• Journal of Korean Neurosurgical Society
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• 제37권3호
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• pp.217-222
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• 2005

Objective: To achieve optimal fit of implant, it is necessary to bend the implant during spine surgery. Bending procedure may decrease stiffness of plate especially made of titanium and stainless steel. Typically titanium suffers adverse effects including early crack propagation when it is bent. We investigate whether 6 degree bending of titanium plates would decrease the stiffness after full cyclic loading by comparing with non-bending titanium plates group. Methods: Authors experimented 40 titanium alloy plates of 57mm in length, manufactured by 5 different companies. Total 40 plates were divided into two groups (20 bent plates for experimental group and 20 non-bent plates for control group). Twenty plates of experimental group were bent to 6 degree with 3-point bending technique and verified with image analyzer. Using the electron microscope, we sought for a initial crack before and after 3-point bending. Mechanical testing by means of 6000 cyclic axial-compression loading of 35N in compression with moment arm of 35mm-1.1 Nm was conducted on each plate and followed by the electron microscopic examination to detect crack or fissure on plates. Results: The stiffness was decreased after 6000 cyclic loading, but there was no statistically significant difference in stiffness between experimental and control group. There was no evidence of change in grain structure on the electron microscopic magnification. Conclusion: The titanium cervical plates can be bent to 6 degree without any crack or weakness of plate. We also assume that minimal bending may increase the resistance to fatigue fracture in cervical flexion-extension movement.

• Journal of Korean Neurosurgical Society
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• 제38권4호
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• pp.265-268
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• 2005

Objective : With the increasing popularity of pedicle screw fixation devices for several indications, the safety and reliability of screw insertion in the small pedicle has become a major issue. Many studies have investigated the accuracy of screw placement after pedicle screw fixation using various method. The reported displacement rates have been very different. The purpose of the study is to investigate the proper placement of pedicle screw insertion in the lumbar spine on 26 consecutive patients. Methods : Between September and December 2003, 26 consecutive patients [16women and 10men] were analyzed after transpedicular screw fixation of the lumbar and lumbosacral spine. After pedicle screw fixation in this study, 2-mm slices of CT scan were performed in all patients to detect caudal and cranial deviation of screw and medial and lateral deviation. Pedcile screw placement related complication was evaluated clinically. Results : A total of 144 inserted pedicle were analyzed in 26patients, and 58pedicle screws [40.3%] were detected to be improper placement. There were 14level [9.0%] of caudal or cranial deviation and 44level [30.6%] of medial or lateral deviation to the pedicle. Extra-pedicle placement was found on 4levels [2.7%] with only lease of neurologic injury. Conclusion : Proper screw placement, though complication rate is low, is important not only for clinical symptom but also for biomechanics. Further study for screw placement related biomechanical changes is needed.

• 대한치과의사협회지
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• 제54권7호
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• pp.529-540
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• 2016

Objective: The objective of this study was to evaluate the osseointegration of narrow-diameter implant with trapezoid-shape and to evaluate the effect of coronal microthreads on trapezoid-shape narrow-diameter implant. Materials and Methods: The experimental narrow-diameter implants were classified into two groups according to absence or presence of coronal microthreads: trapezoid-shape narrow diameter implant (TN group) and trapezoid-shape narrow-diameter implant with microthreads (TNM group). They were installed alternately in bilateral mandible in three dogs. After 8 weeks, the animals were sacrificed. Resonance frequency analysis, removal torque test, and histometric analysis were performed. Results: Statistically higher implant stability quotient (ISQ) values were observed in TNM group than in TN group at the time of implant installation. However, significant ISQ values difference was not observed between groups at 8 weeks. Both groups showed significantly increased ISQ values at 8 weeks, compared to the time of implant installation. There was no significant difference between groups in removal torque test. Bone-implant contact ratio also showed no significant difference between groups in total and coronal part. Conclusion: Within the limitation of this study, it could be concluded that the trapezoid-shape design on narrow-diameter implant showed successful ossointegration, and the microthreads on coronal part did not result in significant bone-implant contact and biomechanical stability at 8 weeks.

