Experimental and numerical analysis of the influence of intramedullary nail position on the cut-out phenomenon.

BACKGROUND AND OBJECTIVE: Proximal femur fractures, colloquially known as hip fractures, are a common pathology with increasing incidence in the last years due to the enhanced ageing population. Regarding the extracapsular fracture, the treatment for this pathology consists of a fixation of the fragments using an osteosynthesis device, mainly the intramedullary nail. This repairing method implies several complications, which may include the failure of the fixation device, frequently occurring due to the "cut-out" mechanism. The present work focuses on the study of how the position of the cephalic screw, which should be fixed during surgery, affects the cut-out risk. Through experimental tests and numerical models some variables that can be critical for the cut-out phenomenon are analysed. METHODS: This study has been carried out through a numerical model based on the finite element method and experimental tests. The digital image correlation technique has been used in experimental tests to measure displacements on the femoral surface with the objective of numerical model validation. Some basic daily activities with different intramedullary nail positions have been analysed through the numerical model, considering variables that can induce the cut-out complication. RESULTS: The results show how the intramedullary nail position clearly influences the cut-out risk, showing that displacements in the upper, anterior and posterior direction increase the cut-out risk, while displacement in the lower direction endangers the intramedullary nail itself. Thus, the centred position is the one which reduces the cut-out risk. CONCLUSIONS: This work supposes an improvement in the knowledge of the cut-out phenomenon thanks to the combination of experimental testing and validated numerical models. The effects of different intramedullary nail positions in the femoral head are studied, including a novelty variable as torque, which is critical for the structural integrity of the fixation. The main conclusion of the work is the determination of the central intramedullary nail position as the most favourable one for decreasing the cut-out risk.

Nutritional management and clinical outcome of critically ill patients with COVID-19: A retrospective study in a tertiary hospital.

BACKGROUND & AIMS: Severe COVID-19 infection is characterized by an inflammatory response and lung injury that can evolve into an acute respiratory distress syndrome that needs support treatment in intensive care unit. Nutritional treatment is an important component of the management of critically ill patients and should be started in the first 48 h of ICU admission to avoid malnutrition. This study describes the characteristics of the patients treated in a tertiary hospital in Madrid during the months of March-May 2020 (first wave), the medical nutrition treatment employed and its influence in the clinical outcome of these patients. METHODS: This is a retrospective study including COVID-19 patients admitted in ICU that needed medical nutrition treatment (MNT). Collected variables included sex, age, BMI, underlying diseases, time from hospitalisation to ICU admission, type of respiratory support (invasive mechanical ventilation (IMV) or high flow nasal cannula (HFNC) or non-invasive ventilation (non-IMV)), caloric and protein requirements (25 kcal/kg adjusted body weight (ABW), 1.3 g/kg ABW/day), MNT type (enteral nutrition (EN), parenteral nutrition (PN), mixed EN + PN), total calories (including propofol) and proteins administered, percentage of caloric and protein goal in ICU day 4th and 7th, metabolic complications, acute kidney failure (AKF), length of stay (LOS) and mortality. Data are expressed as mean ± SD, median (IQR) or frequencies. Statistical analysis was performed with the IBM SPSS Statistics for Windows, Version 25.0. p < 0.05 were considered statistically significant. RESULTS: A total of 176 patients were included (72.7% male), 60.1 ± 13.5 years, BMI 29.9 ± 5.4 kg/m2. Underlying diseases included 47.4% overweight, 39.8% obesity, 49.1% hypertension, 41.4% dyslipidaemia. 88.6% of patients needed IMV, 89.1% prone position, 2.9% ECMO. Time to ICU admission: 2 (4.75) days. Estimated caloric and protein requirements were 1775 ± 202 kcal and 92.4 ± 10.3 g. Calories and proteins administered at days 4th and 7th were 1425 ± 577 kcal and 66 ± 26 g and 1574 ± 555 and 74 ± 37, respectively. Most of the patients received PN (alone or complementary to EN) to cover nutritional requirements (82.4% at day 4th and 77.9% at day 7th). IVM patients received more calories and proteins during the first week of ICU admission. Complications included 77.8% hyperglycaemia, 13.2% hypoglycaemia, 83.8% hypertriglyceridemia, and 35.1% AKF. ICU LOS was 20.5 (26) days. The mortality rate was 36.4%. CONCLUSIONS: In our series, the majority of patients reached energy and protein requirements in the first week of ICU admission due to the use of PN (total or complementary to EN). Patients with HFNC or non-IMV may be at risk of malnutrition if total or complementary PN to oral diet/ONS/tube feeding is not used to cover nutritional requirements. Therefore, if EN is not possible or insufficient, PN can be safely used in critically ill patients with COVID-19 with a close monitoring of metabolic complications.

