• 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.

• 폴리머
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• 제34권1호
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• pp.8-13
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• 2010

발포체의 물성은 발포체의 밀도, 사용된 폴리머의 기계적 물성과 열린 셀의 함량, 셀 크기, 셀 크기 분포, 셀 형태, 스킨층의 두께 등을 포함하는 셀 구조에 의존하며, 이러한 발포체의 밀도는 사용된 폴리머의 종류와 가교제의 농도 그리고 가공 기술 및 가공 조건과 같은 다양한 원료 물질과 가교 조건에 영향을 받는다. 본 연구에서는 폴리에스터 폴리올, MDI, 아민계 촉매, 틴계 촉매, 실리콘 유화제, 물을 기본 폴리우레탄 발포체의 조성으로 설정하였으며, 발포체에 있어서 stiff-chain 요소인 사슬 연장제의 첨가에 의하여 가교 밀도를 증가시켰다. 또한, 폴리우레탄 발포체의 기계적 물성을 높이기 위해 무기 충전제로 입자 크기와 $SiO_2$ 함량이 다른 실리카와 탈크 각각 2종류를 사용하였다. 발포체의 제조시 사슬 연장제와 무기 충전제의 종류와 함량비를 달리하면서 모듈러스, 인장 강도, 압축 강도, 경도의 물성 변화를 알아보았고, 전자현미경을 통해 셀의 크기 변화와 무기 충전제의 분포도를 관찰하였다.

• 제어로봇시스템학회논문지
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• 제11권7호
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• pp.578-586
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• 2005

Air mattress is now used widely to prevent the pressure ulcer by reducing the localized pressure peaks. The pressure control method based on the anthrophometric model of an air-cell mattress developed in this study is presented. The air-cell mattress has 18 cylindrical air cells made of porous material allowing air leakage. Even though the air leakage can contribute to reducing the development of pressure ulcer by lowering the pressure peak, temperature and humidity, the air pressure changes with time and the desired air-cell pressure has to be determined as an optimal value for each user. To select the desired air-cell pressure, we first divide the parts of the body into four sections such as head, trunk, hip, and leg. Then, the pressure of each section grouped with air-cells is calculated from the weight of each part estimated from the individual height and body weight. Air supply system for the air-cell mattress is implemented by using four electronic solenoid valves and an air compressor, and it is driven by a real-time microcontroller. We experimented with five subjects of the contact pressure on skin. The experimental results show that the proposed air-cell mattress is effective for the prevention of the pressure ulcer.

• 한국정밀공학회지
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• 제24권7호
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• pp.126-132
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• 2007

Pressure-induced decubitus is a serious disease among the elderly people. Interface pressure occluding vascular perfusion is known to be a cause of decubitus. Therefore, it is essential to quantify the relationship between vascular perfusion and interface pressure among the elderly people to understand more about decubitus. Nine healthy elderly people (57.8$\pm$ 5.6 years, 63.3$\pm$ 7.0kg, 1.68$\pm$ 0.05m) were participated. Three healthy young people (31.7$\pm$ 3.2 years, 74.7$\pm$ 8.4kg, 1.75$\pm$ 0.04m) were also examined to be compared with the elderly group. Capillary vascular perfusion on the ischial tuberosity was recorded in the sitting posture as pressures were applied from 15mmHg to 135mmHg. The average interface pressure to occlude vascular perfusion (the average occlusion pressure) under the ischial tuberosity was 115.7mmHg in the elderly group. This value was not significantly different from the average occlusion pressure of the young group. Obesity effect on the occlusion pressure was investigated among the elderly group. The result was not significantly different between the obesity and the normal group in this study. This is a preliminary study to unveil the complicated cause of pressure-induced decubitus associated with occlusion of vascular perfusion. More subjects are required for the future study.

• 한국정밀공학회지
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• 제24권8호통권197호
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• pp.130-137
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• 2007

The optimized prosthetic mass distribution was a controversial problem in the previous studies because they are not supported by empirical evidence. The purpose of the present study was to evaluate the effect of prosthetic mass properties by modeling musculoskeletal system, based on the gait analysis data from two above-knee amputees. The joint torque at hip joint was calculated using inverse dynamic analysis as the mass was changed in knee and foot prosthetic components with the same joint kinematics. The results showed that the peak flexion and abduction torque at the hip joint were 5 Nm and 15 Nm when the mass of the knee component was increased, greater than the peak flexion and abduction torque of the control group at the hip joint, respectively. On the other hand, when the mass of the foot component was increased, the peak flexion and abduction torque at the hip joint were 20 Nm and 15 Nm, greater than the peak flexion and abduction torque of the control, respectively. The hip flexion torque was 4.71-fold greater and 7.92-fold greater than the hip abduction torque for the knee mass increase and the foot mass increase on the average, respectively. Therefore, we could conclude that the effect of foot mass increase was more sensitive than that of knee mass increase for the hip flexion torque. On the contrary, the mass properties of the knee and foot components were not sensitive for the hip abduction torque. In addition, optimized prosthetic mass and appropriate mass distributions were needed to promote efficiency of rehabilitation therapy with consideration of musculoskeletal systems of amputees.

• 한국정밀공학회지
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• 제28권6호
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• pp.651-656
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• 2011

Although prosthetic training was received, most of amputees mainly depend on visual feedback to use prostheses, not on cutaneous and proprioceptive sensibility. Our objective of this study was to determine if there are changes in the somatosensory sensibility of amputees compared to non-amputees using multi-channel vibration stimulation system. One transradial amputees and ten non-amputees were involved. To investigate changes of residual somatosensory sensibility at stump, we set up custom-made vibration stimulation system including eight actuators (4 medial and 4 lateral) and GUI-based acquisition system. The results showed that there was similar pattern of subjective response at most of channels among group as stimulation increases. However, amputees' subjective response at channel 8 for 238Hz vibration was more sensitive than that of healthy persons. With respect to channels, response at channel 4 (medial) corresponding region to flexor carpi ulnaris for transradial amputees was most sensitive than other channels. In addition, sensitivity of four medial channels was on average about 0.5 scale than that of four lateral channels. Somatosensory sensibility was amputee, women, and men in sensibility order.

