Study Design.
A radiographic comparative study.
Objective.
To investigate the influence of radiographic lower limb-spinal length proportion on sagittal radiographic parameters.
Summary of Background ...Data.
Although lordotic realignment of the lumbar spine is a well-established surgical strategy, its ideal target has not been fully understood. The widely used pelvic incidence-lumbar lordosis discrepancy (PI-LL) method to guide lordotic restoration of the lumber spine in the standing posture, may be further refined using the novel, radiographic lower limb-spinal length proportion parameter in selected subjects.
Methods.
A 100 healthy subjects were imaged in the standing posture using EOS imaging to obtain whole-body lateral radiographs for the measurement of sagittal radiographic parameters. Univariate analyses were performed to compare radiographic parameters between groups with different radiographic lower limb-spinal length proportion. Multivariate analyses were performed to identify the associations between lower limb-spinal length proportions and other radiographic parameters.
Results.
Regardless of lower limb-spinal length proportion (mean = 1.4), global lumbar angle (GLA) differed from spinal lordosis (SL), with the absolute means of SL and GLA larger and smaller than pelvic incidence (PI) respectively. Univariate analysis showed that patients with proportionately larger lower limb-spinal length proportion are more likely to have larger mean T1-slope, global thoracic angle (GTA), spinal kyphosis (SK), GLA, and SL. Multivariate analysis showed that a larger lower limb length-spinal length proportion is predictive of larger GLA is less than –47.69° (Odds Ratio (OR) 2.660,
P
= 0.026), and larger T1-slope of more than 18.84° (OR 3.695,
P
= 0.012).
Conclusion.
Larger radiographic lower limb-spinal length proportion results in naturally accentuated spinal curves. These patients balance with a larger lumbar lordosis that is closer to the PI and a higher T1-slope which should be considered for spinal realignment. SL differs from GLA and should be separately assessed.
Level of Evidence:
3
STUDY DESIGN.A cross-sectional study on a randomly selected prospective cohort of patients presenting to a single tertiary spine center.
OBJECTIVE.The aim of this study was to describe the clinical ...and radiographic parameters of patients with S- and C-shaped thoracolumbar sagittal spinal profiles, and to identify predictors of these profiles in a natural, relaxed sitting posture.
SUMMARY OF BACKGROUND DATA.Sagittal realignment in adult spinal deformity surgery has to consider the sitting profile to minimize the risks of junctional failure. Persistence of an S-shaped sagittal profile in the natural, relaxed sitting posture may reflect a lesser need to accommodate for this posture during surgical realignment.
METHODS.Consecutive patients with low back pain underwent whole body anteroposterior and lateral radiographs in both standing and sitting. Baseline clinical data of patients and radiographic parameters of both standing and sitting sagittal profiles were compared using χ, unpaired t tests, and Wilcoxon rank-sum test. Subsequently, using stepwise multivariate logistic regression analysis, predictors of S-shaped curves were identified while adjusting for confounders.
RESULTS.Of the 120 patients included, 54.2% had S-shaped curves when sitting. The most common diagnoses were lumbar spondylosis (26.7%) and degenerative spondylolisthesis (26.7%). When comparing between patients with S- and C-shaped spines in the sitting posture, only diagnoses of degenerative spondylolisthesis (odds ratio OR, 5.44; P = 0.01) and degenerative scoliosis (OR, 2.00; P = 0.039), and pelvic incidence (PI) >52.5° (OR, 5.48; P = 0.008), were predictive of an S-shaped sitting sagittal spinal alignment on multivariate analysis.
CONCLUSION.Stiffer lumbar curves (eg, patients with degenerative spondylolisthesis and degenerative scoliosis) or those who have a predilection for an S-shaped standing sagittal profile when sitting (eg, high PI) may be more amenable to fusion in accordance with previously studied sagittal realignment targets. In contrast, more flexible curves may benefit from less aggressive lordotic realignment to prevent potential junctional failures.Level of Evidence3
A retrospective, radiographic comparative study conducted in a single academic institution.
This study aims to compare fulcrum extension with conventional extension imaging to determine maximum "hip ...lordosis" (HL), an important novel patient-specific parameter in spinal realignment surgery, as well as understand the extension capabilities of the lower lumbar spine, which together, are key contributors to whole-body balancing.
