Aplicación del análisis tridimensional de la marcha en pacientes con síndrome centromedular / Application of gait 3d analysis in patients with central cord syndrome

Introducción. El síndrome centromedular es el más común de las lesiones medulares incompletas y el 87-97% de estos pacientes consiguen una marcha independiente, pero no se han encontrado estudios publicados sobre el análisis de la marcha. El objetivo de este estudio fue analizar las características de la marcha de sujetos con síndrome centromedular y comparar los resultados con un grupo control formado por individuos sanos de características antropométricas similares. Métodos. Se analizó a 12 pacientes con síndrome centromedular y a un grupo control formado por 20 sujetos. Los datos cinemáticos se obtuvieron con un sistema de análisis tridimensional del movimiento. El grupo control caminó a velocidad libre y a velocidad similar a la registrada en los pacientes. Las variables espaciotemporales y cinemáticas se compararon entre los dos grupos. Resultados. La abducción de cadera y la flexión de rodilla en el contacto inicial, así como el mínimo de flexión de rodilla durante la fase de apoyo, fueron mayores en el grupo de pacientes (p<0,05). Sin embargo, los rangos de movimiento de la rodilla y el tobillo en el plano sagital fueron mayores en el grupo control (p<0,05). Conclusiones. El patrón de la marcha de los pacientes mostró una disminución del rango de movimiento en el plano sagital de la rodilla y el tobillo y un incremento de la abducción de la cadera para incrementar la base de sustentación. Estos resultados pueden facilitar la planificación objetiva de los tratamientos encargados de mejorar la marcha en estos pacientes(AU)

Background. Central cord syndrome is the most common incomplete spinal cord injury syndrome and 87-97% of these patients achieve independent walking but no gait analysis studies have been reported. The aim of this study was to analyze the characteristics of the gait in subjects with central cord syndrome and to compare the results with a healthy anthropomorphically matched control group. Methods. Twelve patients and a control group with twenty subjects were analyzed. Kinematic data were obtained using a three-dimensional motion analysis system. The control group walked at a self-selected speed and at a speed similar to the speed previously registered in the patient group. Temporal, spatial variables and kinematic variables were compared between the two groups. Results. Hip abduction and knee flexion at initial contact as well as minimal knee flexion during stance were larger in the patient group (P<.05). However, knee and ankle ranges of motion in the sagittal plane were greater in the control group (P<.05). Conclusions. Knee and ankle range of motion in sagittal plane were reduced and hip abduction was increased to improve stability in patients with central cord syndrome. The results can support objective ways to establish the treatment to recover gait in patients with central cord syndrome(AU)

Análisis biomecánico de la fijación del ligamento cruzado anterior / Biomechanical analysis of the anterior cruciate ligament fixation

Objetivo: Desarrollar la metodología experimental para analizar la biomecánica de la fijación del ligamento cruzado anterior. Material y métodología: Se realizó una plastia de LCA en 16 rodillas de cerdo, utilizando el tendón del músculo extensor lateral de los dedos del cerdo. Se ensayaron tres sistemas de fijación diferentes, clasificados como compresión, expansión y suspensión cortico-esponjosa. Todos los especímenes fueron ensayados a tracción hasta el fallo. Se calculó la carga de fallo, elongación y rigidez para cada fijación. Resultados: Atendiendo a la carga de fallo y a la rigidez, los mayores valores medios se obtuvieron para los dispositivos de expansión y suspensión operados con la técnica de doble injerto. Los dispositivos de compresión y expansión implantados con la técnica de un sólo injerto mostraron peores resultados. Conclusiones: El fallo siempre sobrevino en los injertos por lo que no se pudo evaluar ni comparar correctamente el comportamiento de los diferentes tipos de fijación utilizados (AU)

Objective: The aim of the present study was to develop the experimental methodology for the biomechanical analysis of the anterior cruciate ligament reconstruction. Material and method: An ACL reconstruction was performed on 16 porcine knees. The graft used was the pig doubled lateral extensor of toes (DLET). Three different femoral fixation devices were tested and classified according to their fixation mechanism: compression, expansion and cortical-cancellous suspension. A fixation device was developed in order to analyze the unfavorable load case. All GFC were subjected to a load-to-failure test. Failure load, elongation and stiffness were calculated for each device. Results: Regarding stiffness and failure load, cortical-cancellous suspension and expansion, both with the double graft technique, showed the highest mean values. Compression and expansion, both with the single graft technique, showed worse results. Conclusions: Failure always took place in the graft, and thus was impossible to compare correctly the different fixation devices behavior (AU)

