• Geomechanics and Engineering
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• 제21권4호
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• pp.357-369
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• 2020

Different from the conventional planar fracture and simplified Newton model, for power-law slurries with a lower water-cement ratio commonly used in grouting engineering, flow model in geological rough fractures is built based on ten standard profiles from Barton (1977) in this study. The numerical algorithm is validated by experimental results. The flow mechanism, grout superiority, and water plugging of pseudo plastic slurry are revealed. The representations of hydraulic grouting properties for JRCs are obtained. The results show that effective plugging is based on the mechanical mechanisms of the fluctuant structural surface and higher viscosity at the middle of the fissure. The formulas of grouting parameters are always variable with the roughness and shear movement, which play a key role in grouting. The roughness can only be neglected after reaching a threshold. Grouting pressure increases with increasing roughness and has variable responses for different apertures within standard profiles. The whole process can be divided into three stationary zones and three transition zones, and there is a mutation region (10 < JRCs < 14) in smaller geological fractures. The fitting equations of different JRCs are obtained of power-law models satisfying the condition of -2 < coefficient < 0. The effects of small apertures and moderate to larger roughness (JRCs > 10.8) on the permeability of surfaces cannot be underestimated. The determination of grouting parameters depends on the slurry groutability in terms of its weakest link with discontinuous streamlines. For grouting water plugging, the water-cement ratio, grouting pressure and grouting additives should be determined by combining the flow conditions and the apparent widths of the main fracture and rough surface. This study provides a calculation method of grouting parameters for variable cement-based slurries. And the findings can help for better understanding of fluid flow and diffusion in geological fractures.

• Geomechanics and Engineering
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• 제6권2호
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• pp.153-172
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• 2014

In order to investigate the effect of different perforation angles (the angle between the perforation direction and the maximum horizontal principal stress) on the fracture initiation and propagation during hydraulic fracturing of highly deviated well in oil & gas saturated formation, laboratory experiments of the hydraulic fracturing had been carried out on the basis of non-dimensional similar criteria by using 400^3 $mm^3$ cement cubes. A plane fracture can be produced when the perforations are placed in the direction of the maximum horizontal principal stress. When the perforation angle is $45^{\circ}$, the fractures firstly initiate from the perforations at the upper side of the wellbore, and then turn to the maximum horizontal principal stress direction. When the well deviation angle and perforation angle are both between $45^{\circ}$ and $90^{\circ}$, the fractures hardly initiate from the perforations at the lower side of the wellbore. Well azimuth (the angle between the wellbore axis and the maximum horizontal principal stress) has a little influence on the fracture geometries; however it mainly increases the fracture roughness, fracture continuity and the number of secondary fractures, and also increases the fracture initiation and propagation pressure. Oriented perforating technology should be applied in highly deviated well to obtain a single plane fracture. If the well deviation angle is smaller, the fractures may link up.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제47권5호
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• pp.382-387
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• 2021

Objectives: Zygomatic complex (ZMC) fractures comprise up to 40% of all facial fractures. Misaligned bone fragments and misplaced fixation hardware traditionally detected postoperatively on plain radiographs of the skull might require re-operation. The intraoperative O-Arm (Medtronic, USA) is a three-dimensional (3D) computed tomographic imaging system. Materials and Methods: This retrospective single-center study evaluated the utility of O-Arm scanning during corrective surgeries for ZMC and zygomatic arch (ZA) fractures from 2018 to 2020. Three females and 16 males (mean age, 31.52 years; range, 22-48 years) were included. Fracture instability (n=6) and facial deformity (n=15) were the most frequent indications for intraoperative 3D O-Arm scan. Results: The images demonstrated that all fracture lines were properly reduced and fixed. Another scan performed at the end of the fixation or reduction stage, however, revealed suboptimal results in five of the 19 cases, and further reduction and fixation of the fracture lines were required. Conclusion: Implementation of an intraoperative O-Arm system in ZMC and ZA fracture surgeries assists in obtaining predictable and accurate results and obviates the need for revision surgeries. The device should be considered for precise operations such as ZMC fracture repairs.

• 대한두개안면성형외과학회지
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• 제22권5호
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• pp.254-259
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• 2021

Background: Prophylactic antibiotics are commonly used in craniofacial surgeries. Despite the low risk of surgical site infection after nasal surgery, a lack of consensus regarding the use of antibiotic prophylaxis in the closed reduction of nasal bone fractures has led to inappropriate prescribing patterns. Through this study, we aimed to investigate the status of prophylactic antibiotic use in closed reductions of nasal bone fractures in Korea. Methods: This retrospective cohort study was conducted using data from the National Health Insurance Service-National Sample Cohort of Korea from 2005 to 2015. We analyzed the medical records of patients who underwent closed reduction of nasal bone fractures. The sex, age, region of residence, comorbidities, and socioeconomic variables of the patients were collected from the database. Factors that affect the prescription of perioperative antibiotics were evaluated using multivariate logistic regression analysis. Results: A total of 3,678 patients (mean±standard deviation of age, 28.7±14.9 years; 2,850 men [77.5%]; 828 women [22.5%]) were included in this study. The rate of antibiotic prescription during the perioperative period was 51.4%. Approximately 68.8% of prescriptions were written for patients who had received general anesthesia. The odds of perioperative prophylactic antibiotic use were significantly higher in patients who received general anesthesia than who received local anesthesia (odds ratio, 1.59). No difference was found in terms of patient age and physician specialty. Second-generation cephalosporins were the most commonly prescribed antibiotic (45.3%), followed by third- and first-generation cephalosporins (20.3% and 18.8%, respectively). In contrast, lincomycin derivatives and aminoglycosides were not prescribed. Conclusion: The findings of this study showed that there was a wide variety of perioperative antibiotic prescription patterns used in nasal bone surgeries. Evidence-based guidance regarding the prescribing of antimicrobial agents for the closed reduction of nasal bone fractures should be considered in future research.