Recent literature recognizes the hip as an important contributor to whole-body lordosis beyond a compensator for spinal imbalance.
Patients >45-years-old with mechanical low back pain due to degenerative spinal conditions were included and grouped based on the imaging performed - fulcrum or conventional extension. All imaging was performed using EOS® under standardised instructions and visual aids. Radiographic parameters include global lumbar angle (GLA), inflexion-S1 (Inf-S1) angle, segmental lumbar angles, pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), femoral alignment angle (FAA), HL and spinocoxa angle (SCA). Unpaired t-test was used to compare between radiographic parameters.
One hundred patients (40 males and 60 females, mean age 63.0 years) underwent either fulcrum or conventional extension EOS® imaging. Both groups had comparable baseline radiographic parameters. Fulcrum extension gave a larger mean GLA (-60.7° vs -48.5°, p = 0.001), Inf-S1 angle (-58.8° vs -48.8°, p = 0.003), SCA (-36.5° vs -24.8°, p<0.001), L4/5 and L5/S1 lordosis (-20.7° vs -17.7°, p = 0.041, and -22.3° vs -17.1°, p = 0.018, respectively), compared to conventional extension. PI, SS, PT, FAA and HL were similar between both extension postures.
Fulcrum extension, compared to conventional extension, is better at generating lordosis in the lower lumbar spine, thus improving pre-operative assessment of stiffness or instability of the lumbar spine. Both extension methods were equally effective at determining the patient-specific maximum HL to assess the flexibility and compensation occurring at the hip, potentially guiding surgical management of patients with degenerative spines.Level of Evidence: 3.
A cross-sectional study of prospectively collected data.
To compare lumbar spine alignment in six common postures, and estimate loss in range of motion (ROM) relative to standing.
Ideal position for ...fusion of lumbar spine remains unknown. Although surgical fusion is necessary for deformity correction and symptom relief, the final position in which the vertebrae are immobilized should provide maximum residual function.
Data were collected prospectively from 70 patients with low back pain recruited over a year. All subjects had x-rays performed in slump sitting, forward bending, supine, half squatting, standing, and backward bending postures. ROM quantified in terms of sagittal global and segmental Cobb angles was measured from L1 to S1. Loss of ROM relative to standing was calculated for each posture. Analysis of variance and unpaired t tests were used to identify differences in alignment between postures.
Slump sitting gives the greatest lumbar flexion followed by forward bending, and supine postures (P < 0.001). Backward bending produces greater lumbar extension than standing (P = 0.035). Half-squatting and standing postures were not significantly different (P = 0.938). For all postures, L4-5 and L5-S1 segments remained in lordosis, with L4-5 having greater ROM than L5-S1. L1-2 turns kyphotic in lying supine, L2-3 at forward bending, and L3-4 at slump sitting in the form of a "kyphosing cascade." Should the entire lumbar spine be fused in standing position from L1-S1, there would likely be a mean loss of 47.6° of lumbar flexion and 5.9° of lumbar extension.
The present study demonstrates the extent of flexibility required of the lumbar spine in assuming various postures. It also enables comparison of the differences in degree of motion occurring in the lumbar spine, both across postures and across segments. Significant loss in ROM, particularly flexion, is anticipated with fusion modeled after the lordotic standing lumbar spine.
2.
