Effect of athletic fatigue damage and the associated bone targeted remodeling in the rat ulna.

BACKGROUND: Fatigue damage of the long bones is prevalent in running athletes and military recruits due to vigorous mid- and long-term physical activity. The current study attempted to know the features of bony athletic fatigue damage and to explore the mechanism of fatigue damage repair through bone targeted remodeling process. METHODS: Right ulnae of the Wistar rats were fatigue loaded on an INSTRON 5865 to construct the athletic fatigue damage model, and several time points (i.e. experimental days: 0, 7, 13 and 19) were selected to simulate physiological status, preliminary, mid-term and perennial stage during continuous high-intensive training, respectively. The multi-level responses of rat ulnae under the athletic fatigue loading, including cellular protein expression, micro damage or micro-crack and macro mechanical properties, were tested and statistically analyzed. RESULTS: Wistar rats, subjected to the athletic fatigue loading protocol, experienced a decrease of ulna fatigue mechanical properties and an active bone resorption of the loaded ulnae in the early stage, whereafter, a hyperactive bone formation and significant improvements of ulnae fatigue mechanical properties were detected. However, a deterioration of quasi-static mechanical properties in the subsequent period implied limitations of bone remodeling to maintain the bearing capacity of bone during long-term strenuous exercise. CONCLUSIONS: In summary, after athletic fatigue loading, bone targeted remodeling is activated and proceeds to repair fatigue damage, but only to a certain extent.

The influence of icariin on apoptosis and cytoskeleton of osteoblasts in response to overload damage / 医用生物力学

Objective To study the effect of the icariin on apoptosis and cytoskeleton of osteoblasts in response to overload damage. Methods The four-point bending loading device was used to simulate the mechanical environment of overload damage and establish the cell overload damage model. According to whether the drugs were added before or after mechanical loading, the experiment was divided into blank control group, icariin group, damage group, damage prevention group and damage treatment group. Cell apoptosis was detected by flow cytometry. The specific fluorescent dyes were used to label the actin filament and the nucleus, and the changes of cytoskeleton were observed under laser scanning confocal microscope. Results Compared with control group, the apoptosis rate of damage group was the highest, and the icariin group was the lowest (P<0.05). Compared with damage group, the apoptosis rate of the damage prevention group was the lowest (P<0.05). The damage group showed cell shrinkage deformation, microfilaments disorganization, loosely arranged skeleton with vague outline, even broken skeleton. The morphological changes of cytoskeleton in damage prevention group were not significant, and there was no obvious change in cell nucleus. Conclusions Icariin can inhibit the apoptosis of osteoblasts after overload injury and maintain the stability of cytoskeleton to some extent.

The mechanical and biological responses of osteoblasts under hypergravity / 医用生物力学

Objective To explore the effect of hypergravity on morphology and osteogenesis function of preosteoblast MC3T3-E1 cells. Methods The cultured MC3T3-E1 cells under hypergravity by different loading forces were divided into five groups, including control group, 5 g group, 10 g group, 15 g group and 20 g group. The experimental groups were loaded for 30 min each time in the three successive days, and the control group was synchronously exposed to the same surrounding except for difference in g-value. The morphology of cytoskeletal protein was observed by phalloidin staining, The alkaline phosphatase (ALP) content was examined by ALP activity assay kit, the gene expression of ALP, collagen Ⅰ(ColⅠ), osteocalcin (OC), runt-related transcription factors (Runx2) was measured by real-time quantitative PCR, and the protein expression of ColⅠ and OC was tested by Western blot. Results Under the condition of hypergravity, cell body of osteoblast became thinner, but its surface area increased significantly; with the structure of skeletal arrangement becoming loose, actin microfilament structure reduced so that arrangement of actin-like dispersion orderly lowered. The gene expressions of related indicators of osteogenic differentiation including ALP, ColⅠ, OC, Runx2 loaded by hypergravity were significantly up-regulated, which was the same as ColⅠ protein and OC protein after hypergravity loading. There was only a very minute quantity of small red-orange nodules in the control group, while the cells after hypergravity loading in experimental groups obviously formed various sizes of red-orange nodules. Conclusions Under hypergravity, changes in osteoblast morphology can be triggered by rearrangements of skeletal structure. Furthermore, osteoblast maturation and differentiation can be stimulated effectively by up-regulating differentiation-related gene and protein expressions.

