Distal Junctional Failure: A Feared Complication of Multilevel Posterior Spinal Fusions.

Objectives: Distal junctional failure (DJF) is less commonly described than proximal junctional failure following posterior spinal fusion, and particularly adult spinal deformity (ASD) surgery. We describe a case series of patients with DJF, taking into account sagittal spinopelvic alignment, and suggest potential risk factors in light of the current literature. Methods: We performed a single-center, retrospective review of posterior spinal fusion patients with DJF who underwent subsequent revision surgery between June 2009 and January 2019. Demographics and surgical details were collected. Radiographical measurements included the following: preoperative and postoperative sagittal and coronal alignment for each index or revision surgery. The upper-instrumented vertebra (UIV), lower instrumented vertebra (LIV), and fusion length were recorded. Results: Nineteen cases (64.7 ± 13.5 years, 12 women, seven men) were included. The mean follow-up was 4.7 ± 2.4 years. The number of instrumented levels was 6.79 ± 2.97. Among the patients, 84.2% (n = 16) presented at least one known DJF risk factor. LIV was frequently L5 (n = 10) or S1 (n = 2). Six patients had an initial circumferential fusion at the distal end. Initial DJFs were vertebral fracture distal to the fusion (n = 5), screw pull-out (n = 9), spinal stenosis (n = 4), instability (n = 4), and one early DJK. The distal mechanical complications after a first revision included screw pull-out (n = 4), screw fracture (n = 3), non-union (n = 2), and an iatrogenic spondylolisthesis. Conclusions: In this case series, insufficient sagittal balance restoration, female gender, osteoporosis, L5 or S1 LIV in long constructs were associated with DJF. Restoring spinal balance and circumferentially fusing the base of constructs represent key steps to maintain correction and prevent revisions.

Magneto-optical Particles in Isotropic Spinning Fields Mimic Magnetic Monopoles.

In contrast with the typical electric currents accelerated under the influence of a Coulombic force, there are only a few condensed matter examples of particles experiencing a force proportional to a constant, external magnetic field. In this Letter, we present a new alternative, based on an isotropic radiation spinning field and the magneto-optical effect, in which a particle is propelled by a magnetic field just like a magnetic monopole will do. This is a purely nonreciprocal effect as the reciprocal equivalent (a chiral dipole), despite presenting a dichroic response, does not experience any force when illuminated by the spinning field. The "magnetic charge" induced by impinging radiation on the magneto-optical dipole is found to depend linearly on the helicity of the field. In addition, this artificial monopole experiences a dichroic permanent optical torque and does not interact with an external electric field.

Unraveling the relation between cycling accidents and built environment typologies: Capturing spatial heterogeneity through a latent class discrete outcome model.

Today, cities seek to transition to more sustainable transportation modes. Cycling is critical in this shift, promoting a more beneficial lifestyle for most. However, cyclists are exposed to many hazardous circumstances or environments, resulting in accidents, injuries, and even death. Transport authorities must understand why accidents occur, to reduce the risk of those who cycle. This study applies a new modeling framework to analyze cycling accident severities. We employ a latent class discrete outcome model, where classes are derived from a Gaussian-Bernoulli mixture, applied to data from Berlin, and augmented with volunteered geographic information. We jointly estimate model components, combining machine learning and econometric approaches, allowing for more intricate and flexible representations while maintaining interpretability. Results show the potential of our approach. Risk factors are indexed depending on where accidents occurred and their contribution. We can discover complex relations between specific built environments and accident characteristics and uncover differences in the impact of certain accident factors on one environment typology but not others. Using multiple data sources also proves helpful as an additional layer of knowledge, providing unique value to understand and model cycling accidents. Another critical aspect of our approach is the potential for simulation, where locations can be examined through simulated accident features to understand the inherent risk of various locations. These findings highlight the ability to capture heterogeneity in accidents and their relation to the built environment. Capturing such relations allows for more direct countermeasures to risky situations or policies to be designed, simulated, and targeted.

Fano-Like Resonance from Disorder Correlation in Vacancy-Doped Photonic Crystals.

