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Background: Spinal decompression and osteotomies are conventionally performed using high-speed drills (HSDs) and rongeurs. The ultrasonic bone scalpel (UBS) is a tissue-specific osteotome that preferentially cuts bone while sparing the surrounding soft tissues. There is ongoing investigation into its ability to optimize peri- and postoperative outcomes in spine surgery. The purpose of this study was to compare the intraoperative metrics and complications during a transition period from HSD to UBS., Methods: A single-institution, single-surgeon retrospective analysis was conducted of patients undergoing spine surgery from January 2020 to December 2021. Statistical analyses were performed to detect associations between the surgical technique and outcomes of interest. A P value < 0.05 was considered statistically significant., Results: A total of 193 patients met the inclusion criteria (HSD, n = 100; UBS, n = 93). Multivariate logistic regression revealed similar durotomy (P = 0.10), nerve injury (P = 0.20), and reoperation (P = 0.68) rates. Although the estimated blood loss (EBL) and length of stay were similar, the operative time was significantly longer with the UBS (192.81 vs. 204.72 minutes; P = 0.03). Each subsequent surgery using the UBS revealed a 3.1% decrease in the probability of nerve injury (P = 0.026) but had no significant effects on the operative time, EBL, or probability of durotomy or reoperation., Conclusions: The UBS achieves outcomes on par with conventional tools, with a trend toward a lower incidence of neurologic injury. The expected reductions in EBL and durotomy were not realized in our cohort, perhaps because of a high proportion of revision surgeries, although these might be dependent on surgeon familiarity, among other operative factors. Future prospective studies are needed to validate our results and further refine the optimal application of this device in spine surgery., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Objective: Treatment for Chiari malformation type I (CM-I) often includes surgical intervention in both pediatric and adult patients. The authors sought to investigate fundamental differences between these populations by analyzing data from pediatric and adult patients who required CM-I decompression., Methods: To better understand the presentation and surgical outcomes of both groups of patients, retrospective data from 170 adults and 153 pediatric patients (2000-2019) at six institutions were analyzed., Results: The adult CM-I patient population requiring surgical intervention had a greater proportion of female patients than the pediatric population (p < 0.0001). Radiographic findings at initial clinical presentation showed a significantly greater incidence of syringomyelia (p < 0.0001) and scoliosis (p < 0.0001) in pediatric patients compared with adult patients with CM-I. However, presenting signs and symptoms such as headaches (p < 0.0001), ocular findings (p = 0.0147), and bulbar symptoms (p = 0.0057) were more common in the adult group. After suboccipital decompression procedures, 94.4% of pediatric patients reported symptomatic relief compared with 75% of adults with CM-I (p < 0.0001)., Conclusions: Here, the authors present the first retrospective evaluation comparing adult and pediatric patients who underwent CM-I decompression. Their analysis reveals that pediatric and adult patients significantly differ in terms of demographics, radiographic findings, presentation of symptoms, surgical indications, and outcomes. These findings may indicate different clinical conditions or a distinct progression of the natural history of this complex disease process within each population, which will require prospective studies to better elucidate.

Objective: Three-dimensionally (3D) printed polyether-ether-ketone (PEEK) implants are a relatively novel option for cranioplasty that have recently gained popularity. However, there is ongoing debate with respect to material efficacy and safety compared to autologous bone grafts. The purpose of this study was to offer our institution's experience and add to the growing body of literature., Methods: A single-institution retrospective analysis of patients undergoing cranioplasties between 2016 and 2021. Patients were divided into PEEK and autologous cranioplasty cohorts. Parameters of interest included patient demographics as well as perioperative (<3 months postoperative) and long-term outcomes (>3 months postoperative). A P value < 0.05 was considered statistically significant., Results: A total of 31 patients met inclusion criteria (PEEK: 15, Autologous: 16). Mean age of total cohort was 48.9 years (range 19-82 years). Modified Frailty Index (mFI) revealed greater rate of comorbidities among the Autologous group (P = 0.073), which was accounted for in statistical analyses. Multiple logistic regression model revealed significantly higher rate of surgical site infection in the Autologous cohort (31.3% vs. 0%, P = 0.011). Minor complications were similar between groups, while the Autologous group experienced significantly more major postoperative complications (50%) versus PEEK (13.3%) (P = 0.0291). Otherwise perioperative and long term complication profiles were similar between groups. Additionally, generalized linear model demonstrated both cohorts had similar mean hospital length of stay (LoS) (Autologous: 16.1 vs. PEEK: 10.7 days)., Conclusions: PEEK cranioplasty implants may offer more favorable perioperative complication profiles with similar long-term complication rates and hospital LoS compared to autologous bone implants. Future studies are warranted to confirm our findings in larger series, and further examine the utility of PEEK in cranioplasty., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Optical frequency metrology in atoms and ions can probe hypothetical fifth forces between electrons and neutrons by sensing minute perturbations of the electronic wave function induced by them. A generalized King plot has been proposed to distinguish them from possible standard model effects arising from, e.g., finite nuclear size and electronic correlations. Additional isotopes and transitions are required for this approach. Xenon is an excellent candidate, with seven stable isotopes with zero nuclear spin, however it has no known visible ground-state transitions for high resolution spectroscopy. To address this, we have found and measured twelve magnetic-dipole lines in its highly charged ions and theoretically studied their sensitivity to fifth forces as well as the suppression of spurious higher-order standard model effects. Moreover, we identified at 764.8753(16) nm a E2-type ground-state transition with 500 s excited state lifetime as a potential clock candidate further enhancing our proposed scheme.

Background and Aims: Sugammadex (SUG) has been associated with changes in coagulation studies. Most reports have concluded a lack of clinical significance based on surgical blood loss with SUG use at the end of surgery. Previous reports have not measured its use intraoperatively during ongoing blood loss. Our hypothesis was that the use of SUG intraoperatively may increase bleeding., Material and Methods: This was a single site retrospective study. Inclusion criteria were patients undergoing a primary posterior cervical spine fusion, aged over 18 years, between July 2015 and June 2021. The primary outcomes compared were intraoperative estimated blood loss (EBL) and postoperative drain output (PDO) between patients receiving SUG, neostigmine (NEO) and no NMB reversal agent. The objective was to determine if there was a difference in primary endpoints between patients administered SUG, NEO or no paralytic reversal agent. Primary endpoints were compared using analysis of variance with a P value of 0.05 used to determine statistical significance. Groups were compared using the Chi-squared test, rank sum or student's t test. A logistic regression model was constructed to account for differences between the groups., Results: There was no difference in median EBL or PDO between groups. The use of SUG was not associated with an increase in odds for >500 milliliters (ml) of EBL. Increasing duration of surgery and chronic kidney disease were both associated with an increased risk for EBL >500 ml., Conclusion: Intraoperative use of SUG was not associated with increased bleeding. Any coagulation laboratory abnormalities previously noted did not appear to have an associated clinical significance., Competing Interests: There are no conflicts of interest., (Copyright: © 2022 Journal of Anaesthesiology Clinical Pharmacology.)

Background and Importance: Augmented reality (AR) is a novel technology with broadening applications to neurosurgery. In deformity spine surgery, it has been primarily directed to the more precise placement of pedicle screws. However, AR may also be used to generate high fidelity three-dimensional (3D) spine models for cases of advanced deformity with existing instrumentation. We present a case in which an AR-generated 3D model was used to facilitate and expedite the removal of embedded instrumentation and guide the reduction of an overriding spondyloptotic deformity., Clinical Presentation: A young adult with a remote history of a motor vehicle accident treated with long-segment posterior spinal stabilization presented with increasing back pain and difficulty sitting upright in a wheelchair. Imaging revealed pseudoarthrosis with multiple rod fractures resulting in an overriding spondyloptosis of T6 on T9. An AR-generated 3D model was useful in the intraoperative localization of rod breaks and other extensively embedded instrumentation. Real-time model thresholding expedited the safe explanation of the defunct system and correction of the spondyloptosis deformity., Conclusion: An AR-generated 3D model proved instrumental in a revision case of hardware failure and high-grade spinal deformity., (Copyright © The Author(s) 2022. Published by Wolters Kluwer Health, Inc on behalf of Congress of Neurological Surgeons.)

