Spinal Cases Research Articles

Volumetric modulated arc therapy planning based on virtual monochromatic images: Effect of inaccurate CT numbers on dose distributions

PurposeThough virtual monochromatic images (VMIs) at low energy levels can improve image quality, the measured Hounsfield unit (HU) values can be inaccurate. We assessed the dosimetric error due to inaccurate HU estimation in volumetric modulated arc therapy (VMAT) planning. MethodsBased on the VMIs at 50 keV (VMI50keV), 77 keV (VMI77keV) and single-energy CT (SECT) image for a phantom with different sizes, lookup tables (LUTL and LUTS) were created. Using an anthropomorphic phantom (head and spine regions), VMAT plans were generated based on VMI50keV, VMI77keV and SECT using the corresponding LUTL, and then, the doses were re-calculated using LUTS. For clinical cases, 30 VMAT plans (prostate, brain, and spine cases) were generated based on VMI50keV and VMI77keV. ResultsIn the anthropomorphic phantom study, the difference in the dosimetric parameters for planning target volume (PTV) in the VMAT plan based on the VMI77keV was smallest (within 0.1 Gy) among three types of treatment planning approach. In clinical cases, in general, the differences of the 3-dimensional gamma passing rate and dosimetric parameters in the treatment plans based on the VMI50keV were larger than those in the VMI77keV. Especially for brain cases, the difference for PTV was more prominent when AXB was used (the maximum difference was 0.5 Gy) than AAA. ConclusionsThe dosimetric error due to the inaccurate HU estimation was larger in the VMIs at low energy levels. This may be clinically insignificant, but should be avoided in the VMAT treatment planning.

Abstract No. 553 Preoperative embolization of bone cancers: tumor types, location, estimated blood loss, and blood transfusion requirements

Osseous metastases of certain primary cancers are hypervascular, such as renal cell carcinoma (RCC), and lead to concern for life-threatening high intra-operative blood loss and high intra-operative blood transfusion requirements. Some primary bone cancers can also appear hypervascular and in certain locations hemorrhage can lead to significant complications, such as the spine. Preoperative embolization of hypervascular osseous tumors is thought to decrease intra-operative bleeding. To evaluate intra-operative blood loss and blood transfusions after preoperative embolization, we reviewed our experience with preoperative embolization of osseous cancers. We reviewed imaging and medical charts for preoperative embolization by interventional radiology at a large academic institution for the past 4 years. Patient demographics, tumor type, tumor location, embolic agent(s) used, date of procedure and surgery, estimated blood loss (EBL), blood products administered and complications were reviewed. Thirteen bony tumors had preoperative embolization followed by surgical resection. The majority of the cancers, 62%, were renal cell carcinoma, followed by non-squamous cell lung cancer, 15%. The majority of cases involved the lower extremity, 62%, followed by the upper extremity, 23%, followed by the spine, 15%. The mean EBL for spine cases was 2850 mL versus 619 mL for non-spine cases, which was significantly different (p < 0.05). The EBL for lower extremity cases was 726 mL and for upper extremity cases was 333 mL. The mean EBL for RCC cases was higher than non-RCC cases (1051 mL versus 763 mL) but not significantly different (p = 0.8). The average packed red blood cells transfused was also highest for spine cases, 3 units versus 1.1 for extremity cases but this was not significantly different. The mean number of blood transfusions was also not significantly different depending on tumor type. There were no reported complications. No complications were reported with any of the preoperative embolizations or subsequent surgeries. EBL was significantly higher for spine cases. The mean EBL for RCC cases was higher than non-RCC cases but not significantly different.

Unplanned Immediate Return to Operating Room After Spine Surgery

Retrospective analysis; single center data. The purpose of this study is to look at the utility and relevance of immediate postoperative radiographs in providing vital information leading to immediate revision after spine surgery. Immediate postoperative radiographs are routinely obtained in the recovery room after spine surgery to verify the level, alignment of the spine, implant position, and the adequacy of the procedure. However, with the ability to utilize intraoperative fluoroscopy imaging for the same purpose, the requirement for immediate postoperative radiographs needs to be validated. The purpose of this study is to look at the utility and relevance of these postoperative radiographs in providing critical information that may warrant immediate intervention. Retrospective analysis of all spine surgeries (elective and emergent), performed at a single center from 2011 to 2016, was done and cases returning to operating room within 48 hours were identified. Indication of immediate revision was reviewed and utility of immediate postoperative radiographs in guiding immediate revision was analyzed. A total of 1804 elective and urgent spinal surgeries were performed by seven surgeons. Twenty-two patients returned to operating room within 48 hours of their index procedures. Of these 22 cases, only two patients were noted to have positive findings on recovery room radiographs. The findings of suboptimal spinal alignment or failed instrumentation led to the immediate revision in both cases. Both cases involved instrumentation at cervicothoracic region and intraoperative imaging provided only limited visualization. Routine recovery room radiographs played a role in the decision to emergently return to the operating room in 0.10% (2/1804) cases at our institution. The potential benefit of immediate recovery room radiographs after spine surgery should be weighed against the added healthcare cost and patient discomfort associated with obtaining these radiographs routinely. Imaging may be delayed to a more elective time without any significant risk in majority of spine cases. 3.

