• Journal of Korean Foot and Ankle Society
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• v.24 no.3
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• pp.107-112
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• 2020

Purpose: Hallux valgus (HV) is a common foot deformity that causes pain in the first metatarsophalangeal joint. Distal metatarsal osteotomies are commonly performed as a treatment. This retrospective study compared the clinical and radiological results of bioabsorbable magnesium (Mg) versus titanium (Ti) screw fixation for modified distal chevron osteotomy in HV. Materials and Methods: Forty-nine patients, who underwent modified distal chevron osteotomy for HV in 2018 and 2019, were reviewed retrospectively. Bioabsorbable Mg screw fixation was applied in 20 patients (22 feet), and a traditional Ti compression screw was applied in 29 patients (40 feet). The patients were followed up for at least six months. The clinical results were evaluated using the American Orthopaedic Foot and Ankle Society hallux metatarsophalangeal-interphalangeal (AOFAS-MTP-IP) scale and a visual analogue scale (VAS). The hallux valgus angle (HVA), intermetatarsal angle (IMA), and distal metatarsal articular angle (DMAA) were measured before, after surgery, and at the six months follow-up. Results: The AOFAS-MTP-IP scale and VAS points were improved in both groups, with no significant difference between them. At the six-month follow-up, HVA, IMA, and DMAA were similar. Bone union was confirmed in both groups, and there were no significant major complications in both groups. Four people in the Ti screw group underwent implant removal surgery. Conclusion: Bioabsorbable Mg screws showed comparable clinical, radiologic results to Ti standard screws six months after distal modified chevron osteotomy. These screws are an alternative fixation material that can be used safely and avoid the need for implant removal operations.

• Journal of Korean Foot and Ankle Society
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• v.14 no.1
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• pp.21-24
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• 2010

Purpose: The incomplete reduction of the sesamoid has lately been issued as cause for recurrence. In this study, we analysed factors that may influence reduction of sesamoid. Materials and Methods: The study consists of 50 cases operated by single surgeon. Eighteen cases were done by proximal chevron osteotomy, and 32 cases were done by scarf osteotomy. Hallux valgus (HV) angle and intermetatarsal (IM) angle were measured before and three months after the surgery. Sesamoid position (SP) was classified according to Hardy and Clapham grade system. Results: After the proximal chevron osteotomy, the correction of the mean HV angle was $19.5^{\circ}$, and IM angle was $6.2^{\circ}$. SP was changed from 5.6 to 3.4 grade. After the Scarf osteotomy, the correction of the mean HV angle was 25 degree, and IM angle was $9^{\circ}$. SP was changed from 5.5 to 2.8 grade. There was difference of sesamoid's correction between two different method of surgery (p=0.127). However, better correction of sesamoid was witnessed with bigger correction angle regardless of method of surgery (p=0.002, 0.001). Conclusion: We believe surgical method do not effect sesamoid's correction but more correction angle can result in better correction of sesamoid position.

• Structural Engineering and Mechanics
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• v.47 no.6
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• pp.881-898
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• 2013

This paper describes analytical investigation into a new dual function system including a couple of shear links which are connected in series using chevron bracing capable to correlate its performance with magnitude of earthquakes. In this proposed system, called Chevron Knee-Vertical Link Beam braced system (CK-VLB), the inherent hysteretic damping of vertical link beam placed above chevron bracing is exclusively utilized to dissipate the energy of moderate earthquakes through web plastic shear distortion while the rest of the structural elements are in elastic range. Under strong earthquakes, plastic deformation of VLB will be halted via restraining it by Stopper Device (SD) and further imposed displacement subsequently causes yielding of the knee elements located at the bottom of chevron bracing to significantly increase the energy dissipation capacity level. In this paper first by studying the knee yielding mode, a suitable shape and angle for diagonal-knee bracing is proposed. Then finite elements models are developed. Monotonic and cyclic analyses have been conducted to compare dissipation capacities on three individual models of passive systems (CK-VLB, knee braced system and SPS system) by General-purpose finite element program ABAQUS in which a bilinear kinematic hardening model is incorporated to trace the material nonlinearity. Also quasi-static cyclic loading based on the guidelines presented in ATC-24 has been imposed to different models of CK-VLB with changing of vertical link beam section in order to find prime effectiveness on structural frames. Results show that CK-VLB system exhibits stable behavior and is capable of dissipating a significant amount of energy in two separate levels of lateral forces due to different probable earthquakes.

