Estudio biomecánico comparativo de dos configuraciones de tornillos cementados en una fractura simulada de húmero proximal fijada con placa y tornillos bloqueados / Comparative biomechanical study of two configurations of cemented screws in a simulated proximal humerus fracture fixed with locking plate

Introducción: La utilización de tornillos cementados en la fijación interna de fracturas de húmero proximal con placas bloqueadas parece mejorar la estabilidad del implante y disminuir las complicaciones asociadas al fracaso de síntesis. Sin embargo, la combinación óptima de tornillos cementados se desconoce. El objetivo de este estudio fue analizar la estabilidad relativa de dos configuraciones de tornillos cementados sometidos a una fuerza de compresión axial en una fractura simulada de húmero proximal. Material y métodos: Se realizó una osteotomía del cuello quirúrgico en cinco pares de húmeros embalsamados con una edad media de 74 años (rango 46-93), fijados con una placa de acero inoxidable con tornillos bloqueados. En cada par de húmeros, en el húmero derecho se cementaron los tornillos A y E, y en el lado contralateral se cementaron los tornillos B y D. Cada espécimen fue testado inicialmente mediante una carga cíclica de compresión axial durante 6.000 ciclos para evaluar el movimiento interfragmentario (estudio dinámico). Al final de la prueba, los especímenes se sometieron a una carga de compresión axial progresiva para medir la rigidez de la construcción (estudio estático). Resultados: No se encontraron diferencias estadísticamente significativas en la movilidad interfragmentaria entre las dos configuraciones de tornillos cementados en el estudio dinámico (p=0,463). Cuando se sometieron a rotura, los especímenes con tornillos cementados en las hileras B y D presentaron una carga de rotura mayor (2218N vs. 2105, p=0,901) y una mayor rigidez (125N/mm vs. 106N/mm, p=0,672); sin embargo, ninguna de estas diferencias fue estadísticamente significativa. Conclusiones: La configuración de los tornillos cementados utilizadas en este estudio no influyen en la estabilidad del implante cuando se aplica una carga cíclica de baja energía. La cementación de los tornillos de las hileras B y D proporciona una resistencia similar a la cementación de los tornillos...(AU)

Introduction: Screw tip augmentation with bone cement for fixation of osteoporotic proximal humerus fractures seems to improve stability and to decrease the rate of complications related to implant failure. However, the optimal augmentation combinations are unknown. The aim of this study was to assess the relative stability of two augmentations combinations under axial compression load in a simulated proximal humerus fractures fixed with locking plate. Material and methods: A surgical neck osteotomy was created in five pairs of embalmed humeri with a mean age of 74 years (range 46–93 years), secured with a stainless-steel locking-compression plate. In each pair of humeri, on the right humerus were cemented the screws A and E, and in the contralateral side were cemented screws B and D of the locking plate. The specimens were first tested cyclically in axial compression for 6,000 cycles to evaluate interfragmentary motion (dynamic study). At the end of the cycling test, the specimens were loaded in compression force simulating varus bending with increasing load magnitude until failure of the construct (static study). Results: There were no significant differences in interfragmentary motion between the two configurations of cemented screws in the dynamic study (p=0.463). When tested to failure, the configuration of cemented screws in lines B and D demonstrated higher compression load to failure (2218N vs. 2105, p=0.901) and higher stiffness (125N/mm vs. 106N/mm, p=0.672). However, no statistically significant differences were reported in any of these variables. Conclusions: In simulated proximal humerus fractures, the configuration of the cemented screws does not influence the implant stability when a low-energy cyclical load is applied. Cementing the screws in rows B and D provides similar strength to the previously proposed cemented screws configuration and could avoid complications observed in clinical studies.(AU)

[Translated article] Comparative biomechanical study of two configurations of cemented screws in a simulated proximal humerus fracture fixed with locking plate / Estudio biomecánico comparativo de 2 configuraciones de tornillos cementados en una fractura simulada de húmero proximal fijada con placa y tornillos bloqueados