Aim: To compare the perioperative outcomes between single-day combined or separate-day staged surgeries for cervical spinal stenosis., Material and Methods: A retrospective cohort analysis was conducted on consecutive patients admitted at a single institution between July 2015 and April 2019, who underwent either single-day combined or separate-day staged surgeries during the same hospitalization period. Demographics, comorbidities, hospital length of stay, and perioperative complications were compared between the patient groups., Results: Eighty patients (combined surgery: n=68, staged surgery: n=12) were included. Dysphagia was the most commonly reported postoperative complication in 44/80 patients (55%). There were no significant differences in the baseline demographics between the two groups. The staged surgery group had significantly longer total time in the operating room (7.2 vs. 8.5 hours, p=0.002), longer duration of general anesthesia (6.7 vs. 7.6 hours, p=0.006), and higher incidence of postoperative delirium (12.1% vs. 50% p=0.005) than the combined surgery group. The mean hospital length of stay was similar in the two groups (combined surgery: 7.5 days vs. staged surgery: 15.1 days, p=0.09)., Conclusion: Staged anterior and posterior cervical decompressions, stabilizations, and fusions are associated with longer total time in the operating room, longer duration of general anesthesia, and higher incidence of postoperative delirium than combined surgeries.

We present a novel ultrastable superconducting radio-frequency (RF) ion trap realized as a combination of an RF cavity and a linear Paul trap. Its RF quadrupole mode at 34.52 MHz reaches a quality factor of Q ≈ 2.3 × 10 5 at a temperature of 4.1 K and is used to radially confine ions in an ultralow-noise pseudopotential. This concept is expected to strongly suppress motional heating rates and related frequency shifts that limit the ultimate accuracy achieved in advanced ion traps for frequency metrology. Running with its low-vibration cryogenic cooling system, electron-beam ion trap, and deceleration beamline supplying highly charged ions (HCIs), the superconducting trap offers ideal conditions for optical frequency metrology with ionic species. We report its proof-of-principle operation as a quadrupole-mass filter with HCIs and trapping of Doppler-cooled 9 Be + Coulomb crystals.

Introduction: Prenatal closure of open spina bifida via open fetal surgery improves neurologic outcomes for infants in selected pregnancies. Fetoscopic techniques that are minimally invasive to the uterus aim to provide equivalent fetal benefits while minimizing maternal morbidities, but the optimal technique is undetermined. We describe the development, evolution, and feasibility of the laparotomy-assisted 2-port fetoscopic technique for prenatal closure of fetal spina bifida in a newly established program., Methods: We conducted a retrospective cohort study of women consented for laparotomy-assisted fetoscopic closure of isolated fetal spina bifida. Inclusion and exclusion criteria followed the Management of Myelomeningocele Study (MOMS). Team preparation involved observation at the originating center, protocol development, ancillary staff training, and surgical rehearsal using patient-matched models through simulation prior to program implementation. The primary outcome was the ability to complete the repair fetoscopically. Secondary maternal and fetal outcomes to assess performance of the technique were collected prospectively., Results: Of 57 women screened, 19 (33%) consented for laparotomy-assisted 2-port fetoscopy between February 2017 and December 2019. Fetoscopic closure was completed in 84% (16/19) cases. Over time, the technique was modified from a single- to a multilayer closure. In utero hindbrain herniation improved in 86% (12/14) of undelivered patients at 6 weeks postoperatively. Spontaneous rupture of membranes occurred in 31% (5/16) of fetoscopic cases. For completed cases, median gestational age at birth was 37 (range 27-39.6) weeks and 50% (8/16) of women delivered at term. Vaginal birth was achieved in 56% (9/16) of patients. One newborn had a cerebrospinal fluid leak that required postnatal surgical repair., Conclusion: Implementation of a laparotomy-assisted 2-port fetoscopic spina bifida closure program through rigorous preparation and multispecialty team training may accelerate the learning curve and demonstrates favorable obstetric and perinatal outcomes., (© 2021 S. Karger AG, Basel.)

Background: To decrease vehicular traffic in major metropolitan cities throughout the United States, multiple ridesharing companies have launched dockless electric scooters and bicycles throughout cities. From September 2017 through November 2018, Washington, DC, launched a 15-month dockless vehicle pilot program to allow for the rapid entry and growth of electric scooters within the metropolitan area. This rapid growth resulted in a number of minor and significant injuries., Case Description: We reviewed the electronic medical record of The George Washington University Hospital to investigate and characterize the types of electric scooter-related injuries resulting in neurosurgical consultation in the 15-month period of the Washington, DC, scooter pilot program. Thirteen patients sustained injuries serious enough to merit neurosurgical consultation, including 1 patient whose symptoms required procedural intervention by a neurointerventional radiologist and another patient who was pronounced dead soon after arrival to the hospital., Conclusions: In this case series, we highlight more severe injuries that resulted in hospitalization or intervention, including skull fracture, central cord syndrome, and vertebral compression fracture. This case series aims to illustrate the potential severity of injuries related to electric scooters, raise awareness on the issues of safety and public health, and call for further investigation into injuries relating to electric scooters., (Copyright © 2019 Elsevier Inc. All rights reserved.)

OBJECTIVESymptomatic cervical spondylosis with or without radiculopathy can ground an active-duty military pilot if left untreated. Surgically treated cervical spondylosis may be a waiverable condition and allow return to flying status, but a waiver is based on expert opinion and not on recent published data. Previous studies on rates of return to active duty status following anterior cervical spine surgery have not differentiated these rates among military specialty occupations. No studies to date have documented the successful return of US military active-duty pilots who have undergone anterior cervical spine surgery with cervical fusion, disc replacement, or a combination of the two. The aim of this study was to identify the rate of return to an active duty flight status among US military pilots who had undergone anterior cervical discectomy and fusion (ACDF) or total disc replacement (TDR) for symptomatic cervical spondylosis.METHODSThe authors performed a single-center retrospective review of all active duty pilots who had undergone either ACDF or TDR at a military hospital between January 2010 and June 2017. Descriptive statistics were calculated for both groups to evaluate demographics with specific attention to preoperative flight stats, days to recommended clearance by neurosurgery, and days to return to active duty flight status.RESULTSAuthors identified a total of 812 cases of anterior cervical surgery performed between January 1, 2010, and June 1, 2017, among active duty, reserves, dependents, and Department of Defense/Veterans Affairs patients. There were 581 ACDFs and 231 TDRs. After screening for military occupation and active duty status, there were a total of 22 active duty pilots, among whom were 4 ACDFs, 17 TDRs, and 2 hybrid constructs. One patient required a second surgery. Six (27.3%) of the 22 pilots were nearing the end of their career and electively retired within a year of surgery. Of the remaining 16 pilots, 11 (68.8%) returned to active duty flying status. The average time to be released by the neurosurgeon was 128 days, and the time to return to flying was 287 days. The average follow-up period was 12.3 months.CONCLUSIONSAdhering to military service-specific waiver guidelines, military pilots may return to active duty flight status after undergoing ACDF or TDR for symptomatic cervical spondylosis.

OBJECTIVEAdult spinal deformity surgery is an effective way of treating pain and disability, but little research has been done to evaluate the costs associated with changes in health outcome measures. This study determined the change in quality-adjusted life years (QALYs) and the cost per QALY in patients undergoing spinal deformity surgery in the unique environment of a military healthcare system (MHS).METHODSPatients were enrolled between 2011 and 2017. Patients were eligible to participate if they were undergoing a thoracolumbar spinal fusion spanning more than 6 levels to treat an underlying deformity. Patients completed the 36-Item Short Form Health Survey (SF-36) prior to surgery and 6 and 12 months after surgery. The authors used paired t-tests to compare SF-36 Physical Component Summary (PCS) scores between baseline and postsurgery. To estimate the cost per QALY of complex spine surgery in this population, the authors extended the change in health-related quality of life (HRQOL) between baseline and follow-up over 5 years. Data on the cost of surgery were obtained from the MHS and include all facility and physician costs.RESULTSHRQOL and surgical data were available for 49 of 91 eligible patients. Thirty-one patients met additional criteria allowing for cost-effectiveness analysis. Over 12 months, patients demonstrated significant improvement (p < 0.01) in SF-36 PCS scores. A majority of patients met the minimum clinically important difference (MCID; 83.7%) and substantive clinical benefit threshold (SCBT; 83.7%). The average change in QALY was an increase of 0.08. Extended across 5 years, including the 3.5% discounting per year, study participants increased their QALYs by 0.39, resulting in an average cost per QALY of $181,649.20. Nineteen percent of patients met the < $100,000/QALY threshold with half of the patients meeting the < $100,000/QALY mark by 10 years. A sensitivity analysis showed that patients who scored below 60 on their preoperative SF-36 PCS had an average increase in QALYs of 0.10 per year or 0.47 over 5 years.CONCLUSIONSWith a 5-year extended analysis, patients who receive spinal deformity surgery in the MHS increased their QALYs by 0.39, with 19% of patients meeting the $100,000/QALY threshold. The majority of patients met the threshold for MCID and SCBT at 1 year postoperatively. Consideration of preoperative functional status (SF-36 PCS score < 60) may be an important factor in determining which patients benefit the most from spinal deformity surgery.

