• 대한기계학회논문집B
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• 제36권3호
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• pp.351-361
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• 2012

슬관절 내반슬과 외반슬의 부정정렬을 교정하는 방법 중 대표적인 수술법이 근위경골절골술이다. 개방형 쐐기 근위경골절골술(OWHTO)의 경우 근위비골 인접부의 경골외측 비골신경을 손상시킬 우려가 없고, 수술도중 교정각의 개방 정도를 임의대로 조절 변경 가능한 장점으로 최근 선호되고 있다. 그러나 술후 관상면에서의 외반 및 내반 교정은 바르게 이루어지는 반면, 시상면에서는 수술자가 의도하지 않은 경골내측고평부의 후방경사각(PSA) 변화가 발생한다는 문제점이 있다. 저자들은 이와 같은 문제의 극복을 위해 Computer Assisted Surgery를 이용한 근위경골절골술 기법을 자체적으로 개발하였고, 근위경골부의 CT 이미지 3차원 재건과 컴퓨터를 이용한 가상절골술을 수행하였다. 또한 술후에도 후방경사각(PSA)이 변화하지 않는 수술기법에 대해 제시하였다. 본 연구결과는 환자고유의 전내측피질골 경사각(ACOA)과 후방경사각(PSA)의 명확한 관계성에 대해 제시해줄 것이며 환자마다 다른 최적의 후방경사각 결정법에 대해 제시해 줄 것으로 판단된다.

• Advances in pediatric surgery
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• 제11권2호
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• pp.180-185
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• 2005

Superior mesenteric artery (SMA) syndrome is a rare disorder caused by extrinsic compression of the third portion of the duodenum by the SMA. The operative treatment of choice is bypassing the obstructed duodenal segment by duodenojejunostomy. We report one case of SMA syndrome treated by laparoscopic duodenojejunostomy and followed up by 3D-reconstructive CT scan. A fifteen-year-old boy with intermittent vomiting and weight loss was admitted. Ultrasonography showed narrowing of the distance between the SMA and aorta. Hypotonic duodenography showed dilatation of duodenal third portion and barium stasis. On 3Dreconstructive CT scan, the angle between SMA and aorta was $37^{\circ}$. The postoperative course was uneventful. Three months later, he had gained 3 kg of weight and the angle between SMA and aorta increased to $38-39^{\circ}$ on 3D reconstructive CT scan. Laparoscopic duodenojejunostomy for bypassing the obstructive duodenum in SMA syndrome is a feasible and safe method.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제32권1호
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• pp.37-42
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• 2010

Purpose: The mental foramen (MF) is an important anatomical structure during local anesthesia and surgical procedures in terms of achieving effective mental nerve blocks and avoiding injuries to the neurovascular bundles. Thus, understanding the anatomic features of the mandibular canal and accessory mental foramen in Korean could contribute to the surgical anatomic assessment. This study was to elucidate frequency, position and course of AMF (accessory mental foramen) in Korean using 3D cone beam computed tomography. Materials and Methods: The CBCT (Conbeam computed tomography) DICOM data (Alphard, Asahi, Japan) from 540 patients in korean were analyzed. We investigated images of 3D CBCT using Ondemand (CyberMed, Korea) software program on the incidence and anatomical characteristics of accessory foramen. Results: The accessory mental foramina were found in 17 patients. Accessory mental foramina exist predominantly in the apical area of the second premolar and posteroinferior area of the mental foramen. The accessory branches of the mandibular canal showed common characteristics in the course of gently sloping posterosuperior direction in the buccal surface area. The size of most AMF was obviously smaller than that of MF. Conclusion: We could identify frequency, position and course of AMF (accessory mental foramen) by the anatomical study of the accessory mental foramen using 3D cone beam CT in Korean.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 추계학술대회
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• pp.34-38
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• 1995

Using a 3-D finite element method (FEM), the biomechanical characteristics of a threaded truncated acetabular component and a porous coated hemispherical acetabular component were studied. The Von-Mises stress/strain patterns in the acetabulum reconstructed with these two different types of cementless acetabular cups were investigated. The geometry and dimensions of human hemi-pelvis used in the present shape modeling for finite element analysis were scanned with a 3-D laser scanner(TDS-9000, Cyberware, USA). The scanned data was numerically handled with a shape modelling software 'Pro-Engineer'. Using 19836, 16853 tetrahedral elements, respectively, the stress and displacement field of the acetabulum reconstructed with the two different types of the acetabular components were computed. While the hemi-sphere component was found to show a relatively similar stress/strain patterns to those in the normal hip, the results with the threaded cup showed a considerably different patterns from those in the normal condition. Several regions in cancellous bone near the threads and the edge of the truncated cup was found to be overstressed, especially in the superior-lateral part of the acetabulum. It was postulated that the excessive reaming-out of subchondral bone layer when the truncated cup was used can cause the presence of these overstressed regions of cancellous bone. This theoretical prediction for the implanted acetabulum appeared to consistent with the pathological observation of proximal/medial migration of the threaded truncated acetabular prostheses in the previous publications.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제33권4호
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• pp.337-345
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• 2011

