Effectiveness of percutaneous laser disc decompression versus conventional open discectomy in the treatment of lumbar disc herniation; design of a prospective randomized controlled trial

Background. The usual surgical treatment of refractory sciatica caused by lumbar disc herniation, is open discectomy. Minimally invasive procedures, including percutaneous therapies under local anesthesia, are increasingly gaining attention. One of these treatments is Percutaneous Laser Disc Decompression (PLDD). This treatment can be carried out in an outpatient setting and swift recovery and return to daily routine are suggested. Thus far, no randomized trial into cost-effectiveness of PLDD versus standard surgical procedure has been performed. We present the design of a randomized controlled trial, studying the cost-effectiveness of PLDD versus conventional open discectomy in patients with sciatica from lumbar disc herniation. Methods/design. The study is a randomized prospective multi-center trial, in which two treatment strategies are compared in a parallel group design. Patients (age 18-70 years) visiting the neurosurgery department of the participating hospitals, are considered for inclusion in the trial when sciatica due to lumbar disc herniation has lasted more than 8 weeks. Patients with disc herniation smaller than 1/3 of the spinal canal diameter, without concomitant lateral recess stenosis or sequestration, are eligible for participation, and are randomized into one of two treatment arms; either Percutaneous Laser Disc Decompression or conventional discectomy. The functional outcome of the patient, as assessed by the Roland Disability Questionnaire for Sciatica at 8 weeks and 1 year after treatment, is the primary outcome measure. The secondary outcome parameters are recovery as perceived by the patient, leg and back pain, incidence of re-intervention, complications, quality of life, medical consumption, absence of work and secondary costs. Discussion. Open discectomy is still considered to be the golden standard in the surgical treatment of lumbar disc herniation. Whether Percutaneous Laser Disc Decompression has at least as much efficacy as the standard surgical procedure, and is more cost-effective, will be determined by this trial. Trial registration. Current Controlled Trials ISRCTN25884790

Clinical classification criteria for neurogenic claudication caused by lumbar spinal stenosis. The N-CLASS criteria

Background Context Since imaging findings of lumbar spinal stenosis (LSS) may not be associated with symptoms, clinical classification criteria based on patient symptoms and physical examination findings are needed. Purpose To develop clinical classification criteria that identify patients with neurogenic claudication (NC) caused by LSS. Study Design Two stage process. Phase 1: Delphi process; Phase 2: cross-sectional study. Patient Sample Outpatients recruited from spine clinics in 5 countries. Outcome Measure Items from history and physical examination. Methods Phase 1: A list of potential predictors of NC caused by LSS was based on the available literature and evaluated through a Delphi process involving seventeen spine specialists (surgeons and non-surgeons) from 8 countries. Phase 2: Nineteen different clinical spine specialists from 5 countries identified patients they classified as having: 1) NC caused by LSS 2) Radicular pain caused by lumbar disc herniation (LDH), or 3) non-specific low back pain (NSLBP) with radiating leg pain. Patients completed survey items and specialists documented examination signs. Coefficients from General Estimating Equation models were used to select predictors, generate a clinical classification score and obtain a receiver operating characteristic (ROC) curve. Conduction of the Delphi process, data management and statistical analysis were partially supported by an unrestricted grant of less than 15000 US dollars from Merck Sharp and Dohme. No fees were allocated to participating spine specialists. Results Phase 1 generated a final list of 46 items related to LSS. In phase 2, 209 patients with leg pain caused by LSS (n=63), LDH (n=89) or NSLBP (n=57) were included. Criteria which independently predicted NC (p<0.05) were: age over 60; positive 30 second extension test; negative straight leg test; pain in both legs; leg pain relieved by sitting, and leg pain decreased by leaning forward or flexing the spine. A classification score using a weighted set of these criteria was developed. The proposed N-CLASS score ranged from 0 to 19, had an area under the curve of 0.92, and the cutoff (>10/19) to obtain a specificity of >90.0% resulted in a sensitivity of 82.0%. Conclusion Clinical criteria independently associated with neurogenic claudication due to LSS were identified. Use of these symptom and physical variables as a classification score for clinical research could improve homogeneity among enrolled patients