This Cervical and Thoracolumbar Spine Injury Evaluation, Transport, and Surgery Clinical Practice Guideline (CPG) is designed to provide guidance to the deployed provider when they are treating a combat casualty who has sustained a spine or spinal cord injury. The CPG objective for the treatment and the movement of these patients is to maintain spinal stability through transport, perform decompression when urgently needed, achieve definitive stabilization when appropriate, avoid secondary injury, and prevent deterioration of the patient's neurological condition. Thorough and accurate documentation of the patient's neurological examination is crucial to ensure appropriate management decisions are made as the patient transits through the evacuation system. The use of this CPG should be in conjunction with good clinical judgment.

Electron beam driven ionization can produce highly charged ions (HCIs) in a few well-defined charge states. Ideal conditions for this are maximally focused electron beams and an extremely clean vacuum environment. A cryogenic electron beam ion trap fulfills these prerequisites and delivers very pure HCI beams. The Canadian rare isotope facility with electron beam ion source-electron beam ion sources developed at the Max-Planck-Institut für Kernphysik (MPIK) reaches already for a 5 keV electron beam and a current of 1 A with a density in excess of 5000 A/cm 2 by means of a 6 T axial magnetic field. Within the trap, the beam quickly generates a dense HCI population, tightly confined by a space-charge potential of the order of 1 keV times the ionic charge state. Emitting HCI bunches of ≈10 7 ions at up to 100 Hz repetition rate, the device will charge-breed rare-isotope beams with the mass-over-charge ratio required for re-acceleration at the Advanced Rare IsotopE Laboratory (ARIEL) facility at TRIUMF. We present here its design and results from commissioning runs at MPIK, including X-ray diagnostics of the electron beam and charge-breeding process, as well as ion injection and HCI-extraction measurements.

Spine injuries are more prevalent among Iraq and Afghanistan veterans than among veterans of previous conflicts. The purpose of this investigation was to characterize the context, mode, and clinical outcomes of spine injuries sustained by U.S. military personnel in theater. Injury and clinical data from patients who sustained a spine injury in Iraq or Afghanistan between 2003 and 2008 were extracted from the Joint Theater Trauma Registry. Fischer's exact test was used to compare demographic variables between battle and nonbattle spine injuries. Two-sided t tests and univariate analyses were performed to analyze the association between injury context, mechanism, and severity with clinical outcome. A total of 307 patients sustained spine injuries in theater during the study period, and 296 had adequate data for analysis. Most injuries occurred in battle (69.6%), and these injuries were more likely to have an Injury Severity Score considered severe (44.7% vs. 20.0%; p < 0.001) or critical (13.6% vs. 5.6%; p = 0.0458). Blast was the most common mechanism of injury (42.2%) and was more likely to be blunt (81.6%) than penetrating (18.4%; p < 0.0001). Battle-associated spine injuries were most commonly caused by blasts, were more severe, and more likely to involve multiple spinal levels., (Reprint & Copyright © 2016 Association of Military Surgeons of the U.S.)

Objective: To present a conversion from an anterior cervical discectomy and fusion (ACDF) to cervical arthroplasty in a 40-year-old, active duty member and perform a review of the literature., Methods: A helicopter pilot in the U.S. Army underwent a three-level ACDF in 2010 at a nonmilitary institution for symptoms of bilateral upper-extremity radiculopathy. His symptoms resolved; however, per regulations, he was grounded. The patient recently presented at our clinic for evaluation of axial neck and intrascapular pain with radiographic evaluation revealing pseudarthrosis at C6-7 with segmental motion without facet joint degeneration. Surgery was performed to remove the existing allograft and replace it with an artificial disc, thus restoring a motion segment., Results: Postoperative imaging reveals appropriate placement of the artificial disc and range of motion at C6-7 with the patient reporting improvement in neck pain. He has since been granted a waiver to return to active flight status., Conclusions: Revision of ACDF to arthroplasty is an exceedingly rare procedure with only two cases reported in the literature. Here, the authors demonstrate use of the procedure for a military career-specific application. When facet joint degeneration or ankylosis is absent, restoration of motion can successfully, and safely, be achieved., (Reprint & Copyright © 2016 Association of Military Surgeons of the U.S.)

Unlabelled: The pathway to military neurosurgical practice can include a number of accession options. This article is an objective comparison of fiscal, tangible, and intangible benefits provided through different military neurosurgery career paths. Neurosurgeons may train through active duty, reserve, or civilian pathways. These modalities were evaluated on the basis of economic data during residency and the initial 3 years afterwards. When available, military base pay, basic allowance for housing and subsistence, variable special pay, board certified pay, incentive pay, multiyear special pay, reserve drill pay, civilian salary, income tax, and other tax incentives were analyzed using publically available data. Civilians had lower residency pay, higher starting salaries, increased taxes, malpractice insurance cost, and increased overhead. Active duty service saw higher residency pay, lower starting salary, tax incentives, increased benefits, and almost no associated overhead including malpractice coverage. Reserve service saw a combination of civilian benefits with supplementation of reserve drill pay in return for weekend drill and the possibility of deployment and activation. Being a neurosurgeon in the military is extremely rewarding. From a financial perspective, ignoring intangibles, this article shows most entry pathways with initially modest differences between the cumulative salaries of active duty and civilian career paths and with higher overall compensation available from the reserve service option. These pathways become increasingly discrepant over time as civilian pay greatly exceeds that of military neurosurgeons. We hope that those curious about or considering serving in the United States military benefit from our accounting and review of these comparative paths., Abbreviations: FAP, Financial Assistance ProgramNADDS, Navy Active Duty Delay for SpecialistsTMS, Training in Medical Specialties.

Cervical disc arthroplasty has emerged as a viable technique for the treatment of cervical radiculopathy and myelopathy, with the proposed benefit of maintenance of segmental range of motion. There are relatively few, non-industry sponsored studies examining the outcomes and complications of cervical disc arthroplasty. Therefore, we set out to perform a single center evaluation of the outcomes and complications of cervical disc arthroplasty. We performed a retrospective review of all patients from a single military tertiary medical center undergoing cervical disc arthroplasty from August 2008 to August 2012. The clinical outcomes and complications associated with the procedure were evaluated. A total of 219 consecutive patients were included in the review, with an average follow-up of 11.2 (±11.0)months. Relief of pre-operative symptoms was noted in 88.7% of patients, and 92.2% of patients were able to return to full pre-operative activity. There was a low rate of complications related to the anterior cervical approach (3.2% with recurrent laryngeal nerve injury, 8.9% with dysphagia), with no device/implant related complications. Symptomatic cervical radiculopathy is a common problem in both the civilian and active duty military populations and can cause significant disability leading to loss of work and decreased operational readiness. There exist several surgical treatment options for appropriately indicated patients. Based on our findings, cervical disc arthroplasty is a safe and effective treatment for symptomatic cervical radiculopathy and myelopathy, with a low incidence of complications and high rate of symptom relief., (Published by Elsevier Ltd.)

Several studies have established the short-term safety and efficacy of cervical disc arthroplasty (CDA) as compared to anterior cervical discectomy and fusion (ACDF). However, few single-center comparative trials have been performed, and current studies do not contain large numbers of patients. We retrospectively reviewed all patients from a single military tertiary medical center between August 2008 to August 2012 who underwent single-level CDA or single-level ACDF and compared their clinical outcomes and complications. A total of 259 consecutive patients were included in the study, 171 patients in the CDA group with an average follow-up of 9.8 (±9.9)months and 88 patients in the ACDF group with an average follow-up of 11.8 (±9.6)months. Relief of pre-operative symptoms was 90.1% in the CDA group and 86.4% in the ACDF group with rates of return to full pre-operative activity of 93.0% and 88.6%, respectively. Patients who underwent CDA had a higher rate of persistent posterior neck pain (15.8% versus 12.5%), and patients who underwent ACDF were at risk for symptomatic pseudarthrosis at a rate of 3.4%. Reoperation rates were higher in the ACDF group (5.7% versus 3.5%). To our knowledge, this review is the largest, non-funded, comparison study between single-level CDA and single-level ACDF. This study demonstrates that CDA is a safe and reliable alternative to ACDF in the treatment of cervical radiculopathy and myelopathy resulting from spondylosis and acute disc herniation., (Published by Elsevier Ltd.)

