The surgeons of Boulder Neurosurgical & Spine Associates (BNA) founded the Justin Parker Neurological Institute (JPNI) for the purpose of conducting clinical research, as well as to advance knowledge for medical providers, and to practice medicine through innovations in clinical technology. JPNI conducts investigator-initiated research and is often the practice of choice for multiple FDA-controlled clinical research trials. Our physicians have collectively published their research in hundreds of peer-reviewed journals and presented at national and international meetings.
The value of being a research-driven organization is that we practice evidence-based medicine and our patients are afforded access to the most advanced technologies that may not otherwise be available for clinical use at the time. BNA patients are offered to participate in studies evaluating the newest devices and treatment methods, including stem cell therapy, laser-assisted minimally invasive spine surgeries, dynamic motion stabilization systems, cervical and lumbar artificial discs.
Case Report: Chiari Malformation and Hydrocephalus Masking Neurocysticercosis
Sharad Rajpal, MD, Colson Tmoberlan, Andrew Bauer, MD, Robert C. Forsythe, MD, Sigtia Burneikiene, MD
Various diagnostic characteristics associated with neurocysticercosis have been well studied; however, their potential to be implicated in other differential diagnoses has not been well demonstrated. We report the case of a 55-year-old Hispanic man who underwent a Chiari decompression surgery, which was complicated with hydrocephalus.
Despite a ventriculoperitoneal shunt placement, he continued to have headaches and was soon found to have several skull base subarachnoid lesions, which were later diagnosed as the sequelae of an active neurocysticercosis infection. This case report highlights the importance of overlapping symptoms between diseases in a short temporal context.
Medical Complications and Mortality in Octogenarians Undergoing Elective Spinal Fusion Surgeries
Sharad Rajpal, MD, E. Lee Nelson, MD, Alan T. Villavicencio, MD, Jayratna Telang, Roshan Kantha, Kara Beasley, DO, Sigita Burneikiene, MD
The consequences of suffering postoperative complications in elderly undergoing spinal surgeries may be different compared to younger patients. The primary objective of this study was to identify the types and frequency of medical complications and mortality rates in patients 80 years of age or older undergoing elective spinal fusion surgeries for degenerative spinal disease.
The Timing of Surgery and Symptom Resolution in Patients Undergoing Transforaminal Lumbar Interbody Fusion for Lumbar Degenerative Disk Disease and Radiculopathy
Alan T. Villavicencio, MD, E. Lee Nelson, MD, Sharad Rajpal, MD, Sigita Burneikiene, MD
Success rates of surgical interventions for lumbar disorders vary significantly depending on multiple factors and, among them, the duration of symptoms. It is not clear whether there is a “cutoff” time when decompression and fusion surgery becomes less effective in the conditions with chronic nerve root compression symptomatology. The main objective of this study was to analyze whether duration of symptoms has any effect on clinical outcomes and primarily resolution of radicular pain symptoms due to degenerative disk disease and stenosis with spondylolisthesis in patients undergoing transforaminal lumbar interbody fusion (TLIF).
RhBmP-2-Induced Radiculitis in Patients Undergoing Transforaminal Lumbar Interbody Fusion: Relationship to Dose
Alan T. Villavicencio, MD, Sigita Burneikiene, MD
Recombinant human bone morphogenetic protein-2 (rhBMP-2) remains the primary synthetic osteoinductive material used in spinal fusion surgery today. The early inflammation reaction to rhBMP-2 manifesting with radicular symptoms has been previously reported in patients undergoing transforaminal lumbar interbody fusion (TLIF). There is a disagreement with regard to the factors affecting its occurrence and whether such symptoms are dose dependent. The purpose of this analysis was to determine the incidence of rhBMP-2-induced radiculitis and its relationship to dose.
Prediction Based on Preoperative Opioid use of Clinical Outcomes After Transforaminal Lumbar Interbody Fusions
Alan T. Villavicencio, MD, E. Lee Nelson, MD, Vinod Kantha, BA, and Sigita Burneikiene, MD. JNS Spine 2016.
Opioid analgesics have become some of the most prescribed drugs in the world, despite the lack of longterm studies evaluating the benefits of opioid medications versus their risks associated with chronic use. In addition, long-term opioid use may be associated with worse long-term clinical outcomes. The primary objective of this study was to evaluate whether preoperative opioid use predicted inferior clinical outcomes among patients undergoing transforaminal lumbar interbody fusion (TLIF) for symptomatic lumbar degenerative disc disease.
