Foundations in Spinal Endoscopy.

Spinal endoscopy has revolutionized the way spine surgeons deliver minimally invasive care for appropriately selected patients. The evolution of endoscopy has been tumultuous since its beginnings as a "blind" percutaneous procedure to access the disk until the present state, in which complex decompressions and even fusions can be accomplished through subcentimeter incisions. Engineering has played a crucial role in this evolution with advances in optics, illumination, and instrumentation that have allowed surgeons to work safely and efficiently in smaller and smaller corridors. Finally, the adaptation of enhanced recovery after surgery protocols have complemented the benefits offered by spinal endoscopy to help patients return to the quality of life they seek through surgical intervention. In this article, we explore foundational elements of spinal endoscopy and look ahead to the future of this maturing field.

Applications of augmented reality in the neurosurgical operating room: A systematic review of the literature.

Advancements in imaging techniques are key forces of progress in neurosurgery. The importance of accurate visualization of intraoperative anatomy cannot be overemphasized and is commonly delivered through traditional neuronavigation. Augmented Reality (AR) technology has been tested and applied widely in various neurosurgical subspecialties in intraoperative, clinical use and shows promise for the future. This systematic review of the literature explores the ways in which AR technology has been successfully brought into the operating room (OR) and incorporated into clinical practice. A comprehensive literature search was performed in the following databases from inception-April 2020: Ovid MEDLINE, Ovid EMBASE, and The Cochrane Library. Studies retrieved were then screened for eligibility against predefined inclusion/exclusion criteria. A total of 54 articles were included in this systematic review. The studies were sub- grouped into brain and spine subspecialties and analyzed for their incorporation of AR in the neurosurgical clinical setting. AR technology has the potential to greatly enhance intraoperative visualization and guidance in neurosurgery beyond the traditional neuronavigation systems. However, there are several key challenges to scaling the use of this technology and bringing it into standard operative practice including accurate and efficient brain segmentation of magnetic resonance imaging (MRI) scans, accounting for brain shift, reducing coregistration errors, and improving the AR device hardware. There is also an exciting potential for future work combining AR with multimodal imaging techniques and artificial intelligence to further enhance its impact in neurosurgery.

Delayed toxicity from gamma knife radiosurgery to lesions in and adjacent to the brainstem.

The aims of this study were to assess the incidence of, and risk factors for, delayed toxicity following gamma knife stereotactic radiosurgery (GKRS) to lesions in and adjacent to the brainstem. We retrospectively evaluated the delayed toxicity of GKRS following the treatment of 114 lesions in and adjacent to the brainstem in 107 patients. The median tumor volume was 6.2 cm(3) and the median dose to the tumor margin was 16Gy. The mean follow-up was 40 months. Thirteen patients (12%) demonstrated clinical evidence of delayed toxicity, with a median latency to the development of toxicity of 6 months. The actuarial incidence of toxicity at 1 year and 5 years was 10.2% and 13.8%. Larger tumor volume (p=0.02) and larger treatment volume (p=0.04) were associated with an increased incidence of delayed toxicity. Large lesions adjacent to the brainstem have a higher than previously suspected rate of delayed toxicity.

Historical Aspects of Stereotactic Radiosurgery: Concepts, People, and Devices.

Stereotactic radiosurgery is a modern discipline that emerged after World War II. It represents a synthesis of an approach to patient care that was not immediately embraced by either neurosurgeons or radiation oncologists, but which has been shown, time and again, to be advantageous for the treatment of intracranial pathology. Indeed, stereotactic radiosurgical techniques are now being rapidly adapted and adopted for the treatment of extracranial malignant and benign disease. Any examination of the individuals, devices, and technological advances that permitted stereotactic radiosurgery to become a preferred approach for patient care cannot be absolutely comprehensive but can provide insights into the evolution of the specialty and potential future prospects for further improvements in patient care. As Shakespeare wrote in The Tempest, "What's past is prologue."

Worldwide Access to Stereotactic Radiosurgery.