• 한국정밀공학회지
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• 제30권7호
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• pp.769-776
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• 2013

The dynamic compliance characteristics of a prosthetic foot midgait are very important for natural performance in an amputee's gait and should be in a range that provides natural, stable walking. In this study, finite element analysis (FEA) and classical laminate theory were used to examine the mechanical characteristics of a carbon-epoxy composite laminate prosthetic foot as a function of variation in the lamination composition. From this analysis, an FEM model of a prosthetic keel, made from the composite material, was developed. The lamination composition of the keel was designed for improved stiffness. The prototype product was fabricated using an autoclave. Vertical loading response tests were performed to verify the simulation model. The results of the experiments were similar to those from simulations below the loading level of the gait, suggesting use of the proposed simulation model for prosthetic keel design.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 춘계학술대회
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• pp.27-33
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• 1995

A time-dependent large deformation fracture theory is developed for application to soft biological tissues. The theory uses the quasilinear viscoelastic theory of Fung, and particularizes it to constitutive assumptions on polyvinyl-chloride (PVC) (Part I) and cartilage (Part II). This constitutive theory is used in a general viscoelastic theory by Christensen and Naghdi and an energy balance to develop an expression for the fracture toughness of the materials. Experimental methods are developed for measuring the required constitutive parameters and fracture data for the materials. Elastic stress and reduced relaxation functions were determined using tensile and shear tests at high loading rates with rise times of 25-30 msec, and test times of 150 sec. The developed method was validated, using an engineering material, PVC to separate the error in the testing method from the inherent variation of the biological tissues. It was found that the the proposed constitutive modeling can predict the nonlinear stress-strain and the time-dependent behavior of the material. As an approximation method, a pseudo-elastic theory using the J-integral concept, assuming that the material is a time-independent large deformation elastic material, was also developed and compared with the time-dependent fracture theory. For PVC. the predicted fracture toughness is $1.2{\pm}0.41$ and $1.5{\pm}0.23\;kN/m$ for the time-dependent theory and the pseudo-elastic theory, respectively. The methods should be of value in quantifying fracture properties of soft biological tissues. In Part II, an application of the developed method to a biological soft tissue was made by using bovine humeral articular cartilage.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 춘계학술대회
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• pp.19-22
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• 1995

A biomechanical study was made to demonstrate the superior mechanical performance of the newly designed Miniplate staple to the conventional Coventry staple in high tibial osteotomy(HTO). Using twenty fresh porcine tibiae, the fixational strengh of the two different types of staple in HTO was compared. To minimize the error due to the specimen-to-specimen individuality, the bone mineral density of the tibiae was measured with a bone densitometry (Dual photon absorptionometer, Luner, USA) and those with $0.8\;{\sim}\;1.2\;gm/cm^2$ at the proximal tibia was used in the biomechanical test. Testing was performed on a material testing system (Autogram ET-5, Shimatzu, Japan) with aid of a commercial data processor (IBM 80386/ ASYST). Using two differant loading modes, 'pull-out' and 'push-out', the maximum resistant force required to release the staple from the substrate bone was recorded. In the pull-out test, ten non-osteotomized specimens were used and the staple was pullout by subjecting an axial tension on the head of the staple inserted. While in the pull-out test where ten tibiae osteotomized in the usual way of HTO were used, the staple was not directly loaded. In this testing, as a mimic condition of the natural knee, the distal part of the specimen tibia was pushed horizontally in order for the staple to be pulled out while the proximal tibia was fixed. The pull-out strength of Coventry staple and miniplate staple were found to be $27.88\;{\pm}\;5.12\;kgf$ and $182.47\;{\pm}\;32.75\;kgf$, respectively. The push-out strength of Coventry staple and miniplate staple were $18.40\;{\pm}\;4.47\;kgf$ and $119.95\;{\pm}\;19.06\;kgf$, respectively. The result revealed that miniplate staple had the pull-out/ push-out strength at least fivetimes higher than Coventry staple. Based on the measured data, it was believed that the newly designed miniplate staple could provide much better postoperative fixation in HTO. The postoerative application of long leg casting may not be needed after HTO surgery.

• 재활복지공학회논문지
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• 제7권1호
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• pp.13-19
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• 2013

본 연구는 휠체어 사이클 경사로 주행 시 척수 손상으로 인한 하지마비 장애인의 상체의 근전도 특성을 평가하고자 하였다. 이를 위하여 척수손상 장애인 3명을 대상으로 $0^{\circ}$, $3^{\circ}$, $6^{\circ}$의 경사로에서 휠체어 사이클 주행을 하도록 하였으며, 이때 이두근, 삼두근, 전 삼각근, 상승모근, 광배근, 복직근의 근 활성 최대값과 수축 시간, 수축 개시 종료 시기를 측정 및 분석하였다. 본 연구 결과 휠체어 사이클의 경사로 주행 시 수축 시간과 근 수축 종료시간이 경사도가 증가함에 따라 유의하게 길어지고 지연됐으며, 광배근의 최대 근 활성도는 평지 주행보다 유의하게 증가하였다 (p<0.05). 이와 같은 결과는 휠체어 사이클의 경사로 주행 시 광배근의 과도한 사용을 의미한다.