Valoración del daño corporal en amputados de miembros inferiores: prueba de sensibilidad, postura, sobrecarga articular y calidad de vida / Assessment of body damage in subjects with lower-limb amputation: sensitivity test, posture, joint overload and quality of life

Objetivo: Evaluar de forma integral a pacientes amputados de extremidades inferiores, valorando su daño corporal y desarrollar informes objetivos y conclusivos de las pruebas. Material y metodología: Se evaluan veintiocho amputados adultos de ambos sexos, con amputación de cualquier nivel y etiología, muñón estable y utilización de prótesis con marcha independiente. Se estudia la sensibilidad del muñón, temperatura, la marcha y vicios posturales y la calidad de vida de estas personas. La sensibilidad del muñón y miembro inferior se valora a través de los monofilamentos Semmes-Weinstein y la postura de los sujetos con el software SAPO. La calidad de vida fue valorada a través del cuestionario de la Organización Mundial de la Salud, WHOQOL breef, y la temperatura fue obtenida con termografía utilizando una cámara infrarroja. Resultados: Obtuvimos baja calidad de vida física y psicológica, alteraciones posturales en las extremidades inferiores, alteración o pérdida de la sensibilidad y altas temperaturas en la extremidad del muñón de la amputación con sobrecarga en la marcha. Conclusión: El amputado de extremidad inferior tiene una baja calidad de vida física y psicológica, mayores alteraciones posturales en las extremidades inferiores, alteración o pérdida de la sensibilidad y altas temperaturas en la extremidad del muñón de la amputación y sobrecarga durante la marcha (AU)

Objective: To evaluate comprehensively subjects with lower-limb amputation, assessing their body damage, and draw up objective, conclusive reports on the tests. Material and method: Twenty-eight adult male and female amputees, with amputation at any site and aetiology, with stable stump and use of prosthesis with independent walking, were evaluated. The sensitivity of the stump, temperature, gait, postural defects and quality of life of these subjects were studied. Sensitivity of the stump and lower limb were assessed through Semmes-Weinstein monofilaments. The posture of the subjects was evaluated with the SAPO software. Quality of life was assessed through the WHOQUOL breef questionnaire and temperature was obtained by thermography using an infrared chamber. Results:We obtained a low physical and psychological quality of life, postural disorders in the lower limbs, impairment or loss of sensitivity and high temperatures in the edge of the amputation stump, with overload on walking. Conclusion: The subject with amputated lower limb has a low physical and psychological quality of life, postural disorders in the lower limbs, impairment or loss of sensitivity and high temperatures in the edge of the amputation stump, with overload on walking (AU)

Evaluación de la distribución de las presiones de apoyo en la interfaz usuario-cojín para determinar la presión de inflado de los cojines de aire / Evaluation of pressure support in user-cushion interface to determine inflated cushion air

Objetivo: Comprobar si la presión de inflado de los cojines antiescaras de aire en personas con lesión medular es la óptima y determinar su influencia sobre el comportamiento mecánico de los cojines. Material y métodos: Se efectuó el análisis de la distribución de presiones en la interfaz usuario-cojín con una malla de sensores capacitivos en 32 pacientes con lesión medular que disponían de cojines de aire. Se realizó un registro en las condiciones habituales de presión de inflado y otro tras realizar una corrección de ésta una vez identificada la situación óptima de distribución de presiones. Los parámetros analizados fueron los valores de presión máxima, la presión isquiática, la presión media y su desviación estándar y, en cuanto a superficies, la superficie total (Stot), la superficie que soporta una presión mayor de 60mmHg (Stot>60) y su valor porcentual (%Stot>60). Resultados: Los valores de las variables relacionadas con la presión fueron más bajos en los registros efectuados tras la corrección de la presión de inflado y, en las relacionadas con la superficie, la Stot fue más alta en el segundo registro, mientras que tanto Stot>60 y %Stot>60 fueron más bajos. En todos los casos se encontraron diferencias significativas (p<0,05). Conclusión: La diferente presión de inflado de un cojín de aire influye en la distribución de presiones en la interfaz usuario-cojín. La distribución de presiones óptima para un cojín determinado se consigue a un nivel de presión de inflado que ha de ser establecido con unos sistemas de medición objetivos (AU)