Object: Adult spinal deformity (ASD) surgery is increasing in the spinal neurosurgeon's practice., Methods: A survey of neurosurgeon AANS membership assessed the deformity knowledge base and impact of current training, education, and practice experience to identify opportunities for improved education. Eleven questions developed and agreed upon by experienced spinal deformity surgeons tested ASD knowledge and were subgrouped into 5 categories: (1) radiology/spinopelvic alignment, (2) health-related quality of life, (3) surgical indications, (4) operative technique, and (5) clinical evaluation. Chi-square analysis was used to compare differences based on participant demographic characteristics (years of practice, spinal surgery fellowship training, percentage of practice comprising spinal surgery)., Results: Responses were received from 1456 neurosurgeons. Of these respondents, 57% had practiced less than 10 years, 20% had completed a spine fellowship, and 32% devoted more than 75% of their practice to spine. The overall correct answer percentage was 42%. Radiology/spinal pelvic alignment questions had the lowest percentage of correct answers (38%), while clinical evaluation and surgical indications questions had the highest percentage (44%). More than 10 years in practice, completion of a spine fellowship, and more than 75% spine practice were associated with greater overall percentage correct (p < 0.001). More than 10 years in practice was significantly associated with increased percentage of correct answers in 4 of 5 categories. Spine fellowship and more than 75% spine practice were significantly associated with increased percentage correct in all categories. Interestingly, the highest error was seen in risk for postoperative coronal imbalance, with a very low rate of correct responses (15%) and not significantly improved with fellowship (18%, p = 0.08)., Conclusions: The results of this survey suggest that ASD knowledge could be improved in neurosurgery. Knowledge may be augmented with neurosurgical experience, spinal surgery fellowships, and spinal specialization. Neurosurgical education should particularly focus on radiology/spinal pelvic alignment, especially pelvic obliquity and coronal imbalance and operative techniques for ASD.

Symptomatic cervical radiculopathy is a common problem in the active duty military population and can cause significant disability leading to limited duty status and loss of operational readiness and strength. Based on their increasing experience with cervical disc arthroplasty (CDA) in this unique patient population, the authors set out to further evaluate the outcomes and complications of CDA in active duty military patients. A retrospective review of a single military tertiary medical center was performed between August 2008 and August 2012 and the clinical outcomes of patients who underwent cervical disc arthroplasty were evaluated. There were 37 active duty military patients, with a total of 41 CDA. The study found good relief of preoperative symptoms (92%) and the ability to maintain operational readiness with a high rate of return to full unrestricted duty (95%) with an average follow-up of 6 months. There was a low rate of complications related to the anterior cervical approach (5%-8%), with no device- or implant-related complications.

Object: Pulmonary complications are the most common acute systemic adverse events following spinal cord injury (SCI), and contribute to morbidity, mortality, and increased length of hospital stay (LOS). Identification of factors associated with pulmonary complications would be of value in prevention and acute care management. Predictors of pulmonary complications after SCI and their effect on neurological recovery were prospectively studied between 2005 and 2009 at the 9 hospitals in the North American Clinical Trials Network (NACTN)., Methods: The authors sought to address 2 specific aims: 1) define and analyze the predictors of moderate and severe pulmonary complications following SCI; and 2) investigate whether pulmonary complications negatively affected the American Spinal Injury Association (ASIA) Impairment Scale conversion rate of patients with SCI. The NACTN registry of the demographic data, neurological findings, imaging studies, and acute hospitalization duration of patients with SCI was used to analyze the incidence and severity of pulmonary complications in 109 patients with early MR imaging and long-term follow-up (mean 9.5 months). Univariate and Bayesian logistic regression analyses were used to analyze the data., Results: In this study, 86 patients were male, and the mean age was 43 years. The causes of injury were motor vehicle accidents and falls in 80 patients. The SCI segmental level was in the cervical, thoracic, and conus medullaris regions in 87, 14, and 8 patients, respectively. Sixty-four patients were neurologically motor complete at the time of admission. The authors encountered 87 complications in 51 patients: ventilator-dependent respiratory failure (26); pneumonia (25); pleural effusion (17); acute lung injury (6); lobar collapse (4); pneumothorax (4); pulmonary embolism (2); hemothorax (2), and mucus plug (1). Univariate analysis indicated associations between pulmonary complications and younger age, sports injuries, ASIA Impairment Scale grade, ascending neurological level, and lesion length on the MRI studies at admission. Bayesian logistic regression indicated a significant relationship between pulmonary complications and ASIA Impairment Scale Grades A (p = 0.0002) and B (p = 0.04) at admission. Pulmonary complications did not affect long-term conversion of ASIA Impairment Scale grades., Conclusions: The ASIA Impairment Scale grade was the fundamental clinical entity predicting pulmonary complications. Although pulmonary complications significantly increased LOS, they did not increase mortality rates and did not adversely affect the rate of conversion to a better ASIA Impairment Scale grade in patients with SCI. Maximum canal compromise, maximum spinal cord compression, and Acute Physiology and Chronic Health Evaluation-II score had no relationship to pulmonary complications.

Object: The aim of this multicenter, prospective study was to determine the spectrum, incidence, and severity of complications during the initial hospitalization of patients with spinal cord injury., Methods: The study was conducted at 9 university-affiliated hospitals that comprise the clinical centers of the North American Clinical Trials Network (NACTN) for Treatment of Spinal Cord Injury. The study population comprised 315 patients admitted to NACTN clinical centers between June 25, 2005, and November 2, 2010, who had American Spinal Injury Association (ASIA) Impairment Scale grades of A-D and were 18 years of age or older. Patients were managed according to a standardized protocol., Results: The study population was 79% male with a median age of 44 years. The leading causes of injury were falls (37%) and motor vehicle accidents (28%). The distribution of initial ASIA grades were A (40%), B (16%), C (15%), and D (29%). Fifty-eight percent of patients sustained 1 or more severe, moderate, or mild complications. Complications were associated with more severe ASIA grade: 84% of patients with Grade A and 25% of patients with Grade D had at least 1 complication. Seventy-eight percent of complications occurred within 14 days of injury. The most frequent types of severe and moderate complications were respiratory failure, pneumonia, pleural effusion, anemia, cardiac dysrhythmia, and severe bradycardia. The mortality rate was 3.5% and was associated with increased age and preexisting morbidity., Conclusions: Knowledge of the type, frequency, time of occurrence, and severity of specific complications that occur after spinal cord injury can aid in their early detection, treatment, and prevention. The data are of importance in evaluating and selecting therapy for clinical trials.

Objective: Multilevel cervical arthroplasty achieved using the Prestige ST disc can be challenging and often unworkable. An alternative to this system is a hybrid technique composed of alternating total disc replacements (TDRs) and fusions. In the present study, the authors review the safety and radiological outcomes of cervical hybrid arthroplasty in which the Prestige ST disc is used in conjunction with 2 unique fusion techniques., Methods: After obtaining institutional review board approval, the authors completed a retrospective review of all hybrid cervical constructs in which the Prestige ST disc was used between August 2007 and November 2009 at the Walter Reed Army Medical Center. A Prestige ST total disc replacement was performed in 119 patients. Thirty-one patients received a hybrid construct defined as a TDR and fusion (TDR-anterior cervical decompression and fusion [ACDF]) or as 2 TDRs separated by a fusion (TDR-ACDF-TDR). A resorbable plate and graft system (Mystique) or stand-alone interbody spacer (Prevail) was implanted at the fusion levels. Plain radiographs were compared and evaluated for cervical lordosis, range of motion, implant complications, development of adjacent-level disease, and pseudarthrosis. In addition, charts were reviewed for clinical complications related to the index surgery., Results: Thirty-one patients (18 men and 13 women; mean age 50 years, range 32-74 years) received a hybrid construct. All patients were diagnosed with radiculopathy and/or myelopathy. Twenty-four patients received a 2-level and 7 a 3-level hybrid construct. In 2 patients in whom a 2-level hybrid construct was implanted, a noncontiguous TDR was also performed. The mean clinical and radiological follow-up duration was 18 months. There was no significant difference in preoperative (19.3° ± 13.3°) and postoperative (19.7° ± 10.5°) cervical lordosis (p = 0.48), but there was a significant decrease in range in motion (from 50.0° ± 11.8° to 38.9° ± 12.7°) (p = 0.003). There were no instances of screw backout, implant dislodgement, progressive kyphosis, formation of heterotopic bone, pseudarthrosis, or symptomatic adjacent-level disease. Seven patients had dysphasia and 1 patient had vocal cord paralysis at 6 weeks. By 3 months, both the dysphasia and the vocal cord paralysis were resolved in all patients., Conclusions: Hybrid cervical arthroplasty involving the placement of a Prestige ST disc and either the Mystique resorbable plate or Prevail stand-alone interbody device is a safe and effective alternative to multilevel fusion for the management of cervical radiculopathy and myelopathy.

