• Archives of Plastic Surgery
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• 제41권1호
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• pp.29-34
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• 2014

The septal extension graft is a very useful method of controlling nasal lengthening and tip projection, rotation, and shape by fixing a graft to the septum, which leads to a strong supporting structure. Enhancing graft stability is important for better long-term outcomes and minimizing complications or relapse, and even more efficient application of these methods is needed for East Asians who lack enough cartilage to be harvested in addition to possessing a weak cartilage framework. In this paper, the methods for overcoming the drawbacks of the septal extension graft, such as instability, a fixed tip, and insufficiency of cartilage, are presented, and the applications of each method for greater satisfaction with surgical outcomes are also discussed.

• Archives of Reconstructive Microsurgery
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• 제23권2호
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• pp.45-50
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• 2014

Palmar soft tissue defects are best reconstructed using a replacement flap of proper size with adequate soft tissue stability for mechanical resistance as well as with protective sensation. Reconstructive approaches are dictated by injury mechanism, defect size and location, and the status of the wound bed and tendino-skeletal structure. While uninjured portions of the hand can be used as a source for local flaps, the use of free flaps allows for maximal access for selection of the most ideal replacement tissue for the defect to be restored as close to the initial state as possible. Here, we review the garden variety of free flaps used in reconstruction of palmar soft tissue defects.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제41권
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• pp.8.1-8.6
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• 2019

Background: Resorbable devices have recently been adopted in the field of orthognathic surgery with controversies about their postoperative skeletal stability. Hence, we determined the long-term skeletal stability of unsintered hydroxyapatite/poly-ʟ-lactic acid (HA/PLLA) mesh for osteofixation of mandibular sagittal split ramus osteotomy (SSRO), and compared it with that of titanium miniplate. Methods: Patients were divided into resorbable mesh and titanium miniplate fixation groups. A comparative study of the change in the mandibular position was performed with preoperative, 1-day, 6-month, and 2-year postoperative lateral cephalograms. Results: At postoperative 6 months-compared with postoperative 1 day, point B (supra-mentale) was significantly displaced anteriorly in the titanium-fixation group. Moreover, at postoperative 2 years-compared with postoperative 6 months, point B was significantly displaced inferiorly in the titanium-fixation. However, the HA/PLLA mesh-fixation group did not show any significant change with respect to point B postoperatively. Conclusions: The HA/PLLA mesh-fixation group demonstrated superior long-term skeletal stability with respect to the position of mandible, when compared with the titanium-fixation group.

• Computers and Concrete
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• 제20권3호
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• pp.297-310
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• 2017

A CFD software was used to simulate free surface flow of SCC in the T-Box test. In total, seven simulations were developed to study the effect of rheological parameters on the non-restricted flow performance of SCC in both horizontal and vertical directions. Different suspending fluids having five plastic viscosity values between 10 and 50 Pa.s, three yield stress values between 14 and 75 Pa, one density of $2500kg/m^3$, and one shear elasticity modulus of 100 Pa were considered for suspension of 178 spherical particles of 20-mm diameter and $2500kg/m^3$ density. The results of the simulations are found to correlate well to changes in rheological parameters of the suspending fluid. Plastic viscosity was shown to be the most dominant parameter affecting flowability and dynamic stability compared to the yield stress. A new approach was proposed to evaluate performability of SCC based on a trade-off between flowability and dynamic stability.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제37권
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• pp.6.1-6.9
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• 2015

Orthognathic surgery requires stable fixation for uneventful healing of osteotomized bony segments and optimal remodeling. Titanium plates and screws have been accepted as the gold standard for rigid fixation in orthognathic surgery. Although titanium osteofixation is the most widely used approach, the use of bioabsorbable devices has been increasing recently. Biodegradation of bioabsorbable devices eliminates the need for a second operation to remove metal plates and screws. However, long-term stability and relapse frequency in bioabsorbable osteofixation are still insufficiently studied, especially in cases of segmental movements of great magnitude or segmental movements to a position where bony resistance exists. This paper reviews the background, techniques, and complications of bioabsorbable osteofixation and compares bioabsorbable and titanium osteofixation in orthognathic surgery in terms of skeletal stability.

• Geomechanics and Engineering
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• 제8권6호
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• pp.783-799
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• 2015

In this study, effect of horizontal in situ stress on failure mechanism around underground openings excavated in isotropic, elastic rock zones is investigated. For estimating the plastic zone occurrence, an induced stress influence area approach (Bray Equations) was modified to define critical stress ratio according to the Mohr-Coulomb failure criterion. Results obtained from modified calculations were compared with results of some other analytical solutions for plastic zone thickness estimation and the numerical modelling (finite difference method software, FLAC2D) study. Plastic zone and its geometry around tunnels were analyzed for different in situ stress conditions. The modified equations gave similar results with those obtained from the other approaches. However, safer results were calculated using the modified equations for high in situ stress conditions and excessive ratio of horizontal to vertical in situ stresses. As the outcome of this study, the modified equations are suggested to use for estimating the plastic zone occurrence and its thickness around the tunnels with circular cross-section.