Stereotactic radiosurgery is a safe and effective technology that can address a variety of neurosurgical conditions, but in many parts of the world, access remains an issue. Although the technology is increasingly available in the United States, Canada, Europe, and parts of Asia, poor access to central nervous system (CNS) imaging and inadequate treatment equipment in other parts of the world limit the availability of radiosurgery as a treatment option. In addition, epidemiologic data about cancer and CNS metastases in low-income countries are sparse and much less complete than in more developed countries, and the need for radiosurgery may be underestimated as a result. Current radiosurgical platforms can be expensive to install and require a substantial amount of personnel training for safe operation. Socioeconomic and political forces are relevant to limitations to and opportunities for improving access to care. Here we examine the current barriers to access and propose areas for future efforts to improve global availability of radiosurgery for neurosurgical conditions.

De Novo Mutation in Genes Regulating Neural Stem Cell Fate in Human Congenital Hydrocephalus.

Congenital hydrocephalus (CH), featuring markedly enlarged brain ventricles, is thought to arise from failed cerebrospinal fluid (CSF) homeostasis and is treated with lifelong surgical CSF shunting with substantial morbidity. CH pathogenesis is poorly understood. Exome sequencing of 125 CH trios and 52 additional probands identified three genes with significant burden of rare damaging de novo or transmitted mutations: TRIM71 (p = 2.15 × 10-7), SMARCC1 (p = 8.15 × 10-10), and PTCH1 (p = 1.06 × 10-6). Additionally, two de novo duplications were identified at the SHH locus, encoding the PTCH1 ligand (p = 1.2 × 10-4). Together, these probands account for ∼10% of studied cases. Strikingly, all four genes are required for neural tube development and regulate ventricular zone neural stem cell fate. These results implicate impaired neurogenesis (rather than active CSF accumulation) in the pathogenesis of a subset of CH patients, with potential diagnostic, prognostic, and therapeutic ramifications.

Postoperative Gamma Knife surgery for benign meningiomas of the cranial base.

OBJECT: The standard treatment for meningiomas is complete resection, but the proximity of skull base meningiomas to important neurovascular structures makes complete excision of the lesion difficult or impossible. The authors analyzed the mid- and long-term results obtained in patients treated with postresection Gamma Knife surgery (GKS) for residual or recurrent benign meningiomas of the cranial base. METHODS: Thirty-six patients with residual or recurrent benign meningiomas of the skull base following one or more surgical procedures underwent GKS. There were 31 women and five men, ranging in age from 22 to 73 years. The median tumor volume was 4.1 ml (range 0.8-20 ml) and the median radiation dose to the tumor margin was 16 Gy (range 15-16 Gy). RESULTS: Patients were followed for a median of 81 months (range 30-141 months) after GKS. At the end of the follow-up period, overall neurological improvement was observed in 16 patients (44.4%), whereas the condition in 20 patients (55.6%) was unchanged. One patient suffered transient cerebral edema 6 months after GKS. Based on imaging documentation, a partial response was seen in five patients (13.9%), the disease remained stable in 30 patients (83.3%), and in one patient (2.8%) there was an increase in tumor size. The actuarial progression-free survival rate was 100% at 5 years and 94.7% at 10 years. CONCLUSIONS: Gamma Knife surgery was shown to be an excellent adjunct to resection because of its durable rate of tumor control and low toxicity. It should be initially considered along with surgery for the treatment of complex skull base meningiomas.

Theoretical Basis of Vagus Nerve Stimulation.

Despite a myriad of medical and surgical treatments for epilepsy developed over the past few decades, a large subset of patients remains refractory to treatment. Over this time period, vagus nerve stimulation (VNS) has become an accepted and viable treatment modality for this population. Since the earliest report of VNS implantation in 1988, tens of thousands of patients worldwide have received VNS therapy, and >100,000 patient-years of experience have been accrued. The mechanisms underlying the response to VNS therapy continue to be elucidated. As understanding of the VNS mechanisms of action continues to grow, more pathologies will arise as potential treatment indications. Furthermore, current treatment populations with refractory epilepsy, depression, and inflammatory diseases may enjoy improved response to stimulation.

The current status of endoscopy in transsphenoidal surgery: an international survey.