Purpose: The purpose of this study was to define the relation of the degree of menton deviation and 3-D CT (computerized tomography) measurements of the glenoid fossa and the mandible, which are considered to have an influence on menton deviation. Methods: The CT images were obtained in 60 adults and these were transmitted to a computer and reconstructed using computer software. According to the degree of the menton deviation, which was measured on the posteroanterior cephalogram, the subjects were divided into the menton deviated group (30 adults) and the symmetry group (30 adults). A total of 11 measurements that might have an effect on menton deviation were determined and these were measured in the right and left sides using the function of 3-D measurement in the computer program. The 11 measurements consist of 6 measurements in the glenoid fossa (vertical position of the glenoid fossa and articular eminence, the sagittal position of the glenoid fossa and articular eminence, the depth of the glenoid fossa, and the anterior angle of the glenoid fossa), and 5 measurements in the mandible (ramus length, frontal ramal inclination, lateral ramal inclination, body length, body height). Results: The comparison of the differences between the menton deviated and symmetry groups and correlation analysis on the degree of menton deviation were carried out. The results of comparison of the right and the left difference between the menton deviated and symmetry groups showed that the vertical position and depth of the glenoid fossa were significantly increased in the menton deviated group. Conclusion: The results of the present study show that consideration of the shape and position of the glenoid fossa is necessary for making the diagnosis and administering proper treatment in facial asymmetry patients and especially growing patients.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제31권2호
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• pp.116-126
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• 2009

The use of short implants has been accepted risky from biomechanical point of view. However, short implants appear to be a long term viable solution according to recent clinical reports. The purpose of this study was to investigate the effect of different diameter and length of implant size to the different type of bone on the load distribution pattern. Stress analysis was performed using 3-dimensional finite element analysis(3D-FEA). A three-dimensional linear elastic model was generated. All implants modeled were of the various diameter(${\phi}4.0$, 4.5, 5.0 and 6.0 mm) and varied in length, at 7.0, 8.5 and 10.0 mm. Each implant was modeled with a titanium abutment screw and abutment. The implants were seated in a supporting D2 and D4 bone structure consisting of cortical and cancellous bone. An amount of 100 N occlusal load of vertical and $30^{\circ}$ angle to axis of implant and to buccolingual plane were applied. As a result, the maximum equivalent stress of D2 and D4 bones has been concentrated upper region of cortical bone. As the width of implant is increased, the equivalent stress is decreased in cancellous bone and stress was more homogeneously distributed along the implants in all types of bone. The short implant of diameter 5.0mm, 6.0mm showed effective stress distribution in D2 and D4 bone. The oblique force of 100N generated more concentrated stress on the D2 cortical bone. Within the limitations of this study, the use of short implant may offer a predictable treatment method in the vertically restricted sites.

• Restorative Dentistry and Endodontics
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• 제36권2호
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• pp.98-107
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• 2011

치아우식증은 현대 사회에서 여전히 유병률이 높으며, 치과 분야의 주요 상병으로 자리잡고 있다. 치아우식증에 대한 연구에 매우 다양한 방법들이 동원되고 있으나, 최근 미세전산화 단층촬영은 비파괴적인 3차원 분석 기술로서 인기를 얻어 왔으며, 기존의 방법들에 비해 다양한 장점들을 가지고 있다. 미세전산화 단층촬영술은 X선원의 종류에 따라, 모노크로매틱 혹은 폴리크로매틱으로 나뉘어지고, 전자의 경우 몇몇 장점에도 불구하고, 고가의 장비를 요구하므로 후자가 훨씬 널리 사용된다. 투과방사선량의 감소에 따라 결정되는 미네랄 밀도의 차이가 기본 원리이며, 보다 좋은 이미지와 재현 가능한 측정을 위해서는 장비의 교정과 이미지 보정 작업등이 요구된다. 또한, 미세전산화 단층촬영술을 이용하면, 치아우식 병소의 3차원적인 재건이 가능하며, 병소의 내부 구조를 가시화할 수 있다. 최근 컴퓨터 기술의 발전과 더불어 다양한 응용이 시도되고 있는데, 자동화된 충치의 정량적 분석 알고리즘 등이 그 예에 해당된다.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제30권1호
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• pp.60-71
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• 2008