Introducción: La utilización de tornillos cementados en la fijación interna de fracturas de húmero proximal con placas bloqueadas parece mejorar la estabilidad del implante y disminuir las complicaciones asociadas al fracaso de síntesis. Sin embargo, la combinación óptima de tornillos cementados se desconoce. El objetivo de este estudio fue analizar la estabilidad relativa de dos configuraciones de tornillos cementados sometidos a una fuerza de compresión axial en una fractura simulada de húmero proximal. Material y métodos: Se realizó una osteotomía del cuello quirúrgico en cinco pares de húmeros embalsamados con una edad media de 74 años (rango 46-93), fijados con una placa de acero inoxidable con tornillos bloqueados. En cada par de húmeros, en el húmero derecho se cementaron los tornillos A y E, y en el lado contralateral se cementaron los tornillos B y D. Cada espécimen fue testado inicialmente mediante una carga cíclica de compresión axial durante 6.000 ciclos para evaluar el movimiento interfragmentario (estudio dinámico). Al final de la prueba, los especímenes se sometieron a una carga de compresión axial progresiva para medir la rigidez de la construcción (estudio estático). Resultados: No se encontraron diferencias estadísticamente significativas en la movilidad interfragmentaria entre las dos configuraciones de tornillos cementados en el estudio dinámico (p=0,463). Cuando se sometieron a rotura, los especímenes con tornillos cementados en las hileras B y D presentaron una carga de rotura mayor (2218N vs. 2105, p=0,901) y una mayor rigidez (125N/mm vs. 106N/mm, p=0,672); sin embargo, ninguna de estas diferencias fue estadísticamente significativa. Conclusiones: La configuración de los tornillos cementados utilizadas en este estudio no influyen en la estabilidad del implante cuando se aplica una carga cíclica de baja energía. La cementación de los tornillos de las hileras B y D proporciona una resistencia similar a la cementación de los tornillos...(AU)

Introduction: Screw tip augmentation with bone cement for fixation of osteoporotic proximal humerus fractures seems to improve stability and to decrease the rate of complications related to implant failure. However, the optimal augmentation combinations are unknown. The aim of this study was to assess the relative stability of two augmentations combinations under axial compression load in a simulated proximal humerus fractures fixed with locking plate. Material and methods: A surgical neck osteotomy was created in five pairs of embalmed humeri with a mean age of 74 years (range 46–93 years), secured with a stainless-steel locking-compression plate. In each pair of humeri, on the right humerus were cemented the screws A and E, and in the contralateral side were cemented screws B and D of the locking plate. The specimens were first tested cyclically in axial compression for 6,000 cycles to evaluate interfragmentary motion (dynamic study). At the end of the cycling test, the specimens were loaded in compression force simulating varus bending with increasing load magnitude until failure of the construct (static study). Results: There were no significant differences in interfragmentary motion between the two configurations of cemented screws in the dynamic study (p=0.463). When tested to failure, the configuration of cemented screws in lines B and D demonstrated higher compression load to failure (2218N vs. 2105, p=0.901) and higher stiffness (125N/mm vs. 106N/mm, p=0.672). However, no statistically significant differences were reported in any of these variables. Conclusions: In simulated proximal humerus fractures, the configuration of the cemented screws does not influence the implant stability when a low-energy cyclical load is applied. Cementing the screws in rows B and D provides similar strength to the previously proposed cemented screws configuration and could avoid complications observed in clinical studies.(AU)

[Translated article] Comparative biomechanical study of two configurations of cemented screws in a simulated proximal humerus fracture fixed with locking plate.