Venous Thromboembolism After Degenerative Spine Surgery: A Nationwide Readmissions Database Analysis

Venous thromboembolism (VTE) is an appreciable burden on health care. The protracted recumbency experienced by many spinal patients juxtaposed with concerns for postoperative hemorrhage from early anticoagulation results in conflicting stances regarding chemoprophylaxis. Identifying risk factors associated with VTE is therefore instrumental in guiding management. To identify VTE risk factors in patients undergoing degenerative spine surgery. The Nationwide Readmissions Database was searched for adults undergoing spine surgery for degenerative diseases between 2010 and 2014. The 30-day and 90-day VTE incidence was estimated from readmissions with new VTE diagnoses. A multivariate survey-adjusted logistic regression model was used to identify variables associated with VTE diagnoses on readmission. Of 838,507 degenerative spine cases queried, 3499 patients (0.42%) were readmitted with a VTE diagnosis within 30 days and 4321 patients (0.62%) were readmitted within 90 days. In multivariate analysis, steroids were independently associated with a higher likelihood of readmission with VTE at both 30 days (odds ratio, 1.58; P < 0.001) and 90 days (odds ratio, 1.97; P < 0.001). Significant associations were also identified with thoracolumbar surgery, length of stay, and discharge to institutional care. The incidence of readmission with VTE diagnoses in spine surgery is low. However, their devastating consequences underscore the need to identify those patients deemed high risk. These patients include those having thoracolumbar surgery, of advanced age, with prolonged length of stay, using corticosteroids, and with a disposition to institutional care (e.g., skilled nursing facility or long-term acute care). Given the association between steroids and VTE, clinicians should be judicious about perioperative administration despite their obvious antiinflammatory benefits.

An Institutional Review of Tuberculosis Spine Mimics on MR Imaging: Cases of Mistaken Identity

Although MRI has a spectrum of findings which help in the diagnosis of tuberculosis (TB) spine, a broad spectrum of spine pathologies resemble Pott's spine on MRI and are often missed due to inadequate clinical details. As a result, patients are often subject to unnecessary biopsy. A blinded radiologist may misdiagnose such mimic cases as TB. Our aim is to enable the reader to learn the main criteria that differentiate spine TB from other spine etiologies that mimic TB. A retrospective search was done and authors collected only MRI spine reports that showed a differential diagnosis or diagnosis of TB spine from the computer-based data records of the institution over a four-year period. This revealed 306 cases of TB spine out of which 78 cases with an alternate diagnosis that resembled TB spine were included. We describe a single institute review of 78 such cases that resemble and mimic Pott's spine on MRI. The cases being: (n = 15) pyogenic spondylitis, (n = 1) brucellar spondylodiscitis, (n = 12) rheumatoid arthritis, (n = 12) metastases, (n = 8) lymphoma, (n = 5) post-trauma fractures, (n = 10) degenerative disc disease, (n = 2) Baastrup's disease, (n = 9) osteoporotic fracture, (n = 3) spinal neuropathic arthritis, and (n = 1) case of Rosai-Dorfman disease. The clinical and radiological findings of all these cases were correlated with lab findings and histopathology wherever necessary. Appropriate recognition of these entities that resemble and mimic TB spine on MRI is important for optimal patient care. This paper exposes radiologists to a variety of spine pathologies for which biopsy is not indicated, and highlights key imaging findings of these entities to facilitate greater diagnostic accuracy in clinical practice.

The High Cervical Anterolateral Retropharyngeal Approach.

