Comparative analysis of the biomechanical behavior of anterograde/retrograde nailing in supracondylar femoral fractures

Supracondylar femoral fractures account for a noticeable percentage of the femoral shaft fractures, affecting two etiological groups: high energy trauma in young men, with good bone quality, and older women with osteoporotic femur. Surgical treatment of those kind of fractures remains controversial, with different surgical options such as plate and sliding barrel locking condylar plate, less invasive stabilization system (LISS) or intramedullary nailing, which has emerged as a new fixation choice in the treatment of that type of fractures. The present work performs a comparative study about the biomechanical behavior of anterograde and retrograde nailing in supracondylar femoral fractures type A, in order to determine the best choice of nailing and locking configuration. A three-dimensional finite element model of the femur was developed, modeling femoral supracondylar fracture and different nailing configurations, both for anterograde and retrograde nails. The study was focused on the immediately post-operative stage, verifying the appropriate stability of the osteosynthesis. The obtained results show a better biomechanical behavior for anterograde nails, providing a better stability from the point of view of global movements, lower stresses in screws, and less stress concentration in cortical bone. So, for the analyzed fractures and osteosyntheses types, anterograde nailing has demonstrated to be a better surgical option, being an excellent indication in supracondylar fractures of femur, with clear benefits compared to retrograde nailing, providing a better stabilization which enables for a more satisfactory fracture healing

Study of the polycarbonate-urethane/metal contact in different positions during gait cycle

Nowadays, a growing number of young andmore active patients receive hip replacement.More strenuous activities in such patients involve higher friction and wear rates, with friction on the bearing surface being crucial to ensure arthroplasty survival in the long term. Over the last years, the polycarbonate-urethane has offered a feasible alternative to conventional bearings. A finite element model of a healthy hip joint was developed and adjusted to three gait phases (heel strike, mid-stance, and toe-off), serving as a benchmark for the assessment of the results of joint replacement model. Three equivalent models were made with the polycarbonate-urethane Tribofit system implanted, one for each of the three gait phases, after reproducing a virtual surgery over the respective healthy models. Standard body-weight loads were considered: 230% body-weight toe-off, 275% body-weight mid-stance, and 350% body-weight heel strike. Contact pressures were obtained for the different models. When comparing the results corresponding to the healthy model to polycarbonate-urethane joint, contact areas are similar and so contact pressures are within a narrower value range. In conclusion, polycarbonate-urethane characteristics are similar to those of the joint cartilage. So, it is a favorable alternative to traditional bearing surfaces in total hip arthroplasty, especially in young patients

A predictive mechanical model for evaluating vertebral fracture probability in lumbar spine under different osteoporotic drug therapies

Osteoporotic vertebral fractures represent a major cause of disability, loss of quality of life and even mortality among the elderly population. Decisions on drug therapy are based on the assessment of risk factors for fracture from bone mineral density (BMD) measurements.A previously developed model, based on the Damage and Fracture Mechanics, was applied for the evaluation of the mechanical magnitudes involved in the fracture process from clinical BMD measurements. BMD evolution in untreated patients and in patients with seven different treatments was analyzed from clinical studies in order to compare the variation in the risk of fracture. The predictive model was applied in a finite element simulation of the whole lumbar spine, obtaining detailed maps of damage and fracture probability, identifying high-risk local zones at vertebral body.For every vertebra, strontium ranelate exhibits the highest decrease, whereas minimum decrease is achieved with oral ibandronate. All the treatments manifest similar trends for every vertebra. Conversely, for the natural BMD evolution, as bone stiffness decreases, the mechanical damage and fracture probability show a significant increase (as it occurs in the natural history of BMD). Vertebral walls and external areas of vertebral end plates are the zones at greatest risk, in coincidence with the typical locations of osteoporotic fractures, characterized by a vertebral crushing due to the collapse of vertebral walls.This methodology could be applied for an individual patient, in order to obtain the trends corresponding to different treatments, in identifying at-risk individuals in early stages of osteoporosis and might be helpful for treatment decisions

