We intended to evaluate the Young's modulus of trabecular bone and apparent density from Computed Tomography(CT) and Spherical Indentation test and to quantify relation ship between them. The distal femurs(31 age, male, left and right) were prepared for exprimentatin and were embedded with repect to anatomical orientation. Then the specimens were scnned at 1 mm intervals on GE9800 CT scanner and the Hounsfield Units(HU, or CT number) were extracted from each CT image. After scanning, the bones were sectioned with diamond saw, producing 8 mm cubes of trabecular bone(72 eachs) from the metaphyseal region of both distal femur. The cubes were mechanically tested in inferior-superior(IS), anteriorposterior(AP), and medial-lateral(ML) direction with custom-made device, Spherical Indentatin Tester. After testing, the real apparent density of specimens were measured. The results of this study showed that the IS modulus was singificantly greater than both the AP and ML modulus and the AP modulus was also greater than ML modulus significantly(p<0.01). A linear relation ship between HU and real apparent density was found to be significant(R2=0.68) and significant power relationship between the apparent density and the tangent moduli(either by CT or physical measures) was also found.
Diamond ; Elastic Modulus* ; Femur ; Humans* ; Male ; Ships

Many kinds of lumbar diseases cause lumbar segmental instability and/or limitation of motion. But, there is no reliable method for measuring accurate trunk motion. In order to measure relative trunk motion respect to the pelvis in vitro, external linkage type of spine motion analyzer was developed. Special programs for calculation of the relative angular motion and graphical display were also developed. The developed device was tested to compare spine motion pattern between 15 normal volunteers and 18 lumbar fusion patients in flexion, extension, lateral bending and axial rotation. It was rather simple and reliable method for spine motion analysis. And it was possible to measure not only angular displacement but also angular velocity and angular acceleration. There were more coupling motions in lateral bending and axial rotation than in flexion and extension. Compared to the normal subjects, patients showed different angular motion, especially in the angular acceleration. Optimal trajectory of the trunk motion derived from mathematical model in flexion and extension matched well with measurement for normal subjects.
Acceleration ; Healthy Volunteers ; Humans ; Models, Theoretical ; Pelvis ; Spine*

The wear debris of ultra-high molecular weight polyethylene (UHMWPE) used as a bearing material in total joint arthroplasty evokes a serious adverse biological reaction (osteolysis). In this study, therefore, the wear resistance of UHMWPE is enhanced by attaching a hydrophilic graft on the UHMWPE surface and by improving surface hardness without deteriorating the mechanical properties, which may result in the formation of lubrication film and the increased resistance to penetration, scratching or deformation during articulation. This was done by ion-implantation technique. The results showed that the wettability and the surface hardness of the modified UHMWPE by the above treatments increased due to the increased cross-linking density and hydrophilic graft attachment on the surface. The wear test was performed by a wear testing machine of pin-on-disk type. The modified UHMWPE revealed about 30~50% less volumetric wear than the control specimen. It was also shown that the volumetric wear depended not only on the optimal treatment condition but on the applied load and the sliding speed.
Arthroplasty ; Hardness ; Joints ; Lubrication ; Molecular Weight* ; Osteolysis ; Polyethylene* ; Transplants ; Wettability

As one of many cell-many cell-based cartilage repairing methods, transplantation of chondrocyte-embedded-collagen gels in cartilage defect was performed for more satisfactory regeneration of cartilage. The authors performed this study to investigate whether the TGF-beta1 treatment of chondrocytes can do some additional synergistic effect on the transplantation of chondrocyte-embedded-collagen gels for crtilage repair. Chondrocytes were isolated from the articular cartilage of newborn Sprague-Dawley rats. Chondrocytes cultured for 10 days in monolayer were embedded in the 0.45% type I collagen gel. Full-thickness cartilage defect was made in the patellar groove of adult Sprague-Dawley rats. Chondrocytes culdefect was made in the patellar groove of adult Sprague-Dawley rats. The cartilage defects were treated with the following methods in a total of 200 animals, which were assigned to 5 different groups of 40 rats. In the control group, the deffect was left without any treatment, in group I, the defect was filled with collagen gel only, in group II, with collagen gel coontaining 10 ng/ml concentration of TGF-beta1, in group III, with collagen gel containing chondrocytes, and in group IV, with collagen gel containing chondrocytes and TGF-beta1. At 1, 2, 4, 8, 12 weeks after the operation, eight rats of each group were sacrificed, and their distal femurs were harvested for the histologic and biomechanical tests. The section s were stained with hematoxilin and eosin. Alcian-blue, and Safranin-O. Regenerated cartilage was analyzed by the semiquantitative histological grading system. Point indentation test was performed as a biomechanical evaluation, and the stiffness was calculated. The results of the histological grading system revealed that the scores gradually increased with time in all groups, and the scores of group III and IV were higher than those of control, group I and II. The biomechanical study showed that the stiffness gradually increased to reach a plateau level in each group. In control, group I and II, the stiffness increased up to the eighth week and remained around the increased level at the twelfth week, and did not show any statistically significant difference between the groups. In group III and IV, the stiffness was higher than in control group, and increased markedly at the fourth week and the increased level was maintained onwards. The results of this study showed that the transplantation of chondrocyte-embedded-collagen gels enhanced the healing process, and the treatment of TGF-beta1 demonstrated at least partially significant improvement.
Adult ; Animals ; Cartilage ; Cartilage, Articular* ; Chondrocytes ; Collagen ; Collagen Type I ; Eosine Yellowish-(YS) ; Femur ; Gels ; Humans ; Infant, Newborn ; Rats* ; Rats, Sprague-Dawley ; Regeneration ; Transforming Growth Factor beta1

