Highly accurate astrometric positions obtained from eclipses and occultations of planetary satellites are reported. These measurements may be used to test existing ephemerides, to improve upon them, ...and to fit system constants such as satellite masses and planetary zonal harmonics. Eclipse and occultation photometry of 5 uranian satellite mutual events has resulted in precise astrometry for 3 of these moons. Relative satellite positions were determined with an uncertainty of less than 10 milli-arcseconds for 4 of the events. These observations plus two additional data from C. Miller and N.J. Chanover (private communication) indicate that predictions based on the SPICE Acton, C.H., 1996. Planet. Space Sci. 44, 65–70 ephemeris URA083 and those from the LA06 ephemeris in a paper by Arlot et al. Arlot, J.-E., Lainey, V., Thuillot, W., 2006. Astron. Astrophys. 456, 1173–1179 are significantly more accurate than predictions generated by Christou Christou, A.A., 2005. Icarus 178, 171–178 using the GUST86 ephemeris in the along-track component of motion. The observations indicate that Ariel, Umbriel and Titania are lagging behind their predicted positions for all of the ephemerides, but by varying distances and significance levels. Analysis of data recorded by Hidas et al. Hidas, M.G., Christou, A.A., Brown, T.M., 2008. Mon. Not. R. Astron. Soc. 384, L38–L40 suggests a similar lag for Oberon. Photometry recorded during the ingress portion of a saturnian eclipse of Iapetus on 2007 May 5 indicates that the middle of the event occurred at geocentric UTC 02:14:58. At that moment the center of the satellite disk facing the Sun was intersected by a solar-centered ray refracted at a minimum altitude of 240 km above the 1-bar pressure level in the planet's atmosphere. The uncertainty in the timings due to observational scatter was only 5 s which equates to 16 km of Iapetus motion, but other factors increased the overall uncertainty to 111 km or 16 milli-arcseconds at the distance of Saturn from the Sun. The astrometric result is fit very well by the SPICE ephemeris SAT288.
Electrons in materials with linear dispersion behave as massless Weyl- or Dirac-quasiparticles, and continue to intrigue due to their close resemblance to elusive ultra-relativistic particles as well ...as their potential for future electronics. Yet the experimental signatures of Weyl-fermions are often subtle and indirect, in particular if they coexist with conventional, massive quasiparticles. Here we show a pronounced anomaly in the magnetic torque of the Weyl semimetal NbAs upon entering the quantum limit state in high magnetic fields. The torque changes sign in the quantum limit, signalling a reversal of the magnetic anisotropy that can be directly attributed to the topological nature of the Weyl electrons. Our results establish that anomalous quantum limit torque measurements provide a direct experimental method to identify and distinguish Weyl and Dirac systems.
Abstract Background context There are often multiple surgical treatment options for a spinal pathology. In addition, there is a lack of data that define differences in surgical treatment among ...surgeons in the United States. Purpose To assess the surgical treatment patterns among neurologic and orthopedic spine surgeons in the United States for the treatment of one- and two-time recurrent lumbar disc herniation. Study design Electronic survey. Patient sample An electronic survey was delivered to 2,560 orthopedic and neurologic surgeons in the United States. Outcome measures The response data were analyzed to assess the differences among respondents over various demographic variables. The probability of disagreement is reported for various surgeon subgroups. Methods A survey of clinical and radiographic case scenarios that included a one- and two-time lumbar disc herniation was electronically delivered to 2,560 orthopedic and neurologic surgeons in the United States. The surgical treatment options were revision microdiscectomy, revision microdiscectomy with in situ fusion, revision microdiscectomy with posterolateral fusion using pedicle screws, revision microdiscectomy with posterior lumbar interbody fusion/transforaminal lumbar interbody fusion (PLIF/TLIF), anterior lumbar interbody fusion (ALIF) with percutaneous screws, ALIF with open posterior instrumentation, or none of these. Significance of p=.01 was used to account for multiple comparisons. Results Four hundred forty-five surgeons (18%) completed the survey. Surgeons in practice for 15+ years were more likely to select revision microdiscectomy compared with surgeons with fewer years in practice who were more likely to select revision microdiscectomy with PLIF/TLIF (p<.001). Similarly, those surgeons performing 200+ surgeries per year were more likely to select revision microdiscectomy with PLIF/TLIF than those performing fewer surgeries (p=.003). No significant differences were identified for region, specialty, fellowship training, or practice type. Overall, there was a 69% and 22% probability that two randomly selected spine surgeons would disagree on the surgical treatment of two- and one-time recurrent disc herniations, respectively. This probability of disagreement was consistent over multiple variables including geographic, practice type, fellowship training, and annual case volume. Conclusions Significant differences exist among US spine surgeons in the surgical treatment of recurrent lumbar disc herniations. It will become increasingly important to understand the underlying reasons for these differences and to define the most cost-effective surgical strategies for these common lumbar pathologies as the United States moves closer to a value-based health-care system.
STUDY DESIGN.Electronic survey.