Background Context: Recent studies have demonstrated cases of adjacent vertebral body osteolysis when assessing the effect of bone morphogenetic protein (BMP) on fusion rates. However, no study to date has evaluated the course of osteolysis at different periods., Purpose: To determine the incidence and resolution of osteolysis associated with BMP used in transforaminal lumbar interbody fusions (TLIF)., Study Design: Retrospective review., Patient Sample: All TLIF cases using BMP performed at one institution with routine postoperative computed tomography (CT) scans at defined intervals., Outcome Measures: Area of osteolysis and fusion as determined by CT scan., Methods: We performed a retrospective analysis of all patients at our facility who underwent TLIF with BMP. Included were all patients who had obtained a CT scan within 48 hours of surgery, 3 to 6 months postoperatively, and 1 to 2 years postoperatively. Areas of osteolysis were defined as lucency within the vertebral body communicating with the interbody spacer that was not present on the immediately postoperative CT scan. Areas of osteolysis were measured in all three planes and the volume used for comparison of the 3 to 6 months CT scans with the greater than 1 year CT scan., Results: Twenty-three patients who underwent TLIF with BMP had obtained CT scans at all time periods required for evaluation. Seventy-eight vertebral bodies/end plates were assessed for osteolysis (39 levels). The incidence of osteolysis 3 to 6 months postoperatively in the adjacent vertebral bodies was 54% compared with 41% at 1 to 2 years. The mean volume of osteolysis was at 0.216 cm(3) at 1 to 2 years compared with 0.306 cm(3) at 3 to 6 months (p=.082). The area/rate of osteolysis did not appear to significantly affect the rate of fusion or final outcome with an overall union rate of 83%., Conclusions: The rate of osteolysis decreased at 1 year compared with 3 to 6 months, but only 24% of the vertebral bodies with evidence of osteolysis at 3 to 6 months completely resolved by 1 year., (Published by Elsevier Inc.)

Background Context: Lamina screws have been reported to be a biomechanically sound alternative to pedicle screws in the proximal thoracic spine. However, concerns have been raised that midline failure may result in a spinal canal breach., Purpose: To evaluate the catastrophic failure of proximal thoracic lamina screws using two techniques for lamina screw purchase., Study Design: Biomechanical study with human cadaveric vertebrae., Patient Sample: Not applicable., Outcome Measures: Not applicable., Methods: Nineteen fresh-frozen T1-T2 vertebrae were Dual energy X-ray absorptiometry scanned for bone mineral density. Caliper measurements of lamina thickness and lateral mass width for bicortical purchase were obtained. Ten specimens had right-to-left 26-mm lamina screws inserted entirely within the length of the lamina (unicortical). Nine specimens had right-to-left 42-mm lamina screws inserted as to extend the length of the lamina and breach the cortex behind the first and second ribs (bicortical). All screws were placed by experienced spine surgeons under fluoroscopic visualization using 4.5-mm cervicothoracic screws. Insertional torque was recorded while placing all implants and reported in "in-lbs." Tensile loading to failure was performed with the force oriented in the parasagittal plane along the vertebral midline. Pullout loading was applied at a rate of 0.25 mm/s using an MTS 858 MiniBionix II System (MTS Systems, Inc., Minneapolis, MN, USA) with the maximum pullout strength (POS) recorded in Newtons. Video fluoroscopy was performed during midline pullout to evaluate screw failure and ascertain spinal canal breach. After testing, all specimens were visually inspected for spinal canal breach., Results: Neither the unicortical nor the bicortical lamina screws violated the spinal canal during catastrophic midline failure. The ventral lamina cortex remained intact for both the lamina screw techniques. All of the unicortical lamina screws resulted in dorsal avulsion of the spinous process and lamina. All nine bicortical lamina screws separated the dorsal lamina from the ventral but were able to maintain lateral mass purchase. The peak insertional torque for both lamina screw techniques was not significantly different (p = .20). However, bicortical lamina screw POS (584.8 ± 150.2 N) was significantly greater than unicortical lamina screw POS (455.6 ± 100.2 N) (p = .04). Bone mineral density showed a moderate correlation with unicortical (r = 0.67) and bicortical (r = 0.47) lamina screw POS., Conclusion: Our results suggest that catastrophic midline failure of lamina screws does not violate the spinal canal. Of the two techniques tested, bicortical lamina screws have a biomechanical advantage. Lamina screws present a viable option for instrumenting the proximal thoracic spine., (Published by Elsevier Inc.)

Background Context: Pedicle screw placement in the proximal thoracic spine may result in unwanted bicortical breach. An understanding of the potential structures at risk is paramount to safe screw placement., Purpose: To assess the anatomic location of structures at risk with the placement of bicortical pedicle screw fixation in the proximal thoracic spine., Study Design: Retrospective radiographic review., Patient Sample: Twenty patients with dedicated computed tomography (CT) scans of the thoracic spine., Outcome Measures: Radiographic parameters on CT., Methods and Materials: Computed tomography was performed on 20 patients and analyzed from T1 to T4 for proximity of major structures at risk with breach of the anterior vertebral body cortex from pedicle screw placement. Descriptive statistics, analyses of variance and post hoc paired t tests were used to analyze screw position relative to the esophagus, trachea, aortic arch, carotid, and vertebral arteries., Results: One hundred sixty potential anterior cortical violation positions were analyzed. Left-sided pedicle screws posed a significantly higher risk (p<.05) to the esophagus at T1-T3; in particular, the left T2 screw was significantly closer (p<.05). Right-sided pedicle screws posed a significantly higher risk to the trachea at T2-T4 (p<.05). The right T3 and T4 screws posed the greatest risk to the trachea and right main bronchus, respectively (p<.05). The carotid and vertebral arteries were not at risk for injury. The aortic arch was present at T4 in 70% of patients and was not at risk., Conclusions: Careful preoperative evaluation with CT is warranted to determine anatomic structures at risk when placing proximal thoracic pedicle screws. Left-sided screws pose the greatest risk to the esophagus; right-sided screws pose the greatest risk to the trachea. The carotid and vertebral arteries, along with the aortic arch are at minimal risk for injury., (Published by Elsevier Inc.)

Object: In support of Operation Iraqi Freedom (OIF) and Operation Enduring Freedom-Afghanistan (OEF-A), military neurosurgeons in the combat theater are faced with the daunting task of stabilizing patients in such a way as to prevent irreversible neurological injury from cerebral edema while simultaneously allowing for prolonged transport stateside (5000-7000 miles). It is in this setting that decompressive craniectomy has become a mainstay of far-forward neurosurgical management of traumatic brain injury (TBI). As such, institutional experience with cranioplasty at the Walter Reed Army Medical Center (WRAMC) and the National Naval Medical Center (NNMC) has expanded concomitantly. Battlefield blast explosions create cavitary injury zones that often extend beyond the border of the exposed surface wound, and this situation has created unique reconstruction challenges not often seen in civilian TBI. The loss of both soft-tissue and skull base support along with the need for cranial vault reconstruction requires a multidisciplinary approach involving neurosurgery, plastics, oral-maxillofacial surgery, and ophthalmology. With this situation in mind, the authors of this paper endeavored to review the cranial reconstruction complications encountered in these combat-related injuries., Methods: A retrospective database review was conducted for all soldiers injured in OIF and OEF-A who had undergone decompressive craniectomy with subsequent cranioplasty between April 2002 and October 2008 at the WRAMC and NNMC. During this time, both facilities received a total of 408 OIF/OEF-A patients with severe head injuries; 188 of these patients underwent decompressive craniectomies in the theater before transfer to the US. Criteria for inclusion in this study consisted of either a closed or a penetrating head injury sustained in combat operations, resulting in the performance of a decompressive craniectomy and subsequent cranioplasty at either the WRAMC or NNMC. Excluded from the study were patients for whom primary demographic data could not be verified. Demographic data, indications for craniectomy, as well as preoperative, intraoperative, and postoperative parameters following cranioplasty, were recorded. Perioperative and postoperative complications were also recorded., Results: One hundred eight patients (male/female ratio 107:1) met the inclusion criteria for this study, 93 with a penetrating head injury and 15 with a closed head injury. Explosive blast injury was the predominant mechanism of injury, occurring in 72 patients (67%). The average time that elapsed between injury and cranioplasty was 190 days (range 7-546 days). An overall complication rate of 24% was identified. The prevalence of perioperative infection (12%), seizure (7.4%), and extraaxial hematoma formation (7.4%) was noted. Twelve patients (11%) required prosthetic removal because of either extraaxial hematoma formation or infection. Eight of the 13 cases of infection involved cranioplasties performed between 90 and 270 days from the date of injury (p = 0.06)., Conclusions: This study represents the largest to date in which cranioplasty and its complications have been evaluated in a trauma population that underwent decompressive craniectomy. The overall complication rate of 24% is consistent with rates reported in the literature (16-34%); however, the perioperative infection rate of 12% is higher than the rates reported in other studies. This difference is likely related to aspects of the initial injury pattern-such as skull base injury, orbitofacial fractures, sinus injuries, persistent fluid collection, and CSF leakage-which can predispose these patients to infection.