Finite element analysis on the stress concentration effect of osteons in cortical bone / 医用生物力学

Objective To construct a three-dimensional (3D) solid model of the cortical bone including osteons, verify the stress concentration effect of osteons, simulate and predict the stress concentration location under fatigue using finite element analysis (FEA). Methods The 3D solid model of the cortical bone including osteons was constructed in Pro/E wildfire 5.0, and local stress and strain distributions in the cortical bone under different axial compression were calculated and analyzed in ANSYS 12.0. Fatigue simulation on the selected locations was conducted to evaluate fatigue status of the model subjected to different fatigue loading intensities. Results Obvious stress concentration at the junction of osteon and the interstitical bone appeared under axial compressive loads, and the percentage of pathological local strain in the cortical bone increased with the axial compression increasing. Fatigue simulation on the selected locations demonstrated that bone fatigue risk during physiological or daily activities was very low, while a high fatigue or fracture risk might occur during high-intensity exercises or training. Conclusions The 3D solid model of the cortical bone including osteons is successfully established, the stress concentration effect of osteons is verified, and the location of bone fatigue damage under strenuous exercise and its risk are predicted. These experimental results can provide references for training management and athletic fatigue damage prevention in military recruits and long distance running athletes.

The effect of periodic dynamic mechanical load with different intensity on microgravity-induced osteoporosis / 医用生物力学

Objective To investigate the role and influence of physiological loading and overloading on microgravity-induced osteoporosis, so as to find a reliable way to prevent or treat related-orthopedic disorders in astronauts induced by long-time space activity. Methods The microgravity environment in space was simulated by tail-suspension experiment, then the osteoporosis models of mice were built. A total of 32 C57BL/6J mice were randomly and evenly separated into four groups: normal group (normal), tail-suspension group (TS), physiological loading group (loading) and overloading group (overloading). Periodic dynamic mechanical load was applied on the left tibia in loading group and overloading group during tail-suspension test. After four weeks, tibial mechanical properties, micro-parameters of bone trabecular, biochemical indices and osteogenesis-related gene expression in each group were compared and analyzed. Results A great loss of tibial cancellous bone, significantly lower tibial biomechanical expression, serious damage of microstructure and weaker osteogenic activity were found in tail-suspended mice as compared with those of normal group. Physiological loading could clearly improve mechanical properties of bones, microstructure of bone trabecular, osteogenic activity and relative gene expression (P＜0.05). Overloading could also improve the condition of microgravity-induced osteoporosis, but the effect was not obvious (P＞0.05). Conclusions Tail-suspension can successfully simulate microgravity environment and duplicate osteoporosis model. Physiological loading can effectively prevent the emergence and development of microgravity-induced osteoporosis, while overloading can also counter microgravity-induced osteoporosis, but the results have no significant differences.

Finite element analysis on the stress concentration effect of osteons in cortical bone / 医用生物力学