By preparing colloidal crystals with random missing scatterers, crystals are created where disorder is embodied as vacancies in an otherwise perfect lattice. In this special system, there is a critical defect concentration where light propagation undergoes a transition from an all but perfect reflector (for the spectral range defined by the Bragg condition), to a metamaterial exhibiting an enhanced transmission phenomenon. It is shown that this behavior can be phenomenologically described in terms of Fano-like resonances. The results show that the Fano's parameter q experiences a sign change signaling the transition from a perfect crystal exhibiting a reflectance Bragg peak, through a state where background scattering is maximum and Bragg reflectance reaches a minimum to a point where the system reenters a low scattering state recovering ordinary Bragg diffraction. A simple dipolar model considering the correlation between scatterers and vacancies is proposed and the reported evolution of the Fano-like scattering is explained in terms of the emerging covariance between the optical paths and polarizabilities and the effect of field enhancement in photonic crystal (PhC) defects.

Opto-mechanically generated resonant field enhancement.

A link between the resonant cumulative field enhancement experienced by a chain of plasmonic nanoparticles in a light field and the orientation of the chain with respect to the field is obtained. We calculate analytically the optical torque and the equilibrium configuration and we show how stable orientations are triggered by the geometric resonance conditions. Analytical predictions are checked using numerical calculations based on the coupled dipoles method (CDA) for the particular case of a chain of silver nanoparticles. The reported resonance driven optical torque allows for a tuning of the orientation of the chain depending on radiation's wavelength.

Circular dichroism in magneto-optical forces.

In this article we use an exact method to resolve the fields scattered by a spherical magneto-optical particle and calculate the optical forces exerted on it. The resulting force and the contributing components, i.e. magneto-optical gradient force and magneto-optical extinction force, are presented in an analytical form. We also derive analytical expressions for the scattering and extinction cross sections of a magneto-optical particle, expressions which intuitively demonstrate the effect of circular dichroism in magneto-optical scattering and forces. Finally, we demonstrate that the magneto-optical extinction force is the result of circular dichroism in magneto-optical scattering. We show that it is possible to completely cancel the scattering in the forward or in the backward direction, when the incident field is composed of a circularly-polarized reflected beam. Moreover, the directional scattering is interrelated to the direction of the force exerted on the particle.

Thermoresponsive Polymeric Nanolenses Magnify the Thermal Sensitivity of Single Upconverting Nanoparticles.

Lanthanide-based upconverting nanoparticles (UCNPs) are trustworthy workhorses in luminescent nanothermometry. The use of UCNPs-based nanothermometers has enabled the determination of the thermal properties of cell membranes and monitoring of in vivo thermal therapies in real time. However, UCNPs boast low thermal sensitivity and brightness, which, along with the difficulty in controlling individual UCNP remotely, make them less than ideal nanothermometers at the single-particle level. In this work, it is shown how these problems can be elegantly solved using a thermoresponsive polymeric coating. Upon decorating the surface of NaYF4 :Er3+ ,Yb3+ UCNPs with poly(N-isopropylacrylamide) (PNIPAM), a >10-fold enhancement in optical forces is observed, allowing stable trapping and manipulation of a single UCNP in the physiological temperature range (20-45 °C). This optical force improvement is accompanied by a significant enhancement of the thermal sensitivity- a maximum value of 8% °C+1 at 32 °C induced by the collapse of PNIPAM. Numerical simulations reveal that the enhancement in thermal sensitivity mainly stems from the high-refractive-index polymeric coating that behaves as a nanolens of high numerical aperture. The results in this work demonstrate how UCNP nanothermometers can be further improved by an adequate surface decoration and open a new avenue toward highly sensitive single-particle nanothermometry.

Impact of COVID-19 lockdown on the behavior change of cyclists in Lisbon, using multinomial logit regression analysis.