• Journal of Korean Foot and Ankle Society
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• v.18 no.4
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• pp.173-177
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• 2014

Purpose: The purpose of this study is to evaluate the characteristics of hallux valgus with severe hallux valgus angle (HVA) and moderate intermetatarsal angle (IMA) after proximal chevron osteotomy. Materials and Methods: Between January 2008 and December 2010, 41 patients (48 feet) were treated with proximal chevron osteotomy and distal soft tissue procedure for symptomatic severe hallux valgus deformity ($HVA{\geq}40^{\circ}$). Patients were divided into two groups, group M (IMA< $18^{\circ}$) and group S ($IMA{\geq}18^{\circ}$). Mean age of patients was 55.7 years (34~70 years) in group M and 60.0 years (44~78 years) in group S. Mean duration of follow-up was 20.4 months (12~41 months) in group M and 18.5 months (12~35 months) in group S. Radiographic parameters, including HVA, IMA, sesamoid position, metatarsus adductus angle (MAA), and distal metatarsal articular angle (DMAA), were compared between groups. Clinical results were assessed using American Orthopaedic Foot and Ankle Society (AOFAS) score and visual analogue scale (VAS). Recurrence rate at the last follow-up was compared between group M and group S. Results: Preoperative HVA and grade of sesamoid position did not differ between the groups. However, immediate postoperative HVA and grade of sesamoid position were significantly larger in group M. Preoperative MAA and DMAA were significantly larger in group M. No significant difference in AOFAS score and VAS was observed between the groups at the last follow-up. Ten of the 27 feet (37.0%) in group M and two of the 21 feet (9.5%) in group S showed hallux valgus recurrence at the last follow-up. Group M showed a significantly higher recurrence rate than group S. Conclusion: Recurrence rate for severe hallux valgus with moderate IMA is higher than that of severe hallux valgus with severe IMA.

• Journal of Korean Foot and Ankle Society
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• v.15 no.2
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• pp.62-67
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• 2011

Purpose: The authors evaluated the differences between K-wires and Cannulated screw, plate for fixing the proximal metatarsal chevron osteotomy of moderate and severe hallux valgus. Materials and Methods: There were 62 patients (79 feetz) who were moderate and severe degree hallux valgus according to the classification of Mann. They all got the proximal chevron osteotomy when correcting the deformity. We divided the patients into 4 groups, Two K-wire fixed group as A, one cannulated screw fixed group as B. Two cannulated screw fixed group as C, Plate fixed group as D, Group A were patients (26 feet) and Group B were patients z(9 feet), Group C were patients (31 feet) and Group D were patients (13 feet). Preoperative, postoperative and follow-up hallux valgus angle (HVA) and intermetatarsal angle (IMA) were measured for each patient. ANOVA test and Student t-test were done for statistical analysis. Results: Mean follow up period was 43.8 months (range: 12~82 months). Preoperative mean IMA was $16.4{\pm}3.5$, $17.7{\pm}11.3$, $17.3{\pm}5.9$ and $16.6{\pm}2.3$ degrees in respectively group A, B, C, D. Immediate postoperative mean IMA was $5.6{\pm}3.4$, $7.3{\pm}4.4$, $7.6{\pm}4.4$ and $6.7{\pm}2.8$ degrees in respectively group A, B, C, D. The final mean IMA was $8.9{\pm}4.5$, $15.2{\pm}7.5$, $10.3{\pm}4.4$ and D $7.7{\pm}3.5$ degrees in respectively group A, B, C, D. There were significant statistical increase in final mean IMA of group B and C (p<0.05). Conclusion: The IMA was significantly increased in the group which used one or two cannulated screw for fixation on follow up, therefore more caution should be needed when using one or two cannulated screw fixation technique after proximal chevron osteotomy.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.91-100
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• 2004

Plate heat exchangers (PHE) have been widely used in different industrial applications, because of high heat transfer efficiency per unit volume. Basic study is performed for PHE to the application of intercooler in automobile. In order to understand the flow phenomena in the plate heat exchanger, a channel which was formed by the upper and lower plate in single plate was considered as calculation domains. Because chevrons attached on the upper plate are brazed with chevrons attached on the lower plate, the flow channel has very complex configuration. This complex geometry was analyzed by Fluent. In order to validate this methodology the proper experimental and theoretical data are collected and compared with numerical results. Finally, due to the lack of experimental values for PHE to the application of intercooler, various chevron angles and air velocities at inlet were tested in terms of physical phenomena. From this point of view, results of velocity vector, path lines, static pressure, heat flux, heat transfer coefficient, and Nusselt number are physically reasonable and accepted for the solutions. From these results, the correlations for pressure drop and Nusselt number with respect to chevron angle and Reynolds number in specific PHE are obtained for the design purpose. Thus, the methodology of the flow analysis in the full geometry of the channel was established for the predictions of performance in plate heat exchanger.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.8
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• pp.636-645
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• 2012