Objective To construct a three-dimensional (3D) solid model of the cortical bone including osteons,verify the stress concentration effect of osteons,simulate and predict the stress concentration location under fatigue using finite element analysis (FEA).Methods The 3D solid model of the cortical bone including osteons was constructed in Pro/E wildfire 5.0,and local stress and strain distributions in the cortical bone under different axial compression were calculated and analyzed in ANSYS 12.0.Fatigue simulation on the selected locations was conducted to evaluate fatigue status of the model subjected to different fatigue loading intensities.Results Obvious stress concentration at the junction of osteon and the interstitical bone appeared under axial compressive loads,and the percentage of pathological local strain in the cortical bone increased with the axial compression increasing.Fatigue simulation on the selected locations demonstrated that bone fatigue risk during physiological or daily activities was very low,while a high fatigue or fracture risk might occur during high-intensity exercises or training.Conclusions The 3 D solid model of the cortical bone including osteons is successfully established,the stress concentration effect of osteons is verified,and the location of bone fatigue damage under strenuous exercise and its risk are predicted.These experimental results can provide references for training management and athletic fatigue damage prevention in military recruits and long distance running athletes.

The mechanical and biological responses of MC3T3-E1 cells under hypergravity / 医用生物力学

Objective To explore the effect of hypergravity on morphology and osteogenesis function of preosteoblast MC3T3-E1 ceils.Methods The cultured MC3T3-E1 cells under hypergravity by different loading forces were divided into five groups,including control group,5 g group,10 g group,15 g group and 20 g group.The experimental groups were loaded for 30 min each time in 3 successive days,and the control group with no g-value was synchronously exposed to the same surrounding.The morphology of cytoskeletal protein was observed by phalIoidin staining,The alkaline phosphatase (ALP) content was examined by ALP activity assay kit,the gene expression of ALP,collagen Ⅰ (Col Ⅰ),osteocalcin (OC),runt-related transcription factors (Runx2) was measured by real-time quantitative PCR,and the protein expression of Col Ⅰ and OC was tested by Western blotting.Results Under the condition of hypergravity,cell body of osteoblast became thinner,but its surface area increased significantly;with the structure of skeletal arrangement becoming loose,actin microfilament structure reduced so that the orderly arrangement of actin-like dispersion lowered.The gene expressions of related indicators of osteogenic differentiation including ALP,Col][,OC,Runx2 were significantly up-regulated,which was the same as Col Ⅰ protein and OC protein after hypergravity loading.A very minute quantity of small red-orange nodules was found in the control group,while the cells in experimental groups after hypergravity loading obviously formed various sizes of red-orange nodules.Conclusions Under hypergravity,changes in osteoblast morphology can be triggered by rearrangements of skeletal structure.Furthermore,osteoblast maturation and differentiation can be stimulated effectively by up-regulating differentiation-related gene and protein expressions.

The effect of periodic dynamic mechanical load with different intensity on microgravity-induced osteoporosis / 医用生物力学

Objective To investigate the role and influence of physiological loading and overloading on microgravity-induced osteoporosis,so as to find a reliable way to prevent or treat related-orthopedic disorders in astronauts induced by long-time space activity.Metbods The microgravity environment in space was simulated by tail-suspension experiment,then the osteoporosis models of mice were built.A total of 32 C57BL/6J mice were randomly and evenly separated into four groups:normal group (normal),tail-suspension group (TS),physiological loading group (loading) and overloading group (overloading).Periodic dynamic mechanical load was applied on the left tibia in loading group and overloading group during tail-suspension test.After four weeks,tibial mechanical properties,micro-parameters of bone trabecular,biochemical indices and osteogenesis-related gene expression in each group were compared and analyzed.Results A great loss of tibial cancellous bone,significantly lower tibial biomechanical expression,serious damage of microstructure and weaker osteogenic activity were found in tail-suspended mice as compared with those of normal group.Physiological loading could clearly improve mechanical properties of bones,microstructure of bone trabecular,osteogenic activity and relative gene expression (P ＜ 0.05).Overloading could also improve the condition of microgravity-induced osteoporosis,but the effect was not obvious (P ＞ 0.05).Conclusions Tail-suspension can successfully simulate microgravity environment and duplicate osteoporosis model.Physiological loading can effectively prevent the emergence and development of microgravity-induced osteoporosis,while overloading can also counter microgravity-induced osteoporosis,but the results have no significant differences.