The 2019 novel coronavirus outbreak hit most countries and cities globally, dramatically impacting how people live during lockdown periods. Compulsorily, socioeconomic activities and mobility patterns changed while long-lasting structural changes might remain. Focusing on this very particular liminal event, this paper aims to present and analyze the impact of the SARS-CoV-2 virus lockdown on the behavior change of cyclists and previously non-cyclists in Lisbon, Portugal, knowing that no concomitant interventions occurred in the cycling environment during the period analyzed (e.g., pop-up interventions). From a 1-min questionnaire in 5 locations in Lisbon's existing cycling lanes, we aimed to collect (n = 493) revealed preferences on cycling frequency before and after the lockdown, which we used to calibrate a weighted multinomial logit model to analyze respondents' probability of increasing, maintaining, or decreasing their cycling frequency. Results suggest that people tended to cycle more often after the lockdown than before. For every five cyclists, two cycled more frequently while two others maintained their cycling frequency. Most cycling trips were recreational or to exercise, and these increased after the lockdown, while trips for work and school decreased, as expected. Moreover, the lower the individuals' cycling frequency levels before the lockdown, the more they cycled after it. Our study diagnoses the impact of the lockdown on cycling habits, indicating an overall propensity to cycling more by the Lisbon citizens. Hence, authorities need to act and make quick infrastructural changes (e.g., pop-up cycling lanes) and encourage the population to use more bikes (e.g., financial incentives for bike purchases).

CYCLANDS: Cycling geo-located accidents, their details and severities.

Several cities and national authorities across the globe publish records on road accidents and crashes. This data is vital for road safety analysis, enabling researchers to develop models to understand how different factors impact the frequency and severity of accidents. However, researchers studying cycling safety face additional challenges as datasets containing solely cycling accidents are scarce, may contain errors, among others. Thus, we publish CYCLANDS: CYCling geo-Located AccideNts, their Details and Severities. CYCLANDS is a curated collection of 30 datasets on cycling crashes to lower the barrier in objective cycling research comprising nearly 1.6 M cycling accidents. All observations include the severity and location of the accident. This collection fosters the worldwide study of cycling safety by providing a testbed for researchers to develop tools and models for cycling safety analysis, ultimately improving the safety of those who cycle.

Awake Cranial Traction and Isolated Anterior Cervical Discectomy and Fusion in the Treatment of Traumatic Subaxial Cervical Facet Joint Dislocations: Analysis of a Cohort of 70 Patients and Predictors of Surgical Failure.

BACKGROUND: Cervical facet dislocations are among the most common traumatic spinal injuries. The management of this type of lesions is still controversial. The objective of the present study was to analyze the results of subaxial cervical facet dislocations submitted to an isolated anterior cervical discectomy and fusion (ACDF) after attempted closed reduction with cranial traction and to identify risk factors for treatment failure. METHODS: All patients who were operated on in a tertiary trauma center during an 11-year period (2008-2018) for traumatic single-level cervical facet joint dislocation (AO C F4 injuries) were retrospectively reviewed. Age, use of cranial traction, dislocation characteristics, neurologic injury, surgical data, and follow-up records were reviewed. A minimum of 18 months follow-up was required. RESULTS: A total of 70 patients with a mean age of 56 years (18-90) (72% men) were identified. The C6-C7 level was the most frequently affected (36/70 cases). Spinal cord injury (SCI) was present in 34% of the cases. Bilateral dislocations and rigid spines were risk factors for SCI. Cranial traction was performed in 59 cases with success in 52 cases (88%). There were 3 failures after anterior fusion, which required revision surgery with a 360° fusion, all occurring at the C7-T1 level. CONCLUSIONS: Cranial traction of the cervical spine is an effective and fast way to achieve closed reduction of cervical facet dislocations. After successful reduction, ACDF, as a single procedure, offers an excellent surgical option. All cases of failure occurred at the C7-T1 level, suggesting that a 360° fusion may be needed at this level.

Endoscopic en-face optical coherence tomography and fluorescence imaging using correlation-based probe tracking.