• 한국정밀공학회지
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• 제27권5호
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• pp.92-101
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• 2010

This study evaluated the structure and quality of osteoporotic vertebral bone. To induce osteoporosis, eight rats were ovariectomized (OVX). All rats were divided into two groups (Normal group: 4, OVX group: 4). Total lumbar vertebrae for each rat were scanned by in-vivo ${\mu}CT$ at 0, 4 and 8 weeks. Morphological characteristics (BV/TV, Tb.Th, Tb.N, Tb.Sp and SMI) were calculated by in-vivo ${\mu}CT$ image analyzer. Three dimensional finite element models were analyzed to investigate bone strength of OVX and Normal groups. Moreover, the elastic modulus was quantitatively analyzed to evaluate the quality changes of osteoporotic bone. In the OVX group, BV/TV, Tb.Th and Tb.N were significantly decreased at all the lumbar over time (p<0.05). We also investigated a contrary tendency in Tb.Sp and SMI, compared to the above results in each group. A degree of alteration of mechanical characteristics in OVX group was decreased over measuring time (p<0.05). Bone quality presented by distribution of elastic modulus was improved in the Normal group more than OVX group. The findings of the present study indicated that both bone structure and quality of whole lumbar could be tracked and detected by analyzing the morphological and biomechanical characteristics of bones, based on a nondestructive method.

• 대한의용생체공학회:의공학회지
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• 제24권3호
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• pp.209-215
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• 2003

본 연구에서는 지면반발력에 저항하는 족부관절의 기구학적 특성과 운동학적 특성 사이의 관계를 고찰하는 것을 목적으로 하였다. 관절의 수동탄성모멘트와 각변위는 3대의 카메라와 지면반발력 측정기를 이용한 실험을 통하여 얻어졌다. 최소자승법을 이용하여 관절의 각변위와 모멘트의 상관 관계를 수학적으로 모델링 하였다. 관절의 운동 범위(range of motion)는 중족지절관절(metatarsophalangeal joint)을 제외하고는 5$^{\circ}$~7$^{\circ}$ 값을 보였다. 이 모델을 이용하여 지금까지 일반적인 모션 분석으로부터 측정할 수 없었던 족부관절의 기구학적 데이터를 얻을 수 있다. 더 나아가 이러한 수학적은 보행을 시뮬레이션 하는 생체 역학적 모델과 임상적 평가에도 적용 가능하다.

• Journal of Korean Dental Science
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• 제4권2호
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• pp.52-58
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• 2011

Purpose: Modifications of implant design have been related to improving initial stability. The purpose of this study was to investigate their respective effect on initial stability between two tapered implant systems (self-tapping vs. non-self-tapping) in medium density bone using three different analytic methods. Materials and Methods: Self-tapping implant (GS III$^{(R)}$; Osstem Implant Co., Busan, Korea) and non-self-tapping implant (Replace Select$^{(R)}$; Nobel Biocare, G$\H{o}$teborg, Sweden) were investigated. In Solid rigid polyurethane blocks of artificially simulated Quality 2 bone, each of the 5 implants was inserted according to the manufacturer's instructions for medium-bone drilling protocol. Evaluation of initial stability was carried out by recording the maximum insertion torque (IT) and performing the resonance frequency analysis (RFA), and the pull-out test. Results: The IT and RFA values of self-tapping implant were significantly higher than those of non self-tapping implant (P=.009 and P=.047, respectively). In the pull-out values, no significant differences were found in implants between two groups (P=.117). Within each implant system, no statistically significant correlation was found among three different outcome variables. Conclusions: These findings suggest that design characteristics of implant geometry significantly influence the initial stability in medium bone density.

• Physical Therapy Rehabilitation Science
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• 제9권1호
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• pp.36-42
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• 2020

Objective: Many caregivers often carry infants using baby carriers until they are approximately 36 months old. The purpose of this study was to compare the muscular activity of the trunk and lower leg muscles during trunk flexion-extension movements in correspondence to various wearing methods of a baby carrier blanket. Design: Cross-sectional study. Methods: Sixteen healthy adult women were to wear baby carrier blankets in five different ways in terms of direction and height, followed by flexion-extension of the trunk. Erector spinae (ES), rectus abdominis, rectus femoris (RF), biceps femoris (BF) muscle activities and triaxial acceleration of trunk were investigated. Results: The front-wearing method of the baby carrier blanket increased the muscular activity of the ES muscle, and wearing the baby carrier blanket at waist height in the same direction was significantly higher than wearing it at pelvic height (p<0.05). As the angle of flexion increased during trunk flexion-extension, the muscle activity of the ES, BF, and the RF increased. There was a greater increase in muscle activity of the ES and the BF during extension compared to flexion (p<0.05). Conclusions: If it is difficult to wear a baby carrier blanket due to lumbar pain, it is recommended to lower the wearing height of the baby carrier to the pelvic level so that the external load can be transferred to the lower extremity. In addition, it appears to be necessary to hold the baby and distribute the load onto the waist through proper body control when performing flexion-extension movements of the trunk. More objective and scientific research that includes various daily tasks and evaluation methods are needed.