The first high cervical anterolateral retropharyngeal (HCALR) approach was reported by Stevenson et al. for a clivus chordoma in 1966. Anterior approaches to the spine have often been developed in response to problems presented by tuberculous spondylitis. This approach is indicated in anterior high cervical spine cases such as tumour resection, abscess drainage, atlantoaxial subluxation; decompression and stabilization. To our knowledge, only 21 papers in the literature have mentioned this approach. Its main advantage over posterior approaches is easy positioning and minimal need for soft tissue dissection. The HCALR approach provides wide exposure (of the anterior upper cervical spine, lower clivus and brainstem region) and feasibility for instrumentation. The limited space in which important neurovascular and visceral structures course and overlap contributes to the complexity of the anatomy. Navigating this intricate anatomy is essential for the safety of this approach and has been a drawback for utilization of the retropharyngeal corridor. This approach is one of the safest and most effective methods available to access the craniocervical junction. The benefits clearly outweigh the risks and complications.

Hybrid optimization based on non-coplanar needles for brachytherapy dose planning.

PurposeAn ideal dose distribution in a target is the ultimate goal of preoperative dose planning. Furthermore, avoiding vital organs or tissues such as blood vessels or bones during the puncture procedure is significant in low-dose-rate brachytherapy. The aim of this work is to develop a hybrid inverse optimization method based on non-coplanar needles to assist the physician during conformal dose planning, which cannot be properly achieved with a traditional coplanar template.Material and methodsThe hybrid inverse optimization technique include two novel technologies: an inverse optimization algorithm and a dose volume histogram evaluation method. Brachytherapy treatment planning system was designed as an experimental platform. Left lung adenocarcinoma case was used to test the performance of the method in non-coplanar and coplanar needles, and malignant tumor of spine case was involved to test the practical application of this technique. In addition, the optimization time of every test was also recorded.ResultsThe proposed method can achieve an ideal dose distribution, avoiding vital organs (bones). In the first experiment, 13 non-coplanar needles and 24 seeds were used to get an ideal dose distribution to cover the target, whereas 11 coplanar needles and 23 seeds were used to cover the same target. In the second experiment, the new method used 22 non-coplanar needles and 65 seeds to cover the target, while 63 seeds and 22 needles were used in the actual operation. In addition, the computation time of the hybrid inverse optimization method was 20.5 seconds in the tumor of 94.67 cm3 by using 22 needles, which was fast enough for clinical application.ConclusionsThe hybrid inverse optimization method achieved high conformity in the clinical practice. The non-coplanar needle can help to achieve a better dose distribution than the coplanar needle.

161. A crowd-knowledge-based analysis of DVHs in SBRT: First steps towards a national virtual audit

Purpose Currently, most of the multicenter analyses on treatment planning rely on the extraction of selected data from the DVH of each plan. A grouped analysis can be biased due to different algorithms implemented in different TPSs used to generate the DVH. In this work we used a consistent method to present a preliminary analysis of multiple data coming from a national survey on stereotactic body radiotherapy (SBRT) planning. Methods A single spine case was shared among 36 radiation oncology centers. The dose prescription was 30 Gy in 3 fractions with specific constraints on target coverage and dose to nearby organs at risk. Data were collected in DICOM-RT format. A script was developed in R language using the RadOnc R-Package for recalculating the DVHs using the same algorithm. Specific DVH points (V30Gy, D90%, D2%) collected from the centers were compared with those recalculated with RadOnc. A grouped analysis of recalculated DVHs was performed therefore eliminating the bias due to different DVH calculation algorithms. Results Differences between collected and recalculated DVHs were minimal, however in some cases deviations up to 1.5% were observed. The multiple-DVH analysis showed a notable variability on target dose level (Fig. 1), up to 150% likely related to constraints on target coverage and SBRT technique. This variability was caused mainly by different planning optimization strategies, rather than by the use of a specific treatment technology. Conclusions The observed variability suggests that comparable standards in patient treatment among different centers can be obtained if a consistent high-level data sharing capability is granted. In the strive to harmonize the planning process, this analysis constitutes a first step toward the creation of a platform of crowd-knowledge-based planning guidelines. This platform could represent a high-quality benchmark for those centers that are willing to implement SBRT techniques (concept expressed in Fig. 1). Currently, most of the multicenter analyses on treatment planning rely on the extraction of selected data from the DVH of each plan. A grouped analysis can be biased due to different algorithms implemented in different TPSs used to generate the DVH. In this work we used a consistent method to present a preliminary analysis of multiple data coming from a national survey on stereotactic body radiotherapy (SBRT) planning. A single spine case was shared among 36 radiation oncology centers. The dose prescription was 30 Gy in 3 fractions with specific constraints on target coverage and dose to nearby organs at risk. Data were collected in DICOM-RT format. A script was developed in R language using the RadOnc R-Package for recalculating the DVHs using the same algorithm. Specific DVH points (V30Gy, D90%, D2%) collected from the centers were compared with those recalculated with RadOnc. A grouped analysis of recalculated DVHs was performed therefore eliminating the bias due to different DVH calculation algorithms. Differences between collected and recalculated DVHs were minimal, however in some cases deviations up to 1.5% were observed. The multiple-DVH analysis showed a notable variability on target dose level (Fig. 1), up to 150% likely related to constraints on target coverage and SBRT technique. This variability was caused mainly by different planning optimization strategies, rather than by the use of a specific treatment technology. The observed variability suggests that comparable standards in patient treatment among different centers can be obtained if a consistent high-level data sharing capability is granted. In the strive to harmonize the planning process, this analysis constitutes a first step toward the creation of a platform of crowd-knowledge-based planning guidelines. This platform could represent a high-quality benchmark for those centers that are willing to implement SBRT techniques (concept expressed in Fig. 1).