Cementless hydroxyapatite coated hip prostheses

More than twenty years ago, hydroxyapatite (HA), calcium phosphate ceramics, was introduced as a coating for cementless hip prostheses. The choice of this ceramic is due to its composition being similar to organic apatite bone crystals. This ceramic is biocompatible, bioactive, and osteoconductive. These qualities facilitate the primary stability and osseointegration of implants Our surgical experience includes the implantation of more than 4,000 cementless hydroxyapatite coated hip prostheses since 1990 The models implanted are coated with HA in the acetabulum and in the metaphyseal area of the stem.The results corresponding to survival and stability of implants were very satisfactory in the long-term. From our experience, HA-coated hip implants are a reliable alternative which can achieve long termsurvival, provided that certain requirements aremet: good design selection, sound choice of bearing surfaces based on patient life expectancy,meticulous surgical technique, and indications based on adequate bone quality

Evaluation of dimensionality reduction methods applied to numerical weather models for solar radiation forecasting

The interest in solar radiation prediction has increased greatly in recent times among the scientific community. In this context, Machine Learning techniques have shown their ability to learn accurate prediction models. The aim of this paper is to go one step further and automatically achieve interpretability during the learning process by performing dimensionality reduction on the input variables. To this end, three non standard multivariate feature selection approaches are applied, based on the adaptation of strong learning algorithms to the feature selection task, as well as a battery of classic dimensionality reduction models. The goal is to obtain robust sets of features that not only improve prediction accuracy but also provide more interpretable and consistent results. Real data from the Weather Research and Forecasting model, which produces a very large number of variables, is used as the input. As is to be expected, the results prove that dimensionality reduction in general is a useful tool for improving performance, as well as easing the interpretability of the results. In fact, the proposed non standard methods offer important accuracy improvements and one of them provides with an intuitive and reduced selection of features and mesoscale nodes (around 10% of the initial variables centered on three specific nodes).This work has been partially supported by the projects TIN2014-54583-C2-2-R, TEC2014-52289-R and TEC2016-81900-REDT of the Spanish Interministerial Commission of Science and Technology (MICYT), and by Comunidad Autónoma de Madrid, under project PRICAM P2013ICE-2933

Investigation on the Behavior of Austenite and Ferrite Phases at Stagnation Region in the Turning of Duplex Stainless Steel Alloys

This paper investigates the deformation mechanisms and plastic behavior of austenite and ferrite phases in duplex stainless steel alloys 2205 and 2507 under chip formation from a machine turning operation. SEM images and EBSD phase mapping of frozen chip root samples detected a build-up of ferrite bands in the stagnation region, and between 65 and 85 pct, more ferrite was identified in the stagnation region compared to austenite. SEM images detected micro-cracks developing in the ferrite phase, indicating ferritic build-up in the stagnation region as a potential triggering mechanism to the formation of built-up edge, as transgranular micro-cracks found in the stagnation region are similar to micro-cracks initiating built-up edge formation. Higher plasticity of austenite due to softening under high strain is seen responsible for the ferrite build-up. Flow lines indicate that austenite is plastically deforming at a greater rate into the chip, while ferrite shows to partition most of the strain during deformation. The loss of annealing twins and activation of multiple slip planes triggered at high strain may explain the highly plastic behavior shown by austenite

Surrounded by sound: noise, rights and environments

Noise was probably the first environmental pollutant (apart from human waste) in the Ancient world. Yet today, by comparison with other environmental matters, noise and protection from its effects are often overlooked, except in specialist fields such as architecture or planning. One major reason for this may be that noise does not possess the same ability to spread that is characteristic of other forms of pollution. Noise is also an unusual form of environmental pollution in having a physical impact – it is ‘heard’ and can be ‘felt’ – but is predominantly interpreted subjectively. The impact and consequences of anthropogenic noise for humans and biodiversity in general, are currently under-investigated in criminology and are under-addressed in both public and private international environmental law. Here we question why noise has not (so far) been explored within green criminology and only tentatively explored within cultural criminology. The objectives are to provide an overview of noise as a topic, connecting media, culture, anti- and pro-social behaviour, and to unearth interconnections between the matter of noise and its implications for the environment