Forward-viewing endoscopic optical coherence tomography (OCT) provides 3D imaging in vivo, and can be combined with widefield fluorescence imaging by use of a double-clad fiber. However, it is technically challenging to build a high-performance miniaturized 2D scanning system with a large field-of-view. In this paper we demonstrate how a 1D scanning probe, which produces cross-sectional OCT images (B-scans) and 1D fluorescence T-scans, can be transformed into a 2D scanning probe by manual scanning along the second axis. OCT volumes are assembled from the B-scans using speckle decorrelation measurements to estimate the out-of-plane motion along the manual scan direction. Motion within the plane of the B-scans is corrected using image registration by normalized cross correlation. En-face OCT slices and fluorescence images, corrected for probe motion in 3D, can be displayed in real-time during the scan. For a B-scan frame rate of 250 Hz, and an OCT lateral resolution of approximately 20 µ m , the approach can handle out-of-plane motion at speeds of up to 4 mm/s.

Magneto-optical binding in the near field.

In this paper we show analytically and numerically the formation of a near-field stable optical binding between two identical plasmonic particles, induced by an incident plane wave. The equilibrium binding distance is controlled by the angle between the polarization plane of the incoming field and the dimer axis, for which we have calculated an explicit formula. We have found that the condition to achieve stable binding depends on the particle's dielectric function and happens near the frequency of the dipole plasmonic resonance. The binding stiffness of this stable attaching interaction is four orders of magnitude larger than the usual far-field optical binding and is formed orthogonal to the propagation direction of the incident beam (transverse binding). The binding distance can be further manipulated considering the magneto-optical effect and an equation relating the desired equilibrium distance with the required external magnetic field is obtained. Finally, the effect induced by the proposed binding method is tested using molecular dynamics simulations. Our study paves the way to achieve complete control of near-field binding forces between plasmonic nanoparticles.

Modulated flipping torque, spin-induced radiation pressure, and chiral sorting exerted by guided light.

In recent years, optical forces and torques have been investigated in sub-wavelength evanescent fields yielding a rich phenomenology of fundamental and applied interest. Here we demonstrate analytically that guided modes carrying transverse spin density induce optical torques depending on the character, either electric or magnetic, of the dipolar particles. The existence of a nonzero longitudinal extraordinary linear spin momentum suitable to manipulate optical forces and torques modifies optical forces either enhancing or inhibiting radiation pressure. Hybrid modes supported by cylindrical waveguides also exhibit intrinsic helicity that leads to a rich distribution of longitudinal optical torques. Finally, we show that chiral dipolar particles also undergo lateral forces induced by transverse spin density, amenable to chiral particle sorting. These properties are revealed in configurations on achiral and chiral dipolar particles within confined geometries throughout the electromagnetic spectra.

Pseudarthrosis in adult spine deformity surgery: risk factors and treatment options.

PURPOSE: Highlight risk factors for pseudarthrosis in long-segment spinal fusions, collect the approaches carried to address this complication. METHODS: Patients with ASD and fusion of ≥ 4 levels with minimum follow-up (FU) of ≥ 2 years were included. Full-body X-rays were done preoperatively, < 3 months and ≥ 2 years. Oswestry disability index (ODI), Scoliosis Research Society-22 and SF36 assessed pre- and postoperatively. The relationship between demographic, surgical and radiological variables with the development of pseudarthrosis was evaluated. RESULTS: Out of 524 patients included, 65 patients (12.4%) developed pseudarthrosis and 53 underwent revision surgery. Notably, 88% of pseudarthrosis cases are associated with fusion length (OR = 1.17, 95% CI = 1.05-1.292, p = 0.004), osteotomy requirement (OR = 0.28, 95% CI = 0.09-0.85, p = 0.025), pelvic fixation (OR = 0.34, 95% CI = 0.13-0.88, p = 0.026) and combined approaches (OR = 3.29, 95% CI = 1.09-9.91, p = 0.034). Sagittal alignment is not related to the rate of pseudarthrosis. Health related and quality of life scores were comparable at last FU between patients revised for pseudarthrosis and those that didn't require revision surgery (ODI = 28% no revision and 30% revision group). CONCLUSIONS: Pseudarthrosis is not related to malalignment, but with the surgical techniques employed for its treatment. Anterior approaches with anterior support decrease the rate by 30%, while long fusions, osteotomies and pelvic fixation increase its rate.