Enterobacter Infection after Spine Surgery: An Institutional Experience

Gram-negative surgical site infections (SSI) following spine surgery are becoming increasingly more common owing to a broad perioperative antibiotic usage targeting gram-positive organisms. Enterobacter species have been reported to be the most common gram-negative bacteria following spine surgery. We queried our institutional database for Enterobacter SSIs after spine surgery at a single institution from 2009-2016. Relevant demographic, clinical, and operative variables were collected. We compared this cohort to patients who had non-Enterobacter SSI during the same period. Enterobacter species were isolated in 16 patients (9 males) diagnosed with SSI after undergoing spine surgery. This group represented 0.2% of all spine cases and 14.5% of all spinal SSIs. Seven patients (43.8%) required multiple irrigations and debridements (I&Ds) (range: 2-8), whereas only 17 of 94 patients (18.1%) with non-Enterobacter SSI required multiple I&Ds (range: 2-5, P= 0.043). Those infected with Enterobacter were associated with higher BMI (37.6 ± 12.7 vs. 31.7 ± 8, P= 0.036), earlier wound dehiscence (14.8 vs. 24.6 days, P= 0.01), polymicrobial infections (37.5% vs. 10.6%, P= 0.012), and longer length of stay (18 days [9.5-31.5] vs. 5 days [3-8], P= 0.01) when compared to non-Enterobacter SSI cohort. At an average of 24.2 months follow-up, all 15 surviving patients were infection free with no further revision surgeries needed. Enterobacter SSI cases were associated with higher BMI, earlier wound breakdown, polymicrobial infection and longer length of stay. Nevertheless, with vigilant surveillance and timely I&Ds, these challenging infections can be treated successfully with original implant retention in almost all cases.

The Recognition, Incidence, and Management of Spinal Cord Monitoring Alerts in Pediatric Cervical Spine Surgery.

Perioperative spinal cord injury and postoperative neurological deficits are the major complications in spinal surgery. Monitoring of spinal cord function is of crucial importance. Somatosensory evoked potentials and transcranial electric motor-evoked potentials are now widely used in cervical spine surgery. Although much has been written on spinal cord monitoring in adult spinal surgery, very little has been published on the incidence and management of monitoring of cervical spine surgery in the pediatric population. The goal of this research was to review the recognition, incidence, and management of spinal cord monitoring in pediatric patients undergoing cervical spine surgery over the course of twenty years in a single institution. We postulate spinal cord monitoring alerts in pediatric cervical spine surgery are underreported. An IRB-approved retrospective single institution review of pediatric cervical spine cases from 1997 to 2017 was performed. Both the surgeon's dictated operative note and the neuromonitoring team's dictated note were reviewed for each case, and both were cross referenced and correlated with one another to ensure no alerts were missed. All monitoring changes were assumed to be significant and reported. The incidence of alerts, type of changes, and corrective maneuvers were noted. New postoperative neurological injuries were recorded. From 1997 to 2017 fifty-three patients underwent a total of 69 procedures involving the cervical spine. Fourteen procedures (20%) were not monitored, whereas 55 procedures were 80%. There were 12 procedures (21.8%) complicated by neuromonitoring alerts. The number of cases complicated by alerts doubles that previously reported, and it is important to note there were no new permanent neurological deficits recorded over the study period. Corrective strategies were implemented once the operating surgeon was notified of the neuromonitoring alert. Aborting the case was then considered if corrective strategies failed to restore baseline neurophysiology. Level IV.

