Estrategias biomecánicas conservadoras para la gonartrosis mediante ortesis plantares / Conservative biomechanical strategies for knee osteoarthritis through plantar orthoses

Introducción: La gonartrosis representa un importante problema de salud, cuya prevalencia aumenta acorde con el envejecimiento de la población y las crecientes tasas de sobrepeso y obesidad. Asocia dolor, discapacidad funcional y un alto coste económico. Objetivo: Determinar la eficacia del uso de cuñas pronadoras en las plantillas para disminuir los síntomas, la discapacidad y retrasar la cirugía artroplástica. Diseño: Ensayo clínico aleatorizado no cegado. Pacientes con gonartrosis grado 2-4 de Kellgren y Lawrence atendidos en la Unidad de Aparato Locomotor y Rehabilitación del Hospital Infanta Margarita. Se hizo un seguimiento de 9 meses. Material y método: Cincuenta y seis pacientes sin tratamiento ortésico o quirúrgico previo. Valoramos el grado de severidad mediante radiología, el dolor mediante la escala visual analógica pre- y postintervención, y la funcionalidad mediante el índice de artrosis de la Western Ontario and McMaster Universities. Se incluyó a los pacientes de forma aleatoria en uno de los grupos: cuñas pronadoras retropié, cuñas pronadoras con prolongación a cabeza de 5.o metatarsiano o ciclo de infiltraciones corticoideas intraarticulares en rodilla. Resultados: Obtenemos diferencias estadísticamente significativas en las dimensiones del índice de artrosis de la Western Ontario and McMaster Universities. Dolor: mejoría en el grupo 2 (p < 0,001); capacidad funcional: niveles inferiores en el grupo 3 respecto a los otros grupos (p < 0,001). No existieron diferencias en la escala visual analógica (p = 0,927) ni en la dimensión rigidez del índice de artrosis de la Western Ontario and McMaster Universities (p = 0,072). El 12,5% de los pacientes fueron derivados a cirugía. Conclusión: Las ortesis plantares modificadas producen mejoría sintomática y funcional en pacientes con gonartrosis. Se precisan estudios con mayor muestra y a más largo plazo para verificar si este beneficio se mantiene en el tiempo (AU)

Introduction: Knee osteoarthritis is a major health problem whose prevalence increases in line with the aging population and rising rates of overweight and obesity. Associated factors are pain, functional disability, and high economic cost. Objective: To determine the efficacy of using wedge insoles to reduce symptoms, disability and delay arthroplasty surgery. Design: A randomized unblinded study was performed in patients with Kellgren and Lawrence grade 2-4 knee osteoarthritis treated in the Locomotive and Rehabilitation Unit of the Infanta Margarita Hospital. A 9-month follow-up was performed. Material and method: Fifty-six patients received no orthotic or surgical treatment. Severity was assessed by radiological study, pain by visual analog scale pre- and post-intervention, and functionality by the Western Ontario and McMaster Universities osteoarthritis index. We randomly included the patients into one of three groups: pronator rearfoot wedges, pronator wedges with extension to the 5th metatarsal head or three intraarticular corticosteroid infiltrations in the knee. Results: Statistically significant differences were found in Western Ontario and McMaster Universities osteoarthritis index dimensions: pain improved in group 2 (P < .001). Functional capacity was lower in group 3 than in the other groups (P < .001). There were no differences in visual analog scale (P = .927) or the Western Ontario and McMaster Universities osteoarthritis index stiffness scale (P = .072). A total of 12.5% were referred to surgery. Conclusion: The use of modified foot orthoses produces symptomatic and functional improvements in patients with knee osteoarthritis. Long-term studies with a larger sample are needed to verify whether this benefit is maintained over time (AU)

Zero Landau level in folded graphene nanoribbons.

Graphene nanoribbons can be folded into a double layer system keeping the two layers decoupled. In the quantum Hall regime folds behave as a new type of Hall bar edge. We show that the symmetry properties of the zero Landau level in metallic nanoribbons dictate that the zero energy edge states traversing a fold are perfectly transmitted onto the opposite layer. This result is valid irrespective of fold geometry, magnetic field strength, and crystallographic orientation of the nanoribbon. Backscattering suppression on the N=0 Hall plateau is ultimately due to the orthogonality of forward and backward channels, much like in the Klein paradox.

Effective magnetic fields in graphene superlattices.

