improved from a preoperative mean of 57.7 to 36.6 at last follow-up (P < .01). Mean spinal column height reduction was 23.4 ± 2.7 mm. Four complications occurred: intraoperative durotomy (no reoperation), wound infection, instrumentation failure requiring revision, and new sensory abnormality. CONCLUSION: This is the largest study to date assessing the safety and efficacy of PVCSO in adults with TCS caused by lipomyelomeningocele and prior failed detethering. We found PVCSO to be an excellent extradural approach that may afford definitive treatment in this particularly challenging population.

Interventions to minimize blood loss and transfusion risk in spine surgery: A narrative review.

Blood loss is an inevitable reality of spine surgery. Excessive loss is associated with increased morbidity and mortality and is frequently combated with allogeneic blood transfusions. Transfusions themselves are associated with increased morbidity, including circulatory overload, lung injury, and acute kidney injury. It is therefore incumbent upon the practicing spine surgeon to be aware of evidence-based interventions capable of reducing blood loss and the risk of transfusion. Here we review the available literature and make recommendation based upon the available evidence.

Incidental durotomy: predictive risk model and external validation of natural language process identification algorithm.

OBJECTIVE: Incidental durotomy is a common complication of elective lumbar spine surgery seen in up to 11% of cases. Prior studies have suggested patient age and body habitus along with a history of prior surgery as being associated with an increased risk of dural tear. To date, no calculator has been developed for quantifying risk. Here, the authors' aim was to identify independent predictors of incidental durotomy, present a novel predictive calculator, and externally validate a novel method to identify incidental durotomies using natural language processing (NLP). METHODS: The authors retrospectively reviewed all patients who underwent elective lumbar spine procedures at a tertiary academic hospital for degenerative pathologies between July 2016 and November 2018. Data were collected regarding surgical details, patient demographic information, and patient medical comorbidities. The primary outcome was incidental durotomy, which was identified both through manual extraction and the NLP algorithm. Multivariable logistic regression was used to identify independent predictors of incidental durotomy. Bootstrapping was then employed to estimate optimism in the model, which was corrected for; this model was converted to a calculator and deployed online. RESULTS: Of the 1279 elective lumbar surgery patients included in this study, incidental durotomy occurred in 108 (8.4%). Risk factors for incidental durotomy on multivariable logistic regression were increased surgical duration, older age, revision versus index surgery, and case starts after 4 pm. This model had an area under curve (AUC) of 0.73 in predicting incidental durotomies. The previously established NLP method was used to identify cases of incidental durotomy, of which it demonstrated excellent discrimination (AUC 0.97). CONCLUSIONS: Using multivariable analysis, the authors found that increased surgical duration, older patient age, cases started after 4 pm, and a history of prior spine surgery are all independent positive predictors of incidental durotomy in patients undergoing elective lumbar surgery. Additionally, the authors put forth the first version of a clinical calculator for durotomy risk that could be used prospectively by spine surgeons when counseling patients about their surgical risk. Lastly, the authors presented an external validation of an NLP algorithm used to identify incidental durotomies through the review of free-text operative notes. The authors believe that these tools can aid clinicians and researchers in their efforts to prevent this costly complication in spine surgery.

Comparison of complete and near-complete endovascular embolization of hypervascular spine tumors with partial embolization.