Object: In this study, the authors review the technique for inserting the Prestige ST in a contiguous multilevel cervical disc arthroplasty in patients with radiculopathy and myelopathy. They describe the preoperative planning, surgical technique, and their experience with 10 patients receiving a contiguous Prestige ST implant. They present contiguous multilevel cervical arthroplasty as an alternative to multilevel arthrodesis., Methods: After institutional board review approval was obtained, the authors performed a retrospective review of all contiguous multilevel cervical disc arthroplasties with the Prestige ST artificial disc between August 2007 and November 2009 at a single institution by a single surgeon. Clinical criteria included patients who had undergone a multilevel cervical disc arthroplasty performed for radiculopathy and myelopathy without the presence of a previous cervical fusion. Between August 2007 and November 2009, 119 patients underwent cervical arthroplasty. Of the 119 patients, 31 received a Hybrid construct (total disc resection [TDR]-anterior cervical decompression and fusion [ACDF] or TDR-ACDF-TDR) and 24 received a multilevel cervical arthroplasty. The multilevel cervical arthroplasty group consisted of 14 noncontiguous and 10 contiguous implants. This paper examines patients who received contiguous Prestige ST implants., Results: Ten men with an average age of 45 years (range 25-61 years) were treated. Five patients presented with myelopathy, 3 presented with radiculopathy, and 2 presented with myeloradiculopathy. Twenty-two 6 x 16-mm Prestige ST TDRs were implanted. Six patients received 2-level Prestige ST implants. Five patients received TDRs at C5-6 and C6-7, and 1 patient received TDRs at C3-4 and C4-5. One patient received a TDR at C3-4, C5-6, and C6-7 where C4-5 was a congenital block vertebra. Three patients (2 with 3-level disease and 1 with 4-level disease) received contiguous Prestige ST implants as well as a Prevail ACDF as part of their constructs. The mean clinical and radiographic follow-up was 12 months. There has been no case of screw backout, implant dislodgment, progressive kyphosis, formation of heterotopic bone, evidence of pseudarthrosis at the Prevail levels, or development of symptomatic adjacent level disease., Conclusions: Multilevel cervical arthroplasty with the Prestige ST is a safe and effective alternative to fusion for the management of cervical radiculopathy and myelopathy.

Object: Minimal-access transforaminal lumbar interbody fusion (TLIF) has gained popularity as a method of achieving interbody fusion via a posterior-only approach with the aim of minimizing injury to adjacent tissue. While many studies have reported successful outcomes, questions remain regarding the potential learning curve for successfully completing this procedure. The goal of this study, based on a single resident's experience at the only Accreditation Council for Graduate Medical Education-approved neurosurgical training center in the US military, was to determine if there is in fact a significant learning curve in performing a minimal-access TLIF., Methods: The authors retrospectively reviewed all minimal-access TLIFs performed by a single neurosurgical resident between July 2006 and January 2008. Minimal-access TLIFs were performed using a tubular retractor inserted via a muscle-dilating exposure to limit approach-related morbidity. The accuracy of screw placement and operative times were assessed., Results: A single resident/attending team performed 28 minimal-access TLIF procedures. In total, 65 screws were placed at L-2 (1 screw), L-3 (2 screws), L-4 (18 screws), L-5 (27 screws), and S-1 (17 screws) from the resident's perspective. Postoperative CTs were reviewed to determine the accuracy of screw placement. An accuracy of 95.4% (62 of 65) properly placed screws was noted on postoperative imaging. Two screws (at L-5 in the patient in Case 17 and at S-1 in the patient in Case 9) were lateral, and no revision was needed. One screw (at L-4 in Case 24) was 1 mm medial without symptoms or the need for revision. In evaluating the operative times, 2 deformity cases (Grade III spondylolisthesis) were excluded. The average operating time per level in the remaining 26 cases was 113.25 minutes. The average time per level for the first 13 cases was 121.2 minutes; the amount of time decreased to 105.3 minutes for the second group of 13 cases (p = 0.25)., Conclusions: In summary, minimal-access TLIF can be safely performed in a training environment without a significant complication rate due to the expected learning curve.

Object: Minimally invasive lumbar spine surgery has dramatically evolved over the last decade. Minimally invasive techniques and transforaminal lumbar interbody fusion (TLIF) often require a steep learning curve. Surgical techniques require pre-positioning the patient in maximal kyphosis to optimize visualization of the disc space and prevent unnecessary retraction of neural structures. The authors describe their experience in validating the surgical technique recommendation of Wilson frame-induced kyphosis., Methods: Over the past 6 months, data obtained in 20 consecutive patients (40 total levels) undergoing minimally invasive TLIF were reviewed. In each patient, preincision intraoperative radiographs were reviewed at L4-5 and L5-S1 with the patient on a Wilson frame in maximal lordosis and then in maximal kyphosis. The change in disc space angle at L4-5 and L5-S1 after changing from maximal lordosis to maximal kyphosis was reviewed. Descriptive statistics were calculated for sagittal plane angular measures at L4-5 and L5-S1 in lordosis and kyphosis, including absolute differences and percentage of change between positions. Inferential statistics were calculated using paired t-tests with alpha= 0.05., Results: Twenty patients underwent single- or multilevel minimally invasive TLIF. Inducing kyphosis with the Wilson frame aided in optimizing exposure and decreasing the need for neural structure retraction. Both L4-5 and L5-S1 showed statistically significant (p < 0.001) and clinically meaningful changes with increased segmental flexion in the kyphotic position. At L4-5 the mean increase in flexion was 4.5 degrees (95% CI 2.9-6.0 degrees), representing an average 47% change. The mean increase in flexion at L5-S1 was 3.2 degrees (95% CI 2.3-4.2 degrees), representing an average 20.8% change. In lordosis the mean angle at L4-5 was 10.6 +/- 4.4 degrees and at L5-S1 was 17 +/- 7.0 degrees. In kyphosis the mean angle at L4-5 was 6.1 +/- 4.5 degrees and at L5-S1 was 13.8 +/- 6.5 degrees. Additionally, there was a statistically significant difference (p < 0.05) in percentage of change between the 2 levels, with L4-5 showing a greater change (27% more flexion) between positions, but the absolute mean difference between the levels was small (1.3 degrees)., Conclusions: Minimally invasive TLIF is challenging and requires a significant learning curve. The recommended surgical technique of inducing kyphosis with the Wilson frame prior to incision significantly optimizes exposure. The authors' experience demonstrates that this technique is essential when performing minimally invasive lumbar spinal fusions.

Object: Transpedicular instrumentation at C-7 has been well accepted, but salvage techniques are limited. Lamina screws have been shown to be a biomechanically sound salvage technique in the proximal thoracic spine, but have not been evaluated in the lower cervical spine. The following study evaluates the anatomical feasibility of lamina screws at C-7 as well as their bone-screw interface strength as a salvage technique., Methods: Nine fresh-frozen C-7 cadaveric specimens were scanned for bone mineral density using dual energy x-ray absorptiometry. Prior to testing, all specimens were imaged using CT to obtain 1-mm axial sections. Caliper measurements of both pedicle width and laminar thickness were obtained. On the right side, pedicle screws were first inserted and then pulled out. Salvage intralaminar screws were inserted into the left lamina from the right spinous process/lamina junction and then pulled out. All screws were placed by experienced cervical spine surgeons under direct fluoroscopic visualization. Pedicle and lamina screws were 4.35- and 3.5-mm in diameter, respectively. Screws sizes were chosen based on direct and radiographic measurements of the respective anatomical regions. Insertional torque (IT) was measured in pounds per inch. Tensile loading to failure was performed in-line with the screw axis at a rate of 0.25 mm/sec using a MiniBionix II system with data recorded in Newtons., Results: Using lamina screws as a salvage technique generated mean pullout forces (778.9 +/- 161.4 N) similar to that of the index pedicle screws (805.3 +/- 261.7 N; p = 0.796). However, mean lamina screw peak IT (5.2 +/- 2.0 lbs/in) was significantly lower than mean index pedicle screw peak IT (9.1 +/- 3.6 lbs/in; p = 0.012). Bone mineral density was strongly correlated with pedicle screw pullout strength (r = 0.95) but less with lamina screw pullout strength (r = 0.04). The mean lamina width measured using calipers (5.7 +/- 1.0 mm) was significantly different from the CT-measured mean lamina width (5.1 +/- 0.8 mm; p = 0.003). Similarly, the mean pedicle width recorded with calipers (6.6 +/- 1.1 mm) was significantly different from the CT-measured mean pedicle width (6.2 +/- 1.3 mm; p = 0.014). The mean laminar width measured on CT at the thinnest point ranged from 3.8 to 6.8 mm, allowing a 3.5-mm screw to be placed without difficulty., Conclusions: These results suggest that using lamina screws as a salvage technique at C-7 provides similar fixation strength as the index pedicle screw. The C-7 lamina appears to have an ideal anatomical width for the insertion of 3.5-mm screws commonly used for cervical fusions. Therefore, if the transpedicular screw fails, using intralaminar screws appear to be a biomechanically sound salvage technique.

