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"Carlson, Jon"
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Thick subcategories of the bounded derived category of a finite group
A new proof of the classification for tensor ideal thick subcategories of the bounded derived category, and the stable category, of modular representations of a finite group is obtained. The arguments apply more generally to yield a classification of thick subcategories of the bounded derived category of an artinian complete intersection ring. One of the salient features of this work is that it takes no recourse to infinite constructions, unlike previous proofs of these results.
Journal Article
Robotic‐assisted percutaneous pelvis fixation: A case report
Key Clinical Message It may be possible to extend the use of the robotic arm to pelvic and acetabular surgery leading to safe, repeatable screw placement, and less radiation exposure for patients, surgeons and OR staff. In this case, a novel, robotic‐assisted technique was used to place a sacroiliac screw in a patient with unstable injuries of the pelvic ring. Intraoperative and postoperative fluoroscopic, radiographic, and CT imaging demonstrated a safely positioned 6.5 mm cannulated screw without unplanned cortical violation or impingement on neurovascular structures. To our knowledge, this is the first such reported case using a robot widely available in the Americas or Europe.
Journal Article
Placement of LC-II and trans-sacral screws using a robotic arm in a simulated bone model in the supine position – a feasibility study
Purpose
The use of a robotic arm has been well-described in the literature for the placement of pedicle screws in spine surgery as well as implants for sacroiliac joint fusion. There are no reports describing the use of a robotic arm to place screws in osseous fixation pathways (OFPs) employed in the treatment of pelvic ring and acetabular fractures outside of a single center in China. Using a Sawbones model, the authors describe a technique for using a robotic arm widely available in Europe and the Americas for placement of 6.5 mm cannulated screws into two OFPs commonly used in the treatment of pelvic and acetabular fractures.
Methods
Using the Mazor X Stealth Edition (MSXE) robot from Medtronic, the authors were able to place a pin into the pelvis onto which the robot was docked. The authors were then able to designate the area of interest using navigated instruments, and in combination with the MSXE “scan and plan” marker, obtain cross-sectional imaging using the O-Arm and successfully register the MSXE robot. We then used the provided software to plan trajectories for the lateral compression type 2 (LC-II) screw pathway as well as a pathway for a trans-ilio-trans-sacral screw. We describe in detail the steps for setup, planning and placement of 6.5 mm cannulated screws using the MSXE robotic arm into these two OFPs.
Results
Visual inspection and plain x-rays demonstrated successful placement of the screws into the two planned OFPs. No breach of cortical bone was seen on either visual inspection of the model or demonstrated on post-procedure x-rays.
Conclusion
It is possible to use the Mazor X Stealth Edition robot to place screws into the LC-II and trans-ilio-transsacral screw pathways in a Sawbones model. This is only a feasibility study, and should in no way be taken to suggest that clinical application of this technique should be attempted.
Journal Article
Femoral shaft fracture with a third fragment treated with an intramedullary nail: Is the displacement of the third fragment predictive of nonunion?
Purpose
Femoral shaft fractures with third fragments are difficult to reduce anatomically, affecting bone healing chances. The goal of this study is to determine the impact of the third fragment’s radiological characteristics assessed on post-operative radiographs, as well as other factors, on the healing of type 32B femur shaft fractures treated with intramedullary nail.
Methods
We conducted a retrospective study of 93 patients treated for femoral shaft fractures type 32 B. On post-operative X-rays, two radiologic parameters were evaluated: the third fragment size and the mean third fragment displacement. Patients had radiologic follow-up at 2, 4, 6, 9, and 12-months and were separated into 3 groups based on their fracture healing time: within 6 months (group 1), between 6 and 12 months (group 2), or nonunion after 12 months (group 3).
Results
Among the 93 patients, 72 (77.4%) showed fracture healing at 6 months, 13 (14%) at 12 months, and 8 (8.6%) demonstrated nonunion at 12 months. The mean third fragment displacement was notably different between groups (
p
< 0.001) and was considerably greater in group 3 than in groups 1 and 2. The influence of third fragment displacement on outcomes under 6 months was determined by ROC analysis, using a cut-off value of 14 mm. Displacement under 14 mm predicted healing within 6 months with a sensitivity of 90.3% and a specificity of 61.9%. The statistical analysis demonstrated that the odds of experiencing non-union or delayed healing were approximately 15 times higher for patients with a third fragment displacement of 14 mm or greater.