OBJECTIVE: Preoperative endovascular embolization of hypervascular spine tumors can reduce intraoperative blood loss. The extent to which subtotal embolization reduces blood loss has not been clearly established. This study aimed to elucidate a relationship between the extent of preoperative embolization and intraoperative blood loss. METHODS: Sixty-six patients undergoing preoperative endovascular embolization and subsequent resection of hypervascular spine tumors were retrospectively reviewed. Patients were divided into 3 groups: complete embolization (n = 22), near-complete embolization (≥ 90% but < 100%; n = 22), and partial embolization (< 90%; n = 22). Intraoperative blood loss was compared between groups using one-way ANOVA with post hoc comparisons between groups. RESULTS: The average blood loss in the complete embolization group was 1625 mL. The near-complete embolization group had an average blood loss of 2021 mL in surgery. Partial embolization was associated with a mean blood loss of 4009 mL. On one-way ANOVA, significant differences were seen across groups (F-ratio = 6.81, p = 0.002). Significant differences in intraoperative blood loss were also seen between patients undergoing complete and partial embolization (p = 0.001) and those undergoing near-complete and partial embolization (p = 0.006). Pairwise testing showed no significant difference between complete and near-complete embolization (p = 0.57). Analysis of a combined group of complete and near-complete embolization also showed a significantly decreased blood loss compared with partial embolization (p < 0.001). Patient age, tumor size, preoperative coagulation parameters, and preoperative platelet count were not significantly associated with blood loss. CONCLUSIONS: Preoperative endovascular embolization is associated with decreased intraoperative blood loss. In this series, blood loss was significantly less in surgeries for tumors in which preoperative complete or near-complete embolization was achieved than in tumors in which preoperative embolization resulted in less than 90% reduction of tumor vascular blush. These findings suggest that there may be a critical threshold of efficacy that should be the goal of preoperative embolization.

Vertebral Artery Sacrifice versus Skeletonization in the Setting of Cervical Spine Tumor Resection: Case Series.

OBJECTIVE: Tumors of the cervical spine often encase 1 or both vertebral arteries (VA), presenting the treating surgeon with the dilemma of whether to sacrifice or skeletonize the artery. We propose an algorithm for VA management in surgeries for cervical neoplasms METHODS: A retrospective review was carried out of 67 patients undergoing resection of cervical spine tumors with VA involvement. Patients were categorized by tumor origin (primary vs. metastatic) and degree of circumferential VA involvement: 1) abutment only; 2) <180° circumferential involvement; 3) >180° circumferential involvement without complete encasement; or 4) complete encasement. RESULTS: Twelve patients (18%) underwent VA sacrifice, whereas 55 (82%) underwent VA skeletonization. Compared with 11/30 patients with primary tumors (37%), only 1/37 patients (3%) with metastatic disease underwent VA sacrifice (P < 0.01). This patient had invasion of the V2 arterial wall, requiring VA sacrifice. Odds of VA sacrifice also increased with increasing circumferential involvement (P < 0.01). No patients with simple abutment or 0°-180° circumferential involvement underwent sacrifice, whereas 6 of 10 (60%) with 180°-359° involvement and 6 of 29 (21%) with complete encasement underwent VA sacrifice. Of the 27 patients with ≥180° involvement, the reasons for preserving the VA were metastatic disease at the time of treatment (n = 18), a compromised contralateral VA (n = 7), vertebrobasilar junction aplasia (n = 1), and presence of a radiculomedullary artery at the affected level (n = 1). CONCLUSIONS: Primary tumor disease and >180° of circumferential VA involvement should be considered as indications for intraoperative sacrifice of the VA pending preoperative angiographic evaluation for contraindications.

Retroperitoneal approach for the treatment of diaphragmatic crus syndrome: technical note.

OBJECTIVE: Myelopathy selectively involving the lower extremities can occur secondary to spondylotic changes, tumor, vascular malformations, or thoracolumbar cord ischemia. Vascular causes of myelopathy are rarely described. An uncommon etiology within this category is diaphragmatic crus syndrome, in which compression of an intersegmental artery supplying the cord leads to myelopathy. The authors present the operative technique for treating this syndrome, describing their experience with 3 patients treated for acute-onset lower-extremity myelopathy secondary to hypoperfusion of the anterior spinal artery. METHODS: All patients had compression of a lumbar intersegmental artery supplying the cord; the compression was caused by the diaphragmatic crus. Compression of the intersegmental artery was probably producing the patients' symptoms by decreasing blood flow through the artery of Adamkiewicz, causing lumbosacral ischemia. RESULTS: All patients underwent surgery to transect the offending diaphragmatic crus. Each patient experienced substantial symptom improvement, and 2 patients made a full neurological recovery before discharge. CONCLUSIONS: Diaphragmatic crus syndrome is a rare or under-recognized cause of ischemic myelopathy. Patients present with episodic acute-on-chronic lower-extremity paraparesis, gait instability, and numbness. Angiography confirms compression of an intersegmental artery that gives rise to a dominant radiculomedullary artery. Transecting the offending diaphragmatic crus can produce complete resolution of neurological symptoms.