Homogenization technique is employed to investigate the series of stress analyses of mandible for three different types of dental implants. This technique helps to make proper material model of bone and analyze such a non homogeneous structure at the level of individual microstructural unit. The stress analyses with homogenization technique show much higher stress level in the sponge bone, compared to those of conventional FEM. It also manifested that even a minor lateral force results in crucial stresses in the dental implant system and that the macroscale model should take the shape and size after real mandible to produce reasonable solution in the analyses of dental implant systems. The shapes of dental implants simulated in this study are rectangularcross-sectioned type, hemi-sphere rooted type, and wedge type implant. The stress states of mandible with hemisphere rooted type implant and wedge type implant show similar levels, while those with sectioned rectangular implant results in higher stresses. It is suggested that the distance between the implant tip and cortical bone be kept far enough to prevent stress concentrations in the mandible.
Dental Implants ; Mandible ; Porifera

PURPOSE: A compression plate fixation was generally used in the fracture of a femoral diaphysis but it produced the stress shielding problem which resulted in a decrease of bone mass and impaired mechanical properties. This study was designed to compare with the stiffnesses of three different internal fixation types ; fixation with only plate, with only cross-pins, and with both a plate and cross-pins. MATERIALS AND METHODS: To compare the stress distribution and stiffness of three types of fixation devices, the device-bone system are analyzed under axial compression(70Kg) and 3-point bending(500Nmm) in planes using the 2-D finite element method(ABAQUS 5.8). Also the stiffness of each device was evaluated at seven different time points during fracture healing by increasing Young's modulus of callus. RESULTS: The plate fixation model had the highest stress distribution and occurred the stress concentration in the cortex beneath the plate. During the healing of bone fracture, the fixation with cross-pins relatively had a higher compression and bending stiffness. The fixation with only cross-pins was as stiff as that with an only plate in bending but less stiff than in compression. CONCLUSION: The internal fixation added to cross-pins may decrease the stress shielding problems due to dispersing the stress concentration and also improve the stiffness of a device-bone system.
Bony Callus ; Diaphyses ; Elastic Modulus ; Finite Element Analysis ; Fracture Healing ; Fractures, Bone

The mechanical stiffness of Unilateral-Ring Hybrid External Fixation(URHEF) was analyzed and compared with conventional Ilizarov circular external fixation system and unilateral fixation with DynaExtor(R). Our URHEF is basically a unilateral external fixation system which affords easier incorporation and removal of the Ilizarov rings(200mm in diameter) coupled with connecting clamps at anytime, if needed. It allows controlled axial micromotion in due time. For mechanical test, URHEF system was constructed using a DynaExtor(R) fixed with two or three half pins(6 mm in diameter) attached with two proximal and distal Ilizarov rings fixed with an olive pin and a half pin on each ring. Unilateral fixation system was constructed with a DynaExtor(R) fixed with 2 or 3 half pins. Ring fixation system was constructed with four Ilizarov rings(140mm in diameter). Ilizarov system were assembled into 90degrees-90degrees and 45degrees-13 5degrees configurations with 2 olive pins, respectively. The distance between the center of pylon and the pin-clamp interface was equalized, being 70mm, in all the systems. Stiffness in axial compression, anteroposterior and lateral bending was measured. On axial compression and lateral bending tests, URHEF was stiffer than DynaExtor(R) and Ilizarov systems. On anteroposterior bending test, URHEF was less stiff than 90degrees-50degrees configuration of the Ilizarov system but stiffer than 45degrees-135degrees configuration. Considering the fact that instead of 90degrees-90degrees transfixing pin fixatin system, 45degrees-135degrees configuration system is generally used in clinical practice, URHEF appears to be significantly stiffer than unilateral(DynaExtor(R)) and circular (Ilizarov)fixation systems. This mechanical study implicates that URHEF can be beneficially applied in the clinical use with assurance of mechanical stability.
External Fixators ; Olea