The objective of this study is to evaluate the stress distribution according to the thread design and the marginal bone loss of a single unit dental implant under the axial and offset-axial loading by three dimensional finite element analysis. The implants used had the diameter of 5mm and 4mm with 13mm in length and prosthesis with a conical type which is 6mm in height and 12mm in diameter. The thread designs were triangular, square and buttress. In the three dimensional finite element model with $15\times15\times20mm$ hexahedron and 2mm cortical thickness, implants were placed with crown to root ratio 7:12, 10:9, 13:6 and 16:3. And additionally the axial force of 100N were applied into 0mm, 2mm and 4mm away from the center of the implants. The results were as follows 1. The maximum von-Mises stress in cortical bone was concentrated to cervical area of implant, and in cancellous bone, apical portion. 2. Comparing the von-Mises stresses in cortical bone of 2mm and 4mm offset loading with central axial loading, it were increased to 3 and 5 times in diameter 4mm implant, and 2 and 4 times, in diameter 5mm implant. 3. The square threads were more effective than the triangular and butress as the longer diameter, the offset loading, and the worse crown to root ratio. 4. The von-Mises stresses were relatively stable until crown to root ratio 13:6, but it was suddenly increased at 16:3. From the results of this study, minimum requirement of crown to root ratio of implant is 2:1, and in the respect of crown to root ratio, diameter and offset loading, square threads are more effective than triangular and buttress threads.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제33권5호
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• pp.413-419
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• 2011

Purpose: Reposition of the maxilla is a common technique for correction of midfacial deformities. To achieve the goal of the surgery, the maxilla should be repositioned based on the precisely planned position during surgery. The internal reference points (IRPs) and the external reference points (ERPs) are usually used to determine vertical dimension of maxilla, which is an important factor for confirming maxillary position. However, the IRPs are known to be inaccurate in determining the vertical dimension. In this study, we investigated the correlation of positional change of the modified IRPs with repositioned maxilla. Methods: The study group consisted of 26 patients with dentofacial deformities. For the simulation of the surgery, patient maxillary CT data and 3-D virtual surgery programs (V-$Works^{(R)}$ and V-$Surgery^{(R)}$) were used. IRPs of this study were set on both the lateral wall of piriform aperture, inferior margin of both infraorbital foramen, and the labial surfaces of the canine and first molar. The distance from the point on lateral wall of the piriform aperture to the point on the buccal surface of the canine was defined as IRP-C, and the distance from the point on the inferior margin of the infraorbital foramen to the point on the buccal surface of the $1^{st}$ molar was defined as IRP-M. After the virtual simulation of Le Fort I osteotomy, the changes in IRP-C and IRP-M were compared with the maxillary movement. All measures were analyzed statistically. Results: With respect to vertical movements, the IRP-C (approximately 98%) and the IRP-M (approximately 96%) represented the movement of the canine and the $1^{st}$ molar. Regarding rotating movement, the IRPs changed according to the movement of the canine and the $1^{st}$ molar. In particular, the IRP-C was changed in accordance with the canine. Conclusion: IRPs could be good indicators for predicting vertical movements of the maxilla during surgery.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제27권6호
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• pp.552-558
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• 2005

Orthognathic surgery changes patient's mandibular position and environment of related anatomic structures. Many clinicians were interested in these changes and studied about this problem. However, most of them were based on two dimensional cephalogram. According to the development of image and computer system, it would be possible that the airway change is analyzed with three dimensional CT. So we tried to measure the volumetric change of airway and analyzed the relationship between the airway structure and volumetric change. Nineteen patients who experienced orthognathic surgery due to mandibular prognathism were analyzed with 3D CT data (preoperative and postoperative 6 months) and 2D lateral cephalometry. Volumetric change was measured and 3 dimensional change of related structure was assessed with simulation program ($V-works^{(R)}$, 4.0 Cybermed, Korea). Ten patients showed the decrease of airway volume change and nine showed the increase of airway volume change. Volumetric change was determined by dimensional change of mandible and hyoid bone. The dimensional positions of mandible and hyoid bone were the key factor for determining the airway change after surgery. Airway change is also predictable with the dimensional change of mandible and hyoid bone.