OBJECTIVE.To identify the surgical treatment patterns for low back pain (LBP), among U.S. spine surgeons. Specifically determine (1) differences in surgical treatment ...responses based on various demographic variables; (2) probability of disagreement based on surgeon subgroups.
SUMMARY OF BACKGROUND DATA.Multiple surgical and nonsurgical treatments exist for LBP. Without strong evidence or clear guidelines for the indications and optimal treatments, there is substantial variability in surgical treatments used.
METHODS.A total of 445 U.S. spine surgeons completed a survey of clinical and radiographic case scenarios on patients with mechanical LBP, no leg pain, and concordant discograms. Surgical treatment options included no surgery, anterior lumbar interbody fusion (ALIF), posterolateral fusion with pedicle screws, transforaminal/posterior lumbar interbody fusion (TLIF/PLIF), etc. Statistical significance was set at 0.01 to account for multiple comparisons.
RESULTS.There was substantial clinical equipoise (∼75% disagreement) among surgeons on the approach to treat patients with LBP. Disagreement was highest in the southwest and lowest in the Midwest (82% vs. 69%, respectively); there was significantly lower disagreement among those in academic practices versus those in private/hybrid practices (56% vs.79%, respectively). Those in academic practices had approximately four times greater odds of choosing no surgery as compared to those in hybrid and private practices, who were more likely to choose ALIF or PLIF/TLIF. Those with fellowship training had approximately two times greater odds of selecting no surgery and four times greater odds of selecting ALIF as compared to those without fellowship training who were more likely to select TLIF/PLIF.
CONCLUSION.Significant differences exist among U.S. spine surgeons in the treatment of LBP. These differences stem from geographical location of the practice, specialty, practice type, and fellowship training. Recognizing the substantial variability underlies the importance of additional studies aimed at identifying the proper indications and most cost-effective treatments for LBP.Level of Evidence3
There are a multitude of treatments for low-grade lumbar spondylolisthesis. There are no clear guidelines for the optimal approach.
To identify the surgical treatment patterns for spondylolisthesis ...among United States spine surgeons.
445 spine surgeons in the United States completed a survey of clinical/radiographic case scenarios on patients with lumbar spondylolisthesis with neurogenic claudication with (S+BP) or without (S−BP) associated mechanical back pain. Treatment options included decompression, laminectomy with posterolateral fusion, posterior lumbar interbody fusion, or none of the above. The primary outcome measure was the probability of 2 randomly chosen surgeons disagreeing on the treatment method.
There was 64% disagreement (36% agreement) among surgeons for treatment of spondylolisthesis with mechanical back pain (S+BP) and 71% disagreement (29% agreement) for spondylolisthesis without mechanical back pain (S−BP). For S+BP, disagreement was 52% for those practicing 5 to 10 years versus 70% among those practicing more than 20 years. Orthopedic surgeons had greater disagreement than did neurosurgeons (76% vs. 56%) for S+BP. Greater clinical equipoise was seen for S−BP than for S+BP regardless of surgeon characteristics. For spondylolisthesis without mechanical back pain, neurosurgeons were significantly more likely to select decompression-only than were orthopedic surgeons, who more commonly selected fusion.
Clinical equipoise exists for the treatment of spondylolisthesis. Differences are greater when the patient presents without associated back pain. Surgeon case volume, practice duration, and specialty training influence operative decisions for a given pathologic condition. Recognizing this practice variation will hopefully lead to better evidence and practice guidelines for the optimal and most cost-effective treatment paradigms.
•There are a multitude of surgical and nonsurgical treatments for low-grade lumbar spondylolisthesis; there are no clear guidelines for the optimal approach.•To identify the surgical treatment patterns for spondylolisthesis among United States spine surgeons; 445 orthopedic and neurosurgery spine surgeons in the United States were surveyed.•There was 64% disagreement among surgeons for treatment of spondylolisthesis with mechanical back pain and 71% disagreement for spondylolisthesis without mechanical back pain.•Disagreement was 52% for those practicing 5 to 10 years versus 70% among those practicing more than 20 years; orthopedic surgeons had greater disagreement than did neurosurgeons (76% vs. 56%); greater clinical equipoise was seen for management of spondylolisthesis without back pain than for cases with back pain regardless of surgeon characteristics.
Purpose
Spine-related disorders are a leading cause of global disability and are a burden on society and to public health. Currently, there is no comprehensive, evidence-based model of care for ...spine-related disorders, which includes back and neck pain, deformity, spine injury, neurological conditions, spinal diseases, and pathology, that could be applied in global health care settings. The purposes of this paper are to propose: (1) principles to transform the delivery of spine care; (2) an evidence-based model that could be applied globally; and (3) implementation suggestions.
Methods
The Global Spine Care Initiative (GSCI) meetings and literature reviews were synthesized into a seed document and distributed to spine care experts. After three rounds of a modified Delphi process, all participants reached consensus on the final model of care and implementation steps.
