• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.5
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• pp.839-854
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• 2018

This study was performed to evaluate the performance of GFRP plate reinforced segments for TBM tunnel support. Recently, the SFRC segment has been applied to prevent local damage such as reduction of the amount of reinforcing bars of the segment, crack control and breakage. However, the steel fiber used in the SFRC segment has a problem of durability deterioration due to fiber corrosion. Compared with the RC segment, the maximum flexural load reduction of the SFRC segment hinders the broad application range of the TBM tunnel segment. Therefore, GFRP plate was considered as a stiffener for the maximum load increase of SFRC segment, and structural synthetic fiber without corrosive concern was used as a substitute for steel fiber. The flexural performance of the segment was evaluated by using the type of reinforcing fiber and GFRP plate thickness as the main parameters. As a result, the maximum load and the flexural toughness were increased by 21.78~23.03% and 0.5~7.96%, respectively, as compared with the segments reinforced with reinforcing fiber and GFRP plate of 3 mm thickness.

• Journal of Cerebrovascular and Endovascular Neurosurgery
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• v.26 no.1
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• pp.37-45
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• 2024

Objective: To review the characteristics of distal middle cerebral artery (MCA) aneurysm treated by microsurgery, the detailed surgical options, and the clinical result. Methods: We retrospectively reviewed cerebral aneurysm in the M2 and M3 segments of the MCA surgically treated between January 2015 and December 2022. The demographic data, aneurysm-related findings, type of surgical approach, surgical technique, and clinical outcomes of the enrolled patients were analyzed. Results: Sixteen distal MCA aneurysms were treated with microneurosurgery (incidence, 1.0%; female, 12; mean age, 58.1 years; ruptured, three). Twelve aneurysms were in the M2 segment (insular segment), two aneurysms at the M2-M3 junction, and two aneurysms in the M3 segment (opercular segment). Twelve aneurysms were saccular (average size, 4.9 mm; multiplicity, 50%; average aneurysms, 3.0; partially thrombosed, 1; sidewall aneurysm, 2). Three aneurysms were fusiform, of which two were ruptured. Of the ruptured aneurysms, one was a ruptured dissecting aneurysm. The trans-sylvian and trans-sulcal approaches were used in fourteen and two patients, respectively. Neck clipping, wrap clipping, and surgical trapping were performed in twelve, one, and one patient, respectively. Proximal occlusion was performed in one patient. Bypass technique was required in two patients (neck clipping and proximal occlusion). The modified Rankin Score was 6 in the two patients with ruptured aneurysms. The remaining patients did not show further neurological deterioration after microneurosurgery. Conclusions: Distal MCA aneurysms had a high incidence of being diagnosed with multiple other aneurysms and were relatively non-saccular.

• Journal of Korean Neurosurgical Society
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• v.52 no.4
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• pp.353-358
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• 2012

Objective : The purpose of this study was to determine the efficacy of bone cement-augmented short segment fixation using percutaneous screws for thoracolumbar burst fractures in a background of severe osteoporosis. Methods : Sixteen patients with a single-level thoracolumbar burst fracture (T11-L2) accompanying severe osteoporosis treated from January 2008 to November 2009 were prospectively analyzed. Surgical procedures included postural reduction for 3 days and bone cement augmented percutaneous screw fixation at the fracture level and at adjacent levels without bone fusion. Due to the possibility of implant failure, patients underwent implant removal 12 months after screw fixation. Imaging and clinical findings, including involved vertebral levels, local kyphosis, canal encroachment, and complications were analyzed. Results : Prior to surgery, mean pain score (visual analogue scale) was 8.2 and this decreased to a mean of 2.2 at 12 months after screw fixation. None of the patients complained of pain worsening during the 6 months following implant removal. The percentage of canal compromise at the fractured level improved from a mean of 41.0% to 18.4% at 12 months after surgery. Mean kyphotic angle was improved significantly from $19.8^{\circ}$ before surgery to 7.8 at 12 months after screw fixation. Canal compromise and kyphotic angle improvements were maintained at 6 months after implant removal. No significant neurological deterioration or complications occurred after screw removal in any patient. Conclusion : Bone cement augmented short segment fixation using a percutaneous system can be an alternative to the traditional open technique for the management of selected thoracolumbar burst fractures accompanied by severe osteoporosis.

• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.171-177
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• 2005

Fire in underground space may induce severe structural damage as well as heavy casualties. To protect underground structure and passengers from fire, it is very essential to characterize fire-induced damage on construction materials of underground structures. In this study, the high-temperature furnace was manufactured to evaluate fire-induced damage on underground structure materials. Especially, this study aimed at the evaluation of fire-induced damage on the shield TBM concrete segment. In the fire tests, furnace temperature was set to reach 1,200 degrees at five minutes after Ignition. The temperature of 1,200 degrees was kept during one hour, and the fire was extinguished after two hours elapsed. From the temperature measurement by thermocouples embedded in test specimens, the spatting was estimated to reach approximately 20 cm from the surface exposed to fire. After the fire tests, the alteration of physico-mechanical properties and microstructures of concrete segment was investigated from core specimens. The results showed that apart from spatting, the deterioration depth of the remaining concrete material amounted to approximately 10 cm from the spatting surface.

• Journal of Korean Neurosurgical Society
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• v.38 no.5
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• pp.393-395
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• 2005

Cerebral infarction rarely occur following head injury. The authors present the case of a 39-year-old man with complete infarction in the middle cerebral artery[MCA] and anterior cerebral artery[ACA] territories ccurred immediately after head injury. He had compound depressed fracture in right frontal bone with no neurological deficit. After the depressed bone elevation, postoperative computed tomography scan showed the right MCA and ACA territory infarction with midline shift. Cerebral angiography obtained on the day after emergent decompressive craneictomy showed the complete occlusion of the internal carotid artery[ICA] at the level of lacerum ICA segment. There was no evidence of neck vessel dissection and basal skull fracture. Cerebral infarction can occur in an ultraearly period after head injury without neck vessel dissection or basal skull fracture. We stress the need for attention to the cerebral infarction as the cause of a rare neurological deterioration of the head trauma.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.161-164
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• 2004

In these days, composite materials are applied to the military field like parts of air crafts, rockets, ammunitions and so on. As high pressure is loaded on the composite body, however, cracks or delamination phenomena can be occurred between layers of laminate. These cracks or delamination usually cause a deterioration of mechanical properties under the complicated loads. In this study, methods for improvement of the inter-laminar bonding strength of thick carbon/epoxy composite structures are suggested and discussed in terms of segment bending test.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.3
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• pp.311-320
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• 2014

High strength concrete is not only vulnerable to the occurrence of spalling which generates the loss of cross-section in concrete structures but produces faster degradation in its mechanical properties than normal strength concrete in the event of fire. This study aims to evaluate fire resistance of high strength segment concrete with PET fibers mixed to prevent spalling under ISO834 (2hr) and RABT fire curve. As results, the samples without PET fibers show the concrete loss up to the depth of about 8 cm and 9.5 cm from the surface exposed to fire under ISO834 and RABT fire curve respectively. The samples mixed with PET fiber of 0.1% show no spalling under ISO834 fire curve and the spalled thickness of 6.5 cm under RABT fire curve after the fire tests. Finally, the sample mixed with PET fiber of 0.2% shows no spalling under RABT fire curve. The results indicate that the suitable amounts of PET fiber for securing fire resistance performance of this high strength segment concrete are 0.1% under ISO834 fire curve and 0.2% under RABT fire curve. However, even though spalling does not occur, it is necessary to repair the deterioration of concrete up to 4 cm from the surface exposed to fire after fire.