Objective: Verify if the inflation pressure of anti-bedsore air cushions in persons with bone marrow injury is optimum and determine its influence on the mechanical behavior of the cushions. Material and methods: The distribution of the user-cushion inferface was analyzed with a capacitive mesh sensor in 32 subjects with bone marrow injury who used air cushions. A recording was made of the usual conditions of inflated pressure and another one after making a correction of it once identified the optimum pressure distribution situation. Parameters analyzed were maximum pressure value (Pmax), ischiatic pressure (IschP), mean pressure (meanP) and standard deviation (SD) and, in regards to surfaces, total surface (totS), surface that supports a pressure of 60 mmHg (totS>60) and percentile value (%totS>60). Results: The values of the variables related with the pressure were lower in the recordings made after correcting for inflated pressure. In those related with surface, the TotS was higher in the second recording while the totS >60 and %totS>60 were lower. There were significant differences in all of the cases (p<0.05). Conclusion: The different inflation pressure of an air cushion influences the pressure distribution of the user-cushion interface. The distribution of the optimum pressures for a certain cushion is achieved at an inflated pressure level that must be established with some objective measurement systems (AU)

Implicaciones de los nuevos diseños protésicos de baja densidad en la mejora de la reparación de defectos herniarios / Role of the new lightweight prostheses in improving hernia repair

El empleo de materiales protésicos para tratar enfermedades de la pared abdominal y/o torácica ha resuelto, en gran medida, el problema creado por el defecto tisular y las complicaciones de recidiva. Clásicamente, el más empleado ha sido el polipropileno en forma de prótesis reticular. Este material, con una biocompatibilidad óptima, está sufriendo modificaciones, encaminadas a conseguir la mejor adaptación posible al tejido receptor y mantener las mejores propiedades funcionales en el lugar del implante. De esta forma, las prótesis clásicas denominadas de alta densidad están siendo sustituidas por otras más ligeras (de baja densidad), con una configuración espacial sencilla y un poro más amplio. Las prótesis de baja densidad mantienen su elasticidad, lo que genera menos fibrosis y rigidez tras el implante. De cualquier forma, son necesarios estudios que consigan una densidad de material y un tamaño de poro ideales, dos parámetros que condicionan el comportamiento de dichos biomateriales (AU)

The use of a prosthetic material to treat abdominal and/or thoracic disease has, to a great extent, resolved the problem created by the tissue defect itself and complications of recurrence. The most commonly used of these materials has been polypropylene in the form of a reticular mesh. This biomaterial, which boasts optimal biocompatibility, has been the object of constant modification aimed at better adapting it to the functional needs of the host tissue. Hence, the classic prostheses, nowadays known as heavyweights, are being gradually replaced by lighter materials with a simple spatial configuration and, more importantly, with a larger pore size (lightweight prostheses). Lightweight meshes are able to preserve abdominal wall compliance by generating less post-implant fibrosis and rigidity. However, further studies are still needed to achieve the ideal balance between material density and pore size. These two factors will determine the behaviour of these new prosthetic designs (AU)

Evaluación electromiográfica de los músculos masticadores durante la fuerza máxima de mordedura / Electromyography Evaluations of the masticator muscles during the maximum bite force

La actividad de los músculos masetero y de la porción anterior temporalde ambos lados, derecho e izquierdo, respectivamente, durante la fuerza máximade mordedura fue estudiada en voluntarios sanos. El estudio incluyó a 17 voluntariosadultos de ambos sexos, edad promedia de 25 años, que no evidenciaban ningúnindicio de disfunción temporomandibular y eran relacionados con la Facultadde Odontología de Piracicaba. Se registraron los datos electromiográficos en amboslados de la cara del masetero y de la porción anterior de los músculos temporal ysuprahioideo en las posiciones postural e isométrica. Se utilizaron electrodos de superficiepasivos para niños, de Ag/AgCl, con forma circular y descargables de Meditrace® Kendall-LTP, modelo Chicopee MA01. Éstos se conectaron a un preamplificadorcon una ganancia de 20x que formaba un circuito de diferenciales. Se captaron losregistros de las señales eléctricas utilizando un equipo EMG-8OOC de EMG Systemof Brazil, Ltd., de ocho canales, a una frecuencia de 2 KHz con 16 bitios de resolucióny un filtro digital con un paso de banda de 20 a 500Hz. Se utilizó también untransductor de presión que consistía en un tubo de goma con un sensor de presión(MPX 5700)* (Motorola SPS, Austin, TX, EE.UU.) para registrar la fuerza máxima demordedura. El análisis estadístico incluyó la correlación lineal, la prueba t emparejaday el análisis de la varianza. Se consideró estadísticamente significativa una probabilidadde p<0,05. Los resultados pusieron en evidencia cierto grado de asimetríamuscular para el masetero y la porción anterior del músculo temporal que variabaen relación con la tarea realizada y la intensidad de la contracción. El índice deasimetría fue menor en la posición postural que en la de fuerza máxima de mordedura(AU)