INTRODUCTION: Screw tip augmentation with bone cement for fixation of osteoporotic proximal humerus fractures seems to improve stability and to decrease the rate of complications related to implant failure. However, the optimal augmentation combinations are unknown. The aim of this study was to assess the relative stability of two augmentations combinations under axial compression load in a simulated proximal humerus fractures fixed with locking plate. MATERIAL AND METHODS: A surgical neck osteotomy was created in five pairs of embalmed humeri with a mean age of 74 years (range 46-93 years), secured with a stainless-steel locking-compression plate. In each pair of humeri, on the right humerus were cemented the screws A and E, and in the contralateral side were cemented screws B and D of the locking plate. The specimens were first tested cyclically in axial compression for 6000 cycles to evaluate interfragmentary motion (dynamic study). At the end of the cycling test, the specimens were loaded in compression force simulating varus bending with increasing load magnitude until failure of the construct (static study). RESULTS: There were no significant differences in interfragmentary motion between the two configurations of cemented screws in the dynamic study (p=0.463). When tested to failure, the configuration of cemented screws in lines B and D demonstrated higher compression load to failure (2218N vs. 2105, p=0.901) and higher stiffness (125N/mm vs. 106N/mm, p=0.672). However, no statistically significant differences were reported in any of these variables. CONCLUSIONS: In simulated proximal humerus fractures, the configuration of the cemented screws does not influence the implant stability when a low-energy cyclical load is applied. Cementing the screws in rows B and D provides similar strength to the previously proposed cemented screws configuration and could avoid complications observed in clinical studies.

Comparative biomechanical study of two configurations of cemented screws in a simulated proximal humerus fracture fixed with locking plate. / Estudio biomecánico comparativo de dos configuraciones de tornillos cementados en una fractura simulada de húmero proximal fijada con placa y tornillos bloqueados.

INTRODUCTION: Screw tip augmentation with bone cement for fixation of osteoporotic proximal humerus fractures seems to improve stability and to decrease the rate of complications related to implant failure. However, the optimal augmentation combinations are unknown. The aim of this study was to assess the relative stability of two augmentations combinations under axial compression load in a simulated proximal humerus fractures fixed with locking plate. MATERIAL AND METHODS: A surgical neck osteotomy was created in five pairs of embalmed humeri with a mean age of 74 years (range 46-93 years), secured with a stainless-steel locking-compression plate. In each pair of humeri, on the right humerus were cemented the screws A and E, and in the contralateral side were cemented screws B and D of the locking plate. The specimens were first tested cyclically in axial compression for 6,000 cycles to evaluate interfragmentary motion (dynamic study). At the end of the cycling test, the specimens were loaded in compression force simulating varus bending with increasing load magnitude until failure of the construct (static study). RESULTS: There were no significant differences in interfragmentary motion between the two configurations of cemented screws in the dynamic study (p=0.463). When tested to failure, the configuration of cemented screws in lines B and D demonstrated higher compression load to failure (2218N vs. 2105, p=0.901) and higher stiffness (125N/mm vs. 106N/mm, p=0.672). However, no statistically significant differences were reported in any of these variables. CONCLUSIONS: In simulated proximal humerus fractures, the configuration of the cemented screws does not influence the implant stability when a low-energy cyclical load is applied. Cementing the screws in rows B and D provides similar strength to the previously proposed cemented screws configuration and could avoid complications observed in clinical studies.

The influence of pH on dissolved organic matter fluorescence in inland waters.

Fluorescence is an easily available analytical technique used to assess the optical characteristics of dissolved organic matter (DOM). Despite widespread use, there has been some confusion about how robust fluorescence spectroscopy is to differences in solution pH. Here we assess fluorescence characteristics of three natural water samples and one commercially available standard (Nordic Reservoir) by modifying the pH across a range from 3.5 to 9.0 at 0.5 pH increments. We used two statistical approaches to assess if fluorescence intensity shifted significantly across this pH range. We identified that humic-like and protein-like fluorescence was largely stable within the pH range of 5.5 to 7.5, which represents 80% of Swedish lakes and streams. Likewise, we found that the three commonly used fluorescence indices were robust across the full pH range tested with the exception of the humification index, which had a narrower range of stability. The commerical humic substance sample was highly unstable with changes to pH in the regions of protein-like fluorescence being particularly sensitive. One of our conclusions is that differences in fluorescence intensity in the pH range of 5.5 to 7.5, typical for most inland waters, are generally minor. We recommend adjusting the pH when samples fall outside this region and to be especially careful in interpreting results from commercial humic substances.

Primary Elbow Osteoarthritis: Evaluation and Management.