Conclusion
The third fragment displacement is the most important factor influencing healing within twelve months in femur shaft fractures type 32B managed with an intramedullary nail. Inversely, the third fragment size had no effect on the healing of the fractures in our series.
Journal Article
A feasibility cadaver study for placing screws in various pelvic osseous fracture pathways using a robotic arm
Introduction
The use of a robotic system for the placement of pedicle screws in spine surgeries is well documented in the literature. However, there is only a single report in the United States describing the use of a robotic system to place two screws in osseous fixation pathways (OFPs) commonly used in the treatment of pelvic and acetabular fractures in a simulated bone model. The purpose of this study was to demonstrate the use of a robotic system to place screws in multiple, clinically relevant OFPs in a cadaveric model and to quantitatively measure accuracy of screw placement relative to the preoperative plan.
Methods
A single cadaveric specimen was obtained for the purpose of this study. All surrounding soft tissues were left intact. Screws were placed in OFPs, namely iliosacral (IS), trans-sacral (TS), Lateral Compression-II (LC-II), antegrade anterior column (AC) and antegrade posterior column (PC) of the right hemipelvis using standard, fluoroscopically assisted percutaneous or mini-open technique. Following the placement of screws into the right hemipelvis using standard techniques, screws were planned and placed in the same OFPs of the contralateral hemipelvis using the commercially available ExcelsiusGPS
®
robotic system (Globus Medical Inc., Audubon, PA). After robotic-assisted screw placement, a post-procedure CT scan was obtained to evaluate actual screw placement against the pre-procedure plan. A custom-made image analysis program was devised to measure screw tip/tail offset and angular offset on axial and sagittal planes.
Results
For different OFPs, the mean tip offset, tail offset and angular offsets were 1.6 ± 0.9 mm (Range 0.0–3.6 mm), 1.4 ± 0.4 mm (Range 0.3–2.5 mm) and 1.1 ± 0.4° (Range 0.5–2.1), respectively.
Conclusion
In this feasibility study, surgeons were able to place screws into the clinically relevant fracture pathways of the pelvis using ExcelsiusGPS
®
for robotic-assisted surgery. The measured accuracy was encouraging; however, further investigation is needed to demonstrate that robotic-assisted surgery can be used to successfully place the screws in the bony corridors of the pelvis to treat traumatic pelvic injuries.
Journal Article
Maritime Piracy and the Construction of Global Governance
Piratical attacks have become more frequent, violent, costly and increasingly threaten to undermine order in the international system. Much attention has focused on Somalia, but piracy is a problem worldwide. Recent coordination efforts among states in South East Asia appear to have helped in the area, but elsewhere piracy has expanded. Interestingly, international law has long recognized piracy as a crime and provided tools for universal suppression, yet piracy persists.
In this book, a handpicked group of leading experts in the field of International Relations use maritime piracy as a means to expose the incongruities in our understanding of global governance. Using broadly constructivist approaches to understand international actors' responses to the challenges created by maritime piracy, the contributors question a number of myths and misconceptions around piracy and analyze the various ways that international law and organizations channel actors' understandings of maritime piracy and their efforts to respond to it. In doing so, they expose some shaky foundations for IR theorists: how do we conceive of governance and legitimacy when they are delinked from the territorial aspect of the modern nation-state? What happens to prospects for cooperation when we get to the nitty-gritty questions of practice related to paying for trials, imprisoning and maintaining captured pirates, bearing the burden of policing sea-lanes, or even determining what constitutes a pirate? Does anyone have a monopoly on the legitimate use of force at sea, and how is that legitimacy constructed?
Maritime Piracy and the Construction of Global Governance offers an improved theoretical understanding of the response of the international community to maritime piracy and broadens our understanding of the complex and sometimes countervailing motivations of all the actors involved, from international organizations and states down to the pirates th
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