Healthy individuals were examined in terms of the patternof activity of the masseter and temporal muscles in their anteriorportion of both right and left sides, respectively, with the maximumbite force. The study consisted in seventeen adult volunteers withno sign of apparent temporomandibular dysfunction, of both genders,connected to the School of Dentistry of Piracicaba, with averageage of 25 years old. The electromyography data were obtained,bilaterally, of the masseter, anterior portion of temporal andsuprahyoid muscles in the postural and isometric positions. Wereutilized surface passive electrodes for kids of Ag/AgCl, of circularformat and dischargeable of Meditrace® Kendall-LTP, modelChicopee MA01, attached to a pre-amplifier with gain of 20 timesforming a differential circuit. The records of the electrical signs werecaptured by the equipment EMG-8OOC of EMG System of BrazilLtd. of eight channels, with frequency of 2 KHz and 16 bits ofresolution, digital filter with band pass of 20 to 500Hz. It was utilizedalso a pressurized transductor which consists of a pressurized rubbertube connected to a sensor element (MPX 5700) to obtain themaximum bite force. The statistic tests used were linear correlation,test t in pair and analysis of variance. Probability of p<0, 05 weresignificant considered statistically. The results showed a certaindegree of muscular asymmetry for the masseter and anterior portionof temporal muscles that depended on the task performed orcontraction level. The index of asymmetry was lower in the posturalposition than in the maximum bite force(AU)

Electromyography evaluations of the masticator muscles during the maximum bite force

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X-ray kinematography of phase transformations of three-component lipid mixtures: a time-resolved synchrotron X-ray scattering study using the pressure-jump relaxation technique.

By using the pressure-jump relaxation technique in combination with time-resolved synchrotron small-angle X-ray diffraction (TRSAXS), the kinetics of lipid phase transformations of ternary lipid mixtures serving as model systems of heterogeneous raftlike membranes were investigated. To this end, we first established the temperature-pressure phase diagram of a model lipid raft mixture, 1,2-dioleoyl- sn-glycero-3-phosphatidylcholine (DOPC)/1,2-dipalmitoyl- sn-glycero-3-phosphatidylcholine (DPPC)/cholesterol (1:2:1), using Fourier transform infrared spectroscopy and SAXS, covering the pressure range from 1 bar to 10 kbar at temperatures in the range from 7 to 80 degrees C. We then studied the kinetics of interlamellar phase transitions of the ternary lipid system involving transitions from the fluidlike (liquid-disordered, l d) phase to the liquid-ordered (l o)/liquid-disordered (l d) two-phase coexistence region as well as between the two- and three-phase coexistence regions of the system, where also solid-ordered phases (s o) are involved. The phase transition from the all-fluid l d phase to the l o+l d two-phase coexistence region turns out to be rather rapid. Phases appear or disappear within the 25 ms time resolution of the technique, followed by a slow lattice relaxation process, which, depending on the pressure-jump amplitude, takes several seconds. Contrary to many one-component phospholipid phase transitions, the kinetics of the l d <--> l o+l d transition follows a similar time scale and mechanism for the pressurization and depressurization direction. A similar behavior is observed for the phase transition kinetics of the s o+l o+l d <--> l o+l d transformation and even for the s o+l o+l d <--> l d transformation, jumping across the l o+l d two-phase region. All transitions are fully reversible, and no intermediate states are populated. As indicated by the complex relaxation profiles observed, the overall rates observed seem to reflect the effect of coupling of various dynamical processes through the transformation, involving fast conformational changes in the sub-millisecond time regime and slow relaxation of the lattices growing, probably being largely controlled by the transport and redistribution of water into and in the new phases of the multilamellar vesicle assemblies.