Most patients with primary osteoarthritis of the elbow report a history of heavy lifting with the affected upper extremity . Conservative treatment, including activity modifications, nonsteroidal anti-inflammatory drugs and the occasional intraarticular corticosteroid injection, may provide adequate pain relief in earlier stages . When surgery is required, and despite the presence of cartilage wear, many patients with primary elbow osteoarthritis experience substantial pain improvement with joint preserving procedures . The ulnar nerve needs to be carefully assessed and addressed at the time of surgery . Although open debridement procedures are effective, arthroscopic osteocapsular arthroplasty has emerged as the surgical procedure of choice . Total elbow arthroplasty is very successful in terms of pain relief and function, but it is reserved for patients with end-stage osteoarthritis who are relatively older and have failed joint preserving procedures.

Global CO2 emissions from dry inland waters share common drivers across ecosystems.

Many inland waters exhibit complete or partial desiccation, or have vanished due to global change, exposing sediments to the atmosphere. Yet, data on carbon dioxide (CO2) emissions from these sediments are too scarce to upscale emissions for global estimates or to understand their fundamental drivers. Here, we present the results of a global survey covering 196 dry inland waters across diverse ecosystem types and climate zones. We show that their CO2 emissions share fundamental drivers and constitute a substantial fraction of the carbon cycled by inland waters. CO2 emissions were consistent across ecosystem types and climate zones, with local characteristics explaining much of the variability. Accounting for such emissions increases global estimates of carbon emissions from inland waters by 6% (~0.12 Pg C y-1). Our results indicate that emissions from dry inland waters represent a significant and likely increasing component of the inland waters carbon cycle.

Experiencia con la dieta cetogénica como tratamiento en la epilepsia refractaria / Experience with ketogenic diet as treatment for refractory epilepsy

Introducción. La epilepsia es una enfermedad neurológica que se controla con fármacos antiepilépticos en la mayoría de casos. Sin embargo, aproximadamente un 25% de epilepsias son refractarias al tratamiento farmacológico. La dieta cetogénica es una de las opciones terapéuticas para este tipo de epilepsia. A pesar del aumento en los últimos años de la popularidad de ésta como tratamiento anticonvulsivo, no se ha establecido un consenso internacional para sus indicaciones y manejo. Objetivo. Evaluar la respuesta, tolerancia y efectos secundarios en los pacientes con epilepsias refractarias que han recibido dieta cetogénica en nuestra institución en un período de 20 años. Pacientes y métodos. Se revisaron las historias clínicas de 30 pacientes que utilizaron dieta cetogénica como coadyuvante al tratamiento de epilepsia refractaria seguidos en nuestro centro. Se obtuvo información completa para el estudio en 27 casos. Resultados. Diez pacientes (35,7%) presentaron una respuesta positiva en la reducción del número de crisis por más de seis meses; cinco de ellos con una disminución del 50-75% de las crisis y cinco de más del 75%. Los efectos adversos más frecuentes a corto plazo fueron diarrea, vómitos e hipoglucemias, y a largo plazo, estreñimiento y aumento de peso. Conclusiones. Existe una respuesta positiva con la dieta cetogénica en una tercera parte de nuestros pacientes con epilepsia refractaria. La tolerancia es aceptable y los efectos adversos existentes pueden prevenirse o corregirse. Puede considerarse una opción terapéutica frente a epilepsias refractarias antes de iniciar otras medidas más agresivas o cuando no es factible la opción quirúrgica (AU)

Introduction. Epilepsy is a disease where most patients have a good control with pharmacological antiepileptic treatment. Nevertheless, 25% of the patients have a refractory epilepsy to usual antiepileptic drugs. Ketogenic diet is one of the treatment options for this type of epilepsy. In spite of the increased popularity of it as an antiepileptic treatment, it does not exist an international consensus of its indications and management. Aim. To evaluate the response, tolerance and adverse effects of the patients with refractory epilepsy at our hospital during the last 20 years. Patients and methods. We reviewed the data of 30 patients with ketogenic diet and the follow-up at the Neurology and Nutrition Services in our Hospital. Results. Ten patients (35.7%) had a positive response with reduction of their seizures for more than six months; five of them had a 50-75% decrease in seizures and five of them had more than 75% of seizure reduction. The most common short term adverse effects were diarrhea, vomiting and hypoglicemia whereas long term adverse effects were constipation and weight gain. Conclusions. We recommend to use ketogenic diet as treatment in refractory epilepsy since there is a positive response in seizure control in some cases. The adverse effects seen could be prevented or treated without complications. It is a preferabletreatment option before using other aggressive therapeutical measures or when surgery is not feasible (AU)