Methylenetetrahydrofolate reductase polymorphisms as risk factors for retinal venous occlusive disease: A literature review.

The role of polymorphisms of methylenetetrahydrofolate reductase (MTHFR) gene in retinal vein occlusion (RVO) is a theme of discussion since the first reports of RVO in patients with MTHFR C677T mutation and without classic acquired risk factors for retinal vascular disease. The association between MTHFR polymorphisms and RVO has been studied over the last 20 years producing conflicting results. This review aims to summarize the literature concerning the role MTHFR polymorphisms as risk factors for RVO.

Sub-surface characterisation of latest-generation identification documents using optical coherence tomography.

The identification of individuals, particularly at international border crossings, coupled with the evolving sophistication of identity documents are issues that authorities must contend with. Particularly, the ability to distinguish legitimate from counterfeit documents, with high throughput, sensitivity, and selectivity is an ever-evolving challenge. Over the last decade, an increasing number of security features have been introduced by authorities in identification documents. The latest generation of travel documents (such as passports and national ID cards) forego paper substrates for several layers of polycarbonate, allowing security features to be embedded within the documents. These security features may contain information at either the superficial and sub-surface levels, thus increasing the document's resilience to counterfeiting. As the documents become harder to forge, so does the sophistication of forgery detection. There appears to be an unmet and evolving need to identify such sophisticated forgeries, in a non-destructive, high throughput manner. In this publication, we report on the application of optical coherence tomography (OCT) imaging on assessing security features in specimen passports and national ID cards. OCT allows sub-surface imaging of translucent structures, non-destructively enabling quantitative visualisation of embedded security features.

Nanojet Trapping of a Single Sub-10 nm Upconverting Nanoparticle in the Full Liquid Water Temperature Range.

Upconverting nanoparticles (UCNPs) have been used as optical probes in a great variety of scenarios ranging from cells to animal models. When optically trapped, a single UCNP can be remotely manipulated making possible, for instance, thermal scanning in the surroundings of a living cell. When conventional optics is used, the stability of an optically trapped UCNP is very limited. Its reduced size leads to optical potentials comparable to thermal energy, and up to now, stable optical trapping of a UCNP has been demonstrated only close to room temperature. This fact limits their use above room temperature, for instance, the use to investigate protein denaturalization that occurs in the 40-50 °C range. In this work, stable optical trapping of a single UCNP in the 20-90 °C range has been demonstrated by using a photonic nanojet. The use of an optically trapped microsphere makes it possible to overcome the diffraction limit producing another optical trap of smaller size and enhanced strength. This simple strategy leads not only to an improvement in the thermal stability of the optical trap but also to an enhancement of the emission intensity generated by the optically trapped UCNP.

Tuberosity Healing after Reverse Shoulder Arthroplasty for Proximal Humerus Fractures: Is there Clinical Improvement?

Objective To compare the functional results of patients with complex proximal humerus fracture submitted to total shoulder reverse arthroplasty with and without tuberosity healing. The secondary goal was to know the tuberosity healing rate after reverse shoulder arthroplasty with our surgical technique. Methods A retrospective, cohort type study, with a prospective database collection. In total, 28 patients fulfilled the inclusion criteria: age ≥ 65 years, reverse shoulder arthroplasty for complex proximal humerus fracture (type-3 or -4, according to Neer), and a minimum of 24 months of follow-up. At six months of follow-up, all of the patients were evaluated radiographically for tuberosity, and then they were divided into 2 groups: those with healed tuberosities and those with non-healed tuberosities. A clinical evaluation using the Constant score, active range of motion and the Visual Analog Scale (VAS) at the last follow-up was also performed. Results Tuberosity healing occurred in 21 patients (76.3%). There were statistically significant differences in the Constant scoring system ( p < 0.001), forward elevation ( p = 0.020), internal rotation ( p = 0.001) and external rotation ( p = 0.003) when comparing the group of healed tuberosities with the group of non-healed tuberosities. No differences were found regarding the VAS score. Conclusion Tuberosity healing results in an improvement of the functional outcomes of patients submitted to reverse shoulder arthroplasty as a treatment for complex proximal humeral fractures in the elderly.