An instance-based algorithm with auxiliary similarity information for the estimation of gait kinematics from wearable sensors.

Wearable human movement measurement systems are increasingly popular as a means of capturing human movement data in real-world situations. Previous work has attempted to estimate segment kinematics during walking from foot acceleration and angular velocity data. In this paper, we propose a novel neural network [GRNN with Auxiliary Similarity Information (GASI)] that estimates joint kinematics by taking account of proximity and gait trajectory slope information through adaptive weighting. Furthermore, multiple kernel bandwidth parameters are used that can adapt to the local data density. To demonstrate the value of the GASI algorithm, hip, knee, and ankle joint motions are estimated from acceleration and angular velocity data for the foot and shank, collected using commercially available wearable sensors. Reference hip, knee, and ankle kinematic data were obtained using externally mounted reflective markers and infrared cameras for subjects while they walked at different speeds. The results provide further evidence that a neural net approach to the estimation of joint kinematics is feasible and shows promise, but other practical issues must be addressed before this approach is mature enough for clinical implementation. Furthermore, they demonstrate the utility of the new GASI algorithm for making estimates from continuous periodic data that include noise and a significant level of variability.

Quantitative mechanical evaluation and analysis of Drosophila embryos through the stages of embryogenesis.

The fruit fly Drosophila embryo is one of the most important model organisms in genetics and developmental biology research. To better understand the biomechanical properties involved in Drosophila embryo research, this work presents a mechanical characterization of living Drosophila embryos through the stages of embryogenesis. Measurements of the mechanical forces of Drosophila embryos are implemented using a novel, in situ, and minimally invasive force sensing tool with a resolution in the range of microN. The measurements offer an essential understanding of penetration force profiles during the microinjection of Drosophila embryos. Sequentially quantitative evaluation and analysis of the mechanical properties, such as Young's modulus, stiffness, and mechanical impedance of living Drosophila embryos are performed by extracting the force measurements throughout the stages of embryogenesis. Experimental results illustrate the changing mechanical properties of Drosophila embryos during development, and thus mathematical models are proposed. The evaluation provides a critical step toward better understanding of the biomechanical properties of Drosophila embryos during embryogenesis, and could contribute to more efficient and significant genetic and embryonic development research on Drosophila.

Biomechanical modelling of a direct vertebral translation instrumentation system: preliminary results.

Many new spine instrumentation concepts were introduced in recent years, like the incremental direct vertebral translation. The objective was to develop a biomechanical model in order to analyze the biomechanics of this instrumentation system. The patient-specific spine model was built using the 3D reconstruction based on bi-planar radiographs of a scoliotic patient (thoraco-lumbar Cobb: 49 degrees ). The mechanical properties were derived from literature, experiments on cadaver spines and patient's side bending radiographs. Each screw construct was modelled by four rigid bodies connected each other by kinematic joints. The screw-vertebra flexible joint was represented by 3 experimentally derived non-linear springs, and the rods by non-linear flexible elements. The correction manoeuvres were simulated by lowering the rod, tightening the crimps (incremental segmental translation) and applying secondary correction manoeuvres (direct vertebra derotation, compression, distraction and construct tightening). The simulations showed that the system allows a good force distribution among implants. The long post pushing and pulling contributed, to a great extent, to a global correction in the coronal plane, while the crimp tightening had more important effect in the sagittal plane. The preliminary results illustrated the effectiveness of local correction by a direct vertebra translation technique. Our next step is to validate the model and compare the performance of this strategy with other spinal instrumentation systems.

Marker placement for movement analysis in scoliotic patients: a critical analysis of existing systems.

Optoelectronic movement analysis systems has provided an opportunity for a detailed study of both normal and abnormal human walking and has contributed to the planning and documentation of corrective surgical procedures. The majority of reported studies have been on the study of lower limbs which, consequently, have received most attention in movement analysis. In contrast, movement of the trunk and pelvis, important in the identification of spinal mobility and maintaining posture, have received limited attention in relation to clinical conditions such as scoliosis. Any movement analysis requires the identification of anatomical landmarks which are essential contributing factors to the accuracy of the analysis. While there are a plethora of studies on marker placements for the lower limbs, there is a paucity of information on the marker locations for spinal analysis. Present study examines a set of markers previously reported in the literature and examines their usefulness in scoliotic gait analysis. The findings highlight the drawbacks in previously reported techniques and leads to the proposal of a new marker set for spine and back movement analysis.