Groesser, T., Chun, E. and Rydberg, B. Relative Biological Effectiveness of High-Energy Iron Ions for Micronucleus Formation at Low Doses. Radiat. Res. 168, 675–682 (2007). Dose–response curves for ...micronucleus (MN) formation were measured in Chinese hamster V79 and xrs6 (Ku80−) cells and in human mammary epithelial MCF10A cells in the dose range of 0.05–1 Gy. The Chinese hamster cells were exposed to 1 GeV/nucleon iron ions, 600 MeV/nucleon iron ions, and 300 MeV/nucleon iron ions (LETs of 151, 176 and 235 keV/μm, respectively) as well as with 320 kVp X rays as reference. Second-order polynomials were fitted to the induction curves, and the initial slopes (the alpha values) were used to calculate RBE. For the repair-proficient V79 cells, the RBE at these low doses increased with LET. The values obtained were 3.1 ± 0.8 (LET = 151 keV/μm), 4.3 ± 0.5 (LET = 176 keV/μm), and 5.7 ± 0.6 (LET = 235 keV/μm), while the RBE was close to 1 for the repair-deficient xrs6 cells regardless of LET. For the MCF10A cells, the RBE was determined for 1 GeV/nucleon iron ions and was found to be 5.5 ± 0.9, slightly higher than for V79 cells. To test the effect of shielding, the 1 GeV/nucleon iron-ion beam was intercepted by various thicknesses of high-density polyethylene plastic absorbers, which resulted in energy loss and fragmentation. It was found that the MN yield for V79 cells placed behind the absorbers decreased in proportion to the decrease in dose both before and after the iron-ion Bragg peak, indicating that RBE did not change significantly due to shielding except in the Bragg peak region. At the Bragg peak itself with an entrance dose of 0.5 Gy, where the LET is very high from stopping low-energy iron ions, the effectiveness for MN formation per unit dose was decreased compared to non-Bragg peak areas.
Abstract Background Context Sitting spinal alignment is increasingly recognized as a factor influencing strategy for deformity correction. Considering that most individuals sit for longer hours in a ...‘slumped’ rather than erect posture, greater understanding of the natural sitting posture is warranted. Purpose To investigate the differences in sagittal spinal alignment between two common sitting postures: a natural, patient-preferred posture and an erect, investigator-controlled posture that is commonly used in alignment studies. Study Design/Setting A randomized, prospective study of 28 young, healthy patients seen in a tertiary hospital over a 6-month period. Patient Sample Twenty-eight patients (24 males, 4 females), with a mean age of 24 years (range 19-38), were recruited for this study. All patients with first-episode of lower back pain of less than 3 months duration were included. The exclusion criteria consisted of previous spinal surgery, radicular symptoms, red flag symptoms, previous spinal trauma, obvious spinal deformity on forward bending test, significant personal or family history of malignancy and current pregnancy. Outcome Measures Radiographic measurements included sagittal vertical axis (SVA), lumbar lordosis (LL), thoracolumbar angle (TL), thoracic kyphosis (TK) and cervical lordosis (CL). Standard spino-pelvic parameters (PI, PT and SS) and sagittal apex and end vertebrae were also measured. Methods Basic patient demographics (age, gender, ethnicity) were recorded. Lateral sitting whole spine radiographs were obtained using a slot scanner in the imposed erect and the natural sitting posture. Statistical analyses of the radiographical parameters were performed comparing the 2 sitting postures using chi-squared tests for categorical variables and paired t-tests for continuous variables. Results There was forward SVA shift between the 2 sitting postures by a mean of 2.9cm (p<0.001). There was a significant increase in CL by a mean of 11.62° (p<0.001), and TL kyphosis by a mean of 11.48° (p<0.001), as well as a loss of LL by a mean of 21.26° (p<0.001). The mean PT increased by 17.68° (p<0.001). The entire thoracic and lumbar spine has the tendency to form a single C-shaped curve with the apex moving to L1 (p=0.002) vertebra in the majority of patients. Conclusion In a natural sitting posture, the lumbar spine becomes kyphotic and contributes to a single C-shaped sagittal profile comprising the thoracic and the lumbar spine. This is associated with an increase in CL and PT, as well as a constant SVA. These findings lend insight into the body's natural way of energy conservation utilizing the posterior ligamentous tension band while achieving sitting spinal sagittal balance. It also provides information on one of the possible causes of PJK/ PJF.
G protein-coupled receptors (GPCRs) constitute the largest class of drug targets in the human genome, which highlights the importance of understanding the molecular basis of their activation, ...downstream signaling, and regulation. Since 2007, great progress has been made in the field of GPCR structure determination and their signaling complexes at the molecular level. Here, we summarize the high-resolution structures of over 30 different GPCRs with their co-crystallized ligands, and outline the successful strategies involved, including construct design, expression systems, and lipidic cubic phase (LCP) composition, and the many key technical parameters of the crystallization methods. By comparing the success rates of different strategies used in the past, we wish to pave the road for more successful structure–function research for GPCRs in the future.
