Finite element study of the impact of pedicle screw density on the biomechanical response of a Lenke 1AN scoliotic curve.

Introduction: Benefits of increasing screw density in posterior instrumentation used to treat a scoliotic deformity are demonstrated using a three-dimensional finite element model (FEM) of the thoracolumbosacral spine. Methods: The FEM represents a Lenke 1AN scoliotic deformity with a 50° Cobb angle and 20° apical vertebral rotation. The curve is corrected with bilateral pedicle screw fixation and 75 separate randomized screw distributions. Results: Total construct screw density, concave rod screw locations at T6, T10, T11 and T12, and convex rod screw locations at T7 and T12 each correlate strongly with reductions in postoperative Cobb angle (P < 0.05). Apical vertebral rotation is greatly impacted (reduced) by screws placed at the apical vertebra on both concave and convex rods (P < 0.05). Under pure moment loading, intersegmental micromotion is generally reduced when motion segment screw density is increased, with the exception being the upper instrumented joint. Conclusions: These results suggest that increasing the screw density of posterior constructs used to treat a Lenke 1AN scoliotic deformity may improve the de-rotation correction with better postural restoration, reducing the risk of future complications including pseudarthrosis.

Checklists in Healthcare: Operational Improvement of Standards using Safety Engineering - Project CHOISSE - A framework for evaluating the effects of checklists on surgical team culture.

The CHOISSE multi-stage framework for evaluating the effects of electronic checklist applications (e-checklists) on surgical team members' perception of their roles, performance, communication, and understanding of checklists is introduced via a pilot study. A prospective interventional cohort study design was piloted to assess the effectiveness of the framework and the sociotechnical effects of the e-checklist. A Delphi process was used to design the stages of the framework based on literature and expert consensus. The CHOISSE framework was applied to guide the implementation and evaluation of e-checklists on team culture for ten pilot teams across the US over a 24-week period. The pilot results revealed more engagement by surgeons than non-surgeons, and significant increases in surgeons' perception of communication and engagement during surgery with a small sample. Mixed methods analysis of the data and lessons learned were used to identify iterative improvements to the CHOISSE framework and to inform future studies.

Intraoperative neuromonitoring practice patterns in spinal deformity surgery: a global survey of the Scoliosis Research Society.

PURPOSE: Although multimodal IONM has reached a widespread use, several unresolved issues have remained in clinical practice. The aim was to determine differences in approaches to form a basis for taking actions to improve patient safety globally. METHODS: A survey comprising 19 questions in four sections (demographics, setup, routine practices and reaction to alerts) was distributed to the membership of the SRS. RESULTS: Of the estimated 1300 members, 205 (~ 15%) completed the survey. Respondent demographics reflected SRS member distribution. Most of the respondents had > 10 years of experience. TcMEP and SSEP were available to > 95%. Less than 5% reported that a MD/PhD with neurophysiology background routinely examines patients preoperatively, while 19% would consult if requested. After an uneventful case, 36% reported that they would decrease sedation and check motor function if the patient was to be transferred to ICU intubated. Reactions to dropped signals that recovered or did not fully recover varied between attempting the same correction to aborting the surgery with no rods and returning another day, with or without implant removal. After a decrease of signals, 85.7% use steroids of varied doses. Of the respondents, 53.7% reported using the consensus-created checklist by Vitale et al. Approximately, 14% reported never using the wake-up test while others use it for various conditions. CONCLUSION: The responses of 205 experienced SRS members from different regions of the world showed that surgeons had different approaches in their routine IONM practices and in the handling of alerts. This survey indicates the need for additional studies to identify best practices.

Development and Validation of a Computationally Efficient Finite Element Model of the Human Lumbar Spine: Application to Disc Degeneration.