A precision study of the fine tuning in the DiracNMSSM

Recently the DiracNMSSM has been proposed as a possible solution to reduce the fine tuning in supersymmetry. We determine the degree of fine tuning needed in the DiracNMSSM with and without non-universal gaugino masses and compare it with the fine tuning in the GNMSSM. To apply reasonable cuts on the allowed parameter regions we perform a precise calculation of the Higgs mass. In addition, we include the limits from direct SUSY searches and dark matter abundance. We find that both models are comparable in terms of fine tuning, with the minimal fine tuning in the GNMSSM slightly smaller.Comment: 20 pages + appendices, 10 figure

Naturalness of the Non-Universal MSSM in the light of the recent Higgs results

We analyse the naturalness of the Minimal Supersymmetric Standard Model (MSSM) in the light of recent LHC results from the ATLAS and CMS experiments. We study non-universal boundary conditions for the scalar and the gaugino sector, with fixed relations between some of the soft breaking parameters, and find a significant reduction of fine-tuning for non-universal gaugino masses. For a Higgs mass of about 125 GeV, as observed recently, we find parameter regions with a fine-tuning of O(10), taking into account experimental and theoretical uncertainties. These regions also survive after comparison with simplified model searches in ATLAS and CMS. For a fine-tuning less than 20 the lightest neutralino is expected to be lighter than about 400 GeV and the lighter stop can be as heavy as 3.5 TeV. On the other hand, the gluino mass is required to be above 1.5 TeV. For non-universal gaugino masses, we discuss which fixed GUT scale ratios can lead to a reduced fine-tuning and find that the recent Higgs results have a strong impact on which ratio is favoured. We also discuss the naturalness of GUT scale Yukawa relations, comparing the non-universal MSSM with the CMSSM.Comment: 24 pages, 8 figures; version accepted for publication in JHE

Isospin violating dark matter in Stückelberg portal scenarios

Journal of High Energy Physics 2015.4 (2015): 175 reproduced by permission of Scuola Internazionale Superiore di Studi Avanzati (SISSA)Hidden sector scenarios in which dark matter (DM) interacts with the Standard Model matter fields through the exchange of massive Z′ bosons are well motivated by certain string theory constructions. In this work, we thoroughly study the phenomenological aspects of such scenarios and find that they present a clear and testable consequence for direct DM searches. We show that such string motivated Stückelberg portals naturally lead to isospin violating interactions of DM particles with nuclei. We find that the relations between the DM coupling to neutrons and protons for both, spin-independent (fn/fp) and spin-dependent (an/ap) interactions, are very flexible depending on the charges of the quarks under the extra U(1) gauge groups. We show that within this construction these ratios are generically different from ±1 (i.e. different couplings to protons and neutrons) leading to a potentially measurable distinction from other popular portals. Finally, we incorporate bounds from searches for dijet and dilepton resonances at the LHC as well as LUX bounds on the elastic scattering of DM off nucleons to determine the experimentally allowed values of fn/fp and an/apThe authors are grateful to D. G. Cerdeño, L. Ibañez, F. Kahlhoefer and G. Shiu for useful comments. V.M.L. and M.P. would like to thank the support of the European Union under the ERC Advanced Grant SPLE under contract ERC-2012-ADG-20120216-320421, the support of the Consolider-Ingenio 2010 programme under grant MULTIDARK CSD2009-00064, the Spanish MICINN under Grant No. FPA2012-34694, the Spanish MINECO “Centro de excelencia Severo Ochoa Program” under Grant No. SEV-2012-0249, and the Community of Madrid under Grant No. HEPHACOS S2009/ESP-1473. P.S. would like to thank DESY, the University of Hamburg, and the Hong Kong IAS for kind hospitality during the completion of this work. He acknowledges support from the DOE grant DEFG-02-95ER40896 and the HKRGC grant HKUST4/CRF/13G, 604231, as well as the Collaborative Research Center SFB676 of the DFG at the University of Hambur

Cheating on the Edge

We present the results of an individual agent-based model of antibiotic resistance in bacteria. Our model examines antibiotic resistance when two strategies exist: “producers”–who secrete a substance that breaks down antibiotics–and nonproducers (“cheats”) who do not secrete, or carry the machinery associated with secretion. The model allows for populations of up to 10,000, in which bacteria are affected by their nearest neighbors, and we assume cheaters die when there are no producers in their neighborhood. Each of 10,000 slots on our grid (a torus) could be occupied by a producer or a nonproducer, or could (temporarily) be unoccupied. The most surprising and dramatic result we uncovered is that when producers and nonproducers coexist at equilibrium, nonproducers are almost always found on the edges of clusters of producers