Athletes and military recruits are often afflicted by stress fractures. Rigorous training programs consisting of increased repetitive mechanical loading may contribute to the high incidence of tibia stress fracture in...Athletes and military recruits are often afflicted by stress fractures. Rigorous training programs consisting of increased repetitive mechanical loading may contribute to the high incidence of tibia stress fracture in the athletic and army populations. The purpose of this study was to assess the effect of incremented height on tibia bone strains and strain rates during landing. Seven healthy college males performed drop-landing tasks from 26 cm, 39 cm, and 52 cm, respectively. Tibia bone strains and strain rates were obtained through subject-specific multi-body dynamic computer simulations and finite element analyses. One-way repeated measures ANOVAs were conducted. Both 39 cm and 52 cm conditions resulted in larger tibia bone strains and strain rates than the 26 cm condition. The 52 cm condition also resulted in greater bone strains and strain rates than the 39 cm condition. A dose-response relationship exists between incremented landing height and bone strains and strain rates. Activities consisting of high impact landings are associated with increased risk of developing tibia stress fracture. When designing training programs involved high impact activities, athletes and military recruits should consider the effect of impact loading on tibia bone health and giving enough time for bones to adapt to new trainings.展开更多
Although insulin-like growth factor-I （IGF-I） and estrogen signaling pathways have been shown to be involved in mediating the bone anabolic response to mechanical loading, it is not known whether these two signaling...Although insulin-like growth factor-I （IGF-I） and estrogen signaling pathways have been shown to be involved in mediating the bone anabolic response to mechanical loading, it is not known whether these two signaling pathways crosstalk with each other in producing a skeletal response to mechanical loading. To test this, at 5 weeks of age, partial ovariectomy （pOVX） or a sham operation was performed on heterozygous IGF-I conditional knockout （H IGF-I KO） and control mice generated using a Cre-loxP approach. At 10 weeks of age, a 10 N axial load was applied on the right tibia of these mice for a period of 2 weeks and the left tibia was used as an internal non-non-loaded control. At the cortical site, partial estrogen loss reduced total volumetric bone mineral density （BMD） by 5% in control pOVX mice （P=0.05, one-way ANOVA）, but not in the H IGF-I KO pOVX mice. At the trabecular site, bone volume/total volume （BV/TV） was reduced by 5%-6% in both control pOVX （P〈0.05） and H IGF-I KO pOVX （P=0.05） mice. Two weeks of mechanical loading caused a 7 %-8% and an 11%-13% （P〈0.05 vs. non-loaded bones） increase in cortical BMD and cortical thickness （Ct.Th）, respectively, in the control sham, control pOVX and H IGF-I KO sham groups. By contrast, the magnitude of cortical BMD （4%, P=0.13） and Ct.Th （6%, P〈0.05） responses were reduced by 50% in the H IGF-I KO pOVX mice compared to the other three groups. The interaction between genotype and estrogen deficiency on the mechanical loading-induced cortical bone response was significant （P〈0.05） by two-way ANOVA. Two weeks of axial loading caused similar increases in trabecular BV/TV （13%-17%） and thickness （17%-23%） in all four groups of mice. In conclusion, partial loss of both estrogen and IGF-I significantly reduced cortical but not the trabecular bone response to mechanical loading, providing in vivo evidence of the above crosstalk in mediating the bone response to loading.展开更多
AIM:To assess the capacity to isolate and expand mesenchymal stem cells(MSC)from bone marrow of CBA/Ca,ICR and Balb/c mice. METHODS:Bone marrow of tibia and femur were flushed,cultured and maintained in supplemented D...AIM:To assess the capacity to isolate and expand mesenchymal stem cells(MSC)from bone marrow of CBA/Ca,ICR and Balb/c mice. METHODS:Bone marrow of tibia and femur were flushed,cultured and maintained in supplemented Dulbecco’s modified Eagle’s medium.MSC immunophenotype of cultures were tracked along increasing passages for positivity to CD106,Sca-1 and CD44 and negativity to CD45,CD11b and MHC classⅡ.Differentiation capacity of MSC towards osteogenic and adipo-genic lineages were also assessed. RESULTS:MSC were successfully cultured from bone marrow of all 3 strains,albeit differences in the temporal expression of certain surface antigens.Their differentiation into osteocytes and adipocytes were also observed. MSC from all 3 mouse strains demonstrated a shift from a haematopoietic phenotype(CD106-CD45+CD11b+Sca-1low)to typical MSC phenotype(CD106+CD45-CD11b-Sca-1high)with increasing passages. CONCLUSION:Information garnered assists us in the decision of selecting a mouse strain to generate MSC from for downstream experimentation.展开更多