Post-Treatment Gliosarcoma Extension into the Pterygomaxillary Fossa: Literature Review and Case Report
Mason A, Villavicencio AT, Nelson EL, Forsythe RC, Burneikiene S. Cureus 2016.
Only four primary gliosarcoma case reports are described in the literature with transcranial (intradural to extradural) penetration into the region of the infratemporal fossa. This is the first report of a primary glioblastoma (GBM) that evolved into secondary or post-treatment gliosarcoma without evidence of a second de novo tumor and with extension into the left pterygomaxillary fossa.
Guidelines for the Diagnosis and Treatment of Degenerative Lumbar Spondylolisthesis
Matz PG, Meagher RJ, Lamer T, Tontz WL, Annaswamy TM, Cassidy RC, Cho CH, Dougherty P, Easa JE, Enix DE, Gunnoe BA, Jallo J, Julien TD, Maserati MB, Nucci RC, O’Toole JE, Rosolowski K, Sembrano JN, Villavicencio AT, Witt JP. The Spine Journal 2016.
The North American Spine Society (NASS) assembled a group of experts in the field to develop evidence-based clinical guidelines for the diagnosis and treatment of degenerative lumbar spondylolisthesis. Dr. Alan Villavicencio was among the contributing authors in developing the guidelines that were published by The Spine Journal. The published article features evidence-based recommendations for diagnosing and treating degenerative lumbar spondylolisthesis. The guidelines are intended to reflect contemporary treatment concepts for symptomatic degenerative lumbar spondylolisthesis. The NASS guidelines on this topic is the only guidelines on degenerative lumbar spondylolisthesis included in the Agency for Healthcare Research and Quality’s National Guideline Clearinghouse (NGC).
Case Series of Anterior Intervertebral Graft Extrusions in Transforaminal Lumbar Interbody Fusion Surgeries
Villavicencio AT, Nelson EL, Rajpaj S, Otalora F, Burneikiene S. World Neurosurgery 2016.
The main purpose of this chart review study was to report on the clinical course and outcomes of patients who had anterior intervertebral graft extrusions after transforaminal lumbar interbody fusion (TLIF).The incidence of graft extrusion was 0.6% (7 of 1259 patients). All patients remained asymptomatic during the follow-up period and had solid fusion despite extrusions with an average time to fusion of 13 months (range, 10-18 months). The risks of additional and highly invasive revision surgery should be weighed against the potential short-term and long-term complications associated with graft extrusions or migrations. It was demonstrated that fusion may take longer but can be achieved, and close observation may be adequate for asymptomatic patients.
A Preliminary Report on the CO2 Laser for Lumbar Fusion: Safety, Clinical Outcomes and Technical Considerations
Villavicencio AT, Babuska J, Nelson EL, Mason A, Burneikiene S. Cureus 2015.
The purpose of this study was to evaluate potential technical advantages of the CO2 laser technology in mini-open transforaminal lumbar interbody fusion (TLIF) surgeries and report our preliminary clinical data on the safety and clinical outcomes. Safety and clinical outcomes were compared between two groups: 24 patients that underwent CO2 laser-assisted one-level TLIF surgeries and 30 patients that underwent standard one-level TLIF surgeries without the laser. There were no neural thermal injuries or other intraoperative laser-related complications encountered in this cohort of patients. At a mean follow-up of 17.4 months, significantly reduced lower back pain scores (P=0.013) were reported in the laser-assisted patient group compared to a standard fusion patient group. Lower extremity radicular pain intensity scores were similar in both groups. Laser-assisted TLIF surgeries showed a tendency (P = 0.07) of shorter operative times that was not statistically significant. Based on this preliminary clinical report, the safety of the CO2 laser device for lumbar fusion surgeries was assessed. There were no neural thermal injuries or other intraoperative laser-related complications encountered in this cohort of patients. Further investigation of CO2 laser-assisted lumbar fusion procedures is warranted in order to evaluate its effect on clinical outcomes.
Unilateral and Bilateral Pedicle Screw Fixation in Transforaminal Lumbar Interbody Fusion: Radiographic and Clinical Analysis
Villavicencio AT, Serxner BJ, Mason A, Nelson EL, Rajpal S, Faes N, Burneikiene S. World Neurosurgery 2015.