Cost-benefit analysis of tranexamic acid and blood transfusion in elective lumbar spine surgery for degenerative pathologies.

OBJECTIVE: Blood transfusions are given to approximately one-fifth of patients undergoing elective lumbar spine surgery, and previous studies have shown that transfusions are accompanied by increased complications and additional costs. One method for decreasing transfusions is administration of tranexamic acid (TXA). The authors sought to evaluate whether the cost of TXA is offset by the decrease in blood utilization in lumbar spine surgery patients. METHODS: The authors retrospectively reviewed patients who underwent elective lumbar or thoracolumbar surgery for degenerative conditions at a tertiary care center between 2016 and 2018. Patients who received intraoperative TXA (TXA patients) were matched with patients who did not receive TXA (non-TXA patients) by age, sex, BMI, ASA (American Society of Anesthesiologists) physical status class, and surgical invasiveness score. Primary endpoints were intraoperative blood loss, number of packed red blood cell (PRBC) units transfused, and total hemostasis costs, defined as the sum of TXA costs and blood transfusion costs throughout the hospital stay. A subanalysis was then performed by substratifying both cohorts into short-length (1-4 levels) and long-length (5-8 levels) spinal constructs. RESULTS: Of the 1353 patients who met inclusion criteria, 68 TXA patients were matched to 68 non-TXA patients. Patients in the TXA group had significantly decreased mean intraoperative blood loss (1039 vs 1437 mL, p = 0.01). There were no differences between the patient groups in the total costs of blood transfusion and TXA (p = 0.5). When the 2 patient groups were substratified by length of construct, the long-length construct group showed a significant net cost savings of $328.69 per patient in the TXA group (p = 0.027). This result was attributable to the finding that patients undergoing long-length construct surgeries who were given TXA received a lower amount of PRBC units throughout their hospital stay (2.4 vs 4.0, p = 0.007). CONCLUSIONS: TXA use was associated with decreased intraoperative blood loss and significant reductions in total hemostasis costs for patients undergoing surgery on more than 4 levels. Furthermore, the use of TXA in patients who received short constructs led to no additional net costs. With the increasing emphasis put on value-based care interventions, use of TXA may represent one mechanism for decreasing total care costs, particularly in the cases of larger spine constructs.

Robot-Assisted versus Freehand Instrumentation in Short-Segment Lumbar Fusion: Experience with Real-Time Image-Guided Spinal Robot.

OBJECTIVE: Increasing patient demand for minimally invasive surgery and increased payer emphasis on quality-based payment schema have created a need for technologies that provide consistent, high-quality outcomes for patients undergoing spine surgery. Robotic assistance is one such technology. We report our early experience with a novel real-time, image-guided robot system for use in short-segment lumbar fusion in patients diagnosed with degenerative disease. METHODS: A consecutive series of patients undergoing robot-assisted 1-level or 2-level lumbar fusion procedures were compared with matched controls who underwent freehand surgery. Screw accuracy, intraoperative outcomes, and 30-day outcomes were compared. RESULTS: We identified 56 patients who underwent 1-level or 2-level lumbar fusion during the study period: 28 who underwent robot-assisted procedures and 28 matched controls who underwent freehand instrumentation placement. No significant differences were found between the robot-assisted surgery cohort and the freehand surgery cohort with respect to matched variables. Patients who underwent robot-assisted surgery had less intraoperative blood loss (266.1 ± 236.8 mL vs. 598.8 ± 360.2 mL; P < 0.001) and shorter hospitalizations (3.5 ± 1.8 days vs. 4.5 ± 2.0 days; P = 0.01). No differences were noted in complication rates, 30-day outcomes, or screw accuracy. Profiling of our initial series showed an average reduction in operation duration of 4.6 minutes with each additional case. CONCLUSIONS: Patients undergoing robot-assisted fusion experienced less intraoperative blood loss and shorter hospitalizations. The results of this initial experience suggest that an image-guided robotic system may provide similar short-term outcomes compared with freehand instrumentation placement.