El fenómeno de cut-out en fractura intertrocantérica de fémur: análisis mediante modelo de elementos finitos / The cut-out phenomenon in intertrochanteric femur fracture: analysis using a finite element model

Objetivo: El objetivo del trabajo fue analizar el fenómeno de cut-out, fenómeno que supone desplazamientos oblicuos y/o rotaciones de la cabeza femoral alrededor del componente cefálico del clavo intramedular. El análisis se llevó a cabo mediante modelos numéricos de elementos finitos. Con esta técnica se busca entender el fallo de este tipo de fijaciones y establecer qué posicionamiento del sistema favorece o evita el fallo por cut-out. Material y métodos: El estudio se realizó sobre un modelo numérico de la extremidad proximal de un fémur artificial y un clavo intramedular tipo PFNA (femoral proximal de antirrotación). En el modelo numérico se varió la posición del clavo intramedular en dirección anterior/posterior y superior/inferior para analizar la influencia de la posición en el fenómeno de cut-out. Se analizaron las tensiones en zonas críticas y par torsor sobre el clavo bajo una carga en posición normal. Resultados: La posición más crítica fue aquella en la que el clavo intramedular está colocado en la posición superior, debido a las altas compresiones que aparecen en el hueso trabecular de la cabeza femoral. La posición centrada del clavo disminuyó el riesgo de daño óseo y el par torsor que tiene que soportar el clavo intramedular. Conclusión: Este tipo de modelos permite simular la influencia de la posición del clavo y obtener variables que de otra manera son difíciles de analizar. Aunque se trata de un modelo sencillo con carga estática, confirma que una posición centrada del clavo intramedular disminuye el riesgo de cut-out. (AU)

Objetive: This work aimed to analyze the cut-out phenomenon, which involves oblique displacements and/or rotations of the femoral head around the cephalic component of the intramedullary nail. The analysis was carried out using finite element numerical models. This technique seeks to understand the failure of this type of fixation and establish what positioning of the system favors or prevents failure due to cut-out. Material and methods: The study was carried out on a numerical model of the proximal limb of an artificial femur and an intramedullary nail type PFNA (proximal femoral nail anti-rotation). In the numerical model, the position of the intramedullary nail was varied in the anterior/posterior and superior/inferior directions to analyze the influence of the position on the cut-out phenomenon. Stresses in critical areas and torque on the nail under normal position loading were analyzed. Results: The most critical position was the one in which the intramedullary nail is placed in the superior position, due to the high compressions that appear in the trabecular bone of the femoral head. The centered position of the nail decreased the risk of bone damage and the torque that the intramedullary nail has to support. Conclusion: This type of model allows us to simulate the influence of the nail position and obtain variables that are otherwise difficult to analyze. Although it is a simple model with static load, it confirms that a centered position of the intramedullary nail reduces the risk of cut-out. (AU)

Numerical modelling of hip fracture patterns in human femur.

BACKGROUND AND OBJECTIVE: Hip fracture morphology is an important factor determining the ulterior surgical repair and treatment, because of the dependence of the treatment on fracture morphology. Although numerical modelling can be a valuable tool for fracture prediction, the simulation of femur fracture is not simple due to the complexity of bone architecture and the numerical techniques required for simulation of crack propagation. Numerical models assuming homogeneous fracture mechanical properties commonly fail in the prediction of fracture patterns. This paper focuses on the prediction of femur fracture based on the development of a finite element model able to simulate the generation of long crack paths. METHODS: The finite element model developed in this work demonstrates the capability of predicting fracture patterns under stance loading configuration, allowing the distinction between the main fracture paths: intracapsular and extracapsular fractures. It is worth noting the prediction of different fracture patterns for the same loading conditions, as observed during experimental tests. RESULTS AND CONCLUSIONS: The internal distribution of bone mineral density and femur geometry strongly influences the femur fracture morphology and fracture load. Experimental fracture paths have been analysed by means of micro-computed tomography allowing the comparison of predicted and experimental crack surfaces, confirming the good accuracy of the numerical model.