Study Design: In vitro cadaveric biomechanical analysis., Objective: Define the T1 and T2 anatomic lamina size and evaluate the bone-screw interface strength of various pedicle screw options and intralamina techniques., Summary of Background Data: Transpedicular instrumentation is well accepted, but salvage techniques in the proximal thoracic spine are limited. Intralamina fixation has been described at C2 with favorable biomechanical characteristics. In addition, this technique has been introduced clinically in the proximal thoracic spine. However, the biomechanical potential has not been evaluated., Methods: Fourteen fresh-frozen cervicothoracic cadaveric specimens were scanned using dual-energy radiograph absorptiometry for bone mineral density, imaged under computed tomography, and then instrumented in the following configuration: (1) Right-sided pedicle screws in a straight-forward trajectory, (2) "salvage anatomic trajectory pedicle screws, and (3) "salvage" intralamina screws into the contralateral lamina. Insertional torque (IT) was recorded with each revolution and screws were pulled out in-line (POS) with the screw axis to simulate intraoperative failure of fixation., Results: Lamina screws as a salvage technique generated statistically greater peak IT (P = 0.002) and relative POS (P < 0.05) in comparison with straight-forward transpedicular screws as the initial fixation type. Furthermore, lamina screws, when compared to the salvage anatomic trajectory pedicle screws, had a significantly greater peak IT (P = 0.011). The peak IT showed a stronger correlation with POS in lamina screws than straight-forward or anatomic pedicle screws with a similar trend noted in mean IT. Bone mineral density correlated with POS in all methods of fixation. The mean lamina width measured on computed tomography at the thinnest point was 5.9 +/- 0.7 mm (range, 4.9-7.9)., Conclusion: Our results suggest that lamina screws, used as a salvage technique in the proximal thoracic spine, provide stronger fixation than transpedicular screws when using standard 4.5-mm cervical screws. In-tralamina screws appear to be a biomechanically sound salvage technique in the region, and appear to be a safe, effective technique for instrumenting the proximal thoracic spine.

Background Context: With lumbar arthroplasty gaining popularity, limited data are available highlighting changes in adjacent-level mechanics after multilevel procedures., Purpose: Compare operative- and adjacent-segment range of motion (ROM) and intradiscal pressures (IDPs) after two-level arthroplasty versus circumferential arthrodesis., Study Design: Cadaveric biomechanical study., Methods: Ten human cadaveric lumbar spines were used in this investigation. Biomechanical testing was performed according to a hybrid testing protocol using an unconstrained spine simulator under axial rotation (AR), flexion extension (FE), and lateral-bending (LB) loading. Specimens were tested in the following order: 1) Intact, 2) L3-L5 total disc replacement (TDR), 3) L3-L5 anterior interbody cages+pedicle screws. IDP was recorded at proximal and distal adjacent levels and normalized to controls (%intact). Full ROM was monitored at the operative and adjacent levels and reported in degrees., Results: Kinematics assessment revealed L3-L5 ROM reduction after both reconstructions versus intact controls (p < .05). However, global quality of segmental motion distributed over L2-S1 was preserved in the arthroplasty group but was significantly altered after circumferential fixation. Furthermore, adjacent-level ROM was increased for the arthrodesis group under LB at both segments and during AR at L2-L3 relative to controls (p < .05). FE did not reveal any intergroup statistical differences. Nonetheless, after arthrodesis IDPs were increased proximally under all three loading modalities, whereas distally a significant IDP rise was noted during AR and LB (p < .05). No statistical differences in either biomechanical parameter were recorded at the adjacent levels between intact control and TDR groups., Conclusions: Our results indicate no significant adjacent-level biomechanical changes between arthroplasty and control groups. In contrast, significant alterations in ROM and IDP were recorded both proximally (ROM=LB & AR; IDP=AR, FE, LB) and distally (ROM=LB; IDP=AR & LB) after circumferential arthrodesis. Therefore, two-level lumbar arthroplasty maintains a more favorable biomechanical environment at the adjacent segments compared with the conventional transpedicular fixation technique. This, in turn, may have a positive effect on the rate of the transition syndrome postoperatively.

Spinopelvic fixation techniques are evolving and now seem to be converging. Good S1 pedicle fixation is the initial key anchor point. The tricortical technique tests out as the best. Supplemental fixation options are available. The most efficacious seems to be iliac fixation, followed by two-level structural interbody support. Achieving appropriate global sagittal balance also lessens the likelihood of implant pullout and places the fusion mass under relatively more compressive forces than tension forces. Regardless of the method of fixation, the ultimate determinant of long-term implant survival is the achievement of adequate biologic fusion.

Study Design: This is an in vitro biomechanical study., Objective: The current investigation was performed to evaluate the stabilizing potential of anterior, posterior, and circumferential cervical fixation on operative and adjacent segment motion following 2 and 3-level reconstructions., Summary of Background Data: Previous studies reported increases in adjacent level range of motion (ROM) and intradiscal pressure following single-level cervical arthrodesis; however, no studies have compared adjacent level effects following multilevel anterior versus posterior reconstructions., Materials and Methods: Ten human cadaveric cervical spines were biomechanically tested using an unconstrained spine simulator under axial rotation, flexion-extension, and lateral bending loading. After intact analysis, all specimens were sequentially instrumented from C3 to C5 with: (1) lateral mass fixation, (2) anterior cervical plate with interbody cages, and (3) combined anterior and posterior fixation. Following biomechanical analysis of 2-level constructs, fixation was extended to C6 and testing repeated. Full ROM was monitored at the operative and adjacent levels, and data normalized to the intact (100%)., Results: All reconstructive methods reduced operative level ROM relative to intact specimens under all loading methods (P < 0.05). However, circumferential fixation provided the greatest segmental stability among 2 and 3-level constructs (P < 0.05). Moreover, anterior cervical plate fixation was least efficient at stabilizing operative segments following C3-C6 arthrodesis (P < 0.05). Supradjacent ROM was increased for all treatment groups compared to normal data during flexion-extension testing (P < 0.05). Similar trends were observed under axial rotation and lateral bending loading. At the distal level, flexion-extension and axial rotation testing revealed comparable intergroup differences (P < 0.05), while lateral bending loading indicated greater ROM following 2-level circumferential fixation (P < 0.05)., Conclusions: Results from our study revealed greater adjacent level motion following all 3 fixation types. No consistent significant intergroup differences in neighboring segment kinematics were detected among reconstructions. Circumferential fixation provided the greatest level of segmental stability without additional significant increase in adjacent level ROM.