Persistent Postoperative Hyperglycemia as a Risk Factor for Operative Treatment of Deep Wound Infection After Spine Surgery.

BACKGROUND: Surgical site infections (SSIs) affect 1% to 9% of all spine surgeries. Though previous work has found diabetes mellitus type 2 (DM2) to increase the risk for wound infection, the influence of perioperative hyperglycemia is poorly described. OBJECTIVE: To investigate perioperative hyperglycemia as an independent risk factor for surgical site infection. METHODS: We retrospectively identified patients undergoing operative management of SSIs occurring after spinal surgery for degenerative pathologies. These patients were individually matched to controls based upon age, surgical invasiveness, ICD-10CM, race, and sex. Cases and controls were compared regarding medical comorbidities (including diabetes), postoperative hyperglycemia, and operative time. RESULTS: Patients in the infection group were found to have a higher BMI (33.7 vs 28.8), higher prevalence of DM2 (48.5% vs 14.7%), and longer inpatient stay (8.8 vs 4.3 d). They also had higher average (136.6 vs 119.6 mg/dL) and peak glucose levels (191.9 vs 153.1 mg/dL), as well as greater variability in glucose levels (92.1 vs 58.1 mg/dL). Multivariable logistic regression identified BMI (odds ratio [OR] = 1.13), diabetes mellitus (OR = 2.12), average glucose on the first postoperative day (OR = 1.24), peak postoperative glucose (OR = 1.31), and maximal daily glucose variation (OR = 1.32) as being significant independent predictors of postoperative surgical site infection. CONCLUSION: Postoperative hyperglycemia and poor postoperative glucose control are independent risk factors for surgical site infection following surgery for degenerative spine disease. These data suggest that, particularly among high-risk diabetic patients, strict perioperative glucose control may decrease the risk of SSI.

Treatment approaches for Scheuermann kyphosis: a systematic review of historic and current management.

OBJECTIVE: Scheuermann kyphosis (SK) is an idiopathic kyphosis characterized by anterior wedging of ≥ 5° at 3 contiguous vertebrae managed with either nonoperative or operative treatment. Nonoperative treatment typically employs bracing, while operative treatment is performed with either a combined anterior-posterior fusion or posterior-only approach. Current evidence for these approaches has largely been derived from retrospective case series or focused reviews. Consequently, no consensus exists regarding optimal management strategies for patients afflicted with this condition. In this study, the authors systematically review the literature on SK with respect to indications for treatment, complications of treatment, differences in correction and loss of correction, and changes in treatment over time. METHODS: Using PubMed, Embase, CINAHL, Web of Science, and the Cochrane Library, all full-text publications on the operative and nonoperative treatment for SK in the peer-reviewed English-language literature between 1950 and 2017 were screened. Inclusion criteria involved fully published, peer-reviewed, retrospective or prospective studies of the primary medical literature. Studies were excluded if they did not provide clinical outcomes and statistics specific to SK, described fewer than 2 patients, or discussed results in nonhuman models. Variables extracted included treatment indications and methodology, maximum pretreatment kyphosis, immediate posttreatment kyphosis, kyphosis at last follow-up, year of treatment, and complications of treatment. RESULTS: Of 659 unique studies, 45 met our inclusion criteria, covering 1829 unique patients. Indications for intervention were pain, deformity, failure of nonoperative treatment, and neural impairment. Among operatively treated patients, the most common complications were hardware failure and proximal or distal junctional kyphosis. Combined anterior-posterior procedures were additionally associated with neural, pulmonary, and cardiovascular complications. Posterior-only approaches offered superior correction compared to combined anterior-posterior fusion; both groups provided greater correction than bracing. Loss of correction was similar across operative approaches, and all were superior to bracing. Cross-sectional analysis suggested that surgeons have shifted from anterior-posterior to posterior-only approaches over the past two decades. CONCLUSIONS: The data indicate that for patients with SK, surgery affords superior correction and maintenance of correction relative to bracing. Posterior-only fusion may provide greater correction and similar loss of correction compared to anterior-posterior approaches along with a smaller complication profile. This posterior-only approach has concomitantly gained popularity over the combined anterior-posterior approach in recent years.