INTRODUCTION: This study develops and validates an accurate, computationally efficient, 3-dimensional finite element model (FEM) of the human lumbar spine. Advantages of this simplified model are shown by its application to a disc degeneration study that we demonstrate is completed in one-sixth the time required when using more complicated computed tomography (CT) scan-based models. METHODS: An osseoligamentous FEM of the L1-L5 spine is developed using simple shapes based on average anatomical dimensions of key features of the spine rather than CT scan images. Pure moments of 7.5 Nm and a compressive follower load of 1000 N are individually applied to the L1 vertebra. Validation is achieved by comparing rotations and intradiscal pressures to other widely accepted FEMs and in vitro studies. Then degenerative disc properties are modeled and rotations calculated. Required computation times are compared between the model presented in this paper and other models developed using CT scans. RESULTS: For the validation study, parameter values for a healthy spine were used with the loading conditions described above. Total L1-L5 rotations for flexion, extension, lateral bending, and axial rotation under pure moment loading were calculated as 20.3°, 10.7°, 19.7°, and 10.3°, respectively, and under a compressive follower load, maximum intradiscal pressures were calculated as 0.68 MPa. These values compare favorably with the data used for validation. When studying the effects of disc degeneration, the affected segment is shown to experience decreases in rotations during flexion, extension, and lateral bending (24%-56%), while rotations are shown to increase during axial rotation (14%-40%). Adjacent levels realize relatively minor changes in rotation (1%-6%). This parametric study required 17.5 hours of computation time compared to more than 4 days required if utilizing typical published CT scan-based models, illustrating one of the primary advantages of the model presented in this article. CONCLUSIONS: The FEM presented in this article produces a biomechanical response comparable to widely accepted, complex, CT scan-based models and in vitro studies while requiring much shorter computation times. This makes the model ideal for conducting parametric studies of spinal pathologies and spinal correction techniques.

Technical Tips: A Checklist for Responding to Intraoperative Neuromonitoring Changes.

When changes occur in neurological responses during a surgical case, it is very important that all staff in the operating room (OR) understand their role in resolving or improving these conditions. Timely interventions are needed, and each personnel team is responsible for very specific tasks. Our intent was to cut down on confusion and delay by implementing a checklist that assigns tasks and designates a coordinator, so we incorporated the use of a checklist developed by Vitale et al. into our process for neuromonitoring cases. Staff members who used the checklist were surveyed to assess ease of use, understanding and perceptions about patient safety and case efficiency with the incorporation of the checklist. The post-implementation survey showed an increase in confidence and understanding in team responsibilities and workflow. Results showed ease of use and a perception of increased patient safety with no perceived decrease in surgery case efficiency.

Results of the 2015 Scoliosis Research Society Survey on Single Versus Dual Attending Surgeon Approach for Adult Spinal Deformity Surgery.

STUDY DESIGN: An electronic survey administered to Scoliosis Research Society (SRS) membership. OBJECTIVE: To characterize surgeon practices and views regarding the use of two attending surgeons for adult spinal deformity (ASD) surgery. SUMMARY OF BACKGROUND DATA: The use of two experienced attending surgeons can decrease the operative time, estimated blood loss, and perioperative complication rates. However, the current practice patterns for the use of two attending surgeons remains unknown. METHODS: An electronic, 27-question survey regarding single/dual attending surgeons was administered to the SRS membership. Determinants included: surgeon/practice demographics, assistant type/level of training, and questions regarding use of two attending surgeons. Overall reporting and comparisons between groups were made: US versus international, academic versus private practice, and experience <15 years versus >15 years. RESULTS: A total of 199 surgeons responded from 27 different countries. Overall and between the groups, the respondents significantly reported believing that two attending spine surgeons improves safety, decreases complications, and improves outcomes (P < 0.01). Approximately, 67.3% reported using a second attending ≤25% of the time (33.2% do not), and 24.1% use one ≥51% of the time (similar between groups); 51.1% that have a second attending feel it's limited by reimbursement and access concerns and 71.9% have difficulty getting the second attending reimbursed. 72.3% use a second attending for ALL of the following reasons (no difference between groups): "it's safer/reduces complications," "it decreases operative time," "it decreases blood loss," "it results in improved outcomes," "it's less work and stress for me." If reimbursement was equal/assured for a second attending, 67.5% would use one "more often" or "always." CONCLUSION: The respondents feel that having a second attending surgeon improves patient care, however most do not use one often. Reasons include reimbursement/access concerns and the majority would use one if reimbursement was equal and assured. Based on the current literature and these results, there is a need for working with third party payers to improve dual surgeon reimbursement rates in complex cases. LEVEL OF EVIDENCE: 5.

Adult Spinal Deformity: Epidemiology, Health Impact, Evaluation, and Management.