Unilateral pedicle screw plus interspinous process plate fixation was associated with significantly reduced surgical invasiveness. This technique was also associated with a slightly lower reduction in foraminal height and was equally effective as bilateral pedicle screw fixation in regard to fusion rates, clinical outcomes, and other radiographic outcomes studied.
The Duration of Symptoms and Clinical Outcomes in Patients Undergoing Anterior Cervical Discectomy and Fusion for Degenerative Disc Disease and Radiculopathy
Burneikiene S, Nelson EL, Mason A, Rajpal S, Villavicencio AT. Spine Journal 2015.
Anterior cervical discectomy and fusion (ACDF) surgery is quite effective in relieving radiculopathy symptoms in patients suffering from symptomatic cervical spondylosis. However, the optimal timing for surgical treatment has not been clearly defined. Insurance companies require at least a 6-week trial of conservative treatment before approving this procedure. The systematic reviews that analyzed if timing of surgery had any effect on clinical outcomes found insufficient evidence to make any recommendations. On the contrary, the vast majority of reports published in the literature on the duration of symptoms (DOS) and clinical outcome correlation in patients undergoing lumbar surgeries for painful degenerative disc disease and radiculopathy agree that shorter DOS before surgery resulted in improved clinical outcomes. The primary purpose of this study was to analyze if the DOS has any effect on clinical outcomes and resolution of radicular symptoms in patients undergoing ACDF for cervical radiculopathy because of degenerative disc disease.
Recombinant Human Morphogenetic Protein (rhBMP-2). NASS Coverage Policy Recommendation
Bono C, Baisden J, Baker R, Biyani A, Boakye M, Cho C, DePalma M, Dietze D, Easa J, Ghiselli G, Glaser J, Harrop J, Lapinsky A, Lebl D, Matz P, O’Brien D, Patel A, Reiter M, Reitman C, Riley L, Sharan A, Summers J, Tontz W, Toton J, Tromanhauser S, Truumees E, Villavicencio A, Zindrick M.
This coverage policy document addresses the scope and clinical indications for Recombinant human
bone morphogenetic protein-2 (rhBMP-2) in spinal fusion surgeries only. Based on the available evidence, rhBMP is indicated as an adjunct to spinal fusion in cases in which other alternatives are either not available or are not likely to lead to successful fusion. As a clearer picture of the risks and potential for adverse events after rhBMP implantation emerges, a reassessment of the risk-benefit calculus is required. This will likely be an ongoing process in the future. For the purpose of determining coverage at the current time, this calculation can be generalized in several anatomic areas and clinical scenarios in which rhBMP should NOT be used. These include patients very likely to fuse without rhBMP, most pediatric patients, healthy patients undergoing one level lumbar fusion procedures, and routine anterior and posterior cervical fusions.
The Accuracy of Pedicle Screw Placement Using Intraoperative Image Guidance Systems
Mason A, Paulsen R, Babuska JM, Rajpal S, Burneikiene S, Nelson EL, Villavicencio AT. J Neurosurgery Spine 2014.
Several retrospective studies have demonstrated higher accuracy rates and increased safety for navigated pedicle screw placement than for free-hand techniques; however, the accuracy differences between navigation systems has not been extensively studied. In some instances, 3D fluoroscopic navigation methods have been reported to not be more accurate than 2D navigation methods for pedicle screw placement. The authors of this study endeavored to identify if 3D fluoroscopic navigation methods resulted in a higher placement accuracy of pedicle screws.
Preliminary Results on Feasibility of Outpatient Instrumented Transforaminal Lumbar Interbody Fusion
Villavicencio AT, Nelson EL, Mason A, Rajpal S, Burneikiene S. J Spinal Disord Tech 2013.
The primary objective of this study was to analyze our preliminary results to examine whether it is safe and effective to perform instrumented lumbar interbody fusions on an outpatient basis by comparing 2 groups of patients who were discharged the same day versus those who stayed overnight. The secondary objective was to identify the need for prolonged observation for complications that may occur in the immediate postoperative period.
Complications in Patients Undergoing Combined Transforaminal Lumbar Interbody Fusion and Posterior Instrumentation with Deformity Correction For Degenerative Scoliosis and Spinal Stenosis
Burneikiene S, Nelson EL, Mason A, Rajpal S, Serxner B, Villavicencio AT. Surgical Neurology International 2012.