Hybrid Composite-Metal Stack Drilling with Different Minimum Quantity Lubrication Levels.

Hybrid stack drilling is a very common operation used in the assembly of high-added-value components, which combines the use of composite materials and metallic alloys. This process entails the complexity of machining very dissimilar materials, simultaneously, on account of the interactions that are produced between them, during machining. This study analyzed the influence of Minimum Quantity Lubrication (MQL) on the performance of diamond-coated carbide tools when drilling Ti/carbon fiber reinforced plastics (CFRP)/Ti stacks. The main wear mechanism observed was diamond-coating detachment, followed by fragile breaks in the main cutting-edge. The tests done with the lower lubrication levels have shown an important adhesion of titanium (mainly on the secondary cutting-edge) and a higher friction between the tool and the workpiece, producing higher temperatures on the cutting region and a thermal softening effect on the workpiece. These phenomena affect the evolution of cutting power consumption with tool wear in the titanium layer. Regarding the quality of the test specimen, no significant differences were observed between the lubrication levels tested.

Experimental validation of finite elements model in hip fracture and its clinical applicability. / Validación experimental de un modelo de análisis de elementos finitos en fractura de cadera y su aplicabilidad clínica.

Fracture of the proximal extremity of the femur is the subject of research interest. The complexity of the bone framework and the structural inefficiency associated with ageing leave many variables yet to be understood from an experimental perspective. However, there is no clearly defined structural and biomechanical research model for hip fracture. The hypothesis of this paper is that it is possible to create a computational experimentation model that characterises the bone of the proximal extremity of the femur as a heterogeneous material from directly translating the mechanical parameters obtained from anatomical experimentation specimens. MATERIAL AND METHOD: An experimental paper comparing real experimentation on cadavers and a numerical model based on finite element analysis (FEA). The variables uses were: the start point of the fracture, propagation of the fracture, progressive load and maximum load until fracture. The real mechanical parameters obtained from the anatomical specimens were translated to the computational model based on the relationship between the Hounsfield units of the high resolution CAT scan and the bone mineral density of each virtual element, whereas the propagation of the fracture was modelled by the research team's own computational design, reducing the mechanical properties of the damaged elements as the fracture line advanced. RESULTS: The computational model was able to determine the start point of the fracture, with a slight tendency towards anatomical medialisation of this point compared to what happened experimentally. The degree of correlation was very high on comparing the real value of progressive deformation of the samples compared to that obtained by the computational model. Over 32 points analysed, a slope of 1.03 in lineal regression was obtained, with a relative error between the deformations of 16% and a Pearson's coefficient of R2=.99. The computational model slightly underestimated the maximum fracture load, with a relative error of approximately 10%. CONCLUSION: The FEA computational model developed by this multi-disciplinary research team could be considered, as a whole, a complete FEA model of the proximal extremity of the femur with future clinical applicability since it was able to simulate and imitate the biomechanical behaviour of human femurs contrasted with a traditional experimental model made from anatomical specimens. On this basis, qualitative and quantitative interactions can be assessed which consolidate it as a powerful computational experimentation test bench for the human proximal femur.

[Poor premorbid adjustment linked to deterioration in theory of mind skills: a study in stabilised schizophrenic patients]. / Ajuste premórbido pobre vinculado al deterioro en habilidades de teoría de la mente: estudio en pacientes esquizofrénicos estabilizados.