The locking compression plates (LCP) are efficient tools in open reduction and internal fixation (ORIF), especially in osteoporotic bones. Two important factors of screw density and screw position can affect the funct...The locking compression plates (LCP) are efficient tools in open reduction and internal fixation (ORIF), especially in osteoporotic bones. Two important factors of screw density and screw position can affect the functionality of the bone plate. Several studies have assessed the influence of the screw configurations on the bone-plate stiffness, but the effects of screw positions on the interfragmentary strain, εIF of LCP construct have not been investigated yet. In this study, finite element method was used to investigate the influence of screws number and position on the interfragmentary strain of LCP-femur system for a mid-shaft fracture. Results of this study showed that by insertion of screws closer to the fracture site, εIF decreases by 2nd degree polynomial function versus screw position, but by adding the screws from the ends of the plate, or by moving and placing the screws towards the fracture site, the reduction of εIF will be linear. Results of this study were compared and are in agreement with some studies in the literature, even though their scope was mostly stability of the bone-implant system, whereas our scope was focused on the interfragmentary strain.展开更多
We consider the problem of assessing bone fracture risk for a subject hit by a blunt impact projectile. We aim at constructing a framework for integrating test data and Advanced Total Body Model (ATBM) simulations int...We consider the problem of assessing bone fracture risk for a subject hit by a blunt impact projectile. We aim at constructing a framework for integrating test data and Advanced Total Body Model (ATBM) simulations into the risk assessment. The ATBM is a finite element model managed by the Joint Non-Lethal Weapons Directorate for the purpose of assessing the risk of injury caused by blunt impacts from non-lethal weapons. In ATBM simulations, the quantity that determines arm bone fracture is the calculated maximum strain in the bone. The main obstacle to accurate prediction is that the calculated strain is incompatible with the measured strain. The fracture strain measured in bending tests of real bones is affected by random inhomogeneity in bones and uncertainty in measurement gauge attachment location/orientation. In contrast, the strain calculated in ATBM simulations is based on the assumption that all bones are perfectly elastic with homogeneous material properties and no measurement uncertainty. To connect test data and ATBM simulations in a proper and meaningful setting, we introduce the concept of elasticity-homogenized strain. We interpret test data in terms of the homogenized strain, and build an empirical dose-injury model with the homogenized strain as the input dose for predicting injury. The maximum strain calculated by ATBM has randomness due to uncertainty in specifications of ATBM setup parameters. The dose propagation uncertainty formulation accommodates this uncertainty efficiently by simply updating the shape parameters in the dose-injury model, avoiding the high computational cost of sampling this uncertainty via multiple ATBM runs.展开更多
文摘Athletes and military recruits are often afflicted by stress fractures. Rigorous training programs consisting of increased repetitive mechanical loading may contribute to the high incidence of tibia stress fracture in the athletic and army populations. The purpose of this study was to assess the effect of incremented height on tibia bone strains and strain rates during landing. Seven healthy college males performed drop-landing tasks from 26 cm, 39 cm, and 52 cm, respectively. Tibia bone strains and strain rates were obtained through subject-specific multi-body dynamic computer simulations and finite element analyses. One-way repeated measures ANOVAs were conducted. Both 39 cm and 52 cm conditions resulted in larger tibia bone strains and strain rates than the 26 cm condition. The 52 cm condition also resulted in greater bone strains and strain rates than the 39 cm condition. A dose-response relationship exists between incremented landing height and bone strains and strain rates. Activities consisting of high impact landings are associated with increased risk of developing tibia stress fracture. When designing training programs involved high impact activities, athletes and military recruits should consider the effect of impact loading on tibia bone health and giving enough time for bones to adapt to new trainings.