• Journal of Korean Neurosurgical Society
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• v.54 no.2
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• pp.75-80
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• 2013

Objective : Aneurysms arising from the proximal segment of the anterior cerebral artery (A1) are rare and challenging to treat. The aim of this study was to report our experience with endovascular treatment of A1 Aneurysms. Methods : From August 2007 through May 2012, eleven A1 aneurysms in eleven patients were treated endovascularly. Six aneurysms were unruptured and 5 were ruptured. One patient with an unruptured A1 aneurysm presented with subarachnoid hemorrhage due to rupture of an anterior communicating artery aneurysm. Procedural data, clinical and angiographic results were reviewed retrospectively. Results : All of the aneurysms were successfully treated with coil embolization. Six were treated with a simple technique while the remaining 5 required adjunctive technique : double catheters (n=2), balloon-assisted (n=2), and stent-assisted (n=1). The immediate angiographic control showed a complete occlusion in all cases. Procedure-related complication occurred in only one patient : parent artery occlusion, which was not clinically significant. All patients had excellent clinical outcomes but one patient was discharged with a slight disability. No neurologic deterioration or bleeding was seen during the follow-up period in this cohort of patients. Follow-up angiography (mean, 20 months) was available in ten patients and revealed stable occlusion in all cases. Conclusion : Endovascular treatment is a feasible and effective therapeutic modality for A1 aneurysms. Tailored microcatheter shaping and/or adjunctive techniques are necessary for successful aneurysm embolization because of the projection and location of A1 aneurysms.

• Journal of Korean Neurosurgical Society
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• v.64 no.3
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• pp.437-446
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• 2021

Objective : To investigate the radiographic characteristics of the uppermost instrumented vertebrae (UIV) and UIV+1 compression fractures that are predictive of revision surgery following long-segment spinal fixation. Methods : A total 27 patients who presented newly developed compression fracture at UIV, UIV+1 after long segment spinal fixation (minimum 5 vertebral bodies, lowest instrumented vertebra of L5 or distal) were reviewed retrospectively. Patients were divided into two groups according to following management : revisional surgery (group A, n=13) and conservative care (group B, n=14). Pre- and postoperative images, and images taken shortly before and after the occurrence of fracture were evaluated for radiologic characteristics Results : Despite similar degrees of surgical correction of deformity, the fate of the two groups with proximal junctional compression fractures differed. Immediately after the fracture, the decrement of adjacent disc height in group A (32.3±7.6 mm to 23.7±8.4 mm, Δ=8.5±6.9 mm) was greater than group B (31.0±13.9 mm to 30.1±15.5 mm, Δ=0.9±2.9 mm, p=0.003). Pre-operative magnetic resonance imaging indicated that group A patients have a higher grade of disc degeneration adjacent to fractured vertebrae compared to group B (modified Pfirrmann grade, group A : 6.10±0.99, group B : 4.08±0.90, p=0.004). Binary logistic regression analysis indicated that decrement of disc height was the only associated risk factor for future revision surgery (odds ratio, 1.891; 95% confidence interval, 1.121-3.190; p=0.017). Conclusion : Proximal junctional vertebral compression fractures with greater early-stage decrement of adjacent disc height were associated with increased risk of future neurological deterioration and necessity of revision. The condition of adjacent disc degeneration should be considered regarding severity and revision rate of proximal junctional kyphosis/proximal junction failures.

• Journal of Korean Neurosurgical Society
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• v.61 no.2
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• pp.167-179
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• 2018

The prevalence of patients with adult spinal deformity (ASD) has been reported as high as 68%. ASD often leads to significant pain and disability. Recent emphasis has been placed on sagittal plane balance and restoring normal sagittal alignment with regards to the three dimensional deformity of ASD. Optimal sagittal alignment has been known to increase spinal biomechanical efficiency, reduce energy expenditure by maintaining a stable posture with improved load absorption, influence better bony union, and help to decelerate adjacent segment deterioration. Increasingly positive sagittal imbalance has been shown to correlate with poor functional outcome and poor self-image along with poor psychological function. Compensatory mechanisms attempt to maintain sagittal balance through pelvic rotation, alterations in lumbar lordosis as well as knee and ankle flexion at the cost of increased energy expenditure. Restoring normal spinopelvic alignment is paramount to the treatment of complex spinal deformity with sagittal imbalance. Posterior osteotomies including posterior column osteotomies, pedicle subtraction osteotomies, and posterior vertebral column resection, as well anterior column support are well known to improve sagittal alignment. Understanding of whole spinal alignment and dynamics of spinopelvic alignment is essential to restore sagittal balance while minimizing the risk of developing sagittal decompensation after surgical intervention.