An electrohydraulic actuated ankle foot orthosis to generate force fields and to test proprioceptive reflexes during human walking.

The control of human walking can be temporarily modified by applying forces to the leg. To study the neural mechanisms underlying this adaptive capacity, a device delivering controlled forces and high-velocity displacements to the ankle was designed. A new solution, involving a closed circuit hydraulic system composed of two cylinders (master-slave) mutually connected by hoses and controlled by an electric motor was preferred over classical mechanical/electrical approaches. The slave cylinder delivers desired torques to the ankle using a light weight, custom-designed ankle-foot orthosis. This electrohydraulic orthosis (EHO) can produce several types of force fields during walking, including constant, position-dependent, and phase-dependent. With phase-dependent force fields, active torque cancellation maintains low-residual torques ( < or = 1.85 Nm root mean square) outside of the zone of force application for walking speeds ranging from 0.2 to 4.5 km/h. Rapid ankle stretches/unloads ( > 200 degrees/s) can also be produced alone or during force field application, and elicited proprioceptive reflexes in ankle muscles. In conclusion, the EHO is capable of delivering controlled force fields and of activating proprioceptive reflexes during human walking. It will provide the flexibility needed to test the adaptability of healthy and pathological gait control, and to address some of its underlying neural mechanisms.

[Femur lengthening with a telescopic intramedullary nail ISKD--method presentation and early clinical results]. / Wydluzanie kosci udowej przy zastosowaniu gwozdzia sródszpikowego samorozprezalnego ISKD--opis metody, wstepne wyniki leczenia.

INTRODUCTION: Limb discrepancy over 4 cm is an indication for limb lengthening. Surgical techniques rely on osteotomy, external stabilisation and gradual distraction. The ISKD (Intramedullary Skeletal Kinetic Distractor) nail allows distraction osteogenesis and no external fixator is required. AIM OF PAPER: Aims of paper are: presentation of limb elongation method with the ISKD device, and presentation of early own results. MATERIAL AND METHODS: Material consists of 5 patients, age 14-16 years, 3 boys and 2 girls, who underwent femur lengthening with the ISKD nail between 2005 and 2007. We evaluated: initial shortening, surgical procedure, complications, amount of lengthening, lengthening rate, distraction index, time of treatment and mobility of adjacent joints. RESULTS: Initial shortening was 4-11 cm. No surgical complications were observed, mean time of surgery was 145 minutes, mean blood loss--200 ml. In three patients difficulties with initial distraction required manipulations under general anaesthesia. Distraction was complicated in 3 cases--in two patients premature consolidation was noted; in one case the distraction rate was too high. Mean lengthening rate in the study group was 0.7 mm/day (0.6-0.7 mm/day). Mean distraction index was 41.7 days/cm (26.2-55 days/cm). Full weight bearing was allowed after mean 234 days (210-275 days). Transient decrease of adjacent joint mobility was observed. CONCLUSION: The fully implantable, telescopic ISKD eliminates the need of external fixation and associated complications. Early results of limb lengthening with ISKD are encouraging. Careful patient selection and preoperative planning is required. Further studies and longer follow-up periods are needed.

Active optical system for variable view imaging of micro objects with emphasis on kinematic analysis.

Insufficient vision information, such as occlusion, low resolvability, and a small field of view, represent important issues in microassembly and micromanipulation. We propose an active optical system to solve problems related to insufficient vision information through the integration of robotics and optics technologies. The proposed system integrates a double-prism system and a scanning mirror system to supply a compact flexible view. The kinematics of the imaging system is analyzed based on a simplified model initially to investigate the workspace and identify the kinematic performance. A more rigorous analysis of kinematics of the system is then made based on the ray tracing method. The simulation results based on the preliminary design are provided for investigating the workspace and demonstrating the capability of the system in imaging with variable views.