• 지질공학
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• 제32권1호
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• pp.1-12
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• 2022

Based on the extended spatial mobilization plane (SMP) criterion, we present an elastic-brittle-plastic solution for an axisymmetric cylindrical tunnel. The influences of the intermediate principal compressive stress and material strain-softening behavior are considered. Closed-form formulas for the critical support force, radius of plastic zone, and distributions of stress and displacement in surrounding rock are proposed. The elastic-plastic solution based on SMP is compared with the Kastner solution to verify the credibility of the obtained elastic-plastic solution. The elastic-brittle-plastic solution following the SMP criterion and the current solution based on the Mohr-Coulomb criterion are also compared. The rock strain-softening rate and the intermediate principal stress affect the stability of the surrounding rock. The results provide guidance for optimizing the design of support systems for tunnels.

• 터널과지하공간
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• 제14권3호
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• pp.215-228
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• 2004

지하암반의 변형은 단층, 절리 등의 불연속면을 따라 발생하므로 불연속면의 역학적 특성과 공간적인 분포형태는 구조물의 안정성에 근 영향을 미친다. 한편 연약암반에 높은 응력이 작용하는 경우에는 불연속면뿐만 아니라 무결암에서의 변형이 구조물의 안정성에 영향을 줄 수 있다. 이 연구에서는 암반구조물의 안정성 해석을 위하여 무결암과 절리, 그리고 록볼트를 점소성(visco-plastic) 재료로 가정하고, 연속체 개념을 적용하여 유변학적 모델(Rheological model)에 기초한 2차원 점소성 유한요소 프로그램을 개발하였다. 무결암 모델, 절리암반 모델, 록볼트로 보강된 절리암반 모델의 분석을 통하여 개발된 프로그램을 검증하였고, 각각의 모델에서 무결암의 해석 조건(탄성/점소성)에 따른 변위의 차이를 알아보았다. 연약암반에 높은 응력이 작용할 때, 무결암을 탄성으로 해석한 경우보다 점소성으로 해석한 경우에서 지하구조물의 변위가 더 크게 나타났다. 따라서 연약암반 내 지하구조물의 안정성 해석을 위해서는 절리와 록볼트 뿐만 아니라 무결암에 대해서도 점소성 모델을 적용하는 것이 바람직한 것으로 판단되었다.

• Archives of Plastic Surgery
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• 제41권5호
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• pp.493-499
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• 2014

Background Maintaining stability and restoring the aesthetic appearance are the fundamental goals when managing zygomatic fractures. We aimed to evaluate the stability and anthropometric outcomes of zygomatic fracture patients who underwent two-point fixation involving the infraorbital rim and zygomaticomaxillary buttress via the transconjunctival and gingivobuccal approaches without any skin incisions. Methods We examined 15 zygomatic fracture patients who underwent two-point fixation during a 3-year period. Stability was evaluated using three-dimensional facial bone computed tomography. Superoinferior and anteroposterior displacement of the zygoma was quantified. The aesthetic appearance of the periorbital region was evaluated using indirect anthropometry with standardized clinical photographs. The ratios between the eye fissure height and width, and lower iris coverage ratio were used to evaluate aesthetical changes. The bony displacement and aesthetic ratios were analyzed using Wilcoxon or Friedman tests. The correlation between the preoperative zygoma position and anthropometric values was analyzed. Results The positions of the zygoma were similar to those on the contralateral side at the long-term follow-up. The preoperative anthropometric measurements on the fractured side differed from those on the contralateral side, although these values were close to the normal values at the long-term follow-up. Furthermore, we noted that the anteroposterior displacement strongly positively correlated with the lower iris coverage rate (Spearman's coefficient=0.678, P=0.005). Conclusions Two-point fixation of zygomatic fractures achieved stable outcomes on long-term follow-up, and also appeared to be reliable in restoring the aesthetic appearance of the periorbital region.

• Archives of Plastic Surgery
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• 제38권3호
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• pp.273-278
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• 2011

Purpose: It has always been an aspiration for Asians to look more balanced and feminine, considering their facial features regarding relatively flat midface with marked prominences of the zygoma. Many studies have been dealt in this subject. However, the authors would like to emphasize the concept and introduce the technique of repositioning of the malar complex to a cosmetically beneficial point and stationing it on proper position by fixation on zygoma body and arch. Methods: From January 1998 to December 2007, this method was performed in 50 patients of mild to moderate prominence and malposition of the malar complex. A simplified technique of lateral orbital osteotomy and oblique osteotomy on zygomatic arch through intraoral and preauricular incision was developed. Then, liberal malar complex can be moved to a supero-posterior direction and repositioned to a more cosmetically beneficial point. To maintain the stationed position and to protect from vector affected by the attached masticating muscle to zygomatc bone, fixation was done on both zygoma body and arch. Results: We have obtained satisfactory results using this procedure without any observable complications. The advantages of this procedure are proper exposure, inconspicuous scar, safe, more natural contour, improved stability, and shorter healing time. Conclusion: The authors suggest that reduction malarplasty should be approached with underlying concept of repositioning and fixation. In mild moderate malar prominent cases, our technique will provide with maintenance of aesthetic concept, equal to the malar reduction performed under coronal approach and provide with more natural facial contour with stability even with less invasive surgical approach.