National Trends in Spinal Fusion Surgery for Neurofibromatosis

Study DesignAnalysis of a national database. ObjectiveTo analyze trends in spinal fusion surgery for neurofibromatosis type I (NF-1) patients and to compare the surgical approaches. Summary of Background DataThe preferred surgical approach for fusion treatment of spinal deformity in NF is not well established. MethodsWe identified 548 patients with a diagnosis of NF-1 who had received spinal fusion surgery between 2003 and 2014. We compared posterior spinal fusion (PSF), anterior-posterior spinal fusion (APSF), and anterior spinal fusion with respect to patient demographics, institutional characteristics, in-hospital complications, and hospitalization lengths and costs. Significance was set at a value of p less than .05. ResultsThe number of spinal fusions for NF-1 significantly increased (p = .02) over the study period. The rate of PSF surgeries increased 2.9-fold, whereas the rate of APSF surgeries decreased 2.2-fold. There was also a significant association between the location of the fusion and surgical approach (p<.01), with 66% of ASF cases being cervical spine cases. Compared with patients undergoing PSF and ASF, patients undergoing APSF were significantly younger (p<.01) and had significantly higher hospitalization lengths and costs (p<.01). APSF costs were $180,714 as compared to $144,027 for PSF and $105,312 for ASF. ConclusionsThere have been significant increases in the rate of spinal fusion surgeries for NF-1 patients. Surgical treatment has shifted over the years and is dependent on the location of the deformity. Patients undergoing APSF are significantly younger. Level of EvidenceLevel III.

A Review of the Historical Evolution, Biomechanical Advantage, Clinical Applications, and Safe Insertion Techniques of Cervical Pedicle Screw Fixation.

Cervical spine instrumentation is evolving with an aim of stabilizing traumatic and non-traumatic cases of the cervical spine with a beneficial reduction, better biomechanical strength, and a strong construct with minimal intraoperative, as well as immediate and late postoperative complications. The evolution from interspinous wiring till cervical pedicle screws has changed the outlook in treating the cervical spine pathologies with maximum 3D stability, decreasing the duration of postoperative immobilization and hospital stay. Some complications associated with the use of cervical pedicle screw can be catastrophic. This review article discusses the morphometry of cervical pedicle; indications, biomechanical superiority, tricks, and pitfalls of cervical pedicle screw; complications and technical advancements in targeting safe surgery; and future directions of cervical pedicle screw instrumentation.

Minimally invasive direct lateral interbody fusion in the treatment of the thoracic and lumbar spinal tuberculosisMini-DLIF for the thoracic and lumbar spinal tuberculosis

BackgroundTo investigate the clinical efficacy of minimally invasive direct lateral approach debridement, interbody bone grafting, and interbody fusion in the treatment of the thoracic and lumbar spinal tuberculosis.MethodsFrom January 2013 to January 2016, 35 cases with thoracic and lumbar spinal tuberculosis received direct lateral approach debridement, interbody bone grafting, and interbody fusion. Of the 35 cases, 16 patients were male and 19 were female and the median age was 55.2 (range 25–83). The affected segments were single interspace, and the involved vertebral bodies included: 15 cases of thoracic vertebrae (1 cases of T5/6, 2 cases of T6/7, 4 cases of T7/8, 3 cases of T8/9, 5 cases of T9/10) and 20 cases of lumbar spine (2 cases of L1/2, 6 cases of L2/3, 6 cases of L3/4, 6 cases of L4/5). After MIDLIF operation, all the patients received medication of four anti-tubercular drugs for 12 to18 months.ResultsThe patients were followed up for 7 to 40 months with an average of 18.5 months. The visual analogue scale (VAS) at the last follow-up was 2.8 ± 0.5, which was significantly different from the preoperative VAS (8.2 ± 0.7). After MIDLIF, there was 5 cases occurred with transient numbness in one side of the thigh or inguinal region, and 10 cases suffered from flexion hip weakness. All the bone grafts were fused within 6~ 18 months (average of 11.5 months) after the operation.ConclusionMinimally invasive lateral approach interbody fusion technology have the advantage of less injury and quick recovery after surgery, which is the effective and safe treatment for thoracic and lumbar spinal tuberculosis.