Enfermedad de Chagas / Chagas disease

La enfermedad de Chagas es una antropozoonosis provocada por un protozoo flagelado el Trypanosoma cruzi, que se transmite a través de vectores hematófagos infectados. En nuestro país los vectores son Triatoma infestans y spinolai (vinchuca). Su reservorio es humano y alrededor de 150 especies de mamíferos. Se distribuye en toda América pero mayoritariamente en el Cono Sur, con al menos 12 millones de personas infectadas. Los mecanismos de transmisión son principalmente vectorial, transplacentario, transfusional, otras formas de contagio menos frecuentes son el trasplante de órganos, accidentes de laboratorio, transmisión oral y uso de jeringas contaminadas drogadictos). Esta enfermedad dependiendo de si afecta a personas inmunocompetentes presenta tres etapas: aguda, latente y crónica, afectando en forma variable a diversos órganos, principalmente corazón y el tubo digestivo. El compromiso cardíaco se caracteriza por dilatación progresiva y alteración del aparato exitoconductor provocando arritmias y bloqueos auriculoventriculares (AV). A nivel digestivo afecta principalmente al esófago y colon; ocasionando acalasia llevando a dilatación y alteración de la motilidad progresiva, cuyo síntoma clave es la disfagia que se asocia también a odinofagia y regurgitación. A nivel del colon, el Chagas provoca dilatación progresiva por denervación parasimpática intramural, llegando a formar el megacolon chagásico, el síntoma principal es la constipación. Los métodos diagnósticos son clínicos, imagenológicos y la detección de la infección parasitaria, ya sea a través de métodos directos o indirectos, dependiendo de la etapa de la infección. El tratamiento se basa en antiparasitarios principalmente el nifurtimox y benznidazol, ambos son tripanomicidas, con una efectividad de hasta el 76 por ciento dependiendo de la etapa en que se usa.

Chagas disease is an anthropozoonosis caused by the flagellate protozoan Trypanosoma cruzi. It is transmitted in our country by the infected haemophagic vectors Triatoma infestans and Triatoma spinolai. 150 mammal species and the human serve as reservoir of T. cruzi. Chagas disease is distributed throughout the Americas, mostly in the Southern Cone, with at least, 12 million of people infected. Transmission mechanisms are mainly vectorial, transplacentary and transfusional. Other less frequent sources of transmission are organ transplantation, laboratory accidents, oral ransmission and the sharing of contaminated needles among drug users. This disease, depending on the immune state of the affected subject, has three stages of development: acute, latent and chronic, involving several organs at different levels, mostly the heart and gastrointestinal tube. Heart involvement is characterized by progressive dilatation and alteration of the electrical conduction system causing arrhythmia and atrioventricular (AV) block. The digestive compromise affects mainly esophagus and colon. It causes achalasia of the esophagus which causes dilatation and alteration of the propulsive motility with dysphagia being associated to odinophagia and regurgitation. Chagas disease causes progresive colonic dilatation by intramural parasympathetic denervation, reaching Chagasic megacolon with constipation as the characteristic symptom. Diagnostic techniques are clinic, imagenologic, and the detection of the parasitary infection through direct or indirect methods, depending on the stage of the infection. Treatment is based on antiparasitic drugs, mainly Nifurtimox and Benznidazol, both are trypanomicides, with up to 76 percent efficacy, depending on the stage of the disease when they are used.

Mutations of CD40 gene cause an autosomal recessive form of immunodeficiency with hyper IgM.