Tuberosity Healing after Reverse Shoulder Arthroplasty for Proximal Humerus Fractures: Is there Clinical Improvement? / Consolidação dos tubérculos na artroplastia reversa do ombro após fratura proximal do úmero: Existe melhoria nos resultados funcionais?

Abstract Objective To compare the functional results of patients with complex proximal humerus fracture submitted to total shoulder reverse arthroplasty with and without tuberosity healing. The secondary goal was to know the tuberosity healing rate after reverse shoulder arthroplasty with our surgical technique. Methods A retrospective, cohort type study, with a prospective database collection. In total, 28 patients fulfilled the inclusion criteria: age ≥ 65 years, reverse shoulder arthroplasty for complex proximal humerus fracture (type-3 or -4, according to Neer), and a minimum of 24 months of follow-up. At six months of follow-up, all of the patients were evaluated radiographically for tuberosity, and then they were divided into 2 groups: those with healed tuberosities and those with non-healed tuberosities. A clinical evaluation using the Constant score, active range of motion and the Visual Analog Scale (VAS) at the last follow-up was also performed. Results Tuberosity healing occurred in 21 patients (76.3%). There were statistically significant differences in the Constant scoring system (p < 0.001), forward elevation (p = 0.020), internal rotation (p = 0.001) and external rotation (p = 0.003) when comparing the group of healed tuberosities with the group of non-healed tuberosities. No differences were found regarding the VAS score. Conclusion Tuberosity healing results in an improvement of the functional outcomes of patients submitted to reverse shoulder arthroplasty as a treatment for complex proximal humeral fractures in the elderly.

Resumo Objetivo Comparar os resultados funcionais entre pacientes com fratura complexa do úmero proximal submetidos a artroplastia reversa com tubérculos consolidados e tubérculos não consolidados. O objetivo secundário foi determinar a taxa de consolidação dos tubérculos com este tipo de prótese. Métodos Estudo de tipo coorte, retrospectivo, com coleta prospectiva de dados. No total, 28 pacientes cumpriram os critérios de inclusão: idade superior a 65 anos, prótese reversa do ombro por fratura complexa do úmero proximal (3 ou 4 partes, segundo Neer), e tempo de seguimento mínimo de 24 meses. Aos seis meses, todos os pacientes foram avaliados radiograficamente quanto à consolidação dos tubérculos e divididos em dois grupos: grupo com tubérculos consolidados e grupo com tubérculos não consolidados. A avaliação funcional realizou-se segundo o sistema de pontuação de Constant, da amplitude de movimento ativo, e da Escala Visual Analógica (EVA) à data da última consulta. Registaram-se todas as complicações. Resultados A consolidação dos tubérculos ocorreu em 21 pacientes (76,3%). Verificou-se diferenças estatisticamente significativas no sistema de pontuação de Constant (p < 0.001), elevação anterior (p = 0.020), rotação interna (p = 0.001) e externa (p = 0.003), quando se comparou o grupo dos tubérculos consolidados com o grupo dos tubérculos não consolidados. Não houve diferenças significativas na EVA entre os 2 grupos. Conclusão A consolidação dos tubérculos traduz uma melhoria dos resultados funcionais em pacientes submetidos a artroplastia reversa do ombro como tratamento de fraturas complexas do úmero proximal em idosos.

Motion Analysis for People with Cerebral Palsy: A Vision Based Approach.

We propose a methodology to classify motion of subjects with cerebral palsy based on RGB image sequences and present a new dataset with 2D facial landmark trajectories from RGB images of people with and without disabilities while performing specific types of movements. Depending on these movements, parts of the face can be occluded and we are able to recover the 3D face's shape and its motion based on the Structure from Motion framework. Using the 3D structure and the motion, we propose two different motion descriptors, one is focused on describing the spatial distribution of the motion and the other on the temporal distribution. Finally, we discuss the physical meaning of these descriptors and show that they are very informative about the degree of the subjects' disabilities. Our descriptor can classify people with and without cerebral palsy from 2D image sequences.