We examined the effect of an applied cyclic compressive strain on the growth and differentiation of MC3T3-E1 cultured in a three-dimensional chitosan scaffold. The specially designed testing apparatus for mechanical stimulus was developed for uniaxial cyclic compressive strain. Cyclic compressive strain was applied over a period of 17 days with 150 cycles per day at a frequency of 0.5hz. Strain magnitude was 2.5% of the scaffold length. Control group and mechanically stimulated group were incubated and harvested at the indicated times. (day 3, 7, 10, 14, 17) The total amount of protein and alkaline phosphatase activity were examined. The total amount of protein of the control group was higher than that of the mechanically stimulated group. This was due to cell death for the nodule formation and calcium deposit of the mechanical stimuli group which resulted in cell differentiation. The alkaline phosphatase activity increased slightly in the control group. However, in the mechanical stimuli group, it increased significantly and reached its peak level on day 7 and subsequently its activity dropped to a level that was higher than the level at day 4(p < 0.05). Conclusively, it can be noted that the mechanical stimulus significantly accelerated the differentiation of MC3T3-E1 cells.
Alkaline Phosphatase ; Calcium ; Cell Death ; Cell Differentiation ; Chitosan

Purpose: High breast cancer incidence and dense breast prevalence among women in forties are specific to Asian. This study examined the natural history of breast cancer among Korean women. Materials and Methods: We applied a three-state Markov model (i.e., healthy, preclinical, and clinical state) to fit the natural history of breast cancer to data in the Korean National Cancer Screening Program. Breast cancer was ascertained by linkage to the Korean Central Cancer Registry. Disease-progression rates (i.e., transition rates between three states), mean sojourn time (MST) and mammographic sensitivity were estimated across 10-year age groups and levels of breast density determined by the Breast Imaging, Reporting and Data System. Results: Overall prevalence of dense breast was 53.9%. Transition rate from healthy to preclinical state, indicating the preclinical incidence of breast cancer, was higher among women in forties (0.0019; 95% confidence interval [CI], 0.0017 to 0.0021) and fifties (0.0020; 95% CI, 0.0017 to 0.0022), than women in sixties (0.0014; 95% CI, 0.0012 to 0.0017). The MSTs, in which the tumor is asymptomatic but detectable by screening, were also fastest among younger age groups, estimated as 1.98 years (95% CI, 1.67 to 2.33), 2.49 years (95% CI, 1.92 to 3.22), and 3.07 years (95% CI, 2.11 to 4.46) for women in forties, fifties, and sixties, respectively. Having dense breasts increased the likelihood of the preclinical cancer risk (1.96 to 2.35 times) and decreased the duration of MST (1.53 to 2.02 times). Conclusion This study estimated Korean-specific natural history parameters of breast cancer that would be utilized for establishing optimal screening strategies in countries with higher dense breast prevalence.

Increasing evidence suggests an association between elevated serum aminotransferase level and the metabolic syndrome. However, the significance of relatively low levels of aminotransferase in relation to the metabolic syndrome has not been fully investigated in the general population. We investigated the association between serum amiontransferase level and the metabolic syndrome using data from a nationwide survey in Korea. We measured serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and metabolic conditions among 9771 participants aged 20 or more in the 1998 and 2001 Korean National Health and Nutrition Examination Surveys. Metabolic syndrome was defined according to NCEP-ATP III criteria with a modified waist circumference cutoff (men > 90cm; women > 80cm). Serum aminotransferase level, even within normal range, was associated with the metabolic syndrome independent of age, body mass index, waist circumference, smoking, and alcohol intake. Compared with the lowest level (<20IU/L), the adjusted odds ratios (95% CI) for an AST level of 20-29, 30-39, 40-49 and > or = 50IU/L were 1.10 (0.85-1.42), 1.37 (1.02-1.83), 1.62 (1.08-2.43), and 2.25 (1.47-3.44) in men, and 1.18 (0.99-1.41), 1.43 (1.29-1.83), 1.71 (1.09-2.68), and 2.14 (1.20-3.80) in women, respectively. Corresponding odds ratios for ALT levels were 1.27 (0.99-1.63), 1.69 (1.28-2.23), 2.17 (1.58-2.99), and 2.65 (1.96-3.58) in men, and 1.44 (1.22-1.70), 1.65 (1.26-2.15), 2.94 (1.93-4.47), and 2.25 (1.54-3.30) in women, respectively. In conclusion, elevated serum aminotransferase levels, even in the normal to near normal range, are associated with features of the metabolic syndrome.
Reference Values ; Middle Aged ; Metabolic Syndrome X/*blood ; Male ; Korea ; Humans ; Female ; Blood Chemical Analysis/*methods/standards ; Aspartate Aminotransferases/*blood ; Alanine Transaminase/*blood ; Adult