1,720,985 research outputs found
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
Comparison Between Resident and Attending Surgeons as Assistants on Adolescent Idiopathic Scoliosis Surgery: No Differences in Outcomes, Complications Rate, or Pedicle Screw Placement Accuracy
No full textStudy Design: Retrospective cohort study. Objective: The aim of the present study was to determine if the level of training of the first assistant (resident or attending surgeon) has an influence on the radiographic outcome of AIS surgery and on the accuracy rate of the pedicle screws placement. Summary of Background Data: Adolescent idiopathic scoliosis (AIS) surgery is a challenging procedure that requires a dedicated team of skilled professionals. Therefore, understanding the learning curve is of outstanding importance to guarantee the best outcomes and the highest safety to the patients. Methods: A retrospective analysis of patients who underwent surgery for AIS with a minimum follow-up of 2 years was conducted. All patients were operated by an experienced spine surgeon, assisted by and attending surgeon (group A) or a senior resident (group B). Radiographic outcomes were assessed. Through postoperative CT scan, accuracy of pedicle screw placement was measured (using Gertzbein-Robbins classification). Groups were then statistically compared. Results: A total of 120 patients were included (mean age 15.3±3.39 y, major curve Cobb 60.7±11.9 degrees). No difference was found between groups in terms of preoperative characteristics and postoperative radiographic (correction rate, thoracic kyphosis, screw density) outcomes or complications. Operative time and estimated blood loss were significantly higher in Group B (P=0.045 and P=0.024, respectively). Of the 2746 pedicle screws inserted (1319 group A and 1427 group B), 2452 had a perfect intrapedicular trajectory (absolute accuracy of 89.29%) and 2697 had a breach <2 mm (relative accuracy of 97.56%). No difference was found among groups in terms of absolute or relative accuracy (P=0.06 and P=0.23, respectively). Conclusions: AIS cases assisted by senior residents have longer operative time and higher blood loss, but this does not negatively affect the overall radiographic outcome and does not place the patient at increased risk of complications. Level of Evidence: III
Restoration of Spinopelvic Alignment After Reduction of High-grade Spondylolisthesis: Myth or Reality? A Systematic Review of the Literature and Meta-analysis
No full textStudy Design: Systematic review and meta-analysis of literature. Objective: The aim of the presented study is to assess whether the reduction of high-grade spondylolisthesis (HGS) through the correction of lumbosacral kyphosis leads to a decrease in the sagittal spinopelvic compensatory mechanisms. Summary of Background Data: HGS is as an anterior translation of a vertebra, >50%. It is also characterized by a kyphotic deformity of the affected level. This combination of translation and kyphosis leads to compensatory mechanisms on the sagittal plane [pelvic retroversion, increased lumbar lordosis (LL), reduction in thoracic kyphosis (TK)]. Methods: A systematic search of electronic databases was conducted. Inclusion criteria were diagnosis of HGS (Meyerding >II, Slip% >50%), partial or complete reduction surgery (with a significant decrease in Slip%), and report of spinopelvic parameters (pelvic incidence, pelvic tilt, or sacral slope). Clinical and radiographic outcomes were extracted and summarized. Meta-analyses were performed to estimate the differences between preoperative and postoperative spinopelvic alignment measures. P<0.05 was considered significant. Results: Eighteen studies were included. PT showed a statistically significant decrease of -2.1217 (95% CI: -3.4803 to -0.7630), while SS showed a significant increase of 4.8349 (95% CI: 2.7462-6.9236). Conversely, both LL and TK showed nonsignificant changes, -4.7043 (95% CI: -10.4535 to 1.0449) and 6.3881 (95% CI: -0.8344 to 13.6106), respectively. VAS significantly decreased by -3.1950 (95% CI: -4.9462 to -1.4439). Conclusions: The meta-analysis showed mild, yet statistically significant, decrease of PT and an increase in SS after HGS reduction. Conversely, nonstatically significant decrease in LL and an increase in TK occurred. The clinical significance of these results remains questionable. Level of Evidence: Level IV
Multilevel non-contiguous thoracic pedicle subtraction osteotomy for fixed rounded hyperkyphotic deformity of the thoraco-lumbar junction with anterior bony fusion: technical note
Full text linkBackground: Fixed severe hyperkyphotic deformities spread over more than five vertebral levels represent a therapeutic challenge, especially when the deformity apex is located at the thoraco-lumbar junction, thus requiring a huge amount of correction. The aim of this article is to describe an innovative all-posterior corrective technique based on multilevel non-contiguous thoracic pedicle subtraction ostoeotomy (PSO). Materials and methods: A retrospective review of three patients with fixed severe thoracic hyperkyphosis (a deformity angle of over 70°) with a thoraco-lumbar apex (between T11 and L1) treated by simultaneous two-level thoracic PSO and thoraco-lumbar posterior fusion was performed. Radiographic and clinical records were evaluated pre-operatively, post-operatively and at last follow-up (after a minimum of 2 years). Each variable was presented as mean ± SD (standard deviation). Statistical analyses were performed using paired t-tests (P value < 0.05 was considered significant). Results: The mean local deformity angle decreased by 75% (from 81.3° ± 2.1° to 20.7° ± 1.4°, p < 0.001), the post-operative thoracic kyphosis decreased by 46% (from 61.4° ± 2.4° to 33.2° ± 0.9°, p < 0.001) and the sagittal vertical axis decreased by 73% (from 14.7 cm ± 0.8 cm to 3.9 cm ± 0.3 cm, p < 0.001). No differences were observed in the radiological results between post-operative values and those at the final follow-up. The average Oswestry Disability Index (ODI) score reduced from 65.7 ± 1.8 pre-operatively to 17.3 ± 1.7 at last follow-up (p < 0.001). No neurological, mechanical nor infective complication occurred. Conclusions: The presented technique, although technically demanding, proved to be a safe and effective alternative for the management of fixed severe thoraco-lumbar junction hyperkyphotic deformities. Level of evidence: IV TRIAL REGISTRATION Retrospectively registered
5.5-mm Cobalt-Chrome vs 6-mm Titanium Alloy Rods in Surgical Treatment of Lenke 1 Adolescent Idiopathic Scoliosis With High-Density Pedicle Screws and Direct Vertebral Rotation on Differently Shaped Rods: A Retrospective Comparative Cohort Study
Full text linkThe gold standard of surgical treatment of adolescent idiopathic scoliosis (AIS) consists of a posterior approach requiring complex 3-dimensional correction with multisegmental pedicle screws and 2 contoured rods. The substantial corrective forces and the ability of the rod to withstand these forces rely on its biomechanical properties. The aim of this study is to compare outcomes of 5.5-mm cobalt-chrome (CoCr) and 6-mm titanium alloy (TiAl) rods in surgical correction in Lenke 1 AIS patients. TiAl has greater elasticity, which may facilitate the correction maneuver, whereas the stiffness of CoCr may result in stronger correction forces. The literature provides no clear indications about which rod may allow better correction and safety
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