1,720,959 research outputs found
Intermittent visual field defects caused by a dilated Virchow–Robin space close to the optic radiation: therapeutic and pathomechanical considerations
No full textObjective. Virchow-Robin spaces (VRSs) are extensions of subarachnoid spaces that accompany vessels entering the brain. T2-weighted magnetic resonance imaging detects VRS in about 95 percent of patients in a recent study. VRSs are considered a normal variant with benign prognosis. 1 Occasionally, VRS might become symptomatic causing neurological deficits depending on their location. 2 Case description. We report the case of a 55-year-old female patient with dilated VRS presenting with visual field disturbances and cognitive deficits. The patient underwent endoscopic fenestration of a large periventricular VRS located next to the visual radiation into the posterior horn of the right lateral ventricle. During the postoperative course, visual field disturbances were resolved but cognitive deficits remained unchanged. Conclusion. Dilated VRSs can cause a variety of neurological deficits depending on their size and location. Therefore, patients harboring dilated VRS should undergo early close inspection and in case of progressive neurological deficits, an operative therapy should be done; as valve mechanisms can cause a reduction of size when brain scans are conducted and later lead to occurrence of severe neurological deficits during phase of dilation
Upward movement of cerebrospinal fluid in obstructive hydrocephalus—revision of an old concept
No full textUnskilled unawareness and the learning curve in robotic spine surgery
No full textRobotic assistance for the placement of pedicle screws has been established as a safe technique. Nonetheless rare instances of screw misplacement have been reported.The aim of the present retrospective study is to assess whether experience and time affect the accuracy of screws placed with the help of the SpineAssist (TM) robot system. Postoperative computed tomography (CT) scans of 258 patients requiring thoracolumbar pedicle screw instrumentation from 2008 to 2013 were reviewed. Overall, 13 surgeons performed the surgeries. A pedicle breach of > 3 mm was graded as a misplacement. Surgeons were dichotomised into an early and experienced period in increments of five surgeries. In 258 surgeries, 1,265 pedicle screws were placed with the aid of the robot system. Overall, 1,217 screws (96.2 %) were graded as acceptable. When displayed by surgeon, the development of percent misplacement rates peaked between 5 and 25 surgeries in 12 of 13 surgeons. The overall misplacement rate in the first five surgeries was 2.4 % (6/245). The misplacement rate rose to 6.3 % between 11 and 15 surgeries (10/158; p = 0.20), and reached a significant peak between 16 and 20 surgeries with a rate of 7.1 % (8/112; p = 0.03). Afterwards, misplacement rates declined. A major peak in screw inaccuracies occurred between cases 10 and 20, and a second, smaller one at about 40 surgeries. One potential explanation could be a transition from decreased supervision (unskilled but aware) to increased confidence of a surgeon (unskilled but unaware) who adopts this new technique prior to mastering it (skilled). We therefore advocate ensuring competent supervision for new surgeons at least during the first 25 procedures of robotic spine surgery to optimise the accuracy of robot-assisted pedicle screws
Accuracy of robot-guided versus freehand fluoroscopy-assisted pedicle screw insertion in thoracolumbar spinal surgery
No full textOBJECTIVEThe quest to improve the safety and accuracy and decrease the invasiveness of pedicle screw placement in spine surgery has led to a markedly increased interest in robotic technology. The SpineAssist from Mazor is one of the most widely distributed robotic systems. The aim of this study was to compare the accuracy of robot-guided and conventional freehand fluoroscopy-guided pedicle screw placement in thoracolumbar surgery.METHODSThis study is a retrospective series of 169 patients (83 women [49%]) who underwent placement of pedicle screw instrumentation from 2007 to 2015 in 2 reference centers. Pathological entities included degenerative disorders, tumors, and traumatic cases. In the robot-assisted cohort (98 patients, 439 screws), pedicle screws were inserted with robotic assistance. In