The mechanical and biological responses of MC3T3-E1 cells under hypergravity / 医用生物力学

Objective To explore the effect of hypergravity on morphology and osteogenesis function of preosteoblast MC3T3-E1 ceils.Methods The cultured MC3T3-E1 cells under hypergravity by different loading forces were divided into five groups,including control group,5 g group,10 g group,15 g group and 20 g group.The experimental groups were loaded for 30 min each time in 3 successive days,and the control group with no g-value was synchronously exposed to the same surrounding.The morphology of cytoskeletal protein was observed by phalIoidin staining,The alkaline phosphatase (ALP) content was examined by ALP activity assay kit,the gene expression of ALP,collagen Ⅰ (Col Ⅰ),osteocalcin (OC),runt-related transcription factors (Runx2) was measured by real-time quantitative PCR,and the protein expression of Col Ⅰ and OC was tested by Western blotting.Results Under the condition of hypergravity,cell body of osteoblast became thinner,but its surface area increased significantly;with the structure of skeletal arrangement becoming loose,actin microfilament structure reduced so that the orderly arrangement of actin-like dispersion lowered.The gene expressions of related indicators of osteogenic differentiation including ALP,Col][,OC,Runx2 were significantly up-regulated,which was the same as Col Ⅰ protein and OC protein after hypergravity loading.A very minute quantity of small red-orange nodules was found in the control group,while the cells in experimental groups after hypergravity loading obviously formed various sizes of red-orange nodules.Conclusions Under hypergravity,changes in osteoblast morphology can be triggered by rearrangements of skeletal structure.Furthermore,osteoblast maturation and differentiation can be stimulated effectively by up-regulating differentiation-related gene and protein expressions.

The effect of periodic dynamic mechanical load with different intensity on microgravity-induced osteoporosis / 医用生物力学

Objective To investigate the role and influence of physiological loading and overloading on microgravity-induced osteoporosis,so as to find a reliable way to prevent or treat related-orthopedic disorders in astronauts induced by long-time space activity.Metbods The microgravity environment in space was simulated by tail-suspension experiment,then the osteoporosis models of mice were built.A total of 32 C57BL/6J mice were randomly and evenly separated into four groups:normal group (normal),tail-suspension group (TS),physiological loading group (loading) and overloading group (overloading).Periodic dynamic mechanical load was applied on the left tibia in loading group and overloading group during tail-suspension test.After four weeks,tibial mechanical properties,micro-parameters of bone trabecular,biochemical indices and osteogenesis-related gene expression in each group were compared and analyzed.Results A great loss of tibial cancellous bone,significantly lower tibial biomechanical expression,serious damage of microstructure and weaker osteogenic activity were found in tail-suspended mice as compared with those of normal group.Physiological loading could clearly improve mechanical properties of bones,microstructure of bone trabecular,osteogenic activity and relative gene expression (P ＜ 0.05).Overloading could also improve the condition of microgravity-induced osteoporosis,but the effect was not obvious (P ＞ 0.05).Conclusions Tail-suspension can successfully simulate microgravity environment and duplicate osteoporosis model.Physiological loading can effectively prevent the emergence and development of microgravity-induced osteoporosis,while overloading can also counter microgravity-induced osteoporosis,but the results have no significant differences.

Review of biomechanical researches on fatigue damage in bone / 医用生物力学

Bone, acting as the main load-bearing organ in human body, is of mechanical adaptability. It is prevalent but perilous that under fatigue loading, bone suffers from fatigue damage characterized as the initiation, propagation of micro-cracks, deterioration of bone mechanical properties or even stress fracture, which is commonly seen in long distance running of athletes, fitness training of military recruits and daily activities of the elderly. Bone fatigue damages exist in multi-levels of ultra-micro structure, microstructure and macrostructure. The anti-fatigue units in cortical bone (osteons) and cellular components (osteocytes) inside have been proved to play important roles in fatigue damage prevention, micro-cracks recognition and bone-targeted remodeling activation. Therefore, a general review and summing-up of relative research findings can help to provide a systematic understanding of fatigue behavior and corresponding repair process, and to give some useful references and insights for subsequent clinical researches aiming at prevention and treatment for bone fatigue damage.