• Hip & pelvis
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• 제30권4호
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• pp.254-259
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• 2018

Purpose: Internal fixation using compression hip screws (CHS) and traction tables placing patients in the supine position is a gold standard option for treating intertrochanteric fractures; however, at our institution, we approach this treatment with patients in a lateral decubitus position. Here, the results of 100 consecutive elderly (i.e., ${\geq}45$ years of age) patients who underwent internal fixation with CHS in lateral decubitus position are analyzed. Materials and Methods: Between March 2009 and May 2011, 100 consecutive elderly patients who underwent internal fixation with CHS for femoral intertrochanteric fracture were retrospectively reviewed. Clinical outcomes (i.e., Koval score, Harris hip score [HHS]) and radiographic outcomes (i.e., bone union time, amount of sliding of lag screw, tip-apex distance [TAD]) were evaluated. Results: Clinical assessments revealed that the average postoperative Koval score decreased from 1.4 to 2.6 (range, 0-5; P<0.05); HHS was 85 (range, 72-90); and mean bone union time was 5.0 (range, 2.0-8.2) months. Radiographic assessments revealed that anteroposterior average TAD was 6.95 (range, 1.27-14.63) mm; lateral average TAD was 7.26 (range, 1.20-18.43) mm; total average TAD was 14.21 (range, 2.47-28.66) mm; average lag screw sliding was 4.63 (range, 0-44.81) mm; and average angulation was varus $0.72^{\circ}$(range, $-7.6^{\circ}-12.7^{\circ}$). There were no cases of screw tip migration or nonunion, however, there were four cases of excessive screw sliding and six cases of varus angulation at more than $5^{\circ}$. Conclusion: CHS fixation in lateral decubitus position provides favorable clinical and radiological outcomes. This technique is advisable for regular CHS fixation of intertrochanteric fractures.

• Asian Spine Journal
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• 제12권6호
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• pp.1053-1059
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• 2018

Study Design: Retrospective review. Purpose: To detect the effect of cannulated (poly-axial head) and solid (mono-axial head) screws on the local kyphotic angle, vertebral body height, and superior and inferior angles between the screw and the rod in the surgical management of thoracolumbar fractures. Overview of Literature: Biomechanics studies showed that the ultimate load, yield strength, and cycles to failure were significantly lower with cannulated (poly-axial head) pedicle comparing to solid core (mono-axial head). Methods: The medical charts of patients with thoracolumbar fractures who underwent pedicle screw fixation with cannulated or solid pedicle screws were retrospectively reviewed; the subjects were followed up from January 2011 to December 2015. Results: Total 178 patients (average age, $36.1{\pm}12.4years$; men, 142 [84.3%]; women, 28 [15.7%]) with thoracolumbar fractures who underwent surgery and were followed up at Hamad Medical Corporation were classified, based on the screw type as those with cannulated screws and those with solid screws. The most commonly affected level was L1, followed by L2 and D12. Surgical correction of the local kyphotic angle was significantly different in the groups; however, there was no significant difference in the loss of correction of the local kyphotic angle of the groups. Surgical correction of the reduction in the vertebral body height showed statistical significance, while the average loss of correction in the reduction of the vertebral body height was not significantly different. The measurement of the angles made by the screws on the rods was not significantly different between the cannulated (poly-axial head) and solid (mono-axial head) screw groups. Conclusions: Solid screws were superior in terms of providing increased correction of the kyphotic angle and height of the fractured vertebra than the cannulated screws; however, no difference was noted between the screws in the maintenance of the superior and inferior angles of the screw with the rod.