基金supported by the National Institutes of Health grant R01 AR48139 (to SM)National Institute of Arthritis and Musculoskeletal Skin Diseases R03 grant AR056827 (to CK)
文摘Although insulin-like growth factor-I （IGF-I） and estrogen signaling pathways have been shown to be involved in mediating the bone anabolic response to mechanical loading, it is not known whether these two signaling pathways crosstalk with each other in producing a skeletal response to mechanical loading. To test this, at 5 weeks of age, partial ovariectomy （pOVX） or a sham operation was performed on heterozygous IGF-I conditional knockout （H IGF-I KO） and control mice generated using a Cre-loxP approach. At 10 weeks of age, a 10 N axial load was applied on the right tibia of these mice for a period of 2 weeks and the left tibia was used as an internal non-non-loaded control. At the cortical site, partial estrogen loss reduced total volumetric bone mineral density （BMD） by 5% in control pOVX mice （P=0.05, one-way ANOVA）, but not in the H IGF-I KO pOVX mice. At the trabecular site, bone volume/total volume （BV/TV） was reduced by 5%-6% in both control pOVX （P〈0.05） and H IGF-I KO pOVX （P=0.05） mice. Two weeks of mechanical loading caused a 7 %-8% and an 11%-13% （P〈0.05 vs. non-loaded bones） increase in cortical BMD and cortical thickness （Ct.Th）, respectively, in the control sham, control pOVX and H IGF-I KO sham groups. By contrast, the magnitude of cortical BMD （4%, P=0.13） and Ct.Th （6%, P〈0.05） responses were reduced by 50% in the H IGF-I KO pOVX mice compared to the other three groups. The interaction between genotype and estrogen deficiency on the mechanical loading-induced cortical bone response was significant （P〈0.05） by two-way ANOVA. Two weeks of axial loading caused similar increases in trabecular BV/TV （13%-17%） and thickness （17%-23%） in all four groups of mice. In conclusion, partial loss of both estrogen and IGF-I significantly reduced cortical but not the trabecular bone response to mechanical loading, providing in vivo evidence of the above crosstalk in mediating the bone response to loading.
基金Supported by The Research University Grant Scheme UPM,04-02-10-0924RUExploratory Research Grant Scheme,Ministry of Higher Education,ERGS/1/2012/5527106
文摘AIM:To assess the capacity to isolate and expand mesenchymal stem cells(MSC)from bone marrow of CBA/Ca,ICR and Balb/c mice. METHODS:Bone marrow of tibia and femur were flushed,cultured and maintained in supplemented Dulbecco’s modified Eagle’s medium.MSC immunophenotype of cultures were tracked along increasing passages for positivity to CD106,Sca-1 and CD44 and negativity to CD45,CD11b and MHC classⅡ.Differentiation capacity of MSC towards osteogenic and adipo-genic lineages were also assessed. RESULTS:MSC were successfully cultured from bone marrow of all 3 strains,albeit differences in the temporal expression of certain surface antigens.Their differentiation into osteocytes and adipocytes were also observed. MSC from all 3 mouse strains demonstrated a shift from a haematopoietic phenotype(CD106-CD45+CD11b+Sca-1low)to typical MSC phenotype(CD106+CD45-CD11b-Sca-1high)with increasing passages. CONCLUSION:Information garnered assists us in the decision of selecting a mouse strain to generate MSC from for downstream experimentation.
文摘The locking compression plates (LCP) are efficient tools in open reduction and internal fixation (ORIF), especially in osteoporotic bones. Two important factors of screw density and screw position can affect the functionality of the bone plate. Several studies have assessed the influence of the screw configurations on the bone-plate stiffness, but the effects of screw positions on the interfragmentary strain, εIF of LCP construct have not been investigated yet. In this study, finite element method was used to investigate the influence of screws number and position on the interfragmentary strain of LCP-femur system for a mid-shaft fracture. Results of this study showed that by insertion of screws closer to the fracture site, εIF decreases by 2nd degree polynomial function versus screw position, but by adding the screws from the ends of the plate, or by moving and placing the screws towards the fracture site, the reduction of εIF will be linear. Results of this study were compared and are in agreement with some studies in the literature, even though their scope was mostly stability of the bone-implant system, whereas our scope was focused on the interfragmentary strain.
文摘We consider the problem of assessing bone fracture risk for a subject hit by a blunt impact projectile. We aim at constructing a framework for integrating test data and Advanced Total Body Model (ATBM) simulations into the risk assessment. The ATBM is a finite element model managed by the Joint Non-Lethal Weapons Directorate for the purpose of assessing the risk of injury caused by blunt impacts from non-lethal weapons. In ATBM simulations, the quantity that determines arm bone fracture is the calculated maximum strain in the bone. The main obstacle to accurate prediction is that the calculated strain is incompatible with the measured strain. The fracture strain measured in bending tests of real bones is affected by random inhomogeneity in bones and uncertainty in measurement gauge attachment location/orientation. In contrast, the strain calculated in ATBM simulations is based on the assumption that all bones are perfectly elastic with homogeneous material properties and no measurement uncertainty. To connect test data and ATBM simulations in a proper and meaningful setting, we introduce the concept of elasticity-homogenized strain. We interpret test data in terms of the homogenized strain, and build an empirical dose-injury model with the homogenized strain as the input dose for predicting injury. The maximum strain calculated by ATBM has randomness due to uncertainty in specifications of ATBM setup parameters. The dose propagation uncertainty formulation accommodates this uncertainty efficiently by simply updating the shape parameters in the dose-injury model, avoiding the high computational cost of sampling this uncertainty via multiple ATBM runs.