The performance of various type plate exchangers with different chevron angle, dimple size and arrangement was analysed by using Ansys v13.0. Heat transfer performance, pressure drop and flow patten of plate heat exchanger were investigated according to mass flow ratio investigated and compared. As a result, the $60^{\circ}$-chevron type plate heat exchanger showed the highest heat transfer performance but pressure drop was relatively high. The efficiency of $45^{\circ}$-chevron type plate heat exchanger showed the best performance in considering of heat transfer performance and pressure drop simultaneously. Among dimple type plate heat exchangers, the highest heat transfer performance was shown in a dim_zigzag type plate heat exchanger but pressure drop was very high. Besides, the dim_upsize plate heat exchanger showed very low pressure drop.

• Proceedings of the SAREK Conference
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• 2004.06a
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• pp.15-15
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• 2004

• Journal of Korean Foot and Ankle Society
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• v.17 no.4
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• pp.302-308
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• 2013

Purpose: To present clinical results of proximal first metatarsal opening wedge osteotomy and low profile plate fixation in hallux valgus deformity. Materials and Methods: Thirty-two patients (39 feet) underwent surgery for hallux valgus deformity. Fourteen patients (18 feet; Group A) underwent proximal first metatarsal opening wedge osteotomy fixed with low profile titanium plate ($Arthrex^{(R)}$), and 18 patients (21 feet; Group B) underwent proximal chevron osteotomy with two K-wires. Improvement in hallux valgus angle (HVA), 1, 2 intermetatarsal angle (IMA), range of motion of 1st metatarsophalangeal joint, VAS score, and the length of first metatarsal on weight-bearing radiograph were evaluated preoperatively and at final follow-up. Results: HVA improved from $36.2{\pm}6.6$ degrees to $11.7{\pm}5.1$ degrees, and 1, 2 IMA improved from $15.7{\pm}2.6$ degrees to $7.2{\pm}1.9$ degrees. VAS score improved from $7.2{\pm}1.2$ to $1.4{\pm}0.9$. There were no significant differences clinically and radiologically. Conclusion: Proximal first metatarsal opening wedge osteotomy with stable fixation using low profile plate may be an effective surgical option for correction of hallux valgus deformity.

• Journal of Korean Foot and Ankle Society
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• v.11 no.1
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• pp.28-34
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• 2007

Purpose: To evaluate the clinical and radiographical results of triple osteotomy as a treatment for adult hallux valgus with highly increased distal metatarsal articular ankle (DMAA). Materials and Methods: From October 2003 to April 2005, we retrospectively reviewed 7 hallux valgus patients (3 cases: moderate, 4 cases: severe) treated with triple osteotomy and followed-up for more than 1 year after operation. The mean follow up was 15.1 months. The hallux valgus angle (HVA), intermetatarsal angle (IMA), distal metatarsal articular angle (DMAA) and the length of 1 : 2 metatarsal bone were measured. Proximal chevron osteotomy and distal biplanar chevron osteotomy were done in 1st metatarsal bone. Akin osteotomy was added to the base of the proximal phalanx. The clinical result was assessed using the AOFAS Hallux score, tenderness on the medial eminence, ROM of 1st metatarsophalangeal joint, calluses and patient satisfaction. Results: The mean HVA and IMA was improved from $37.5^{\circ}$ and $13.4^{\circ}$ to $10.5^{\circ}$ and $6.2^{\circ}$ respectively. The mean DMAA was corrected from $34.2^{\circ}$ to $11.2^{\circ}$ and mean shortening of 1st metatarsal was 2.4 mm (0.9-5.8 mm). The mean AOFAS hallux score was improved from 66.4 to 92.5 and VAS score (pain on the medial eminence) from 4.3 points to 0.4 points. Metatarsalgia disappeared in all cases and there was no complications such as necrosis of the metatarsal head. Conclusion: Triple osteotomy for adult hallux valgus with a highly increased DMAA is effective and should be considered as a part of the treatment armamentarium.