Utilization of the transforaminal lumbar interbody fusion (TLIF) approach for scoliosis offers the patients deformity correction and interbody fusion without the additional morbidity associated with more invasive reconstructive techniques. The purpose of this study was to quantify the intra- and postoperative complications associated with the TLIF surgical approach in patients undergoing surgery for spinal stenosis and degenerative scoliosis correction.
Surgical Treatment Strategies for the Previously Operated Lumbar Spine
Villavicencio AT, Nelson EL, Burneikiene S, Arends G. Contemporary Spine Surgery 2012.
This review focuses on some contemporary surgical treatment strategies for the previously operated lumbar spine. Patients who fail to improve after spine surgery or those who develop new symptoms after initially “successful” surgery are commonly labeled with failed back surgery syndrome (FBSS). Multiple factors may be responsible for this complex syndrome, and various therapeutic approaches should be employed for structural anatomic and nonstructural problems in the previously operated spine. Any surgical intervention should be considered with a specific etiologic cause in mind. Newer technologies in spine surgery are discussed with an emphasis on technical difficulties involved in the revision surgery.
Effect on Clinical Outcomes of Patient Pain Expectancies and Preoperative Mental Component Summary Scores from the 36-item Short Form Health Survey following Anterior Cervical Discectomy and Fusion
Carr F, Healey K, Villavicencio AT, Nelson EL, Mason A, Burneikiene S, Hernandez T. J Neurosurgery Spine 2011.
The primary purpose of this study was to analyze what effect preoperative patient expectations and 36-Item Short Form Health Survey (SF-36) Mental Component Summary (MCS) scores have on clinical outcomes.
Prospective, Randomized, Double-Blind Clinical Study Evaluating the Correlation of Clinical Outcomes and Cervical Sagittal Alignment
Villavicencio AT, Babuska JM, Ashton A, Busch E, Roeca C, Nelson EL, Mason A, Burneikiene S. Neurosurgery 2011.
Sagittal alignment of the cervical spine has received increased attention in the literature as an important determinant of clinical outcomes after anterior cervical discectomy and fusion. Surgeons use parallel or lordotically fashioned grafts depending on preference or simple availability. The objective of this study was to quantitatively assess and compare cervical sagittal alignment and clinical outcome when lordotic or parallel allografts were used for fusion.
Minimally Invasive versus Open Transforaminal Lumbar Interbody Fusion
Villavicencio AT, Burneikiene S, Roeca C, Nelson EL, Mason A. Surgical Neurology International 2010.
The purpose of this study was to directly compare safety and effectiveness for minimally invasive (MI) and open approaches for transforaminal lumbar interbody fusion (TLIF).
Current Status of Clinical Evidence and Indications for Cervical Arthroplasty
Villavicencio AT, Hernandez T, Hughes BD, Healey K, Burneikiene S. Contemporary Neurosurgery 2010.
It has been predicted that cervical arthroplasty will replace fusion and become the new “gold standard” in the near future. Although short-term clinical results associated with cervical artificial disc replacement are promising, long-term benefits of reduced stress on the adjacent levels or effectiveness of cervical arthroplasty compared with anterior cervical discectomy and fusion (ACDF) remain unknown. The advantage of preserved segmental mobility should be weighed against potential negative effects on the facet joints and the possibility of late implant failure or loosening. Strict patient selection based on clear indications and absence of exclusion criteria should heavily outweigh the marketing enthusiasm.
Survival Following Stereotactic Radiosurgery for Newly Diagnosed and Recurrent Glioblastoma Multiforme: A Multicenter Experience
Villavicencio AT, Burneikiene S, Romanelli P, McNeeley L, Lipani JD, Fariselli L, McIntyre M, Chang SD, Nelson EL, Broggi G, Adler JR, Thramann JJ. Neurosurgical Review 2009.
The purpose of the current study was to retrospectively review the ability of CyberKnife radiosurgery to provide local tumor control of newly diagnosed or recurrent GBM. Twenty patients (43.5%) underwent CyberKnife treatment at the time of the initial diagnosis and/or during the first 3 months of their initial clinical management. The median survival from the CyberKnife treatment was 9.5 months (range, 0.25-31 months) and 7 months (range, 1-34 months) for patients in the newly diagnosed and recurrent GBM groups (Kaplan-Meier analysis, P = 0.79), respectively. There was no apparent survival advantage in using CyberKnife in initial management of glioblastoma patients and it should be reserved for patients whose tumors recur or progress after conventional therapy.
