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Vivek Palepu, Jonathan H. Peck, David D. Simon, Melvin D. Helgeson and Srinidhi Nagaraja

occur over time. Fatigue testing of these constructs provides an advantage over quasi-static testing as it has the ability to assess implant performance in a simulated postoperative environment. This type of mechanical testing is not frequently performed, likely due to the complexities of longer-duration testing, such as tissue degradation observed in spines at ambient temperatures. 30 Early fatigue studies focused on the stability of spinal rods, plates, and screws. 5 , 14 , 15 , 20 , 24 More recently, there have been studies investigating interbody cages and facet

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Kathrin Zimmerman, Bobby May, Katherine Barnes, Anastasia Arynchyna, Elizabeth N. Alford, Caroline Arata Wessinger, Laura Dreer, Inmaculada Aban, James M. Johnston, Curtis J. Rozzelle, Jeffrey P. Blount and Brandon G. Rocque

, such as depression, anxiety, and fatigue. 3–12 For example, a link has been shown between anxiety and headache in patients with chronic migraine. 13 However, evaluation of the psychological comorbidities of pediatric hydrocephalus has not been performed. The purpose of this study was to determine the prevalence and severity of headache, depression, anxiety, and fatigue in a sample of children with hydrocephalus. Understanding these factors may play a crucial role in improving the care provided to children with hydrocephalus and their families, enhancing outcomes

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Andrew L. Freeman, William J. Camisa, Glenn R. Buttermann and James R. Malcolm

5 women) were scanned using dual-energy x-ray absorptiometry (DEXA; GE Lunar, iDXA) to quantify bone density. The specimens were dissected, preserving all ligamentous structures, into a total of 26 L2–3 and L4–5 motion segments. The motion segments were divided into a flexibility and pullout testing group and a fatigue testing group, with 6 anterior and 7 oblique devices in each group. Specimens were potted as previously described. 1 For both the anterior and oblique interbody cages, flexibility testing was performed on the following configurations: 1) intact

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Aaron J. Clark, Jessica A. Tang, Jeremi M. Leasure, Michael E. Ivan, Dimitriy Kondrashov, Jenni M. Buckley, Vedat Deviren and Christopher P. Ames

between the inferior L-5 endplate and the iliac portion of the sacroiliac joints bilaterally for the same reason. 18 For larger resections, an expandable cage has been used for vertebral body replacement. 7 Some of these methods have been subjected to biomechanical testing. 2 , 13 , 22 However, no studies have evaluated the resistance of reconstruction methods to fatigue, and therefore may not provide a true indication of in vivo performance. With advances in instrumentation, it is likely to be fatigue and not static overload that is driving clinical failures such

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R. Lawrence Ferguson and Kirk Jobe

neighboring countries or older general/vascular surgeons from neighboring towns in Illinois. The anxiety of the former group stood in stark contrast to the relaxed attitude of the more experienced surgeons. We began a study of the many factors that affect tremor and incorporated our findings into a syllabus to enhance training. In addition, we developed a biofeedback machine that both measured the error of motion and allowed for self correction. 1 Experience has revealed the limitations of our concept. The major tremor-enhancing factor, fatigue, is the constant companion

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M. Sean Grady, H. Hunt Batjer and Ralph G. Dacey

and Quality. On December 2, 2008, the IOM committee issued its report ( http://www.iom.edu/CMS/3809/48553/60449.aspx ) calling for a number of new changes in the ACGME duty hour rules, including a recommendation that resident duty hours be reduced to 16 hours for a maximum shift length. Others continue to advocate further reductions in the work week, perhaps not to exceed 56 hours as is the case in Great Britain. Clearly, resident fatigue has the potential to cause adverse patient outcomes, but if the neurosurgical educational process is further compromised, it is

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Tobias Pitzen, Frederick Franta, Dragos Barbier and Wolf-Ingo Steudel

for the 4.5-mm rescue screws. This finding contradicts the results of our study. We found that rescue screws inserted into a fatigued initial pilot hole did not strengthen the screw—bone interface compared with that initially achieved using a standard screw. Yerby, et al., 15 have compared pullout forces associated with uncemented 6-mm pedicle screws and those associated with uncemented 7-mm pedicle screws placed within the same hole. They found that 7-mm pedicle screws yielded only 73% of the force of the smaller screws. This finding is similar to ours. A strong

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Jessica A. Tang

S ynthetic (artificial) models have a wide variety of applications for spine biomechanics, especially in studies that investigate the effect of fatigue testing on different spinal fixation constructs. The advantages of these synthetic models over cadaver tissue lie not only in their relatively inexpensive cost, but also in their controlled setup that effectively eliminates inconsistencies present in cadaver tissue due to donor variability. Currently, the ASTM has a set of established guidelines for fabricating and testing spinal implant constructs in vertebral

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Jessica A. Tang

T o T he E ditor : I am writing to request the retraction of my article, “Comparison of a novel pedicle subtraction osteotomy model using the traditional American Society of Testing and Materials standard for spinal biomechanics fatigue testing. Laboratory investigation,” which was published online in the Journal of Neurosurgery: Spine on October 26, 2012; DOI: 10.3171/2012.9.SPINE12687. There was a misunderstanding about the ownership of the data collected for this study. To preserve the academic integrity of published results, I request that the

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Aruna Ganju, Kanav Kahol, Peter Lee, Narina Simonian, Steven J. Quinn, John J. Ferrara and H. Hunt Batjer

G raduate medical education was redefined in 2003 with the ACGME's implementation of work-hour restrictions. These restrictions imposed a “one size fits all” solution to the issues of resident fatigue and patient safety. Under these guidelines, work hours were limited to 80 hours per week, averaged over a period of 4 weeks. In December 2008, the Institute of Medicine released a report calling for further restrictions to be imposed, including mandatory rest time during residents' duty shifts. In response, in March 2009, the ACGME convened to critically