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Background: Bow hunter syndrome describes a mechanical compression of the vertebral artery on head rotation leading to reversible symptomatic vertebrobasilar insufficiency. Patients are commonly presenting with syncope, vertigo, dizziness, and visual disturbances. These symptoms usually resolve when the head is turned back into neutral position. Treatment options involve surgical decompression with or without fusion, bypass surgery, or endovascular intervention., Case Description: We report about a 49-year-old female who presented with vague neck pain and severe vertigo, nausea, and near syncope when her head turned up and right. Computed tomography angiography revealed a pseudoaneurysm at the dominant left V3 and near total occlusion of the left vertebral artery as it exited the C2 foramen when the head was turned to the previously mentioned position. The patient could be successfully treated by computed tomography-navigated posterior instrumentation using bilateral C1 lateral mass screws and C2 translaminar screws. To promote segmental fusion, bilateral intrafacet cages were implanted. Postoperatively, the patient remained without neurologic deficits and experienced no further episodes of the preoperatively reported transient vertebrobasilar insufficiency symptoms., Conclusions: The reported case is unique as the bow hunter syndrome was further complicated by a pseudoaneurysm of the V3 segment. Surgical intervention proved to be an efficient treatment by stabilizing the affected segment in this patient., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background: Superficial siderosis of the central nervous system is a rare neurologic disorder characterized by the superficial deposition of hemosiderin in the subpial layer resulting in iron-related progressive neurodegeneration., Case Description: In this report, we present a case of superficial siderosis of the central nervous system secondary to an intradural thoracic disk herniation causing a cerebrospinal fluid (CSF) leak., Conclusions: The patient was successfully treated with T6-T8 transpedicular partial corpectomy, as well as diskectomy with decompression followed by watertight closure of the CSF leak. Intraoperative watertight closure of the CSF leak was achieved., (Copyright © 2018. Published by Elsevier Inc.)

Objective: The aim is assessing the in vivo efficacy of annulus fibrosus (AF) cells seeded into collagen by enhancing the reparative process around annular defects and preventing further degeneration in a rat-tail model., Summary of Background Data: Treating disc herniation with discectomy may relieve the related symptoms but does not address the underlying pathology. The persistent annular defect may lead to re-herniation and further degeneration. We recently demonstrated that riboflavin crosslinked high-density collagen gels (HDC) can facilitate annular repair in vivo., Methods: 42 rats, tail disc punctured with an 18-gauge needle, were divided into 3 groups: untreated (n = 6), injected with crosslinked HDC (n = 18), and injected with AF cell-laden crosslinked HDC (n = 18). Ovine AF cells were mixed with HDC gels prior to injection. X-rays and MRIs were conducted over 5 weeks, determining disc height index (DHI), nucleus pulposus (NP) size, and hydration. Histological assessments evaluated the viability of implanted cells and degree of annular repair., Results: Although average DHIs of both HDC gel groups were higher than those of the puncture control group at 5 weeks, the retention of disc height, NP size and hydration at 1 and 5 weeks was significant for the cellular group compared to the punctured, and at 5 weeks to the acellular group. Histological assessment indicated that AF cell-laden HDC gels have accelerated reparative sealing compared to acellular HDC gels., Conclusions: AF cell-laden HDC gels have the ability of better repairing annular defects than acellular gels after needle puncture., Statement of Significance: This project addresses the compelling demand of a sufficient treatment strategy for degenerative disc disease (DDD) perpetuated by annulus fibrosus (AF) injury, a major cause of morbidity and burden to health care systems. Our study is designed to answer the question of whether injectable, photo-crosslinked, high density collagen gels can seal defects in the annulus fibrosus of rats and prevent disc degeneration. Furthermore, we investigated whether the healing of AF defects will be enhanced by the delivery of AF cells (fibrochondrocytes) to these defects. The use of cell-laden collagen gels in spine surgery holds promise for a wide array of applications, from current discectomy procedures to future nucleus pulposus reparative therapies, and our group is excited about this potential., (Copyright © 2018. Published by Elsevier Ltd.)

Background: Two-dimensional radiographic methods have been proposed to evaluate the radiographic outcome after indirect decompression through extreme lateral interbody fusion (XLIF). However, the assessment of neural decompression in a single plane may underestimate the effect of indirect decompression on central canal and foraminal volumes. The present study aimed to assess the reliability and consistency of a novel 3-dimensional radiographic method that assesses neural decompression by volumetric analysis using a new generation of intraoperative fan-beam computed tomography scanner in patients undergoing XLIF., Methods: Prospectively collected data from 7 patients (9 levels) undergoing XLIF was retrospectively analyzed. Three independent, blind raters using imaging analysis software performed volumetric measurements pre- and postoperatively to determine central canal and foraminal volumes. Intrarater and Interrater reliability tests were performed to assess the reliability of this novel volumetric method., Results: The interrater reliability between the three raters ranged from 0.800 to 0.952, P < 0.0001. The test-retest analysis on a randomly selected subset of three patients showed good to excellent internal reliability (range of 0.78-1.00) for all 3 raters. There was a significant increase in mean volume ≈20% for right foramen, left foramen, and central canal volumes postoperatively (P = 0.0472; P = 0.0066; P = 0.0003, respectively)., Conclusions: Here we demonstrate a new volumetric analysis technique that is feasible, reliable, and reproducible amongst independent raters for central canal and foraminal volumes in the lumbar spine using an intraoperative computed tomography scanner., (Copyright © 2017. Published by Elsevier Inc.)