The research on mechanobiology mechanism of bone remodeling / 医用生物力学

Bone growth, development and maintenance, which become multidisciplinary with the rapid development of biomechanics, tissue engineering and cell biology, are intimately linked with bone remodeling. Mechanobiology has become an important method to study bone remodeling. This article summarizes related skeletal mechanobiology researches in recent years to provide theoretical basis for bone remodeling, bone tissue engineering and clinical treatments of related orthopedic disorders.

Research progress of mechanical overload on osteoblast injury and its repair by traditional Chinese medicine / 医用生物力学

The growth and metabolism of bone are controlled by osteogenesis of osteoblasts and absorption of osteoclasts, and osteoblasts play a main role in the process of osteogenesis. Overload will affect proliferation and differentiation of osteoblasts, while the loading mode, intensity, duration and other factors can change the biological properties of osteoblasts and further affect the functional activity of osteoblasts. However, the mechanism of osteoblast response to overload is still at the exploratory stage and needs in-depth study. Numerous studies have demonstrated that icariin, a kind of Chinese herbal medicine, can promote proliferation and differentiation of osteoblasts, and icariin with a certain concentration plays an important role in the repair of osteoblast injuries. In this paper, the response of osteoblasts to overload stimulation and repair of osteoblast injuries by icariin were summarized.

The mechanobiology responses of osteoblasts under hypergravity / 医用生物力学

In the environment of adaptive mechanics, osteoblasts, which are the main functional cells of bone formation, are one of the main cells in response to the mechanical loading. With the development of technology, more and more astronauts, pilots and other are exposed to the hypergravity environment. In order to better understand the mechanobiology response of osteoblasts under hypergravity, this paper reviews the mechanobiological research progress in morphology, gene expression, cytokine secretion and signal transduction pathways of ostoblasts, so as to thoughts and preparations for mechanobiology research of bone tissues in hypergravity environment.

Effect of 1, 25-dihydroxy vitamin D3 combined with mechanical strain treatment on proliferation, differentiation, and expression of OPG and RANKL in osteoblastic MC3T3-E1 cells / 医用生物力学

Objective To investigate the effect of 1,25-(OH)2-vitamin D3 (VD3) or mechanical strain alone and their combined treatment on proliferation and differentiation of pre-osteoblast MC3T3-E1 cells in vitro, as well as gene and protein expression of osteoprotegerin (OPG) and receptor activator of nuclear factor-кB ligand (RANKL) in those cells. Methods MC3T3-E1 cells were treated with 10 nmol/L VD3, intermitted mechanical strain or with a combination of these two factors. Cell proliferation was assessed with flow cytometry, and alkaline phosphatase (ALP) activity was measured using a fluorometric detection kit. The mRNA expression of ALP, runt-related transcriptional factor 2 (Runx2), OPG, and RANKL genes was determined by real-time PCR. The proteins expression of Runx2, OPG, and RANKL was determined by Western blotting. ResultsVD3 inhibited the proliferation of MC3T3-E1 cells, but the mechanical strain had no effect on cell proliferation. Mechanical strain, VD3, and the combined treatment enhanced the ALP activity of MC3T3-E1 cells as well as the protein expression of Runx2. The effect of combined treatment was less pronounced than the effect of VD3 or mechanical strain alone. Mechanical strain promoted the gene and protein expression of osteoprotegerin (OPG) and increased the ratio of OPG/RANKL. However, the combination of VD3 and mechanical strain led to a decrease in ratio of OPG/RANKL. Conclusions Mechanical strain might be effective in inducing osteogenic differentiation and increasing bone formation. A joint stimulation with VD3 and strain can decrease proliferation and osteogenic differentiation and increase RANKL expression, which might affect bone remodeling. This study supplies some new data, which might be important in theoretical and clinical research of osteoporosis (OP) and other related bone diseases.