OBJECTIVE: A survey-based study was designed to assess opinions related to transsphenoidal endoscopy, to evaluate the current global attitudes of neurosurgeons regarding the use of this procedure, and to solicit basic data from key institutions worldwide, with the advantage that large series of cases become available for analysis. METHODS: A web-based multi-item questionnaire was distributed to the surgical departments of 393 neurosurgical centers by means of an invitation e-mail. The questionnaire was composed of 2 sections: section 1 focused on the surgical technique for pituitary adenomas (standard technique), and section 2 concentrated on surgery for skull base tumors (extended technique). Each section was composed of 2 parts: multiple choice questions and free textual responses. RESULTS: From a total of 393 neurosurgical centers, from 23 countries, that received the questionnaire, 87 of them (22%) submitted complete or incomplete responses. The surgical procedure, in 60 cases had been performed by a neurosurgeon, in 53 cases by a neurosurgeon and an otolaryngologist, and in 4 cases by an otolaryngologist only. The endoscope (2- and 3-dimensional) was used in 85.2% of transsphenoidal procedures versus the microscope in 14.8% of cases. The endonasal route was used for approach in 93.2% versus the sublabial route in 6.8% of cases. Computer-guided navigation was used by survey population in 71 cases, micro-Doppler in 51 cases, and Cavitron Ultrasonic Surgical Aspirator in 43 cases. Several hundreds of extrasellar tumors were operated using the extended technique. CONCLUSIONS: Transsphenoidal endoscopy for pituitary and anterior skull base tumors has become established as a routine method of dealing with a variety of lesions. The level of interest in the neurosurgical surgery community is reflected by the geometric expansion of contributions to the literature on endoscopic surgery.

Metastatic melanoma to the brain: prognostic factors after gamma knife radiosurgery.

PURPOSE: To identify important prognostic factors predictive of survival and tumor control in patients with metastatic melanoma to the brain who underwent gamma knife radiosurgery. METHODS AND MATERIALS: A total of 122 consecutive patients with 332 intracranial melanoma metastases underwent gamma knife radiosurgery over a 5-year period. Of these, 39 (32%) also received whole-brain irradiation (WBI). The median tumor volume was 0.8 cm(3) (range: 0.02-30.20 cm(3)), and the median prescribed dose was 20 Gy (range: 14-24 Gy). Median follow-up was 6.8 months. Univariate and multivariate analyses of survival and freedom from progression were performed using the following parameters: status of systemic disease, intracranial tumor volume, number of lesions, tumor location, Karnofsky performance status, gender, age, and WBI. RESULTS: Overall median survival was 7.0 months from time of radiosurgery and 9.1 months from the onset of brain metastasis. In multivariate analysis, improved survival was noted in patients with total intracranial tumor volume <3 cm(3) (p = 0.003) and inactive systemic disease (p = 0.0065), whereas other parameters studied were of lesser importance (tumor location, p = 0.056, and Karnofsky performance status, p = 0.086), or of no significance (number of lesions, WBI, age, and gender). Freedom from subsequent brain metastasis depended on intracranial tumor volume (p = 0.0018) and status of systemic disease (p = 0.034). CONCLUSIONS: Stereotactic radiosurgery is an effective treatment modality for patients with intracranial metastatic melanoma. Tumor volume and status of systemic disease are good independent predictors of survival and freedom from tumor progression.

Virtual reality surgery: neurosurgery and the contemporary landscape.

OBJECTIVE: Virtual reality-simulated environments have been used for the training of personnel, most notably for military applications, for more than 35 years. The advantages conferred by being able to train novice personnel in a low- to no-risk simulated environment have long been appreciated by the medical community. The recent availability of affordable gigahertz-range microprocessors (once the exclusive domain of the Cray supercomputer) has made photorealistic graphical rendering and manipulation of virtual surgical substrates a reality. Concomitant advances in artificial intelligence systems and the portability of patient-specific magnetic resonance imaging, computed tomographic scanning, and angiographic image data presage the emergence of the surgical simulator as a modern surgical training adjunct. An overview of the status of surgical simulation with regard to its adaptability to current surgical training regimens is presented. METHODS: Extensive MEDLINE, Internet, and other database searches spanning the years 1960 to 2002 were conducted in an effort to delineate the status of simulated surgical environments. RESULTS: As would be expected, most articles addressing surgical simulation as their primary focus have been published in the past decade. A review of this literature demonstrates the broadest application in the field of endoscopic (and laparoscopic) procedures, most likely as a result of the reduced engineering burden with respect to incorporation of a haptic interface. CONCLUSION: The realization of ergonomically acceptable haptic interfaces remains elusive. Improvements in graphical rendering and the incorporation of artificial intelligence functions signal the certain emergence of surgical simulators as a viable supplement to the Halstedian method of surgical training.

The genesis of neurosurgery and the evolution of the neurosurgical operative environment: part I-prehistory to 2003.