Spinal deformity in the adult is a common medical disorder with a significant and measurable impact on health-related quality of life. The ability to measure and quantify patient self-reported health status with disease-specific and general health status measures, and to correlate health status with radiographic and clinical measures of spinal deformity, has enabled significant advances in the assessment of the impact of deformity on our population, and in the evaluation and management of spinal deformity using an evidence-based approach. There has been a significant paradigm shift in the evaluation and management of patients with adult deformity. The paradigm shift includes development of validated, disease-specific measures of health status, recognition of deformity in the sagittal plane as a primary determinant of health status, and information on results of operative and medical/interventional management strategies for adults with spinal deformity. Since its inception in 1966, the Scoliosis Research Society (SRS) has been an international catalyst for improving the research and care for patients of all ages with spinal deformity. The SRS Adult Spinal Deformity Committee serves the mission of developing and defining an evidence-based approach to the evaluation and management of adult spinal deformity. The purpose of this overview from the SRS Adult Deformity Committee is to provide current information on the epidemiology and impact of adult deformity, and to provide patients, physicians, and policy makers a guide to the evidence-based evaluation and management of patients with adult deformity.

Results of the 2014 SRS Survey on PJK/PJF: A Report on Variation of Select SRS Member Practice Patterns, Treatment Indications, and Opinions on Classification Development.

STUDY DESIGN: An electronic survey administered to Scoliosis Research Society membership. OBJECTIVE: To characterize surgeon views regarding proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) management providing the framework in which a PJK/PJF classification system and treatment guidelines could be established. SUMMARY OF BACKGROUND DATA: PJK/PJF are common complications of adult spinal deformity surgery. To date, there is no consensus on PJK/PJF definitions, classification, and indications for revision surgery. There is a paucity of data on deformity surgeon practice pattern variations and consensus opinion on treatment and prevention. METHODS: An electronic 19-question survey regarding PJK/PJF was administered to members of the Scoliosis Research Society who treat adult spinal deformity. Determinants included the surgeons' type of practice, number of years in practice, agreement with given PJK/PJF definitions, importance of key factors influencing prevention and revision, prevention methods currently used, and the importance of developing a classification system. RESULTS: A total of 226 surgeons responded (38.8% response rate). Both 44.4% of surgeons selected "extremely important" and 40.8% selected "very important" that PJK in adult spinal deformity surgery is a very important issue and that a Scoliosis Research Society PJK/PJF classification system and guidelines for detection and prevention of PJK/PJF is a "must have" (18.1%) and "very likely helpful" (31.9%). Both 86.2% and 90.7% of surgeons agreed with the provided definitions of PJK and PJF, respectively. Top 5 revision indications included neurological deficit, severe focal pain, translation or subluxation fracture, a change in kyphosis angle of greater than 30°, chance fracture, spondylolisthesis greater than 6 mm, and instrumentation prominence. The majority of respondents use a PJK/PJF prevention strategy 60% of the time or more, the most common were terminal rod contour, preoperative bone mineral density testing, and frequent radiographical studies during first 3 months postoperative, preoperative bone mineral density medication for low bone mineral density. CONCLUSION: The results of this study provide insight from the practicing surgeons' perspective of the management of PJK and PJF that may aid in the validation of current definitions and consensus-based treatment decisions and prevention guidelines. LEVEL OF EVIDENCE: 5.

Proximal junctional kyphosis and failure after spinal deformity surgery: a systematic review of the literature as a background to classification development.

STUDY DESIGN: Systematic review of literature. OBJECTIVE: To perform a comprehensive English language systematic literature review of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF), concentrating on incidence, risk factors, health related quality of life impact, prevention strategy, and classification systems. SUMMARY OF BACKGROUND DATA: PJK and PJF are well described clinical pathologies and are a frequent cause of revision surgery. The development of a PJK classification that correlates with clinical outcomes and guides treatment decisions and possible prevention strategies would be of significant benefit to patients and surgeons. METHODS: The phrases "proximal junctional," "proximal junctional kyphosis," and "proximal junctional failure" were used as search terms in PubMed for all years up to 2014 to identify all articles that included at least one of these terms. RESULTS: Fifty-three articles were identified overall. Eighteen articles assessed for risk factors. Eight studies specifically reviewed prevention strategies. There were no randomized prospective studies. There were 3 published studies that have attempted to classify PJK. The reported incidence of PJK ranged widely, from 5% to 46% in patients undergoing spinal instrumentation and fusion for adult spinal deformity. It is reported that 66% of PJK occurs within 3 months and 80% within 18 months after surgery. The reported revision rates due to PJK range from 13% to 55%. Modifiable and nonmodifiable risk factors for PJK have been characterized. CONCLUSION: PJK and PJF affect many patients after long segment instrumentation after the correction of adult spinal deformity. The epidemiology and risk factors for the disease are well defined. A PJK and PJF scoring system may help describe the severity of disease and guide the need for revision surgery. The development and prospective validation of a PJK classification system is important considering the prevalence of the problem and its clinical and economic impact. LEVEL OF EVIDENCE: N/A.