Background: Recently, novel mobile intraoperative fan-beam computed tomography (CT) was introduced, allowing for real-time navigation and immediate intraoperative evaluation of neural decompression in spine surgery. This study sought to investigate whether intraoperatively assessed neural decompression during minimally invasive spine surgery (MISS) has a predictive value for clinical and radiographic outcome., Methods: A retrospective study of patients undergoing intraoperative CT (iCT)-guided extreme lateral interbody fusion or transforaminal lumbar interbody fusion was conducted. 1) Preoperative, 2) intraoperative (after cage implantation, 3) postoperative, and 4) follow-up radiographic and clinical parameters obtained from radiography or CT were quantified., Results: Thirty-four patients (41 spinal segments) were analyzed. iCT-based navigation was successfully accomplished in all patients. Radiographic parameters showed significant improvement from preoperatively to intraoperatively after cage implantation in both MISS procedures (extreme lateral interbody fusion/transforaminal lumbar interbody fusion) (P ≤ 0.05). Radiologic parameters for both MISS fusion procedures did not show significant differences to the assessed radiographic measures at follow-up (P > 0.05). Radiologic outcome values did not decrease when compared intraoperatively (after cage implantation) to latest follow-up., Conclusions: Intraoperative fan-beam CT is capable of assessing neural decompression intraoperatively with high accuracy, allowing for precise prediction of radiologic outcome and earliest possible feedback during MISS fusion procedures. These findings are highly valuable for routine practice and future investigations toward finding a threshold for neural decompression that translates into clinical improvement. If sufficient neural decompression has been confirmed with iCT imaging studies, additional postoperative and/or follow-up imaging studies might no longer be required if patients remain asymptomatic., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: Kidney disease in spine surgery can be associated with serious complications., Objective: To investigate the rate of acute tubular necrosis (ATN) and surgical site infection (SSI) after lumbar fusion in patients with kidney disease., Methods: A review of the U.S. Nationwide Inpatient Sample from 2002 to 2011 was performed to identify patients who underwent lumbar fusion for degenerative spine disease or disk herniation. Four groups were established: no kidney disease, chronic kidney disease (CKD), end-stage renal disease (ESRD), and posttransplant. A multivariate analysis was performed to control for age, sex, and comorbidities., Results: A total of 268,158 patients met the criteria; 263,757 with no kidney disease (98.4%), 3576 with CKD (1.3%), 586 with ESRD (0.2%), and 239 posttransplant (0.1%). Rates of ATN were 0.1%, 2.9%, 3.6%, and 0.0% for the 4 groups, respectively (P < 0.001). Rates of SSI were 0.3%, 0.4%, 1.0%, and 0.0%, respectively (P = 0.002). After controlling for patient age, sex, and medical comorbidities, patients with CKD (odds ratio [OR], 5.42; 95% confidence interval [CI], 4.14-7.09; P < 0.001) and ESRD (OR, 6.32; 95% CI, 3.89-10.33; P < 0.001) were significantly more likely to develop ATN compared with patients without kidney disease. However, CKD (OR, 0.80; 95% CI, 0.20-3.12; P = 0.754) or ESRD (OR, 1.96; 95% CI, 0.38-10.00; P = 0.415) did not increase the risk for SSI on multivariate analysis., Discussion: The rate of ATN significantly increases based on severity of kidney disease. However, patients with transplants have ATN and SSI rates comparable with patients without kidney disease., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: Extreme lateral interbody fusion (ELIF) has gained popularity as a minimally invasive technique for indirect decompression. However, graft subsidence potentially threatens long-term success of ELIF. This study evaluated whether 26-mm-wide cages can eliminate subsidence and subsequent loss of decompression in ELIF., Methods: Patients undergoing ELIF surgery using a 26-mm-wide cage were analyzed retrospectively. Patient demographics and perioperative data for radiographic and clinical outcomes were recorded. Radiographic parameters included regional sagittal lumbar lordosis and foraminal and disc height. Clinical parameters were evaluated using the Oswestry Disability Index and visual analog scale. Subsidence of 26-mm-wide cages was compared with previous outcomes of patients undergoing ELIF using 18-mm-wide and 22-mm-wide cages., Results: There were 21 patients and 28 spinal segments analyzed. Radiographic outcome measures such as disc and foraminal height revealed significant improvement at follow-up compared with before surgery (P = 0.001). Postoperative to last follow-up cage subsidence translated into 0.34 mm ± 0.26 and -0.55 mm ± 0.64 in disc and foraminal height loss, respectively. Patients with 26-mm-wide cages experienced less subsidence by means of disc (26 mm vs. 18 mm and 22 mm, P ≤ 0.05) and foraminal height (26 mm vs. 18 mm, P = 0.005; 26 mm vs. 22 mm, P = 0.208) loss compared with patients receiving 18-mm-wide and 22-mm-wide cages., Conclusions: The 26-mm-wide cages almost eliminated cage subsidence in ELIF. Compared with 18-mm-wide and 22-mm-wide cages, 26-mm-wide cages significantly reduced cage subsidence in ELIF at midterm follow-up. A 26-mm-wide cage should be used in ELIF to achieve sustained indirect decompression., (Copyright © 2017. Published by Elsevier Inc.)