Despite its singular importance, little attention has been given to the neurosurgical operative environment in the scientific and medical literature. This article focuses attention on the development of neurosurgery and the parallel emergence of its operative setting. The operative environment has, to a large extent, defined the "state of the art and science" of neurosurgery, which is now undergoing rapid reinvention. During the course of its initial invention, major milestones in the development of neurosurgery have included the definition of anatomy, consolidation of a scientific basis, and incorporation of the practicalities of anesthesia and antisepsis and later operative technical adjuvants for further refinement of action and minimalism. The progress, previously long and laborious in emergence, is currently undergoing rapid evolution. Throughout its evolution, the discipline has assimilated the most effective tools of modernity into the operative environment, leading eventually to the entity known as the operating room. In the decades leading to the present, progressive minimalization of manipulation and the emergence of more refined operative definition with increasing precision are evident, with concurrent miniaturization of attendant computerized support systems, sensors, robotic interfaces, and imaging devices. These developments over time have led to the invention of neurosurgery and the establishment of the current state-of-the-art neurosurgical operating room as we understand it, and indeed, to a broader definition of the entity itself. To remain current, each neurosurgeon should periodically reconsider his or her personal operative environment and its functional design with reference to modernity of practice as currently defined.

Endovascular restorative neurosurgery: a novel concept for molecular and cellular therapy of the nervous system.

The amalgam of molecular biology and neurosurgery offers immense promise for neurorestoration and the management of neurodegenerative deficiencies, developmental disorders, neoplasms, stroke, and trauma. This article summarizes present strategies for and impediments to gene therapy and stem cell therapy of the central nervous system and advances the concept of a potential new approach, namely endovascular restorative neurosurgery. The objectives of gene transfer to the central nervous system are efficient transfection of host cells, selective sustained expression of the transgene, and lack of toxicity or immune excitation. The requisite elements of this process are the identification of candidate diseases, the construction of vehicles for gene transfer, regulated expression, and physical delivery. In the selection of target disorders, the underlying genetic events to be overcome, as well as their spatial and temporal distributions, must be considered. These factors determine the requirements for the physical dispersal of the transgene, the duration of transgene expression, and the quantity of transgene product needed to abrogate the disease phenotype. Vehicles for conveying the transgene to the central nervous system include viral vectors (retroviruses, lentiviruses, adenoviruses, adeno-associated viruses, and herpes simplex virus), liposomes, and genetically engineered cells, including neural stem cells. Delivery of the transgene into the brain presents several challenges, including limited and potentially risky access through the cranium, sensitivity to volumetric changes, restricted diffusion, and the blood-brain barrier. Genetic or cellular therapeutic agents may be injected directly into the brain parenchyma (via stereotaxy or craniotomy), into the cerebrospinal fluid (in the ventricles or cisterns), or into the bloodstream (intravenously or intra-arterially). The advantages of the endovascular route include the potential for widespread distribution, the ability to deliver large volumes, limited perturbation of neural tissue, and the feasibility of repeated administration.

Measurements of the relative output factors for CyberKnife collimators.

OBJECTIVE: To determine accurately the relative output factors, defined as the ratio of the nominal dose rate for a given collimator to that of the 60-mm collimator. This is particularly important for radiosurgical treatment of functional disorders, such as trigeminal neuralgia, in which a single large radiation dose is delivered to the target with a small collimator, such as the 5-mm collimator for CyberKnife radiosurgery. Numerous studies on the output factors have been reported for the Leksell gamma knife unit but none for the CyberKnife system. METHODS: Measurements of the relative output factors for all 12 collimators were performed by three different methods: silicon diode, radiographic film, and thermoluminescent dosimetry microcubes. The silicon diode is designed for measurements in small (1-50 MV) photon beams performed in water or air. Film and thermoluminescent dosimetry measurements were performed in a plastic phantom. RESULTS: The measured relative output factors for the three methods were very similar except for the three smallest collimators (5, 7.5, and 10 mm). The measured difference between the above methods was approximately 2%. The mean value of the output factor for the 5-mm collimator was 0.686 +/- 0.024. The uncertainties of the output factors are expected to increase with the decrease of collimator diameter. They range from approximately 1 to 4% of the relative output factor. CONCLUSION: The relative output factor can be measured with an acceptable accuracy even for the smallest (5-mm) CyberKnife collimators. This requires the selection of appropriate dosimetric detectors and measuring procedures. The results obtained with the diode are considered more accurate than with the other two methods.