Patterns and trends in opioid use among individuals with back pain in the United States.

STUDY DESIGN: Secondary analysis of Medical Expenditure Panel Survey from 1996 to 1999. OBJECTIVE: To examine patterns in opioid use in 1996, 1997, 1998, and 1999 among individuals with back pain in the United States and to investigate trends in the use of overall and individual opioid category. SUMMARY OF BACKGROUND DATA: To the authors' best knowledge, no study has examined at a national level the patterns and trends in opioid use among individuals with back pain in the United States. METHODS: Individuals with back pain were stratified by sociodemographic characteristics and geographic regions. Rates of overall opioid use were compared among different strata by the use of simple and multivariate logistic regression models. To investigate trends in opioid use, use rates of the overall and individual opioid category in each year were calculated and compared. RESULTS: From 1996 to 1999, wide variations in overall opioid use were consistently observed among individuals with different educational levels, family income, and health insurance status. Regional variation in opioid use was also observed for most of the 4 years. After adjustment for covariates, health insurance status and geographic regions were consistent predictors of opioid use from 1997 to 1999. Trend analysis indicated that the rates of overall opioid use increased slightly across the 4-year span. Among individual opioid categories, the use of oxycodone or hydrocodone increased, whereas the use of propoxyphene decreased. CONCLUSIONS: The variation in overall opioid use among individuals with back pain with different sociodemographic characteristics and from different geographic regions suggested an opportunity to improve opioid prescribing patterns. The increase in the use of hydrocodone and oxycodone indicated a need to better assess the efficacy and safety associated with these drugs among individuals with back pain.

Relationships of clinical, psychologic, and individual factors with the functional status of neck pain patients.

OBJECTIVE: The objective of this study was to use both generic and disease-specific functional measures examining relationships of clinical, psychologic, and individual factors with the functional status of neck pain patients. METHODS: Patients who visited a university-based spine clinic and reported neck pain were included in this study. A comprehensive computerized survey questionnaire was used to collect the information related to this study. The questionnaire also contained a generic measure, short form 12-item survey (SF-12), and a disease-specific measure, neck disability index (NDI). Correlation and multiple regression analysis were conducted to examine the relationships. RESULTS: A range of clinical, psychologic, and individual factors emerged to be significant predictors of the NDI or physical component of the SF-12 (PCS). The predictors of higher NDI included higher levels of neck pain, higher levels of back pain, higher levels of pain in arm or shoulder areas, not working, lower education, higher stress, the presence of depression or anxiety, and smoking. The predictors of lower PCS included not working, higher levels of back pain, higher levels of neck pain, lower education, female sex, the presence of cardiovascular disorders, the absence of cervical disk disorders, and older age. CONCLUSIONS: The predictors of the NDI or PCS appear to be multidimensional. Interventions designed to maximally improve the functional status of neck pain patients should be multifaceted and involve multidisciplinary teams. Selection of the most appropriate functional measures for an intervention study should consider differences between the generic and disease-specific measures in terms of their respective relationships with targeted factors. Prospective studies are needed to confirm the relationships observed in this study.

Children's health insurance status and emergency department utilization in the United States.