Intra- and interobserver reliability of the Spinal Instability Neoplastic Score system for instability in spine metastases: a systematic review and meta-analysis.

Mechanical instability is one of the two main indications for surgical intervention in patients with metastatic spine disease. Since its publication in 2010, the Spinal Instability Neoplastic Score (SINS) has been the most commonly used means of assessing mechanical instability. To prove clinically valuable though, diagnostic tests must demonstrate consistency across measures and across observers. Here we report a systematic review and meta-analysis of all prior reports of intraobserver and interobserver reliability of the SINS score. To identify articles, we queried the PubMed, CINAHL, EMBASE, Cochrane, and Web of Science databases for all full-text English articles reporting interobserver or intraobserver reliability for the SINS score, category, or a domain of the SINS score. Articles reporting confidence intervals for these metrics were then subjected to meta-analysis to identify pooled estimates of reliability. Of 167 unique studies identified, seven met inclusion criteria and were subjected to qualitative review and meta-analysis. Intraobserver reliability for SINS score was found to be near perfect [estimate =0.815; 90% CI (0.661-0.969)] and interobserver reliability was substantial [0.673; (0.227-1.12)]. Intraobserver and interobserver reliability among spine surgeons was significantly better than reliability across all observers (both P<0.0001). Qualitative analysis suggested that increased surgeon experience may be associated with greater intraobserver and interobserver reliability among spine surgeons. On the whole, meta-analysis of the available literature suggests SINS to have good intraobserver and interobserver reliability, giving it the potential to be a valuable guide to the management of patients with spinal metastases. Further research is required to demonstrate that SINS score correlates with the clinical decision to stabilize.

Lactate and cancer: a "lactatic" perspective on spinal tumor metabolism (part 1).

Spine tumors are among the most difficult tumors to treat given their proximity to the spinal cord. Despite advances in adjuvant therapies, surgery remains a critical component of treatment, both in primary tumors and metastatic disease. Given the significant morbidity of these surgeries and with other current adjuvant therapies (e.g., radiation, chemotherapy), interest has grown in other methods of targeting tumors of the spine. Recent efforts have highlighted the tumor microenvironment, and specifically lactate, as central to tumorigenesis. Once erroneously considered a waste product that indicated hypoxia/hypoperfusion, lactate is now known to be at the center of whole-body metabolism, shuttling between tissues and being used as a fuel. Diffusion-driven transporters and the near-equilibrium enzyme lactate dehydrogenase (LDH) allow rapid mobilization of large stores of muscle glycogen in the form of lactate. In times of stress, catecholamines can bind muscle cell receptors and trigger the breakdown of glycogen to lactate, which can then diffuse out into circulation and be used as a fuel where needed. Hypoxia, in contrast, is rarely the reason for an elevated arterial [lactate]. Tumors were originally described in the 1920's as being "glucose-avid" and "lactate-producing" even in normoxia (the "Warburg effect"). We now know that a broad range of metabolic behaviors likely exist, including cancer cells that consume lactate as a fuel, others that may produce it, and still others that may change their behavior based on the local microenvironment. In this review we will examine the relationship between lactate and tumor metabolism with a brief look at spine-specific tumors. Lactate is a valuable fuel and potent signaling molecule that has now been implicated in multiple steps in tumorigenesis [e.g., driving vascular endothelial growth factor (VEGF) expression in normoxia]. Future work should utilize translational animal models to target tumors by altering the local tumor microenvironment, of which lactate is a critical part.

Lactate and cancer: spinal metastases and potential therapeutic targets (part 2).