Engineering of the extracellular matrix: working toward neural stem cell programming and neurorestoration--concept and progress report.

In the concept of neurorestoration, cellular and structural elements that have been lost are replaced, and their function is restored. Central to this therapeutic strategy is the transplantation of neural progenitor cells such as clonogenically expanded stem cells. Stem cells make decisions regarding fate and patterning in response to external environmental signals. The therapeutic effectiveness of neural stem cells may be facilitated by the ability to manipulate these signals in a temporal and spatially appropriate fashion. Artificial deoxyribonucleic acid and artificial protein technology combines elements of protein engineering, molecular biology, and recombinant deoxyribonucleic acid technology to produce proteins with functional domains derived from naturally occurring proteins and represents a potentially powerful tool to modulate stem cell behavior. To this end, we have developed three artificial extracellular matrix proteins that incorporate the active domain of hJagged1 and hDelta1 into an elastin backbone. hJagged1 and hDelta1 are members of the DSL family of ligands to the Notch receptor, a signaling system that is very important in development and is the strongest known signal to instruct neural progenitor cells to choose glial fates over neuronal fates. The successful cloning of the artificial genes was confirmed by test digestions with appropriate restriction enzymes as well as direct deoxyribonucleic acid sequencing. In addition, we have demonstrated that all three artificial extracellular matrix proteins express at a high level in a prokaryotic host. This report describes the concept and progress in an entirely novel and previously unreported approach to modulate neural stem cell behavior. Its future application could include in vitro processing of stem cells before transplantation, supporting and programming the cells after transplantation, as well as the development of bioactive biomaterials.

Dosimetric comparison of CyberKnife with other radiosurgical modalities for an ellipsoidal target.

OBJECTIVE: To compare treatment plans obtained with the CyberKnife (CK) (Accuray, Inc., Sunnyvale, CA) with those of other commonly used radiosurgical modalities, such as the gamma knife (GK), linear accelerator multiple arcs, conformally shaped static fields, and intensity-modulated radiotherapy (IMRT). METHODS: An ellipsoidal simulated target was chosen centrally located in a three-dimensional model of a patient's head acquired with magnetic resonance or computed tomographic imaging. It was 25 mm in diameter and 35 mm long. The aims of treatment plans were 100% target volume coverage with an appropriate isodose line, minimum radiation dose to normal tissue, and clinically acceptable delivery. These plans were evaluated by use of a dose-volume histogram and other commonly used radiosurgical parameters such as target coverage, homogeneity index, and conformity index. RESULTS: All selected treatment modalities were equivalent in providing full target coverage. For dose homogeneity, all modalities except for multiple isocenter plans for GK (homogeneity index, 2.0) were similar (homogeneity index, congruent with 1.25). Dose conformity was essentially equivalent for all treatment plans except for IMRT, which had a slightly higher value (conformity index, congruent with 1.27). There was a substantial variation in the radiation dose to normal tissue between the studied modalities, particularly at the lower dose levels. CONCLUSION: CK plans seemed to be more flexible for a given target size and shape. For a target of limited volume and essentially of any shape, one could obtain similarly good conformal dosimetry with CK and GK. For a regular-shaped but other than spherical target, homogeneous dose distribution could be obtained with all selected modalities except for multiple isocenters, linear accelerator multiple arcs, or GK. Both IMRT and conformally shaped static fields offered good alternative treatment modalities to CK, GK, or linear accelerator multiple arc radiosurgery, with slightly inferior dosimetry in conformity (IMRT).

The genesis of neurosurgery and the evolution of the neurosurgical operative environment: part II--concepts for future development, 2003 and beyond.