Síndrome de los isquiotibiales acortados / Shortened hamstring syndrome

La falta de flexibilidad en los músculos isquiotibiales condiciona una disminución de la movilidad pelviana que lleva invariablemente al cambio biomecánico en la distribución de presiones en la columna vertebral. La incidencia del síndrome de los isquiotibiales acortados es mayor en varones y puede tener relación con lesiones musculares, alteraciones articulares, actividad deportiva y estilo de vida. Muchos de los actuales estudios se centran en los beneficios de entrenamiento de la flexibilidad, actuando en los mecanismos involucrados en ellos mediante la aplicación de programas de estiramientos, con el objetivo de incrementar la longitud musculotendinosa(AU)

Lack of flexibility in the hamstring muscle conditions a decrease of pelvic mobility. Thisinvariably leads to biomechanical changes in the distribution of pressures in the spine.The incidence of the shortened hamstrings syndrome is greater in men and can beassociated to muscles injuries, joint alterations, sport activity and style of life.Many of the present investigations are focused on the benefits of training flexibility, actingon the mechanisms involved in such through the application of stretching programs,in order to increase the muscle tendinuos length(AU)

Digital craniocorpography and peripheral vestibular diseases.

Peripheral vestibular diseases (PVDs) often produce many symptoms but few or no measurable signs. Tests that capture and measure signs permit the comparison between normal and vertiginous populations. The aim of our research was to find movement patterns that could identify PVD patients, using a motion analysis laboratory. The results from 21 asymptomatic volunteers who underwent the Unterberger-Fukuda stepping test were compared to those of 38 PVD patients. We established diagnosis after a complete otoneurological workup prior to the stepping test. The VICON 370 (Oxford Metrics Ltd, Oxford, UK) was used for digital capture and analysis of the stepping tests. Lateral sway, linear and total displacement, shoulder height oscillation, and torticollis angle were the same for individuals in both groups, but stepping time, body spin, and angular deviation were statistically greater in those in the patient group and might help in the diagnosis of PVDs.

Stress-strain experiments on individual collagen fibrils.

Collagen, a molecule consisting of three braided protein helices, is the primary building block of many biological tissues including bone, tendon, cartilage, and skin. Staggered arrays of collagen molecules form fibrils, which arrange into higher-ordered structures such as fibers and fascicles. Because collagen plays a crucial role in determining the mechanical properties of these tissues, significant theoretical research is directed toward developing models of the stiffness, strength, and toughness of collagen molecules and fibrils. Experimental data to guide the development of these models, however, are sparse and limited to small strain response. Using a microelectromechanical systems platform to test partially hydrated collagen fibrils under uniaxial tension, we obtained quantitative, reproducible mechanical measurements of the stress-strain curve of type I collagen fibrils, with diameters ranging from 150-470 nm. The fibrils showed a small strain (epsilon < 0.09) modulus of 0.86 +/- 0.45 GPa. Fibrils tested to strains as high as 100% demonstrated strain softening (sigma(yield) = 0.22 +/- 0.14 GPa; epsilon(yield) = 0.21 +/- 0.13) and strain hardening, time-dependent recoverable residual strain, dehydration-induced embrittlement, and susceptibility to cyclic fatigue. The results suggest that the stress-strain behavior of collagen fibrils is dictated by global characteristic dimensions as well as internal structure.

Laser-detected lateral muscle displacement is correlated with force fluctuations during voluntary contractions in humans.

Fluctuations in muscle force during steady voluntary contractions result from the summation of twitch forces produced by asynchronous activation of multiple motor units. We hypothesized that oscillatory lateral muscle displacement, measured with a non-contact high-resolution laser displacement sensor, is correlated with force fluctuations during steady, voluntary contractions with a human muscle. Eight healthy young adults (20-33 yrs) performed steady isometric contractions with the first dorsal interosseus muscle. Contraction intensity ranged from 2.5% to 60% of the maximal voluntary contraction force. Oscillatory lateral displacement of the muscle surface was measured with a high-resolution laser displacement sensor (0.5 microm resolution), concurrently with abduction force of the index finger. In the time-domain analysis, there was a significant positive peak in the cross-correlation function between lateral muscle displacement and force fluctuations. In addition, the amplitude increased linearly with contraction intensity in both signals. In the frequency-domain analysis, frequency content was similar in both signals, and there was significant coherence between signals for the major frequency range of the signals (<5 Hz). In conclusion, laser-detected lateral displacement of a hand muscle is correlated with force fluctuations across a wide range of contraction intensity during steady voluntary contractions in humans.