OBJECTIVES: Emergency department (ED) overcrowding has become a national problem. Children account for nearly 25% of overall ED visits. It has been reported that uninsured and publicly insured children are likely to visit the ED for urgent and nonurgent problems, yet it remains unclear to what extent health insurance status would influence children's overall ED utilization or ED utilization for nonurgent problems at the national level after controlling for other confounding factors. The objective of this study was to examine the effect of health insurance status on children's overall ED utilization and children's ED utilization for nonurgent problems among the general pediatric population in the United States. METHODS: Secondary analysis of the household component of the 1997 Medical Expenditure Panel Survey on 10 193 children younger than 18 years. The main outcome measures were annual overall ED utilization and ED utilization for nonurgent problems. RESULTS: During 1997, 10.8% of children were uninsured for the entire year. A total of 17.5% of children were publicly insured the entire year, whereas 55.3% of children held private insurance the entire year. There were also 16.5% of children who were insured only part of the year. Without adjusting for covariates, publicly insured children were more likely to have an ED visit during the year than both privately insured children (unadjusted odds ratio [OR]: 1.26; 95% confidence interval [CI]: 1.03-1.55) and uninsured children (unadjusted OR: 1.46; 95% CI: 1.1-1.95). The difference between publicly insured and privately insured children (adjusted OR: 0.90; 95% CI: 0.70-1.16) and between publicly insured and uninsured children (adjusted OR: 1.12; 95% CI: 0.84-1.49) became insignificant after controlling for covariates. With or without adjustments for covariates, there was no significant difference in the likelihood of having an ED visit between privately insured and uninsured children. Similar to the utilization pattern of overall ED visits, publicly insured children were more likely to have a nonurgent ED visit than both privately insured (unadjusted OR: 1.86; 95% CI: 1.36-2.53) and uninsured children (unadjusted OR: 1.81; 95% CI: 1.15-2.84). Both differences disappeared after controlling for covariates. There was no significant difference in the likelihood of nonurgent ED visits between privately insured and uninsured children with or without adjustments for covariates. CONCLUSIONS: Health insurance status was not associated with children's overall ED use or children's ED use for nonurgent problems at the national level. Our findings suggest that policy efforts in an attempt to relieve ED overcrowding conditions should look for measures beyond solely making changes in health insurance coverage for children.

Estimates and patterns of direct health care expenditures among individuals with back pain in the United States.

STUDY DESIGN: Secondary analysis of the 1998 Medical Expenditure Panel Survey. OBJECTIVE: To estimate total health care expenditures incurred by individuals with back pain in the United States, calculate the incremental expenditures attributable to back pain among these individuals, and describe health care expenditure patterns of individuals with back pain. SUMMARY OF BACKGROUND DATA: There is a lack of updated information on health care expenditures and expenditure patterns for individuals with back pain in the United States. METHODS: This study used data from the 1998 Medical Expenditure Panel Survey, a national survey on health care utilization and expenditures. Total health care expenditures and per-capita expenditures among individuals with back pain were calculated. Multivariate regression models were used to estimate the incremental expenditures attributable to back pain. The expenditure patterns were examined by stratifying individuals with back pain by sociodemographic characteristics and medical diagnosis, and calculating per-capita expenditures for each stratum. RESULTS: In 1998, total health care expenditures incurred by individuals with back pain in the United States reached 90.7 billion dollars and total incremental expenditures attributable to back pain among these persons were approximately 26.3 billion dollars. On average, individuals with back pain incurred health care expenditures about 60% higher than individuals without back pain (3,498 dollars vs. 2,178 dollars). Among back pain individuals, at least 75% of service expenditures were attributed to those with top 25% expenditure, and per-capita expenditures were generally higher for those who were older, female, white, medically insured, or suffered from disc disorders. CONCLUSIONS: Health care expenditures for back pain in the United States in 1998 were substantial. The expenditures demonstrated wide variations among individuals with different clinical, demographic, and socioeconomic characteristics.

Prescription of nonsteroidal anti-inflammatory drugs and muscle relaxants for back pain in the United States.

