A Case Study for the Reconstruction of Crime Scene by Computer Simulation / 대한법의학회지

Especially in design of automobile, there are many professional softwares based finite element or multi-body like Madymo, Pam-Crash, Ansys. These program have been released almost every car maker and university. Also in accident reconstruction fields, there are some softwares like PC-Crash, HVE was developed. Unfortunately these programs for accident reconstruction are so general and its input data are so limited, it is very difficult or even impossible to analyze some special cases. In this study, we reconstruct two crime scenes using Madymo program. Although this program was developed for design of car, we apply to crime scene reconstruction. First case is regarding traffic accident. A car was fell under 5m from the road and turn over and then move about 40m. Finally the driver eject from the car. Second case is regarding suicide by hanging. When the police investigate the crime scene at first time, they assume that this crime is a murder case but we carried out autopsy and investigated the crime scene again and analyzed by computer simulation and finally find out this crime is suicide case not murder.

A Case Study for the Spine Fracture of a Pedestrian Impacted by SUV / 대한법의학회지

The civilization has given us a great comfort and convenience but also it has been threatening our life at the same time. Among these causes of death the traffic accident is the most dangerous thing to threat our life in recent years. According to the report of traffic accident in 2003, the pedestrian to car accident is almost 50% of all types of traffic accident and this percentage is very high level compare to other countries. So this is why we have to focus on this field of accident. This case is as follows, when a pedestrian was riding a bicycle and crossing the road, a taxi hit the bicycle with left outside mirror. The impact was not so severe, the pedestrian stood up by himself. Unfortunately he was impacted once again by a SUV which was following behind the taxi. The evidence were the SUV, clothing and victim. A complete autopsy was performed on the victim. The skull was slightly fractured with line shape and showed hypodermal bleeding under the head skin. The thoracic vertebrae of No. 11-12 was fractured. The cause of death was apparently head trauma and fracture of thoracic vertebrae. But we could not explain why the thoracic vertebrae was fractured without damage of internal organs in chest and abdomen. To analyze this case, we used a dynamic analysis program Madymo V6.2 and applied the Hybrid-III human model. Finally we could prove that if the pedestrian stand against the SUV, the bending moment in spine was raised suddenly at the beginning of impact. At this moment the leg was started to be move to the backward of pedestrian but the upper part of body could not move because of inertia. This bending moment make the spine hyper-extension and this level of moment can fracture the spine enough in low speed of SUV. In this study we analysis the car to pedestrian accident with engineering view and introduce the detail analysis method to reconstruct the accident involving the human trauma.

A Case Study of Stress Analysis for Compression Tank Using Finite Element Method / 대한법의학회지

A compression tank is normally made like round column shape to the middle part and plate shape in both sides. These kinds of tanks are usually designed to resist inner pressure but if the inner pressure is too high the tank will be exploded and some pieces can severe damage to human. If the shape of corner is about 90 degrees the stress will be very high at corner. So this kind of tank have been manufactured as smooth round corner even though its cost. Although smooth round type of corner, there is always some area of high level of stress and it is very difficult to calculate exactly because of complicate shape of corner. In this case study, here we introduce the FEM method to calculate the exact solution and compare the result with engineering fomula. The edge of tank was modeled like actual edge of tank and the critical inner pressure is 2.5 kg/cm2. This result is proven by engineering formula and we knew that this FEM method would be trustable to calculate a plenty of delicate problem whether the structures have original defect or not.

A Case Study for Runover Accident by Automobile / 대한법의학회지

When a pedestrian was hit by bumper and runover by tire of car, tire impression marks or damaged skin and fractured born marks were remained on dead body. Namely, to obtain the best result for analysis of traffic accident involved damaged human body, it must be considered both the analysis of autopsy and the analysis of traffic accident reconstruction. As these kinds of cases were managed to solve when one part of analysis was not for sure but some cases were missing because we have any regulated system to comply the results of both parts. This case is as follows, As soon as the child run across the street, the automobile was passing by and he went into between front tire and read tire and he was runover by rear tire and he died. Unfortunately this case was treated by police as the child was fault. However we studied this case both the analysis of tire impression and damaged mark of dead body and the aspect of traffic accident reconstruction. Finally, we found out the fact that the car hit the child and runover front and rear tire of the car. This case is valuable because we could find the truth that the child was not fault. Like this manner, here we would like to suggest a system or any kinds of organization should be considered so that the two forensic parts can be analyze together.

Micromotion of Cementless Straight and Curved Femoral Stems by Three Dimensional FEM analysis / 대한정형외과학회잡지

PURPOSE: The purpose of this study was to analyze the relative micromotions between the straight and the curved stems during the immediate postoperative stage of noncemented total hip replacement which load simulating the single leg stance and stair climbing. MATERIALS AND METHODS: The authors developed 3-dimensional numerical finite element models implanted with the straight stem, which was composed of a total of 1,170 elements of 8 nodes, and which had a curved stem composed of a total of 885 elements of 8 nodes, and then analyzed the relative micromotions of the straight and curved stems. RESULTS: In the single leg stance, the curved stem was more stable especially in terms of its rotational stability. Rotational displacement accounted for over 90% of the total micromotion in both types of stem and this was highest for the proximal medial portion of the stem, but markedly less distally. Stair climbing produced more micromotion than the single leg stance regardless of the stem configuration. CONCLUSION: It is recommended that surgeons do not allow patient weight bearing until bony ingrowth has been achieved. In the future more attention should be placed upon increasing the initial rotational stability of the two types of femoral stem to prevent loosening by excessive micromotion.

Biomechanical Analysis of Proximal Fitting-Distal Filling Stem and Proximal Fitting- Distal Tapered Stem in Cementless Hip Prosthesis: A 3 Dimensional Finite Element Study / 대한정형외과학회잡지

PURPOSE: This study was undertaken to compare the initial micromotion and stress shielding of a "fit and fill" stem to a "proximal fitting and distal tapered" stem in the early postoperative period using the load simulating single leg stance and stair climbing. MATERIALS AND METHODS: Using the data from 3-D human CT scan, authors developed two types of 3-dimensional finite element total hip replacement model of proximal femur, which were inserted with a "fit and fill" stem and a "proximal fitting and distal tapered" stem. The constructions of stems were based on the OmnifitTM stem (about 13,000 element & 20,000 nodes). We compared micromotion, maximal principal stress and strain energy of each stems. RESULTS: The results indicate that micromotion in a fit and fill stem were slightly lower than that of a tapered stem, especially in stair climbing over that in the single leg stance. The maximum principal stress on the cortex of femur was slightly higher in a tapered stem in the case of single leg stance, and 2 times higher in the case of stair climbing. Strain energy also was much higher in a tapered stem in both single leg stance and stair climbing gait. CONCLUSION: These findings indicate that a tapered stem design could provide more favorable biomechanical benefits rather than a fit & fill stem after cementless total hip replacement.