Thursday, September 27, 2018 3:35 PM–5:05 PM Section on Motion Technology Abstract Presentations: 132. Subsequent cervical spine surgery after cervical disc arthroplasty and anterior cervical discectomy and fusion

BACKGROUND CONTEXT Cervical disc arthroplasty (CDA) has emerged as an alternative surgical option to anterior cervical discectomy and fusion (ACDF) for cervical disc pathology, with recent trials demonstrating non-inferiority of CDA to ACDF. While short-term trends regarding utilization rates, revision procedures and complications have been explored, longer-term outcomes, specifically involving re-operation rates and type of reoperation are lacking. Therefore, we used the New York Statewide Planning and Research Cooperative Systems (SPARCS) database to characterize subsequent cervical spine surgery in patients undergoing primary elective CDA and ACDF. PURPOSE Characterize subsequent cervical spine surgery in patients undergoing primary elective CDA and ACDF. STUDY DESIGN/SETTING Retrospective state database study. PATIENT SAMPLE Patients who underwent elective inpatient CDA and ACDF in New York State. METHODS We analyzed the SPARCS inpatient database from 2005 to 2013 to identify patients who underwent elective inpatient CDA and ACDF procedures. International Classification of Diseases, Ninth Revision (ICD-9) codes were used to extract the index procedures (CDA: 84.61, 84.62; ACDF: 81.02) and to identify patient demographics and cervical re-operation procedures. Patients were longitudinally followed until September 2015, corresponding to a minimum of two year follow-up, to determine the incidence of subsequent cervical spine reoperation, which included another primary CDA or ACDF, revision CDA or ACDF, and posterior cervical fusion. Logistic regression analysis was used to determine the odds of subsequent cervical spine reoperation. RESULTS Between January 2005 and September 2013, 731 patients underwent an inpatient CDA and 45,204 underwent an inpatient ACDF. Patients undergoing CDA were more likely to be younger (43.6 vs. 50.7, p CONCLUSIONS Compared to patients undergoing ACDF, patients undergoing CDA are more likely to be younger, to have fewer comorbidities and to have a primary diagnosis of cervical disc displacement. While there is no significant difference in subsequent cervical spine re-operation rates between ACDF and CDA, surgeons performing revision procedures at the same cervical level or performing primary procedures at adjacent cervical levels are more likely to utilize ACDF rather than CDA. Further investigation in outpatient primary and revision cervical spine cases is needed to assess these findings. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Wednesday, September 26, 2018 2:00 PM – 3:00 PM Increasing Value: Lumbar Spine Surgery: 66. Cost-benefit analysis of intraoperative EMG for pedicle screw placement in routine lumbar fusions

BACKGROUND CONTEXT Advances in intraoperative neuromonitoring have increased the safety and shown clear benefit for complex spine cases. However, controversy exists regarding the utility of intraoperative EMG for identification of pedicle wall breaches for uncomplicated posterolateral lumbar fusions. PURPOSE To perform a cost-benefit analysis of pedicle screw stimulation via triggered EMG in routine lumbar pedicle screw cases. STUDY DESIGN/SETTING Prospective case series. PATIENT SAMPLE Patients undergoing primary instrumented posterior lumbar fusion with pedicle screws from L1 to S1. OUTCOME MEASURES EMG screw stimulation, need for screw repositioning, variable direct cost. METHODS A prospective study was conducted at single institution. Patients undergoing instrumented posterolateral lumbar fusion were monitored with intraoperative triggered EMGs. Pedicle screws were placed freehand from L1 to S1 by attending physicians and spine fellows. Concern for pedicle breach was identified with a screw stimulation value less than 10 mA. RESULTS There were 145 cases with a total of 725 pedicle screws placed. Mean age was 57.8±14.2 years, OR time was 238±95 minutes, EBL was 426.8±354.3cc. Mean number of surgical levels fused was 2.7±1.1. 686 (95%) screws stimulated at >10 mA and 39 (5%) screws stimulated at CONCLUSIONS Only 1% of the 725 lumbar pedicle screws placed in 8 of 145 cases required repositioning. Due to the infrequency of pedicle wall breaches and the cost of ION, the utility of this modality in straightforward lumbar fusions should be critically evaluated. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Wednesday, September 26, 2018 3:35 PM – 5:05 PM How to Avoid Complications: 95. Factors associated with the decision to culture and positive growth in aseptic revision spine surgery