Metastatic spine disease is a heterogeneous clinical condition commonly requiring surgical intervention. Despite this heterogeneity, all cases share the common theme of altered tumor metabolism, characterized by aerobic glycolysis and high lactate production. Here we review the existing literature on lactate metabolism as it pertains to tumor progression, metastasis, and the formation of painful bone lesions. We included articles from the English literature addressing the role of lactate metabolism in the following: (I) primary tumor aggressiveness, (II) local tissue invasion, (III) metastasis formation, and (IV) generation of oncologic pain. We also report current investigations into restoring normal lactate metabolism as a means of impeding tumor growth and the formation of bony metastases. Both in vivo and in vitro experiments suggest that high lactate levels may be necessary for tumor cell growth, as small molecules inhibitors of lactate dehydrogenase (LDH5/LDHA) decrease both the rate of tumor growth and formation of metastases. Additionally, in vitro evidence strongly implicates lactate in tumor cell migration by driving the amoeboid movements of these cells. Acidification of the local bony tissue by excess lactate production activates CGRP+ neurons in the bone marrow and periosteum to generate oncologic bone pain. High lactate may also increase expression of acid sensing receptors in these neurons to generate the neuropathic pain seen in some patients with metastatic disease. Lastly, investigation into lactate-directed therapeutics is still early in development. Initial preclinical trials looking at LDH5/LDHA inhibitors as well as inhibitors of lactate transporters (MCT1) have demonstrated promise, but clinical work has been restricted to a single phase I trial. Lactate appears to play a crucial role in the pathogenesis of metastatic spine disease. Efforts are ongoing to identify small molecules inhibitors of targets in the lactogenic pathway capable of preventing the formation of osseous metastatic disease.

Systematic review on the utility of magnetic resonance imaging for operative management and follow-up for primary sarcoma-lessons from extremity sarcomas.

Primary sarcomas of the vertebral column affect roughly 5 in every million persons annually, of which half to one-third are malignant. Treatment of these lesions requires multimodal management, often employing attempts at en bloc resection of the lesion with negative margins. This may be facilitated using magnetic resonance imaging for preoperative margin planning, but current literature is lacking regarding the use of such imaging to accurately predict planned surgical margins. Here we review prior studies describing the use of magnetic resonance imaging for en bloc resection of sarcomas of the extremities to identify learning points for application to the treatment of spinal neoplasms. We conducted a systematic review of the PubMed and EMBASE literature. Included studies described the accuracy of MRI for preoperative evaluation of tumor margins, intraoperative guidance for en bloc resection, or post-operative evaluation of residual or recurrent disease. All included studies described patients treated for osseous or soft tissue sarcoma of the limbs. We found 1,705 unique references of which 27 met criteria for inclusion. Seven studies reported MR had an overall diagnostic accuracy of 93.6-96% for preoperative margin evaluation with non-contrast T1 most accurately reflecting true margins. In the nine articles reporting results of MR-guided resection, negative margins were achieved in 88.8-100% of cases with a closest margin of 2-4 mm. Eleven articles combined reported the accuracy of MR for residual disease or local recurrence, with a mean sensitivity and specificity of 71.7% and 79.3%, respectively for residual disease and 87.9% and 85.9%, respectively for local recurrence. The current literature for appendicular musculoskeletal sarcoma suggests that MR is highly accurate for defining tumor margins preoperatively, guiding osteotomy cuts intraoperatively, and documenting recurrence or residual disease. Further evidence is necessary to evaluate the degree to which it can accurately guide osteotomy planning for en bloc resection of vertebral primaries.

Prolonged Post-surgical Drain Retention Increases Risk for Deep Wound Infection After Spine Surgery.

OBJECTIVE: Surgical site infections (SSIs) complicate 1% to 9% of elective spine surgeries. Previously identified risk factors include diabetes mellitus type 2, obesity, and chronic kidney disease. We sought to determine whether the use of postoperative surgical site drains is associated with deep SSIs. METHODS: We retrospectively identified patients operated for deep SSIs after surgery for degenerative spine pathologies between July 2016 and December 2018. Patients were excluded if the reason for operation was other than deep SSI or if their primary operation was for infection or tumor. Using their index procedure and the electronic medical record, patients were matched to controls based on age, surgical invasiveness, International Classification of Diseases, Tenth Revision, Clinical Modification code, race, and sex. Our main outcome of interest was whether drain retention time, total output, or daily output differed significantly between cases and controls. RESULTS: We identified 38 patients who met inclusion criteria. Infected patients had a higher body mass index (34.2 vs. 29.9 kg/m2; P = 0.001), higher odds of having diabetes mellitus type 2 (55.3% vs. 18.4%; P = 0.002), longer drain retention time (5.5 vs. 3.5 days; P = 0.02), and longer inpatient stay (9.5 vs. 4.3 days; P = 0.005). Multivariable logistic regression demonstrated that even after controlling for the other risk factors, drain retention time independently predicted postoperative surgical site infection (odds ratio: 1.36; P = 0.02). CONCLUSIONS: Prolonged surgical drain retention correlates with risk of deep SSI after surgery for degenerative spine disease independent of surgical invasiveness, diabetes mellitus type 2 status, and total drain output. Our data suggest early postoperative drain removal may potentially decrease the risk of SSI and shorten duration of hospital stay.