We demonstrate that the electronic spectrum of graphene in a one-dimensional periodic potential will develop a Landau level spectrum when the potential magnitude varies slowly in space. The effect is related to extra Dirac points generated by the potential whose positions are sensitive to its magnitude. We exploit a chiral symmetry in the Dirac Hamiltonian description with a superlattice potential to show that the low energy theory contains an effective magnetic field. Numerical diagonalization of the Dirac equation confirms the presence of Landau levels. Possible consequences for transport are discussed.

Carbon nanoelectronics: unzipping tubes into graphene ribbons.

We report on the transport properties of novel carbon nanostructures made of partially unzipped carbon nanotubes, which can be regarded as a seamless junction of a tube and a nanoribbon. We find that graphene nanoribbons act at certain energy ranges as perfect valley filters for carbon nanotubes, with the maximum possible conductance. Our results show that a partially unzipped carbon nanotube is a magnetoresistive device, with a very large value of magnetoresistance. We explore the properties of several structures combining nanotubes and graphene nanoribbons, demonstrating that they behave as optimal contacts for each other, and opening a new route for the design of mixed graphene-nanotube devices.

Emerging zero modes for graphene in a periodic potential.

We investigate the effect of a periodic potential on the electronic states and conductance of graphene. It is demonstrated that for a cosine potential V(x) = V_{0}cos(G_{0}x), new zero energy states emerge whenever J0(2V_{0}/variant Planck's over 2piv_{F}G_{0}) = 0. The phase of the wave functions of these states is shown to be related to periodic solutions of the equation of motion of an overdamped particle in a periodic potential, subject to a periodic force. Numerical solutions of the Dirac equation confirm the existence of these states, and demonstrate the chirality of states in their vicinity. Conductance resonances are shown to accompany the emergence of these induced Dirac points.

Diluted graphene antiferromagnet.

We study RKKY interactions between local magnetic moments for both doped and undoped graphene. In the former case interactions for moments located on definite sublattices fall off as 1/R2, whereas for those placed at interstitial sites they decay as 1/R3. The interactions are primarily (anti)ferromagnetic for moments on (opposite) equivalent sublattices, suggesting that at low temperature dilute magnetic moments embedded in graphene can order into a state analogous to that of a dilute antiferromagnet. In the undoped case we find no net magnetic moment in the ground state, and demonstrate numerically this effect for ribbons, suggesting the possibility of an unusual spin-transfer device.

Luttinger liquid at the edge of undoped graphene in a strong magnetic field.

We demonstrate that an undoped two-dimensional carbon plane (graphene) whose bulk is in the integer quantum Hall regime supports a nonchiral Luttinger liquid at an armchair edge. This behavior arises due to the unusual dispersion of the noninteracting edge states, causing a crossing of bands with different valley and spin indices at the edge. We demonstrate that this stabilizes a domain wall structure with a spontaneously ordered phase degree of freedom. This coherent domain wall supports gapless charged excitations, and has a power law tunneling I-V with a nonintegral exponent. In proximity to a bulk lead, the edge may undergo a quantum phase transition between the Luttinger liquid phase and a metallic state.

Ferromagnetism mediated by few electrons in a semimagnetic quantum dot.

A (II,Mn)VI diluted magnetic semiconductor quantum dot with an integer number of electrons controlled with a gate voltage is considered. We show that a single electron is able to induce a collective spontaneous magnetization of the Mn spins, overcoming the short range antiferromagnetic interactions, at a temperature order of 1 K, 2 orders of magnitude above the ordering temperature in bulk. The magnetic behavior of the dot depends dramatically on the parity of the number of electrons in the dot.

Lattice-spin mechanism in colossal magnetoresistive manganites.

We present a single-orbital double-exchange model, coupled with cooperative phonons (the so called breathing modes of the oxygen octahedra in manganites). The model is studied with Monte Carlo simulations. For a finite range of doping and coupling constants, a first-order metal-insulator phase transition is found, which coincides with the paramagnetic-ferromagnetic phase transition. The insulating state is due to the self-trapping of every carrier within an oxygen octahedron distortion.

Phase diagram of diluted magnetic semiconductor quantum wells

The phase diagram of diluted magnetic semiconductor quantum wells is investigated. The interaction between the carriers in the hole gas can lead to first-order ferromagnetic transitions, which remain abrupt in applied fields. These transitions can be induced by magnetic fields or, in double-layer systems, by electric fields. We make a number of precise experimental predictions for observing these first-order phase transitions.