Loading rate-dependent property of different layers for articular cartilage / 医用生物力学

Objective To investigate the loading rate-dependent property of different layers for articular cartilage by unconfined compression testing on articular cartilage at different loading rates. Methods The non-contact digital image correlation (DIC) technique was applied to investigate the mechanical properties of different layers for fresh pig articular cartilage at different loading rates. Results At constant loading rate, the compressive strain of superficial layer and deep layer was the largest, while that of middle layer was in between under the same compressive stress. The Poisson’s ratio increased from superficial layer to deep layer along with cartilage depth increasing. The stress-strain curves of cartilage were different at different loading rates, indicating that the mechanical properties of cartilage were dependent on the loading rate. The elastic modulus of cartilage increased with loading rates increasing, and the compressive strains of different layers decreased under the same compressive stress with loading rates increasing. Conclusions The compressive strain decreased while the Poisson’s ratio increased from superficial layer to deep layer along the cartilage depth. The mechanical properties of different layers for cartilage were dependent on the loading rate. This study can provide the basis for clinical cartilage disease prevention and treatment, and is important for mechanical function evaluation of artificial cartilage as well.

Bone formation in rabbit cancellous bone explant culture model is enhanced by mechanical load.

BACKGROUND: When studying and designing an artificial bone in vitro with similar features and functionality of natural bone by tissue engineering technology, the culturing environment, especially the mechanical environment is supposed to be an important factor, because a suitable mechanical environment in vitro may improve the adaptability of the planted-in tissue engineering bone in the body. Unfortunately, up to now, the relationship between mechanical stimuli and natural bone growth has not yet been precisely determined, and it is so imperative for a prior study on effect of mechanical loading on growth of the natural bone cultured in vitro. METHODS: Under sterile conditions, explant models of rabbit cancellous bone with 3 mm in thickness and 8 mm in diameter were prepared and cultured in a dynamic loading and circulating perfusion bioreactor system. By Micro-CT scanning, a 3D model for finite element (FEM) analysis was achieved. According to the results of FEM analysis and physiological load bearing capacity of the natural bone, these models were firstly subjected to mechanical load with 1Hz frequency causing average apparent strain of 1000 µÎµ, 2000 µÎµ, 3000 µÎµ and 4000 µÎµ respectively for 30 min every day, activities of alkaline phosphatase (AKP) were detected on the 5th and the 14th loading day and on the 14th and the 21st day, mechanical properties, tissue mineral density (TMD) of the bone explant models were investigated and Von-kossa staining and fluorescence double labeling assays were conducted to evaluate whether there were fresh osteoid in the bone explant models. In addition, Western blot, Elisa and Real-time PCR were employed to analyze expression of Collagen-I (COL-1), bone morphogenetic protein-2 (BMP-2) and osteoprotegerin (OPG) protein and RNA. RESULTS: The explant models of rabbit cancellous bone prepared under sterile conditions grew well in the bioreactor system. With the increasing culturing time and load levels, bone explant models in groups with 1000 µÎµ and 2000 µÎµ average apparent strain experienced improving mechanical properties and TMD (P<0.05), and results of Von-kossa staining and fluorescence double labeling also showed apparent fresh osteoid formation. Under the same loading conditions, a up-regulations in protein and RNA of COL-1, BMP-2 and OPG were detected, especially, relative genes notably expressed after 21 days. CONCLUSION: Our study demonstrated that mechanical load could improve function and activity of osteoblasts in explant models of cancellous bone. Through regulations of COL-1, OPG and BMP-2 secreted by osteoblasts, the mechanical load could improve the tissue structural density and stiffness due to formation of fresh osteoid.

