1,720,955 research outputs found
Surgical strategies for high-energy fractures in patients with osteoporosis
No full textThe most obvious clinical pattern of osteoporosis is represented by the so-called low energy fractures. These are slight trauma bone lesions that would not occur in a subject with normal bone mineral density (BMD). The most frequently affected sites of this type of fracture are the last dorsal and lumbar vertebrae, the proximal femur, humerus, and the distal radius. These fractures are a challenge for the orthopedic surgeons because they occur on an altered bone, with decreased load resistance, reduced elasticity and decreased ability to absorb mechanical stresses. This physio-pathological pattern results in lower stability of the hardware, lower screws purchase, less resistance to bone-prosthesis interface, lower quality of the healing process. The problem becomes more complex when high-energy trauma occur in osteoporotic bone with fractures in nontypical locations such as distal femur, tibial plate, tibial malleolus, elbow or peri-phrostetic fractures after Total Knee or Hip Replacement. The surgical approach to these fractures aims to use devices that assure greater bone-implant stability and a great distribution of stresses by reducing the forces acting on the bone-implant interface. It is possible to use scaffolds such as bioactive cement and porous coating surfaces to increase the hardware purchase and homologous/autologous transplantation, post-operative pharmacological implementation and growth factors to stimulate potential repair of fractures. The use of locking plates allows converting the sliding forces, which the traditional plates generated, into compression forces to increase the stability of the system. There are also versatile hardware with dynamic angular stability screws that can be freely oriented in space unlike conventional plates where the direction of the screw is dictated by the placement of the plate. The philosophy of minimal invasive surgery is well represented by the use of intramedullary nails, which can stabilize the fracture from the inside of the bone marrow. This characteristic ensures a load distribution within the bone especially in meta-diaphysis areas, which are most affected by typical reduction of bone quality of osteoporosis. In the elderly, the total joint replacement is also indicated in cases of peri-articular fractures in which there is a high risk of bone fragments necrosis. Such fractures can be treated with a prosthetic implant to ensure immediate joint stability and thus allow an early recovery of the range of motion and the function of the affected limb. Treatment of peri-prosthetic fractures is another important chapter in surgery of traumatic fractures in osteoporosis as we find more and more frequent patients who have a prosthetic implant and who undergo a trauma that causes a peri-implant fracture. In this case, the evaluation of the implant's stability to the bone-prosthesis interface is crucial to decide whether to perform a synthesis with angular stability, nails and/or cerclage wires, or to perform a revision. In all cases, treatment of traumatic fractures in osteoporosis requires a multidimensional evaluation of the problem, as it is not only the type of fracture and site that can be considered, but also the bone quality by carefully evaluating the patient's functional and metabolic state and its comorbidity. It is a surgery that requires specific implants and devices that must be carried out by experienced hands
Atypical femur fractures
No full textAlready from the late 1970s, some fractures of the subtrochanteric and diaphyseal region of the femur were defined "atypical" and described as "fatigue" fractures. In 2005, Odvina reported an unusual type of femoral fracture after the administration of alendronate as a result of a severely repressed bone turnover and Lenart defined femoral fractures occurring on the subtrocanteric or diaphyseal region in post-menopause women after alendronate therapy as "atypical" (AFFs). Hence the hypothesis that these fractures could be associated with the use of bisphosphonates (BP). Even with a "normal" dose of BP, the risk of fracture is highest if therapy lasts more than 5 years, although cases have recently been reported with short-term therapies. However, many of the studies on this association did not consider the radiographic patterns and the atypical or typical radiographic definition did not evaluate the BP doses used and patient compliance; they just state if there was an association or not, and this had led to an underestimation of the real incidence of these fractures. It is the latest revision of the diagnostic criteria made in 2013 by the American Society for Bone and Mineral Research (ASBMR) Task Force to determine that to be defined as AFF, a fracture localized along the femoral diaphysis just distal from the small trochanter to just proximal to the supracondylar region must have certain clinical and radiographic patterns. They also defined exclusion and minor criteria. In general, incidence is still low. Considering the incidence of all femoral fractures of about 460/100,000 people-year, the sub-trochanteric ones represent 7 to 10% of these, and atypical ones are even rarer: 32 per million people-year and 5, 9 per 100,000 person-years in a retrospective study from 1996 to 2009. Morbidity and mortality are similar to neck or intertrochanteric femoral fractures. However, AFF was also found in patients who had never used BP, so BP therapy could not be the only risk factor. Among them, recent attention has been given to hypoposphatasia, picnodisostosis with mutant catepsin gene, osteopetrosis, tumors, use of glucocorticoids (GC), high body mass index (BMI) and use of proton pump inhibitors (PPI). About pathogenesis it seems that the accumulation of microlesions, the increase of mineralization with reduced heterogeneity of mineralization, accumulation of Advanced Glycation End-products (AGEs), reduced vascularization and reduced antiangiogenic effects, alterations of normal collagen reticulation and maturation variations of crosslinks of collagen are all factors involved. Histological studies have demonstrated how these stress fractures occur: at the fracture site there are thin cracks that even micro-movements can distort and bring to their enlargement. In presence of predisposing conditions (femoral conformation, hypophosphatasia, use of GC...) in BP patients, these cracks are trapped in free mineral deposits at the site of the fracture, particularly at intracortical level and act longer by suppressing just in that site where the remodeling processes are essential to healing. Initial alteration occurs precisely on the lateral cortex, which is subjected to increased stress in the subtrochanteric and diaphyseal region, causing a femur bending. This observation has led to studies that have shown how femoral conformation plays a role in determining an increased risk of AFF. With a same BP therapy duration, for conformation characteristics, more is the lateral curvature of the femur and greater the knee valgus and more frequent are the AFFs; these features are more common in some breeds (Asiatic). Recently AFF case reports have also been published with denosumab, a monoclonal antibody that similarly to BP has an anti-resorptive effect. Some Authors and the ASBMR themselves have outlined guidelines for AFF diagnosis and management. Following patients who are taking BP therapy with DEXA is useful: evidence of certain pre-lesions to DEXA and the presence of prodromal symptoms are strong predictors of a subsequent fracture. Also useful is the dosage and monitoring of biochemical markers of bone remodeling. With regard to surgical strategy, the use of an intramedullary nail is the best treatment. In cases of particularly curved femur it is more appropriate to use angular stability plates because in the case of incomplete fracture the use of a nail may turn it into complete and because even in the case of complete fractures, the risk of non-union is higher. To date, even stopping of BP alone in the AFF suspect and the use of teriparatide as supportive drug therapy are two key elements to enable proper AFF healing
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