Study Design: Single institution retrospective review., Objectives: To report a series of pyogenic spinal infections treated with single-stage debridement and reconstruction with titanium mesh cages., Summary of Background Data: Various studies have reported surgical results of pyogenic spinal osteomyelitis with anterior debridement, strut grafting and fusion, including delayed posterior spinal instrumentation. Additionally, various authors have recommended against the use of instrumentation because of the concern about glycocalyx formation on the metal and chronic infection. At our institution, we routinely treat chronic vertebral osteomyelitis with single-stage debridement, reconstruction with a titanium mesh cage filled with allograft chips and demineralized bone matrix, and posterior pedicle screw instrumentation. To our knowledge, this is the largest single series reporting single-stage debridement and instrumentation of pyogenic spinal infection with titanium mesh cages and posterior instrumentation., Materials and Methods: We retrospectively reviewed the patient records and radiographs of 21 consecutive patients (average age 49.3 years, range 23 to 80 years) with pyogenic vertebral osteomyelitis, all treated with titanium mesh cages. Average follow-up was 44 months (range, 25 to 70 months). Spinal levels included 6 thoracic, 4 thoracolumbar, 9 lumbar, and 2 lumbosacral (L5-S1) lesions. All patients had preoperative serum evaluation, which usually included blood cultures, complete blood count, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP), in addition to plain radiographs and magnetic resonance imaging. A positive needle biopsy was available in only 2/7 patients (29%), and overall, preoperative pathogen identification was available in only 7/21 patients (33%). All patients were treated postoperatively with a minimum of 6 weeks of intravenous antibiotics, with a specific antibiotic regimen directed toward the postoperative pathogen when identified (17/21 cases). Extensive radiographic evaluation was also performed., Results: ESR and CRP were routinely elevated (18/20 and 11/17 cases respectively), whereas the white blood count was elevated in only 8 out of 21 cases (38%). The average duration of symptoms to diagnosis was approximately 13.6 weeks (range 3 weeks to 10 months). The indications for surgery included neurologic compromise, significant vertebral body destruction with loss of sagittal alignment, failure of medical treatment, and/or epidural abscess. All patients had resolution of infection, as noted by normalization of the ESR and CRP. Further, 16 out of 21 patients also had a significant reduction of pain. There were no deaths or new postoperative neurologic compromise. The most common pathogen was Staphylococcus aureus. Two patients required a second surgery (posterior irrigation and debridement) during the same admission for persistent wound drainage. Radiographically, the average segmental kyphosis (or loss of lordosis) was 11.5 degrees (range, 0 to 24 degrees) preoperatively, and +0.8 degrees (range, -3 to +5 degrees) at latest postoperative follow-up. There was an average of 2.2 mm cage settling (range, 0 to 5 mm) on latest follow-up. There were no instrumentation failures, signs of chronic infection, or rejection., Conclusions: Titanium mesh cages present a viable option for single-stage anterior surgical debridement and reconstruction of vertebral osteomyelitis, without evidence of chronic infection or rejection. When used in conjunction with pedicle screw instrumentation, there is minimal cage settling without loss of sagittal alignment.

Eosinophilic meningitis has been defined as meningitis in which a total cerebrospinal fluid (CSF) sample is found to have more than 10 eosinophils per millimeter or is composed of greater than 10% eosinophils. The differential diagnosis is broad and the clinical presentation, lacking an internalized CSF diversion system, is often nonspecific. With respect to patients with shunt systems, a positive correlation exists between CSF eosinophilia and eventual shunt failure requiring revision. In this paper the authors present the highest reported level of CSF eosinophilia in conjunction with a rifampin and minocycline-impregnated ventriculostomy catheter recently approved by the Food and Drug Administration.

Object: Disc arthroplasty in the lumbar spine is an alternative to fusion when treating discogenic pain. Its theoretical benefits include preservation of the motion segment and the potential prevention of adjacent-segment degeneration. Despite the need to evaluate the benefit of preserving the adjacent segments after disc replacement, no study has been conducted to assess the ability of magnetic resonance (MR) imaging to depict the adjacent segments in patients who have undergone disc replacement surgery., Methods: Postoperative lumbar MR images were obtained in the first 10 patients in whom a metal-on-metal disc arthroplasty system was used to treat the L4-5 or L5-S1 levels. At the superior adjacent level, the superior endplate and disc space were demonstrated on 90% of the images on both T1-weighted fluid-attenuated inversion-recovery (FLAIR) and T2-weighted sequences despite the presence of artifacts. The inferior endplate at this level was documented on 70% of both T1-weighted FLAIR and T2-weighted sequences. At the level below the disc replacement in patients who underwent L4-5 surgery, the superior endplate was demonstrated on 66.7% of the T1-weighted FLAIR sequences but only 33.3% of the T2-weighted images. The disc space and inferior endplate were depicted on 66.7% of both T1-weighted FLAIR and T2-weighted sequences. Axial images revealed an artifact in every adjacent space except at the L5-S1 level., Conclusions: Based on the results of this pilot study, it appears that sagittal MR imaging can be undertaken to evaluate the adjacent motion segment for degenerative changes following total disc arthroplasty in most patients. This imaging modality will provide an additional measure to assess the long-term efficacy of this intervention compared with other treatment modalities and the natural history of lumbar disc degeneration.

Study Design: Analysis of radiographic interpretation and vertebral level identification., Objectives: To assess the intra- and interobserver reliability by observer training level used for selecting the end vertebra (EV), neutral vertebra (NV), and stable vertebra (SV) in adolescent idiopathic scoliosis patients., Summary of Background Data: Various radiographic and clinical factors are important in surgical planning. For adolescent idiopathic scoliosis, an analysis of the end, neutral, and stable vertebrae are of paramount importance for understanding spinal deformity management and determining the distal fusion level. Additionally, the development and comparison of optimal surgical techniques requires reliable, reproducible radiographic parameters., Methods: One hundred consecutive radiographs of operative cases of adolescent idiopathic scoliosis were evaluated on three separate occasions by three surgeons (2700 data points) at various levels of training (fellowship-trained spine surgeon, fellow in-training, orthopedic surgery resident). For each iteration, the observers attempted to identify the distal structural Cobb curve EV, NV, and SV. The radiographs included preselected Lenke type 1, 3, and 5 curves in random order. The average main thoracic curve was 53 degrees (range, 30-82 degrees) with a T8-T9 average apex, whereas the average thoracolumbar curve was 33 degrees (range, 18-65 degrees). Intra- and interobserver reliability was assessed by means of Cohen's Kappa correlation coefficient, and raw percentages of agreement were recorded., Results: Intraobserver reliability was good to excellent for determining the EV (kappaa = 0.69-0.88), good for determining the NV (kappaa = 0.65-0.73), and good to excellent for determining the SV (kappaa = 0.74-0.91) with 83.5, 72.2, and 85.6% intraobserver agreement, respectively. A trend was noted towards greater intraobserver reliability with increasing levels of observer experience. Interobserver reliability was poor (kappaa = 0.26-0.39) for each vertebral level, with interobserver agreement for only 48.7% of EV, 41.7% of NV, and 51.0% of SV. However, interobserver agreement increased significantly when concurrence within one vertebral level was assessed, with 91, 73, and 76% agreement for identifying the EV, NV, and SV, respectively., Conclusions: Radiographic determination of the EV, NV, and SV demonstrated good to excellent intraobserver, but poor interobserver, reliability. Interobserver agreement was fair to good when concurrence within one adjacent level was assessed. Observer experience level may be a factor. The difficulties in identifying these vertebral levels represent a potential obstacle to reproducible patient-specific fusion level determination and to the optimization and uniformity of patient care.

Object: The purpose of this study was to evaluate the safety and efficacy of prophylactic inferior vena cava (IVC) filter placement in high-risk patients who undergo major spine reconstruction., Methods: In the pilot study, 22 patients undergoing major spine reconstruction received prophylactic IVC filters. These patients were prospectively followed to evaluate complications related to the filter, the rate of deep venous thrombosis (DVT) formation, and the rate of pulmonary embolism (PE). These data were compared with those obtained in a retrospective review for PE in a matched cohort treated at the same institution. At a second institution the treatment guidelines were implemented in 17 patients undergoing complex spine surgery with the same follow-up criteria. In the pilot study, no patient experienced PE (0%), whereas two had DVT (9%). Bilateral DVT developed postoperatively in one patient (associated morbidity rate 4.5%), who required thrombolytic therapy. One patient died of unrelated surgical complications. The PE rate in the matched cohort at the same institution was 12%. At the second institution, no patient had PE, and no complications were noted., Conclusions: In this patient population, prophylactic IVC filter placement appears to decrease the PE rate substantially, from 12 to 0%. The placement of IVC filters appears to be a safe and efficacious intervention for prevention of PE in high-risk patients.

Object: Synthetic bioabsorbable implants have recently been introduced in spinal surgery; consequently, the indications, applications, and results are still evolving. The authors used absorbable interbody spacers (Medtronic Sofamor Danek, Memphis, TN) packed with recombinant bone morphogenetic protein (Infuse; Medtronic Sofamor Danek) for single- and multiple-level transforaminal lumbar interbody fusion (TLIF) procedures over a period of 18 months. This is a consecutive case series in which postoperative computerized tomography (CT) scanning was used to assess fusion status., Methods: There were 22 patients (17 men, five women; 39 fusion levels) whose mean age was 41.6 years (range 23-70 years) and in whom the mean follow-up duration was 12.4 months (range 6-18 months). Bridging bone was noted as early as the 3-month postoperative CT scan when obtained; solid arthrodesis was routinely noted between 6 and 12 months in 38 (97.4%) of 39 fusion levels. In patients who underwent repeated CT scanning, the fusion mass appeared to increase with time, whereas the disc space height remained stable. Although the results are early (mean 12-month follow-up duration), there was only one noted asymptomatic delayed union/nonunion at L5-S1 in a two-level TLIF with associated screw breakage. There were no infections or complications related to the cages., Conclusions: The bioabsorbable cages appear to be a viable alternative to metal interbody spacers, and may be ideally suited to spinal interbody applications because of their progressive load-bearing properties.