Surgical management of giant presacral schwannoma: systematic review of published cases and meta-analysis.

OBJECTIVE: Giant presacral schwannomas are rare sacral tumors found in less than 1 of every 40,000 hospitalizations. Current management of these tumors is based solely upon case reports and small case series. In this paper the authors report the results of a systematic review of the available English literature on presacral schwannoma, focused on identifying the influence of tumor size, tumor morphology, surgical approach, and extent of resection (EOR) on recurrence-free survival and postoperative complications. METHODS: The medical literature (PubMed and EMBASE) was queried for reports of surgically managed sacral schwannoma, either involving 2 or more contiguous vertebral levels or with a diameter ≥ 5 cm. Tumor size and morphology, surgical approach, EOR, intraoperative and postoperative complications, and survival data were recorded. RESULTS: Seventy-six articles were included, covering 123 unique patients (mean age 44.1 ± 1.4 years, 50.4% male). The most common presenting symptoms were leg pain (28.7%), lower back pain (21.3%), and constipation (15.7%). Most surgeries used an open anterior-only (40.0%) or posterior-only (30%) approach. Postoperative complications occurred in 25.6% of patients and local recurrence was noted in 5.4%. En bloc resection significantly improved progression-free survival relative to subtotal resection (p = 0.03). No difference existed between en bloc and gross-total resection (GTR; p = 0.25) or among the surgical approaches (p = 0.66). Postoperative complications were more common following anterior versus posterior approaches (p = 0.04). Surgical blood loss was significantly correlated with operative duration and tumor volume on multiple linear regression (both p < 0.001). CONCLUSIONS: Presacral schwannoma can reasonably be treated with either en bloc or piecemeal GTR. The approach should be dictated by lesion morphology, and recurrence is infrequent. Anterior approaches may increase the risk of postoperative complications.

SINS Score and Stability: Evaluating the Need for Stabilization Within the Uncertain Category.

OBJECTIVE: The Spinal Instability Neoplastic Score (SINS) is widely used to assess mechanical instability in metastatic spine disease. We sought to identify a cutoff within the "potentially unstable" category, above which lesions were more likely than not to be stabilized. METHODS: We retrospectively reviewed all patients consulted for metastatic spine disease over a 1-year period. Patients were included if they were neurologically intact and had complete medical records, including preoperative imaging of every tumor-involved level. Examined variables included epidural spinal cord compression, SINS, revised Tokuhashi grade, age at consultation, and Karnofsky Performance Status. The primary endpoint was whether or not the lesions were stabilized. RESULTS: The study cohort comprised 51 patients (average age, 61 ± 2 years) with a total of 436 lesions; 50.5% were lytic, and 31.4% were blastic. The most common primaries were lung (n = 12), breast (n = 10) and prostate (n = 8). The median SINS across all lesions was 5. In both lesion- and patient-based analysis, a SINS ≥10 portended a >50% probability of undergoing stabilization; only 11% of all patients with a SINS ≤9 underwent instrumented fusion. Multivariable analysis demonstrated that SINS (odds ratio [OR], 2.44; P < 0.01) and Karnofsky Performance Status (OR, 1.10; P < 0.01) were independent predictors of stabilization. CONCLUSIONS: For vertebrae affected by metastatic disease, the decision to stabilize remains dependent on both the radiographic lesion properties and the patient's clinical picture. However, our results suggest that lesions with a SINS of ≤9 might not require stabilization.