The future development of the neurosurgical operative environment is driven principally by concurrent development in science and technology. In the new millennium, these developments are taking on a Jules Verne quality, with the ability to construct and manipulate the human organism and its surroundings at the level of atoms and molecules seemingly at hand. Thus, an examination of currents in technology advancement from the neurosurgical perspective can provide insight into the evolution of the neurosurgical operative environment. In the future, the optimal design solution for the operative environment requirements of specialized neurosurgery may take the form of composites of venues that are currently mutually distinct. Advances in microfabrication technology and laser optical manipulators are expanding the scope and role of robotics, with novel opportunities for bionic integration. Assimilation of biosensor technology into the operative environment promises to provide neurosurgeons of the future with a vastly expanded set of physiological data, which will require concurrent simplification and optimization of analysis and presentation schemes to facilitate practical usefulness. Nanotechnology derivatives are shattering the maximum limits of resolution and magnification allowed by conventional microscopes. Furthermore, quantum computing and molecular electronics promise to greatly enhance computational power, allowing the emerging reality of simulation and virtual neurosurgery for rehearsal and training purposes. Progressive minimalism is evident throughout, leading ultimately to a paradigm shift as the nanoscale is approached. At the interface between the old and new technological paradigms, issues related to integration may dictate the ultimate emergence of the products of the new paradigm. Once initiated, however, history suggests that the process of change will proceed rapidly and dramatically, with the ultimate neurosurgical operative environment of the future being far more complex in functional capacity but strikingly simple in apparent form.

Study of magnetic resonance imaging-based arteriovenous malformation delineation without conventional angiography.

OBJECTIVE: In this study, we aimed to assess the feasibility of arteriovenous malformation (AVM) delineation for gamma knife radiosurgery without conventional angiography and to correlate factors that may affect AVM delineation. METHODS: A series of 57 consecutive patients with AVMs treated with gamma knife radiosurgery from August 1994 to December 2000 were reviewed. All patients in the study had undergone pretreatment angiography. The mean AVM volume was 2.8 cm(3), with a median of 2.0 cm(3) (range, 0.04-22 cm(3)). All AVMs were delineated on the original frame-based magnetic resonance imaging (MRI) scans by a vascular neurosurgeon without the assistance of angiography and then compared with the actual AVM delineation on the basis of previously performed angiography and MRI. Univariate correlation analysis was used to determine the relationship of AVM coverage, size, diffuseness, previous embolization, and hemorrhage parameters. RESULTS: The study volume or MRI-based volume alone coincided with the actual treatment volume by a mean of 58% for diffuse and 87% for nondiffuse AVMs (P = 0.0005). At AVM volume greater than 2 cm(3), the median percentage of coinciding volume was 63% for embolized AVMs and 82% for nonembolized AVMs (P = 0.0315). Conversely, the study volume overestimated the actual treatment volume by a mean of 57% for AVMs larger than 2 cm(3) versus 25% for AVMs smaller than 2 cm(3) (P = 0.0012). In general, the percentage of the coinciding volume was inversely related to that of the excess volume, whereas both the study volume and the coinciding volume were proportionate to AVM volume at treatment. CONCLUSION: MRI-based AVM delineation without conventional angiography may be feasible only for selected patients, such as those with nondiffuse and large nonembolized AVMs.

Reliability of three-dimensional fluoroscopy for detecting pedicle screw violations in the thoracic and lumbar spine.

OBJECTIVE: Thoracic and lumbar pedicle screws have become popular because of their biomechanical superiority over other methods of spinal fixation. However, the safety and efficacy of transpedicular screws depend on their proper placement. Recent advances in imaging have resulted in the ability to acquire three-dimensional (3-D) axial images of the spine during surgery, and this study was undertaken to assess the reliability of this technology to detect pedicle violations. METHODS: Pedicle screws were placed in six human cadaver spines from T1 to S1 using standard techniques. Intentional pedicle violations were created in 74 of 216 pedicles, and violations were graded on a four-point scale (range, 0-3). Radiographic images were then obtained using a conventional spiral computed tomographic scanner and the Siremobil Iso-C 3D (Siemens Medical Solutions, Erlangen, Germany) 3-D fluoroscopy unit. An independent neuroradiologist then graded pedicle violations as ascertained by the two imaging modalities. RESULTS: Using direct inspection of the pedicles as the "gold standard," the overall sensitivity and specificity for detecting pedicle violations were 0.716 and 0.789, respectively, with 3-D fluoroscopy. The overall sensitivity and specificity for detecting pedicle violations were 0.608 and 0.937, respectively, with conventional computed tomography. All Grade 2 pedicle violations were detected in the thoracic spine by both modalities, and all Grade 3 violations were detected by both modalities. CONCLUSION: Axial images obtained with 3-D fluoroscopy demonstrate a higher sensitivity but lower specificity than conventional computed tomographic scanning for assessing pedicle violations. By providing real-time intraoperative imaging, 3-D fluoroscopy may enhance the safety of thoracic transpedicular instrumentation.