• 대한의용생체공학회:의공학회지
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• 제22권6호
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• pp.543-550
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• 2001

본 연구에서는 하퇴 절단환자에서 고정형. 단축형, 다축형 인공족관절 장착시 지면반발력과 에너지 소비량을 측정하여 하퇴의지에 대한 생체역학적 평가를 하였다. 실험에는 각각 2명의 남성과 여성 하퇴 절단 환자가 3종류의 의지를 착용하고 참여하였으며. 3차원 보행분석은 7개의 기준점에 대하여 전체 입각기에 대한 지면 반발력의 체중에 대한 비율로 나타내었다. 하퇴의지 에너지 소비량은 피 실험자들이 각각 2km/h, 3km/h 그리고 가장 걷기 편한 속도로 런닝머신 위에서 보행하게 하면서 측정하였다 실험결과는 지면반발력에서 다축형 인공족관절 장착시 추진력과 후진력의 보행특성에 대하여 우위를 보이며, 고정형 인공족관절 장착시에는 보행균형과 무게중심의 이동에 대해 상대적인 우위를 보였다. 에너지 소비량은 2.3km/h 이상의 보행속도에서 단축형 인공족관절 장착시 다른 두 의지에 비해 적은량의 에너지 소비를 보였다.

• 한국운동역학회지
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• 제26권4호
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• pp.369-375
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• 2016

Objective: The purpose of this study was to investigate the possibility of injuries and the types of movement related to damage by body parts, and to prepare for prevention of injuries and development of a training program. Method: For this study, the experiment was conducted according to levels of 60 percentages (ST) and 85 percentages (MA) and 10 subjects from the Korean elite national weightlifting team were included. Furthermore, we analyzed joint moment and muscle activation pattern with three-dimensional video analysis. Ground reaction force and EMG analyses were performed to measure the factors related to injuries and motion. Results: Knee reinjuries such as anterior cruciate ligament damage caused by deterioration of the control ability for the forward movement function of the tibia based on the movement of the biceps femoris when the rectus femoris is activated with the powerful last-pull movement. In particular, athletes with previous or current injuries should perceive a careful contiguity of the ratio of the biceps femoris to the rectus femoris. This shows that athletes can exert five times greater force than the injury threshold in contrast to the inversion moment of the ankle, which is actively performed for a powerful last pull motion and is positively considered in terms of intentional motion. It is activated by excessive adduction and internal rotation moment to avoid excessive abduction and external rotation of the knee at lockout motion. It is an injury risk to muscles and ligaments, causing large adduction moment and internal rotation moment at the knee. Adduction moment in the elbow joint increased to higher than the injury threshold at ST (60% level) in the lockout phase. Hence, all athletes are indicated to be at a high risk of injury of the elbow adductor muscle. Lockout motion is similar to the "high five" posture, and repetitive training in this motion increases the likelihood of injuries because of occurrence of strong internal rotation and adduction of the shoulder. Training volume of lockout motion has to be considered when developing a training program. Conclusion: The important factors related to injury at snatch include B/R rate, muscles to activate the adduction moment and internal rotation moment at the elbow joint in the lockout phase, and muscles to activate the internal rotation moment at the shoulder joint in the lockout phase.

• Journal of Korean Neurosurgical Society
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• 제64권2호
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• pp.247-254
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• 2021

Objective : The subaxial cervical pedicle screwing technique shows powerful biomechanical properties for posterior cervical fusion. When applying a pedicle screw using the freehand technique, it is essential to analyse cervical computed tomography and plan the surgery accordingly. Normal cervical computed tomography is usually performed in the supine position, whereas during surgery, the patient lies in a prone position. This fact leads us to suppose that radiological evaluations may yield misleading results. Our study aimed to investigate whether there is any superiority between preoperative preparation on computed tomography performed in the prone position and that performed in the supine position. Methods : This study included 17 patients (132 pedicle screws) who were recently operated on with cervical vertebral computed tomography in the prone position and 17 patients (136 pedicle screws) who were operated on by conventional cervical vertebral computed tomography as the control group. The patients in both groups were compared in terms of age, gender, pathological diagnosis, screw malposition and complications. A screw malposition evaluation was made according to the Gertzbein-Robbins scale. Results : No statistically significant difference was observed between the two groups regarding age, gender and pathological diagnosis. The screw malposition rate (from 11.1% to 6.9%, p<0.05), mean malposition distance (from 2.18 mm to 1.86 mm, p <0.05), and complications statistically significantly decreased in the prone position computed tomography group. Conclusion : Preoperative surgical planning by performing cervical vertebral computed tomography in the prone position reduces screw malposition and complications. Our surgical success increased with a simple modification that can be applied by all clinicians without creating additional radiation exposure or additional costs.