CyberKnife Radiosurgery for Trigeminal Neuralgia Treatment: A Preliminary Multicenter Experience
Villavicencio AT, Lim M, Burneikiene S, Romanelli P, Adler JR, McNeeley L, Chang SD, Fariselli L, McIntyre M, Bower R, Broggi G, Thramann JJ. Neurosurgery 2008.
Radiosurgery has gained acceptance as a treatment option for trigeminal neuralgia. Our preliminary multicenter experience treating trigeminal neuralgia with the CyberKnife was reported.
Neck Pain in Multisport Athletes
Villavicencio AT, Hernandez D, Burneikiene S, Thramann J. J Neurosurgery Spine 2007.
The sport of triathlon is very physically demanding and has experienced rapid growth in recent years. The number of triathletes seen for spine disorders at neurosurgery clinics is increasing. Neck pain and overuse injuries have not been adequately studied in multisport athletes. The authors undertook an epidemiological study to establish the lifetime incidence of neck pain and the prevalence of possible discogenic pain, and to identify risk factors among triathletes in the Boulder, Colorado area.
Spinal Artificial Disc Replacement: Cervical Arthroplasty Part I: History, Design, and Types of Artificial Discs
Villavicencio AT, Burneikiene S, Pashman R, Johnson JP. Contemporary Neurosurgery 2007.
Cervical arthroplasty is a rapidly developing surgical treatment option for degenerative disc disease of the cervical spine. This article reviews design features of the cervical devices currently being evaluated in FDA-controlled Investigational Device Exemption (IDE) prospective randomized clinical trials. Neural decompression and arthrodesis have been the mainstays of treatment for many cervical spinal conditions for more than 50 years. Artificial disc replacement surgery allows for effective decompression without sacrificing segmental motion, theoretically preserving the patient’s functional capacity. The importance of preservation of the spinal motion segment and restoration of normal physiologic biomechanics of the cervical spine is becoming increasingly recognized. Arthrodesis alters the biomechanics of the spine, possibly leading to further degeneration at adjacent levels. Early clinical studies have shown promise, but whether arthroplasty is capable of reducing adjacent level degeneration has not yet been proved in long-term prospective clinical trials.
Artificial Disc Replacement: Cervical Arthroplasty, Part II: Indications, Surgical Technique, and Complications
Villavicencio AT, Burneikiene S, Pashman R, Johnson JP. Contemporary Neurosurgery 2007.
Cervical arthroplasty is a rapidly advancing surgical treatment option for cervical spine degenerative disc disease. Although early clinical studies have shown promise, long-term prospective clinical trials are needed to prove whether arthroplasty is capable of reducing adjacent level degeneration, preserving motion and normal biomechanics of the spine, or achieving effective clinical outcomes. This article reviews indications, surgical technique, available preliminary clinical outcomes, and complications for cervical devices currently being evaluated in FDA-controlled Investigational Device Exemption prospective randomized clinical trials.
The Safety of Instrumented Outpatient Anterior Cervical Discectomy and Fusion
Villavicencio AT, Pushchak E, Burneikiene S, Thramann JJ. The Spine Journal 2007.
The purpose of this study was to evaluate the safety and feasibility of performing single, two- and three-level ACDF with instrumentation on an outpatient or 23-hour observation period basis without compromising the purported benefits of surgery.
Back and Neck Pain in Triathletes
Villavicencio AT, Burneikiene S, Hernandez T, Thramann JJ. Neurosurg Focus 2006.
As the sport of triathlon has continued to grow, increasing numbers of triathletes have presented in the neurosurgery clinics with various spinal disorders. This epidemiological study was undertaken to establish the lifetime incidence of neck and back pain, to gauge the prevalence of discogenic pain, and to identify risk factors among triathletes in the Boulder, Colorado, area.
Perioperative Complications in Transforaminal Lumbar Interbody Fusion versus Anterior–Posterior Reconstruction for Lumbar Disc Degeneration and Instability
Villavicencio AT, Burneikiene S, Bulsara KR, Thramann JJ. Spinal Disord Tech 2006.