BACKGROUND CONTEXT The indications for obtaining cultures in revision spinal surgery remain unclear in the absence of a definitive diagnosis of infection. Surgeon behavior related to obtaining cultures and risk factors for positive cultures in this setting have not been previously studied. PURPOSE To report on the specimen collection patterns and culture results during presumed aseptic revision spine cases. An improved understanding of what leads surgeons to exclude infection as well as the risk factors for having a positive culture will help inform future culturing practices, highlighting underlying characteristics which may increase the yield of taking intraoperative cultures in presumed aseptic revision cases. This data will aid surgeons, hospitals, and payers in what is currently a challenging clinical scenario. STUDY DESIGN/SETTING Retrospective review. PATIENT SAMPLE A total of 578. OUTCOME MEASURES Factors associated with the decision to obtain cultures intraoperatively in cases of aseptic revision spine surgery; risk factors for positive cultures obtained in such cases METHODS Following approval of the institutional review board, 595 consecutive revision spine surgeries performed by four senior surgeons between 2008 and 2013 were retrospectively reviewed. All revision surgeries including the cervical, thoracic, and lumbosacral spine employing fusion and non-fusion techniques with and without instrumentation were included. Routine preoperative evaluation of each of these patients included clinical examination, radiographs, and advanced imaging. In cases of suspected infection, preoperative measurement of serum white blood cell count, erythrocyte sedimentation rate, and C-reactive protein were obtained. The primary diagnosis at the time of revision surgery was identified in each case by the first ICD-9 code listed at the time of surgery. Cases were presumed aseptic if the principle preoperative diagnosis was not infection. Preoperative work-up revealed the diagnosis of infection in 17 cases which were excluded. A detailed chart review was performed on the remaining 578 cases. RESULTS Cultures were obtained in 112 (19.4%) cases and were positive in 40.2%. Pseudarthrosis was the most common revision diagnosis when cultures were obtained (49.1%) and Propionibacterium acnes was the most common organism isolated from positive cultures (48.8%). Multivariate analysis demonstrated that obesity (OR=2.4), instrumentation (OR=2.4), thoracolumbar surgery (OR=5.2), and diagnosis of implant failure (OR=9.0) or pseudarthrosis (OR=8.0) were significantly correlated with decision to culture while time between index and revision procedures (OR=0.9) and cervical surgery (OR=0.2) were negatively correlated, with AUC 0.85. Regarding culture results, multivariate analysis demonstrated that male sex (OR=3.4) and pseudarthrosis (OR=4.1) were significantly associated with having positive cultures while fusion procedures (OR = 0.3) were negatively correlated, with AUC 0.71. CONCLUSIONS Unexpected positive cultures occurred commonly and Propionibacterium acnes was the predominant isolated organism. Obesity, instrumentation, thoracolumbar surgery, implant failure, and pseudarthrosis all predicted culture collection. Male sex, pseudarthrosis, and non-fusion cases predicted positive cultures. Considering these results, we recommend cultures be obtained in revision cases for pseudarthrosis, even in the setting of negative infectious work-up preoperatively. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Laboratory Evaluation of a Robotic Operative Microscope - Visualization Platform for Neurosurgery.

BackgroundWe assessed a new robotic visualization platform with novel user-control features and compared its performance to the previous model of operative microscope.MethodsIn a neurosurgery research laboratory, we performed anatomical dissections and assessed robotic, exoscopic, endoscopic, fluorescence functionality. Usability and functionality were tested in the operating room over 1 year.ResultsThe robotic microscope showed higher sensitivity for fluorescein sodium, higher detail in non-fluorescent background, and recorded/presented pictures with color quality similar to observation through the oculars. PpIX visualization was comparable to the previous microscope. Near-infrared indocyanine green imaging 3-step replay allowed for more convenient accurate assessment of blood flow. Point lock and pivot point functions were used in dissections to create 3D virtual reality microsurgical anatomy demonstrations. Pivot point control was particularly useful in deep surgical corridors with dynamic retraction. 3D exoscopic function was successfully used in brain tumor and spine cases. Endoscopic assistance was used for around-the-corner views in minimally invasive approaches. We present illustrative cases highlighting utility and new ways to control the operative microscope.ConclusionImprovements of the robotic visualization platform include intraoperative fluorescence visualization using FNa, integrated micro-inspection tool, improved ocular imaging clarity, and exoscopic mode. New robotic movements positively assist the surgeon and provide improved ergonomics and a greater level of intraoperative comfort, with the potential to increase the viewing quality. New operational modes also allow significant impact for anatomy instruction. With the increasing number and complexity of functions, surgeons should receive additional training in order to avail themselves of the advantages of the numerous novel features.