CD40 is a member of the tumor necrosis factor receptor superfamily, expressed on a wide range of cell types including B cells, macrophages, and dendritic cells. CD40 is the receptor for CD40 ligand (CD40L), a molecule predominantly expressed by activated CD4(+) T cells. CD40/CD40L interaction induces the formation of memory B lymphocytes and promotes Ig isotype switching, as demonstrated in mice knocked-out for either CD40L or CD40 gene, and in patients with X-linked hyper IgM syndrome, a disease caused by CD40L/TNFSF5 gene mutations. In the present study, we have identified three patients with an autosomal recessive form of hyper IgM who fail to express CD40 on the cell surface. Sequence analysis of CD40 genomic DNA showed that one patient carried a homozygous silent mutation at the fifth base pair position of exon 5, involving an exonic splicing enhancer and leading to exon skipping and premature termination; the other two patients showed a homozygous point mutation in exon 3, resulting in a cysteine to arginine substitution. These findings show that mutations of the CD40 gene cause an autosomal recessive form of hyper IgM, which is immunologically and clinically undistinguishable from the X-linked form.

Somatic hypermutation shapes the antibody repertoire of memory B cells in humans.

High-affinity antibodies produced by memory B cells differ from antibodies produced in naive B cells in two respects. First, many of these antibodies show somatic hypermutation, and second, the repertoire of antibodies expressed in memory responses is highly selected. To determine whether somatic hypermutation is responsible for the shift in the antibody repertoire during affinity maturation, we analyzed the immunoglobulin lambda light chain (Iglambda) repertoire expressed by naive and antigen-selected memory B cells in humans. We found that the Iglambda repertoire differs between naive and memory B cells and that this shift in the repertoire does not occur in the absence of somatic hypermutation in patients lacking activation-induced cytidine deaminase (AID). Our work suggests that somatic hypermutation makes a significant contribution to shaping the antigen-selected antibody repertoire in humans.

Tendencias en la etiología de la meningitis bacteriana aguda en niños chilenos período 1989-1998: impacto de la vacuna anti-H influenzae tipo b Hib / Etiology of acute bacterial meningitis in chilean children from 1989 to 1998: impact of anti H influenzae type b vaccine

Background: Acute bacterial meningitis still has a high mortality and rate of complications. Aim: To assess the impact of anti H influenzae vaccination on the epidemiology of acute bacterial meningitis in Chilean children. Material and methods: A retrospective study of hospital discharge records of patients with acute bacterial meningitis. Causative agents were studied globally, by hospital and by age group. The changes in etiology from 1989 to 1995 were also assessed. Between 1996 and 1998, only those patients with acute bacterial meningitis caused by H influenzae were recollected. Results: In the period prior to vaccination (1989-1995), 1000 cases were registered. The main causative agents were N meningitidis in 33.8 percent, H influenzas type b in 21.9 percent and S pneumoniae in 15.4 percent. The incidence of H influenzae decreased in the period from 36.4 to 9.9 percent (p<0.001) and the incidence of N meningitidis increased from 22.9 to 52.1 percent (p <0.001). The incidence of S pneumoniae did not change significantly. H influenzae predominated in children between 4 and 24 months of age and N meningitidis predominated in children over 25 months of age. In the period after the introduction of vaccination (1995-1998), there was a further decrease in the incidence of H influenzae from 10 to 2 percent (p <0.001). Until 1997, there was a considerable increase in the incidence of N meningitidis, specially in children over 25 months of age. It declined in 1998 to 38 percent. Conclusions: There was a reduction in the incidence of acute bacterial meningitis caused by H influenzae prior to the introduction of the vaccine against H influenzae type b. The decrease was more pronounced after the introduction of the vaccine

Activation-induced cytidine deaminase (AID) deficiency causes the autosomal recessive form of the Hyper-IgM syndrome (HIGM2).

The activation-induced cytidine deaminase (AID) gene, specifically expressed in germinal center B cells in mice, is a member of the cytidine deaminase family. We herein report mutations in the human counterpart of AID in patients with the autosomal recessive form of hyper-IgM syndrome (HIGM2). Three major abnormalities characterize AID deficiency: (1) the absence of immunoglobulin class switch recombination, (2) the lack of immunoglobulin somatic hypermutations, and (3) lymph node hyperplasia caused by the presence of giant germinal centers. The phenotype observed in HIGM2 patients (and in AID-/- mice) demonstrates the absolute requirement for AID in several crucial steps of B cell terminal differentiation necessary for efficient antibody responses.