STUDY DESIGN: Secondary analysis of the 2000 Medical Expenditure Panel Survey (MEPS). OBJECTIVE.: To examine national prescription patterns of nonsteroidal anti-inflammatory drugs (NSAIDs) and muscle relaxants among individuals with back pain in the United States. SUMMARY OF BACKGROUND DATA: There is a lack of information on national prescription patterns of NSAIDs and muscle relaxants among individuals with back pain in the United States. METHODS: Traditional NSAIDs, cyclooxygenase-2-specific (COX-2) inhibitors, and muscle relaxants were investigated. Individuals with back pain were stratified by socio-demographic characteristics and geographic regions. For each medication category, overall prescribing frequency was compared across different strata and individual drug prescription was analyzed. RESULTS: Traditional NSAIDs, COX-2 inhibitors, and muscle relaxants, respectively, accounted for 16.3%, 10%, and 18.5% of total prescriptions for back pain in 2000. Among individual drugs, ibuprofen and naproxen accounted for most of the prescriptions for traditional NSAIDs (60%), whereas two thirds of the prescriptions for muscle relaxants were attributable to cyclobenzaprine, carisoprodol, and methocarbamol. Prescription of COX-2 inhibitors or muscle relaxants demonstrated wide variations across different regions. Several individual characteristics including age, race, and educational level were associated with the prescription of some of the medications. CONCLUSIONS: Neither traditional NSAIDs, nor COX-2 inhibitors, nor muscle relaxants dominated prescriptions for back pain. However, a small number of individual drugs were attributable to most of the prescriptions for traditional NSAIDs or muscle relaxants. The prescription of some of the medications demonstrated wide variations across different regions or different racial and educational groups. More studies are needed to understand the source of the variations and what constitutes optimal prescribing.

Reliability, validity, and responsiveness of the short form 12-item survey (SF-12) in patients with back pain.

STUDY DESIGN: Secondary analysis of data collected from spine patients' normal clinic visits from 1998 to 2001. OBJECTIVE: To evaluate the reliability, validity, and responsiveness of the short form 12-item survey in patients with back pain. SUMMARY OF BACKGROUND DATA: The reliability, validity, and responsiveness of the short form 12-item survey in patients with back pain has not been previously evaluated. METHODS: Patients were asked to complete a comprehensive computerized survey questionnaire during their regular clinic visits. A total of 2520 patients who indicated in their first surveys that they had back pain were included in the study of the reliability and validity of the short form 12-item survey. Of these, 506 patients completed another survey within 3-6 months of follow-up and were included in the responsiveness evaluation. RESULTS: The two summary scales of the short form 12-item survey, physical component summary and mental component summary, demonstrated internal consistency reliability, with Cronbach alpha for both scales exceeding the recommended level of 0.70. Correlation of physical component summary and mental component summary with six other measures theoretically related or unrelated to these scales performed as expected without exception, demonstrating the construct validity of the short form 12-item survey. The responsiveness of the short form 12-item survey was supported by several pieces of evidence. First, the changes in physical component summary and mental component summary scores were correlated with the changes in back pain intensity. Second, for patients whose back pain improved, there was a significant increase in the follow-up physical component summary and mental component summary scores as compared to the baseline. Third, small to moderate effect size was observed for patients whose back pain became improved or became worse. CONCLUSIONS: The short form 12-item survey demonstrated good internal consistency reliability, construct validity, and responsiveness in patients with back pain.

Observer variability in assessing lumbar spinal stenosis severity on magnetic resonance imaging and its relation to cross-sectional spinal canal area.

STUDY DESIGN: Magnetic resonance image grading of lumbar spinal stenosis severity was analyzed retrospectively using a common clinical format. OBJECTIVE: To assess the interobserver and intraobserver reliability of magnetic resonance image used to grade patients with lumbar spinal stenosis, as compared with cross-sectional spinal canal area. SUMMARY OF BACKGROUND DATA: Physicians currently classify the degree of lumbar spinal stenosis on magnetic resonance imaging as mild, moderate, or severe. Unfortunately, there is no consensus on criteria for these definitions. METHODS: The magnetic resonance image scans of 15 patients with lumbar stenosis were blindly rated by seven observers for the degree of central, lateral recess, and foraminal stenosis between L1-L2 and L5-S1. Weighted kappa statistics were performed to analyze the inter- and intraobserver agreement. Digitized spinal canal area measurements were calculated. Linear regression models were used to assess the reliability of the grading system in predicting the cross-sectional area. RESULTS: The average interobserver kappa score was 0.26. Within different specialties, the interobserver reliability was higher among radiologists (0.40), followed by neurosurgeons (0.21) and orthopedic surgeons (0.15). The average intraobserver kappa score was 0.11, rising to 0.43 after categories were combined (P = 0.001). The classification of central stenosis highly predicted spinal canal area (P < 0.001). CONCLUSIONS: The findings indicate only a fair level of agreement among all observers. However, the ability of the various readers to predict the degree of central stenosis was high. Further studies should evaluate a consensus-based, standardized magnetic resonance image classification aimed at improved agreement among observers.