Mechanical stimulus inhibits the growth of a bone tissue model cultured in vitro △ / 中国医学科学杂志(英文版)

<p><b>OBJECTIVES</b>To construct the cancellous bone explant model and a method of culturing these bone tissues in vitro, and to investigate the effect of mechanical load on growth of cancellous bone tissue in vitro.</p><p><b>METHODS</b>Cancellous bone were extracted from rabbit femoral head and cut into 1-mm-thick and 8-mm-diameter slices under sterile conditions. HE staining and scanning electron microscopy were employed to identify the histomorphology of the model after being cultured with a new dynamic load and circulating perfusion bioreactor system for 0, 3, 5, and 7 days, respectively. We built a three-dimensional model using microCT and analyzed the loading effects using finite element analysis. The model was subjected to mechanical load of 1000, 2000, 3000, and 4000 με respectively for 30 minutes per day. After 5 days of continuous stimuli, the activities of alkaline phosphatase (AKP) and tartrate-resistant acid phosphatase (TRAP) were detected. Apoptosis was analyzed by DNA ladder detection and caspase-3/8/9 activity detection.</p><p><b>RESULTS</b>After being cultured for 3, 5, and 7 days, the bone explant model grew well. HE staining showed the apparent nucleus in cells at the each indicated time, and electron microscope revealed the living cells in the bone tissue. The activities of AKP and TRAP in the bone explant model under mechanical load of 3000 and 4000 με were significantly lower than those in the unstressed bone tissues (all P<0.05). DNA ladders were seen in the bone tissue under 3000 and 4000 με mechanical load. Moreover, there was significant enhancement in the activities of caspase-3/8/9 in the mechanical stress group of 3000 and 4000 με(all P<0.05).</p><p><b>CONCLUSIONS</b>The cancellous bone explant model extracted from the rabbit femoral head could be alive at least for 7 days in the dynamic load and circulating perfusion bioreactor system, however, pathological mechanical load could affect the bone tissue growth by apoptosis in vitro. The differentiation of osteoblasts and osteoclasts might be inhibited after the model is stimulated by mechanical load of 3000 and 4000 με.</p>

Liver tissue separation by medical water-jet scalpel and its mechanical property study / 医用生物力学

Objective To study mechanical properties of the medical water-jet scalpel when cutting parenchyma such as liver and verify its tissue-selective cutting characteristic. Methods The tension mechanical properties of porcine liver parenchyma and its vessels with different sizes were determined. Porcine and Wistar rat liver tissues were cut with arteriovenous vessels well reserved, and pathological section of the rats were analyzed by HE staining to explain the experimental phenomena. Results When the working pressure was set at 3 MPa, the incising and separating on the right lobe of porcine liver by medical water-jet scalpel in this experiment were done with minimal vessels of 0.8 mm in diameter left. Pathological sections from ordinary scalpel and medical water-jet scalpel showed that the medical water-jet scalpel caused smaller tissue damage. Conclusions The medical water-jet scalpel could cut heterogeneity soft tissue with highly-selective characteristics, which may effectively avoid the existing “one size fits all” phenomenon caused by ordinary scalpel.

Simulation for internal structure of proximal tibia in both normal and valgus knees / 医用生物力学

Objective To simulate the internal structure of proximal tibia in both normal and valgus knees. Methods The internal structure of proximal tibia under normal mechanical environment was simulated using quantitative bone remodeling theory combined with finite element method. Based on this structure as the initial model and the changing pattern of pressure distributions on tibial plateau in valgus knee, the internal structure of proximal tibia in valgus knee was simulated with the action point of resultant force on the lateral tibial plateau. Results The simulated distributions of bone mineral density (BMD) were compared with the real tibia, and found the simulated results highly consistent with the actual ones both under normal mechanical environment and in valgus cases. Conclusions The method and the load distributions adopted in this study can accurately simulate and predict the internal structure of proximal tibia, thus could be served as the basis for further study on periprosthetic bone remodeling behavior after the total knee arthroplasty.