• 대한두개안면성형외과학회지
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• 제19권4호
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• pp.264-269
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• 2018

Background: Orbital resorbable mesh plates are adequate to use for isolated floor and medial wall fractures with an intact bony buttress, but are not recommended to use for large orbital wall fractures that need load bearing support. The author previously reported an orbital wall restoring surgery that restored the orbital floor to its prior position through the transnasal approach and maintained temporary extraorbital support with a balloon in the maxillary sinus. Extraorbital support could reduce the load applied on the orbital implants in orbital wall restoring surgery and the use of resorbable implants was considered appropriate for the author's orbital wall restoring technique. Methods: A retrospective review was conducted of 31 patients with pure unilateral orbital floor fractures between May 2014 and May 2018. The patients underwent transnasal restoration of the orbital floor through insertion of a resorbable mesh plate and maintenance of temporary balloon support. The surgical results were evaluated by the Hertel scale and a comparison of preoperative and postoperative orbital volume ratio (OVR) values. Results: The OVR decreased significantly, by an average of 6.01% (p<0.05) and the preoperative and postoperative Hertel scale measurements decreased by an average of 0.34 mm with statistical significance (p<0.05). No complications such as buckling or sagging of the implant occurred among the 31 patients. Conclusion: The use of resorbable mesh plate in orbital floor restoration surgery is an effective and safe technique that can reduce implant deformation or complications deriving from the residual permanent implant.

• 대한족부족관절학회지
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• 제22권3호
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• pp.95-99
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• 2018

Purpose: The purpose of this study was to evaluate the radiologic outcomes of distal fibular fractures and to analyze the risk factors associated with nonunion. Materials and Methods: Between January 2009 and March 2016, 13 patients who had final nonunion with ankle fracture were included. In the control group, 370 patients who had undergone bony union and removed metal implants were included. All patients underwent the same surgical procedure and had the same treatment method, ultimately achieving satisfactory open reduction results with less than 2 mm fracture gap. Surgical treatment of fracture was considered to have the same effect on nonunion, and factors that might be associated with nonunion were evaluated. SPSS ver. 13.0 (SPSS Inc., USA) was used for all statistical analyses. Pearson's chi-square test and multi-variate regression analysis were performed to determine the factors affecting nonunion of distal fibular fracture. A p-value less than 0.05 was considered statistically significant, and relative risk was assessed. Results: The mean age of 13 patients was 46.9 years (range, 16~57 years); there were 8 men and 5 women. Among the 13 patients with nonunion, atrophic was the most common (12 cases). The association between the injury mechanism and the Lauge-Hansen classification and diabetes mellitus was not statistically significant. Distal fibular fractures with tibia shaft fracture (p=0.015) and Danis-Weber type C fracture (p=0.023), open fracture (p=0.011), and smoking (p=0.023) were significantly associated with nonunion. Conclusion: In this study, the combined injury of the ipsilateral tibia shaft fracture, open fracture, and Danis-Weber type C fracture may increase the possibility of nonunion. Therefore, caution is advised to prevent nonunion.

• Geomechanics and Engineering
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• 제18권6호
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• pp.585-594
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• 2019

In-situ leaching could be one of the promising mining methods to extract the minerals from deep fractured rock mass. Constrained by the low permeability at depth, however, the performance does not meet the expectation. In fact, the rock mass permeability mainly depends on the pre-existing natural fractures and therefore play a crucial role in in-situ leaching performance. More importantly, fractures have various characteristics, such as aperture, persistence, and density, which have diverse contributions to the promising method. Hence, it is necessary to study the variation of fluid rate versus fracture parameters to enhance in-situ leaching performance. Firstly, the subsurface fractures from the depth of 1500m to 2500m were mapped using the discrete fracture network (DFN) in this paper, and then the numerical model was calibrated at a particular case. On this basis, the fluid flow through fractured rock mass with various fracture characteristics was analyzed. The simulation results showed that with the increase of Fisher' K value, which determine the fracture orientation, the flow rate firstly decreased and then increased. Subsequently, as another critical factor affecting the fluid flow in natural fractures, the fracture transmissivity has a direct relationship with the flow rate. Sensitive study shows that natural fracture characteristics play a critical role in in-situ leaching performance.

• 대한두개안면성형외과학회지
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• 제22권4호
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• pp.193-198
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• 2021

Background: Nasal bone fractures are frequently encountered in clinical practice. Although fracture reduction is simple and correction requires a short operative time, low patient satisfaction and relatively high complication rates remain issues for many surgeons. These challenges may result from inaccuracies in fracture recognition and assessment or inappropriate surgical planning. Findings from immediate postoperative computed tomography (CT) scans and those performed at 4 to 6 weeks postoperatively were compared to evaluate the accuracy and outcomes of nasal fracture reduction. Methods: This retrospective study included patients diagnosed with nasal bone fractures at our department who underwent closed reduction surgery. Patients who did not undergo additional CT scans were excluded from the study. Clinical examinations, patient records, and radiographic images were evaluated in 20 patients with nasal bone fractures. Results: CT findings from immediately after surgery and a 1month follow-up were compared in 20 patients. Satisfactory nasal projection and aesthetically acceptable results were observed in patients with accurate correction or mild overcorrection, while undercorrection was associated with unfavorable results. Conclusion: Closed reduction surgery for correcting nasal bone fractures usually provides acceptable outcomes with relatively few complications. If available, immediate postoperative CT scans are recommended to guide surgeons in the choice of whether to perform secondary adjustments if the initial results are unsatisfactory. Based on photogrammetric data, nasal bone reduction with accurate correction or mild overcorrection achieved acceptable and stable outcomes at 1 month postoperatively. Therefore, when upward dislocation is observed on postoperative CT, one can simply observe without a subsequent intervention.