Variation in pediatric orthopedic case volume among residents: an assessment of Accreditation Council for Graduate Medical Education case logs.

The aim of this investigation was to examine graduating orthopedic resident case logs to evaluate trends in performing pediatric orthopedic procedures and compare pediatric orthopedic case volume among residents in the 90th, 50th, and 10th percentiles (by case volume) to identify caseload variation. Accreditation Council for Graduate Medical Education orthopedic resident case logs were examined for graduating years 2007-2013. Linear regression analyses were carried out to assess temporal trends in pediatric orthopedic case volume. Subgroup analyses were carried out to assess trends in cases by anatomic location. Comparisons of the number of pediatric cases performed by the 90th, 50th, and 10th percentiles of graduating residents were also performed. Pediatric orthopedic case volume increased significantly per graduating resident (295.9-373.2; P<0.001) from 2007 to 2013. Graduating residents in the 90th (494-573; P=0.001), 50th (264-334; P<0.001), and 10th (144-216; P=0.003) percentiles of case volume all sustained significant increases in the number of pediatric orthopedic cases performed. Subgroup analyses showed significant increases in pediatric orthopedic shoulder (4.8-7.3; P<0.001), humerus/elbow (25.9-32.7; P<0.001), forearm/wrist (28.6-40.4; P<0.001), hand/finger (15-16.9; P=0.005), femur/knee (44.5-51.9; P=0.002), leg/ankle (39.4-41.1; P=0.004), and spine case volume (24.9-33.6; P<0.001). On average, graduating residents in the 90th, 50th, and 10th percentiles performed 524, 302, and 169 cases, respectively. The current investigation shows significant growth in the number of pediatric orthopedic cases performed by graduating residents, particularly among upper extremity procedures. However, considerable variation in pediatric orthopedic case volume exists among residents. Although the educational effects of this case volume variation are incompletely understood, the current investigation may be beneficial in efforts to improve pediatric orthopedic educational quality.

Does Nasal Carriage of Staphylococcus aureus Increase the Risk of Postoperative Infections After Elective Spine Surgery: Do Most Infections Occur in Carriers?

Wound infections after adult spinal deformity surgery place a high toll on patients, providers, and the healthcare system. Staphylococcus aureus is a common cause of postoperative wound infections, and nasal colonization by this organism may be an important factor in the development of surgical site infections (SSIs). The aim is to investigate whether post-operative surgical site infections after elective spine surgery occur at a higher rate in patients with methicillin-resistant S.aureus (MRSA) nasal colonization. Consecutive patients undergoing adult spinal deformity surgery between 2011-2013 were enrolled. Enrolled patients were followed up for a minimum of 3 months after surgery and received similar peri-operative infection prophylaxis. Baseline characteristics, operative details, rates of wound infection, and microbiologic data for each case of post-operative infection were gathered by direct medical record review. Local vancomycin powder was used in all patients and sub-fascial drains were used in the majority (88%) of patients. 1200 operative spine cases were performed for deformity between 2011 and 2013. The mean ± standard deviation age and body mass index were 62.08 ± 14.76 years and 30.86 ± 7.15 kg/m2, respectively. 29.41% had a history of diabetes. All SSIs occurred within 30 days of surgery, with deep wound infections accounting for 50% of all SSIs. Of the 34 (2.83%) cases of SSIs that were identified, only 1 case occurred in a patient colonized with MRSA. Our study suggests that the preponderance of SSIs occurred in patients without nasal colonization by methicillin-resistant S.aureus. Future prospective multi-institutional studies are needed to corroborate our findings.

Radiation exposure for the surgical team in a hybrid-operating room.

Hybrid-operating rooms enable the surgeon to acquire intraoperative high-resolution 2- and 3D images and use them for navigation. The radiation dose of the operating personal and the patient remains the major concern. In 9months, 109 pelvic and spine cases were performed using a hybrid operating room. Radiation dose of the surgeon and the assisting nurse was recorded using real-time dosimeters. Lower radiation doses for the main surgeon in navigated dorsal instrumentations of the thoracic spine were recorded. Standing between the C-arm during screw placement increased the radiation dose sixfold. Lumbar dorsal instrumentation showed a similar radiation dose compared to the previous studies in traditional operating room settings. The use of a hybrid-operating room for dorsal spine instrumentation showed no increase in radiation dose compared to traditional settings. Intraoperative navigation can help to reduce the radiation dosage for the operating personnel.