Results
Sixty-six experts representing 24 countries participated. The GSCI model of care has eight core principles: person-centered, people-centered, biopsychosocial, proactive, evidence-based, integrative, collaborative, and self-sustaining. The model of care includes a classification system and care pathway, levels of care, and a focus on the patient’s journey. The six steps for implementation are initiation and preparation; assessment of the current situation; planning and designing solutions; implementation; assessment and evaluation of program; and sustain program and scale up.
Conclusion
The GSCI proposes an evidence-based, practical, sustainable, and scalable model of care representing eight core principles with a six-step implementation plan. The aim of this model is to help transform spine care globally, especially in low- and middle-income countries and underserved communities.
Graphical abstract
These slides can be retrieved under Electronic Supplementary Material.
Study Design:
Cross-sectional analysis.
Objectives:
Given the lack of strong evidence/guidelines on appropriate treatment for lumbar spine disease, substantial variability exists among surgical ...treatments utilized, which is associated with differences in costs to treat a given pathology. Our goal was to investigate the variability in costs among spine surgeons nationally for the same pathology in similar patients.
Methods:
Four hundred forty-five spine surgeons completed a survey of clinical and radiographic case scenarios on patients with recurrent lumbar disc herniation, low back pain, and spondylolisthesis. Those surveyed were asked to provide various details including their geographical location, specialty, and fellowship training. Treatment options included no surgery, anterior lumbar interbody fusion, posterolateral fusion, and transforaminal/posterior lumbar interbody fusion. Costs were estimated via Medicare national payment amounts.
Results:
For recurrent lumbar disc herniation, no difference in costs existed for patients undergoing their first revision microdiscectomy. However, for patients undergoing another microdiscectomy, surgeons who operated <100 times/year had significantly lower costs than those who operated >200 times/year (P < .001) and those with 5-15 years of experience had significantly higher costs than those with >15 years (P < .001). For the treatment of low back pain, academic surgeons kept costs about 55% lower than private practice surgeons (P < .001). In the treatment of spondylolisthesis, there was significant treatment variability without significant differences in costs.
Conclusions:
Significant variability in surgical treatment paradigms exists for different pathologies. Understanding why variability in treatment selection exists in similar clinical contexts across practices is important to ensure the most cost-effective delivery of care among spine surgeons.
Purpose
The purpose of this report is to describe the development of an evidence-based care pathway that can be implemented globally.
Methods
The Global Spine Care Initiative (GSCI) care pathway ...development team extracted interventions recommended for the management of spinal disorders from six GSCI articles that synthesized the available evidence from guidelines and relevant literature. Sixty-eight international and interprofessional clinicians and scientists with expertise in spine-related conditions were invited to participate. An iterative consensus process was used.
Results
After three rounds of review, 46 experts from 16 countries reached consensus for the care pathway that includes five decision steps: awareness, initial triage, provider assessment, interventions (e.g., non-invasive treatment; invasive treatment; psychological and social intervention; prevention and public health; specialty care and interprofessional management), and outcomes. The care pathway can be used to guide the management of patients with any spine-related concern (e.g., back and neck pain, deformity, spinal injury, neurological conditions, pathology, spinal diseases). The pathway is simple and can be incorporated into educational tools, decision-making trees, and electronic medical records.
Conclusion
A care pathway for the management of individuals presenting with spine-related concerns includes evidence-based recommendations to guide health care providers in the management of common spinal disorders. The proposed pathway is person-centered and evidence-based. The acceptability and utility of this care pathway will need to be evaluated in various communities, especially in low- and middle-income countries, with different cultural background and resources.
Graphical abstract
These slides can be retrieved under Electronic Supplementary Material.
Purpose
Spinal disorders, including back and neck pain, are major causes of disability, economic hardship, and morbidity, especially in underserved communities and low- and middle-income countries. ...Currently, there is no model of care to address this issue. This paper provides an overview of the papers from the Global Spine Care Initiative (GSCI), which was convened to develop an evidence-based, practical, and sustainable, spinal healthcare model for communities around the world with various levels of resources.
Methods
Leading spine clinicians and scientists around the world were invited to participate. The interprofessional, international team consisted of 68 members from 24 countries, representing most disciplines that study or care for patients with spinal symptoms, including family physicians, spine surgeons, rheumatologists, chiropractors, physical therapists, epidemiologists, research methodologists, and other stakeholders.
Results
Literature reviews on the burden of spinal disorders and six categories of evidence-based interventions for spinal disorders (assessment, public health, psychosocial, noninvasive, invasive, and the management of osteoporosis) were completed. In addition, participants developed a stratification system for surgical intervention, a classification system for spinal disorders, an evidence-based care pathway, and lists of resources and recommendations to implement the GSCI model of care.
Conclusion
The GSCI proposes an evidence-based model that is consistent with recent calls for action to reduce the global burden of spinal disorders. The model requires testing to determine feasibility. If it proves to be implementable, this model holds great promise to reduce the tremendous global burden of spinal disorders.
Graphical abstract
These slides can be retrieved under Electronic Supplementary Material.
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