INTRODUCTION: Previous studies suggest that there is a deficit in theory of mind (ToM) in stabilised schizophrenic patients. More specifically, it has been claimed that poor premorbid adjustment covaries with the abnormalities in ToM skills detected in such patients. It has also been suggested that this deficit could be a trait marker for schizophrenic disorders. PATIENTS AND METHODS: The aim of this study was to examine the performance in mentalistic skills in 36 stabilised schizophrenic patients in comparison to a standard control group. We also sought to examine the relation between ToM skills and premorbid adjustment in our target sample. Premorbid adjustment was evaluated using the modified Cannon-Spoor premorbid adjustment scale, and ToM measurements were obtained by means of first- and second-order verbal experimental tasks. RESULTS: Schizophrenic patients presented statistically significant poorer performances in first- and second-order ToM tasks, although no differences were observed between these patients and the control sample as regards overall cognitive acuity. Poor premorbid adjustment in areas of social functioning in the patients was also associated with statistically significant poorer performance in both ToM tasks. CONCLUSIONS: Deficient premorbid adjustment in schizophrenia may be linked to a ToM deficit that can be assessed with simple tasks.

Ajuste premórbido pobre vinculado al deterioro en habilidades de teoría de la mente: estudio en pacientes esquizofrénicos estabilizados / Poor premorbid adjustment linked to deterioration in theory of mind skills: A study in stabilised schizophrenic patients

Introducción. Estudios previos indican que existe un déficit en teoría de la mente (ToM) en pacientes esquizofrénicos estabilizados. En particular, se ha señalado que un ajuste premórbido pobre covaría con las anomalías en habilidades ToM detectadas en esos pacientes. Se sugiere que este déficit podría ser un marcador de rasgo para el trastorno esquizofrénico.Pacientes y métodos. El objetivo del presente estudio fue investigar el rendimiento en habilidades mentalísticas en 36 pacientes esquizofrénicos estabilizados comparados con un grupo normativo control, así como explorar la relación entre las aptitudesToM y el ajuste premórbido en la muestra diana. El ajuste premórbido se evaluó mediante la escala de ajuste premórbido modificada de Cannon-Spoor, y las medidas ToM se obtuvieron mediante tareas experimentales verbales de primer y segundo orden. Resultados. Los pacientes esquizofrénicos presentaron peores rendimientos, significativos estadísticamente, enlas tareas ToM de primer y de segundo orden, a pesar de la ausencia de diferencias entre ellos y la muestra control en la agudeza cognitiva global. Un ajuste premórbido desfavorable en áreas de funcionamiento social en los pacientes se asoció, además,a un peor rendimiento, estadísticamente significativo, en ambas tareas ToM. Conclusión. El ajuste premórbido deficiente en la esquizofrenia puede vincularse a un déficit ToM evaluable en tareas sencillas

Introduction. Previous studies suggest that there is a deficit in theory of mind (ToM) in stabilised schizophrenic patients. More specifically, it has been claimed that poor premorbid adjustment covaries with the abnormalities in ToM skills detected in such patients. It has also been suggested that this deficit could be a trait marker for schizophrenic disorders.Patients and methods. The aim of this study was to examine the performance in mentalistic skills in 36 stabilised schizophrenic patients in comparison to a standard control group. We also sought to examine the relation between ToM skills and premorbid adjustment in our target sample. Premorbid adjustment was evaluated using the modified Cannon-Spoor premorbid adjustmentscale, and ToM measurements were obtained by means of first- and second-order verbal experimental tasks. Results. Schizophrenic patients presented statistically significant poorer performances in first- and second-order ToM tasks, although no differences were observed between these patients and the control sample as regards overall cognitive acuity. Poor premorbid adjustmentin areas of social functioning in the patients was also associated with statistically significant poorer performance in both ToM tasks. Conclusions. Deficient premorbid adjustment in schizophrenia may be linked to a ToM deficit that can be assessed with simple tasks

Behavioral and physiological effects of a single injection of rat interferon-alpha on male Sprague-Dawley rats: a long-term evaluation.