Background: Extreme lateral interbody fusion (ELIF) is a powerful tool for interbody fusion and coronal deformity correction. However, evidence regarding the success of ELIF in decompressing foraminal, lateral recess, and central canal stenosis is lacking. We performed a systematic review of current literature on the potential and limitations of ELIF to indirectly decompress neural elements., Methods: A literature search using PubMed, Cochrane, and ScienceDirect databases was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria. Information on study design, sample size, population, procedure, number and location of involved levels, follow-up time, and complications as well as information on conflict of interest was extracted and evaluated., Results: We selected 20 publications including 1080 patients for review. Most publications (90%) were retrospective case series. Most frequent indications for ELIF included degenerative disc disease, spinal stenosis, spondylolisthesis, and degenerative scoliosis. Most studies revealed significant improvement in radiographic and clinical outcome after ELIF. Mean foraminal area, central canal area, and subarticular diameter increased by 31.6 mm 2 , 28.5 mm 2 , and 0.85 mm. ELIF successfully improved foraminal stenosis. Contradictory results were found for indirect decompression of central canal stenosis. Data on lateral recess stenosis were scarce., Conclusions: Current data suggest ELIF to be an efficient technique in decompression of foraminal stenosis. Evidence on decompression of central canal or lateral recess stenosis via ELIF is low, and results are inconsistent. Most studies are limited by study design, sample size, and potential conflicts of interest., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: Extreme lateral interbody fusion (ELIF) has gained popularity as a minimally invasive treatment allowing for indirect decompression of neural elements. However, evidence regarding the influence of facet degeneration (FD) and facet tropism (FT) toward indirect decompression is lacking. The aim of the study was to evaluate whether indirect decompression is impaired by FD and FT in patients undergoing ELIF., Methods: Thirty-seven patients undergoing ELIF were included in a retrospective study. Radiographic parameters including disk height, segmental disk angle, foraminal area, FD, FT, and clinical outcome parameters (Oswestry Disability Index and Visual Analog Scale) were measured preoperatively and postoperatively. FD and FT were correlated with radiographic and clinical outcome parameters in order to determine predictors restricting indirect decompression., Results: Thirty-seven patients with a total of 74 levels were analyzed. Clinical and radiographic outcome measures including central canal area (Δ = +17.2 mm 2 ), mean disk height (Δ = +3 mm), and foraminal area (Δ = +9.9 mm 2 ) revealed significant improvement compared with before surgery (P ≤ 0.05). Patients with severe FD (grade 4) were more likely to have FT ≥ 12 degrees (32.3%) than patients without/mild (grades 0 and 1; 10%) or moderate FD (grades 2 and 3; 13%), P ≤ 0.05. FD and FT did not affect disk height restoration, foraminal area, canal surface area, or clinical outcome measures (P ≥ 0.05)., Conclusions: Indirect decompression of neural elements in ELIF is not impaired by FD and FT are not relative contraindications in patients undergoing ELIF., (Copyright © 2016. Published by Elsevier Inc.)

Background: Portable intraoperative computed tomography (iCT) with integrated 3-dimensional navigation (NAV) offers new opportunities for more precise navigation in spinal surgery, eliminates radiation exposure for the surgical team, and accelerates surgical workflows. We present the concept of "total navigation" using iCT NAV in spinal surgery. Therefore, we propose a step-by-step guideline demonstrating how total navigation can eliminate fluoroscopy with time-efficient workflows integrating iCT NAV into daily practice., Methods: A prospective study was conducted on collected data from patients undergoing iCT NAV-guided spine surgery. Number of scans, radiation exposure, and workflow of iCT NAV (e.g., instrumentation, cage placement, localization) were documented. Finally, the accuracy of pedicle screws and time for instrumentation were determined., Results: iCT NAV was successfully performed in 117 cases for various indications and in all regions of the spine. More than half (61%) of cases were performed in a minimally invasive manner. Navigation was used for skin incision, localization of index level, and verification of implant position. iCT NAV was used to evaluate neural decompression achieved in spinal fusion surgeries. Total navigation eliminates fluoroscopy in 75%, thus reducing staff radiation exposure entirely. The average times for iCT NAV setup and pedicle screw insertion were 12.1 and 3.1 minutes, respectively, achieving a pedicle screw accuracy of 99%., Conclusions: Total navigation makes spine surgery safer and more accurate, and it enhances efficient and reproducible workflows. Fluoroscopy and radiation exposure for the surgical staff can be eliminated in the majority of cases., (Copyright © 2017 Elsevier Inc. All rights reserved.)