Multiple different approaches are used to treat lumbar degenerative disc disease and spinal instability. Both anterior–posterior (AP) reconstructive surgery and transforaminal lumbar interbody fusion (TLIF) provide a circumferential fusion and are considered reasonable surgical options. The purpose of this study was to quantitatively assess clinical parameters such as surgical blood loss, duration of the procedure, length of hospitalization, and complications for TLIF and AP reconstructive surgery for lumbar fusion.
Elements of the Pre-Operative Workup, Case Examples
Villavicencio AT, Burneikiene S. Pain Medicine 2006.
Spinal cord stimulation (SCS) is a well-recognized method of treating a variety of chronic neuropathic conditions that are refractory to conservative management. One of the most challenging aspects of this technique is proper patient selection. In this study we reviewed available knowledge, differential diagnosis, and strategies utilized for the management of patients who were considered for a neurostimulation procedure. Clinical and neurological evaluation, complete diagnostic workup, a behavioral assessment, and a screening trial are all essential to determine a patient’s suitability for SCS implantation. A correct diagnosis and proper indications will help to achieve optimal treatment results and improve quality of life for a considerable number of patients suffering from intractable pain.
Safety of Transforaminal Lumbar Interbody Fusion and Intervertebral Recombinant Human Bone Morphogenetic Protein–2
Villavicencio AT, Burneikiene S, Nelson EL, Bulsara KR, Favors M, Thramann JJ. J Neurosurgery Spine 2005.
Recombinant human bone morphogenetic protein–2 (rhBMP-2) is being increasingly used for spinal fusion. This study analyzed its clinical safety, effectiveness, and clinical outcome when applied on an absorbable collagen sponge (ACS) in conjunction with allograft for transforaminal lumbar interbody fusion (TLIF).
Spinal Artificial Disc Replacement: Lumbar Arthroplasty Part I
Villavicencio AT, Burneikiene S, Johnson JP. Contemporary Neurosurgery 2005.
Artificial disc technology is designed to replace degenerated or injured discs with a prosthesis that allows for normal physiologic movement of the spine. Artificial discs offer an alternative to arthrodesis, and arthroplasty is expected to replace up to 25% of fusion surgeries in the future.
Spinal Artificial Disc Replacement: Lumbar Arthroplasty, Part II
Villavicencio AT, Burneikiene S, Johnson JP. Contemporary Neurosurgery 2005.
Indications for artificial disc replacement (ADR) are still being developed for each of the different devices. The ideal candidate for artificial disc replacement surgery has low back pain of discogenic origin with no significant facet joint changes, no previous fusion surgeries or other operations involving the facet joints at the level in question, no canal stenosis, and no more than 3 mm of spondylolisthesis. The patient should have received at least 6 months of conservative treatment with unsuccessful results.
Utility of Computerized Isocentric Fluoroscopy for Minimally Invasive Spinal Surgical Techniques
Villavicencio AT, Burneikiene S, Bulsara KR, Thramann JJ. Spinal Disord Tech 2005.
The purpose of this study was to prospectively evaluate the clinical utility and accuracy of intraoperative three-dimensional fluoroscopy as an adjunct for the placement of a complex spinal instrumentation.
CyberKnife Radiosurgery for Idiopathic Trigeminal Neuralgia
Lim M, Villavicencio AT, Burneikiene S, Chang SD, Romanelli P, McNeeley L, McIntyre M, Thramann JJ, Adler JR. Neurosurg Focus 2005.
The safety and efficacy of CyberKnife radiosurgery as a treatment option for TN is analyzed.
Intraoperative Three-Dimensional Fluoroscopy-Based Computerized Tomography Guidance for Percutaneous Kyphoplasty
Villavicencio AT, Burneikiene S, Bulsara KR, Thramann JJ. Neurosurg Focus 2005.
Percutaneous kyphoplasty is an established method for the treatment of pathological vertebral compression fractures (VCFs). This procedure is usually performed with the aid of biplanar fluoroscopic image guidance. There are currently no published clinical studies in which the use of three-dimensional (3D) image guidance to facilitate this technique has been evaluated. The purpose of this study was to evaluate the efficacy of isocentric fluoroscopy-based navigation for the kyphoplasty procedure, with special reference to operating time and the amount of radiation exposure.