Interferon-alpha (IFN-alpha) is a cytokine used as a first line of defense against diseases such as cancer and hepatitis C. However, reports indicate that its effectiveness as a treatment is countered by central nervous system (CNS) disruptions in patients. Our work explored the possibility that it may also cause long-term behavioral disruptions by chronicling the behavioral and physiological disturbances associated with a single injection of vehicle, 10, 100, or 1,000 units of IFN-alpha in male Sprague-Dawley rats (n = 5/dose). Following 1 day of locomotor baseline collection, we monitored sickness behaviors (ptosis, piloerection, lethargy, and sleep), food and water intake, body weight, temperature, and motor activity. Observations were recorded 4 days prior to and 4 days following the IFN-alpha injection. Temperature and sickness behaviors were recorded three times daily at 9:00, 15:00, and 21:00 h, and all other indices, once daily. On the injection day, temperature values were highest in the animals receiving the 10-unit IFN-alpha dose 15 min and 13 h post-injection. In the case of sickness behaviors, a significant increase was observed in piloerection in all IFN-alpha groups at each time point measured, while the scores of the rats in the vehicle condition remained unchanged between pre- and post-injection days. Analyses of overall sickness behaviors during morning and night observation periods indicated increased scores in all IFN-alpha groups following injection. Cumulatively, these data suggest that a single IFN-alpha exposure may elicit long-term behavioral disruptions and that its consequences should be thoroughly investigated for its use in clinical populations.

Short- and long-term effects of interleukin-2 on weight, food intake, and hedonic mechanisms in the rat.

In the present work, we investigated the short- and long-term effects of a single systemic injection of rat recombinant interleukin-2 on weight, food intake, and brain stimulation reward thresholds elicited from the ventral tegmental area. An inverted U-shaped dose-function was obtained with 0.5 microg producing the greatest increases in the threshold for rewarding brain stimulation which were sustained during the month long tests. No differences between groups in terms of maximum response rates, a measure of performance, were observed. Although all injected groups showed a minor decline in the rate of weight gain over time, percent efficiency of food utilization (percent weight gain/food intake) was the same across groups, suggesting that metabolic function was not affected by the cytokine. In animals with bilateral ventral tegmental area implants, there was no consistent correspondence between the threshold change obtained from ipsilateral stimulation and that associated with the contralateral site; side-to-side differences ranged from 0 to 100%, suggesting a specific interaction between cytokine activity and the locus of rewarding brain stimulation. These data suggest that peripheral IL-2 significantly modifies hedonic processes arising from medial forebrain bundle stimulation in a long-term manner. We further suggest that since this modulation appears to be notably site-specific, IL-2 receptors or its metabolites may not be evenly distributed within the medial forebrain bundle.

Prevención de efectos adversos relacionados con el examen oftalmológico en prematuros / Prevention of adverse effects related to ophthalmological examination in premature infants

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Pilot study for the neonatal screening of fragile X syndrome.

Fragile X syndrome (SFX) is the commonest form of inherited mental retardation. Due to the highly variable phenotype clinical diagnosis is complicated. In nearly all cases, the disorder is caused by expansion of a CGG-repeat in the 5'-untranslated region of the FMR1 (fragile X mental retardation-1) gene. We have evaluated the feasibility, efficiency and costs of two methodologies in order to develop a simple test to screen large populations: PCR and fragile X mental retardation-1 protein (FMRP) immunodetection. We studied 100 newborn males using PCR and immunodetection (26.91 Euro). All but one amplified the CGG repeat of the FMR1 gene within the normal size range. The sample that failed to amplify showed only 28% of FMRP expression by immunodetection study; both results indicated an affected male. A further 100 males were studied only by polymerase chain reaction (PCR) (7.8 Euro); all of them amplified within the normal size range. Both methodologies, PCR and immunodetection, are feasible for screening large populations, PCR being the most suitable, economical and less time-consuming. However, it is advisable to keep slides for immunodetection when PCR fails or the external control shows no amplification. Early detection of SFX-affected individuals would represent a great benefit for their maximum social integration, due to appropriate treatment and early stimulation and would permit a cascade screening in their pedigree.

Skull size and cheek-tooth length in wild-caught and captive-bred chinchillas.

Chinchillas are herbivorous rodents with teeth that all grow continuously. In captivity, they are commonly affected by dental disease. As the range of dental disease occurring in wild chinchillas is unknown, the dentition of museum specimens originally obtained from the wild was assessed and compared with specimens prepared from captive-bred animals. Skulls from wild-caught chinchillas showed minimal evidence of dental disease and the teeth were all short, cheek-tooth lengths averaging 5.9 mm. Cheek-tooth lengths in zoo specimens (average 6.6 mm), clinically normal (average 7.4 mm) and captive-bred animals with dental disease (average 10 mm) were significantly elongated by comparison (P<0.0001). Captive-bred specimens showed a wide range of tooth-related lesions. These results suggest that some aspect of captivity is responsible for the development of dental disease in chinchillas. It is suggested that the diet (its physical form and composition) is the main aetiological factor, and that provision of a diet closely matching that of wild chinchillas should significantly reduce the incidence of dental disease in captive animals.