the freehand fluoroscopy-guided cohort (71 patients, 441 screws), screws were inserted using anatomical landmarks and lateral fluoroscopic guidance. Patients treated before 2009 were included in the fluoroscopy cohort, whereas those treated since mid-2009 (when the robot was acquired) were included in the robot cohort. Since then, the decision to operate using robotic assistance or conventional freehand technique has been based on surgeon preference and logistics. The accuracy of screw placement was assessed based on the Gertzbein-Robbins scale by a neuroradiologist blinded to treatment group. The radiological slice with the largest visible deviation from the pedicle was chosen for grading. A pedicle breach of 2 mm or less was deemed acceptable (Grades A and B) while deviations greater than 2 mm (Grades C, D, and E) were classified as misplacements.RESULTSIn the robot-assisted cohort, a perfect trajectory (Grade A) was observed for 366 screws (83.4%). The remaining screws were Grades B (n = 44 [10%]), C (n = 15 [3.4%]), D (n = 8 [1.8%]), and E (n = 6 [1.4%]). In the fluoroscopy-guided group, a completely intrapedicular course graded as A was found in 76% (n = 335). The remaining screws were Grades B (n = 57 [12.9%]), C (n = 29 [6.6%]), D (n = 12 [2.7%]), and E (n = 8 [1.8%]). The proportion of non-misplaced screws (corresponding to Gertzbein-Robbins Grades A and B) was higher in the robot-assisted group (93.4%) than the freehand fluoroscopy group (88.9%) (p = 0.005).CONCLUSIONSThe authors’ retrospective case review found that robot-guided pedicle screw placement is a safe, useful, and potentially more accurate alternative to the conventional freehand technique for the placement of thoracolumbar spinal instrumentation.</jats:sec
Robot guidance for percutaneous minimally invasive placement of pedicle screws for pyogenic spondylodiscitis is associated with lower rates of wound breakdown compared to conventional fluoroscopy-guided instrumentation
No full textRobot guidance for percutaneous minimally invasive placement of pedicle screws for pyogenic spondylodiscitis is associated with lower rates of wound breakdown compared to conventional fluoroscopy-guided instrumentation
Full text linkPostoperative wound healing can pose a problem
in patients undergoing instrumented surgery for pyogenic
spondylodiscitis. Robotic guidance allows the minimally
invasive placement of pedicle screws in the
thoracolumbar spine. We assessed whether using this
technique to perform minimally invasive surgery had an
impact on wound healing in patients with pyogenic
spondylodiscitis when compared to conventional open
fluoroscopy-guided surgery. We reviewed charts of 206
consecutive patients who underwent instrumentation for
pyogenic spondylodiscitis. The need for wound revision
was the primary outcome measure. Patient variables and
comorbidities as well as surgical technique (robotic versus
fluoroscopy-guided) were analyzed. We also compared
fluoroscopy times between the two groups. Multivariate
regression analysis was performed to identify predictors
of wound breakdown. A total of 206 patients underwent
surgery for spondylodiscitis. Robotic surgical assistance
was used for percutaneous instrumentation in 47.6% of
cases (n = 98). Wound healing problems requiring
revision occurred in 30 out of 206 patients (14.6%).
Univariate analysis revealed a potential association of
wound breakdown with (1) robotic technique, (2)
age > 70 years, and (3) the presence of methicillinresistant
Staphylococcus aureus. After multivariate correction
however, only robotic technique retained significance
with an odds ratio of 0.39 (CI 95% 0.16–0.94;
p = 0.035). Wound revision was required in eight out of
98 patients (8.1%) in the robot group and 22/108 (20%) in
the conventional surgery group. Fluoroscopy times were
significantly lower in the robot group with a mean of
123 ± 86 s in comparison with a mean of 157 ± 99 s in
the conventional group (p = 0.014). While initially designed
to improve the accuracy of pedicle screw placement,
robot-assisted minimally invasive technique had a
tangible effect on both radiation exposure and the rate of
wound breakdown i n p a t i e n t s wi t h pyogenic
spondylodiscitis in our large single-center study
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
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