Purpose
To describe normal variations in sagittal spinal radiographic parameters over an interval period and establish physiological norms and guidelines for which these images should be interpreted.
...Methods
Data were prospectively collected from a continuous series of adult patients with first-episode mild low back pain presenting to a single institution. The sagittal parameters of two serial radiographic images taken 6-months apart were obtained with the EOS
®
slot scanner. Measured parameters include CL, TK, TL, LL, PI, PT, SS, and end and apical vertebrae. Chi-squared test and Wilcoxon Signed Rank test were used to compare categorical and continuous variables, respectively.
Results
Sixty patients with a total of 120 whole-body sagittal X-rays were analysed. Mean age was 52.1 years (SD 21.2). Mean interval between the first and second X-rays was 126.2 days (SD 47.2). Small variations (< 1°) occur for all except PT (1.2°), CL (1.2°), and SVA (2.9 cm). Pelvic tilt showed significant difference between two images (
p
= 0.035). Subgroup analysis based on the time interval between X-rays, and between the first and second X-rays, did not show significant differences. Consistent findings were found for end and apical vertebrae of the thoracic and lumbar spine between the first and second X-rays for sagittal curve shapes.
Conclusions
Radiographic sagittal parameters vary between serial images and reflect dynamism in spinal balancing. SVA and PT are predisposed to the widest variation. SVA has the largest variation between individuals of low pelvic tilt. Therefore, interpretation of these parameters should be patient specific and relies on trends rather than a one-time assessment.
Purpose
Evidence guiding the use of CT and MRI scans in blunt trauma patients who are obtunded remains controversial. This study aims to determine and predict if computed tomography (CT) scans alone ...can be performed without risking oversight of substantial injuries found on follow-up magnetic resonance imaging (MRI).
Methods
This is a retrospective cohort study of 63 blunt trauma patients with a Glasgow Coma Scale of < 8. Data were collated from electronic medical records and included patient demographics, premorbid mobility, mechanism of injury, suspected level of injury and neurological examination findings. Patients were urgently evaluated using CT scans, followed by non-contrast MRI scans within 48 h of admission. The accuracy of CT scan was evaluated using MRI as a reference. Adjusted multivariable analysis was also performed to identify predictors for findings detected on MRI but not on CT.
Results
The mean age of patients was 42.3 years and 90.5% were males. CT scans had a high specificity of 100% and sensitivity of 87.2%. Predictors of MRI abnormalities include females, patients with relatively milder mechanisms of injury, patients with suspected thoracic spine injury, and CT scan findings of facet dislocation and intracranial haemorrhage. There was no predictor for spinal cord oedema.
Conclusions
MRI should be performed in the presence of the aforementioned predictive factors and in the presence of neurological deficits. Otherwise, patients can be treated medically without the fear of missing a substantial cervical injury.
Members of the opioid receptor family of G-protein-coupled receptors (GPCRs) are found throughout the peripheral and central nervous system, where they have key roles in nociception and analgesia. ...Unlike the 'classical' opioid receptors, δ, κ and μ (δ-OR, κ-OR and μ-OR), which were delineated by pharmacological criteria in the 1970s and 1980s, the nociceptin/orphanin FQ (N/OFQ) peptide receptor (NOP, also known as ORL-1) was discovered relatively recently by molecular cloning and characterization of an orphan GPCR. Although it shares high sequence similarity with classical opioid GPCR subtypes (∼60%), NOP has a markedly distinct pharmacology, featuring activation by the endogenous peptide N/OFQ, and unique selectivity for exogenous ligands. Here we report the crystal structure of human NOP, solved in complex with the peptide mimetic antagonist compound-24 (C-24) (ref. 4), revealing atomic details of ligand-receptor recognition and selectivity. Compound-24 mimics the first four amino-terminal residues of the NOP-selective peptide antagonist UFP-101, a close derivative of N/OFQ, and provides important clues to the binding of these peptides. The X-ray structure also shows substantial conformational differences in the pocket regions between NOP and the classical opioid receptors κ (ref. 5) and μ (ref. 6), and these are probably due to a small number of residues that vary between these receptors. The NOP-compound-24 structure explains the divergent selectivity profile of NOP and provides a new structural template for the design of NOP ligands.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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