Factors that influence the persistence of stimulation-induced aversion.

Brain stimulation reward in certain regions has been shown to produce analgesia to externally applied painful stimuli. In the present experiments, we studied how electrical self-stimulation of the dorsal raphe (DR) nucleus modifies the aversive effects of electrical stimulation of the nucleus reticularis gigantocellularis (Gi) or of the dorsal tegmentum (DTg). In the first study, the threshold for latency to escape aversive Gi stimulation was tracked before and after exposure to rewarding DR stimulation. Only a few sessions of DR self-stimulation were required to produce a complete and long-lasting inhibition of Gi aversion. In the second study, the aversion induced by DTg stimulation rapidly disappeared following a few test sessions at that site. Unlike our previous experience with Gi aversion that required either pairing with rewarding lateral hypothalamic (LH) or ventral tegmental area (VTA) pulses in order to increase the threshold for latency to escape Gi aversion, in this study, simply brief experience with rewarding DR stimulation in unpaired trials was sufficient to entirely suppress Gi-induced aversion. Even more surprising was the finding that unlike the Gi, aversion obtained from activation of the DTg does not persist, its threshold for escape quickly increases, and within a few sessions is no longer evident. One interpretation of these findings is that the aversion mechanisms associated with the Gi and DTg are differentially susceptible to analgesic processes.

Dynamic changes in cytochrome oxidase activity in the amygdala following lesions of rewarding sites in the lateral hypothalamus.

The aim of this study was to evaluate neural changes in oxidative metabolism in amygdaloid sub-nuclei following unilateral electrolytic lesions of lateral hypothalamic sites that supported brain stimulation reward. A histochemical analysis of cytochrome oxidase activity, comparing lesioned to non-lesioned sides in the amygdala, revealed a significant reduction of oxidative metabolism in the cortical nucleus and, to a lesser degree, in the adjacent piriform cortex; this effect was observed 2-4 weeks after the lesion, with complete recovery by the eighth week in the case of the cortical nucleus only. No particular pattern in cytochrome oxidase activity was detected in other amygdaloid sub-nuclei that were examined, including the basolateral and medial nucleus. Within both structures, the most pronounced decreases in metabolic activity were observed at roughly the same level, corresponding to the posterolateral and posteromedial levels of the cortical nucleus and just anterior to the amygdalopiriform transition. These results suggest that within the amygdaloid complex, the cortical sub-nuclei and possibly the neighbouring piriform cortex contribute more to modulating lateral hypothalamic self-stimulation than components of the central extended amygdala.

Interactions between rewarding lateral hypothalamic and aversive nucleus reticularis gigantocellularis stimulation.

The interaction between rewarding and aversive consequences of brain stimulation were assessed in two studies. In the first, the frequency threshold for 300 ms trains of combined lateral hypothalamic (LH) and nucleus reticularis gigantocellularis (Gi) stimulation, in which each LH pulse was followed 2 ms later by the Gi one, was determined for one month. Compared to the threshold for trains of single LH pulses, combined LH-Gi stimulation initially increased the frequency threshold; however, this effect reversed within one session and was subsequently maintained for the duration of the study. The aversion produced by Gi stimulation, as measured by latency to escape, was abolished following a single session of LH-Gi pairs. In the second study, a subset of animals received both presentations of combined pulses, LH followed by Gi, and the reverse; the interval between pulses was varied from 0.2 to 6.4 ms. The effectiveness of combined stimulation, determined by the ratio of LH frequency thresholds to that of the LH-Gi ranged from 0 to 50% across animals but the individual effectiveness functions within animals did not vary with different intervals. In addition, the order of presentation of pulses was of no consequence. Thus, not only did exposure to LH stimulation appear to obliterate Gi aversion, but the combination of LH and Gi pulses added to the rewarding effect produced by LH stimulation alone.