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Differences in radius strength between male elite rock climbers and runners determined by FE analysis of bone in-vivo
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Journal of Biomechanics 2006, Vol. 39 (Suppl 1)
(BL6, FVB, aging SAM/P6, Calcitonin- and src-deficient mice, total specimen number: n =94) were analyzed. Improved mechanical test conditions were achieved, since vertebral endplates were not transected and specimens were embedded in cement layers. Furthermore, the specimen-specific approach allowed an derivation of trabecular tissue characteristics (strength and stiffness), which correlated moderately with the tissue mineralization (R 2=0.44-0.64, power-law function). A strong correlation (R 2 = 0.99)was observed between individual morphometrical traits, such as BV/TV and trabecular architecture or BS/BV and trabecular thickness. Vertebral strength and stiffness were predicted (R 2 =0.85) using non-linear regression analysis allowing the identification of individual contribution from the cortical and trabecular structure, tissue, and architecture, independently of the mouse models analyzed. All mouse models exhibited individual skeletal phenotypes, while the aging SAM/P6 showed many similarities to senile osteoporosis and the src-deficient mouse exhibited a severe osteopetrotic phenotype. 6648 Mo, 09:30-09:45 (P5) Strain measurements in bovine cortical bone using X-ray imaging plate system K. Fujisaki, S. Tadano. Division of Human Mechanical Systems and Design,
Graduate School of Engineering, Hokkaido University, Sapporo, Japan A non-destructive measurement of strain is much important to investigate the mechanical state of bone tissue in vivo. Bone tissue is a composite material composed of HAp and collagen. As HAp is a crystalline structure, an X-ray diffraction method is available to measure the lattice strain of HAp crystals. Authors have proposed a method to measure the lattice strain of HAp with low degree of crystallinity in the bone tissue. The relationship between the macroscopic bone tissue strain and lattice strain of HAp was investigated under tensile loading. The bone tissue strain could be estimated from the lattice strains of HAp. In these measurements, a scintillation counter was used to obtain a strain at the loading direction. It is difficult to measure concurrently the strains at the several directions using the counter scanning system. In this work, X-ray imaging plate system was innovated to measure the lattice strains of HAp in various directions. In this experiment, the strip specimens were cut from cortical region in a shaft of bovine femur. When a simple tensile loading was applied to the specimen, the diffracted X-ray pattern was detected in the X-ray transmitted side. The crystal orientation of HAp was confirmed from the diffracted X-ray pattern of (002) plane detected on the imaging plate. The lattice strains of (211) plane were obtained from the patterns at the non-strained and strained state. The lattice strain was lower value than the bone tissue strain and increased linearly with the bone tissue strain at the loading direction. The two dimensional distribution of lattice strains was obtained from the patterns. The difference of the strains between the tensile or compressive side was clearly shown on the microscopic scale of HAp crystal lattice. 6541 Mo, 11:00-11:15 (PT) Cervical hip fractures predominate at low fracture loads P. Pulkkinen 1, F. Eckstein 2,3, E.-M. LochmLiller 2, V. Kuhn 2,4, T. J~ms~ 1.
1Department of Medical Technology, University of Oulu, Oulu, Finland, 2Ludwig-Maximilians-Universit~t, MEmchen, Germany, 3paracelsus Medical Private University, Salzburg, Austria, 4Medical University, Innsbruck, Austria Bone geometry has been shown to be a risk factor for osteoporotic fractures, being different in cervical and trochanteric hip fractures. However, the determinants of fracture types at different levels of fracture load are not known. The aim of the present study was to investigate the incidence of cervical and trochanteric fractures at different fracture load levels and to find the geometry and BMD determinants for the fracture type. The sample comprised left femurs of 140 cadavers (77 females, mean age 81.7, 63 males, mean age 79.1). The bones were radiographed and a set of geometrical parameters was determined from the digitized X-rays. BMD was measured in vitro using a standard DXA scanner. The femurs were mechanically tested in a side impact configuration. After the mechanical test, the fracture patterns were classified into cervical and trochanteric. The statistics was performed at fracture load quartiles. The overall proportion of cervical fractures was higher in females (74%) than in males (49%) (p=0.002). The fracture type distribution differed significantly across load quartiles in females (p=0.025), but not in males (p=0.205). At the lowest load quartiles, 94.7% of fractures in female and 62.5% in male were femoral neck fractures. At the highest quartiles, in contrast, only 52.6% of fractures in female and 33.3% in male were cervical fractures. Neck-shaft angle was the best predictor of fracture type, with higher values in subjects with cervical fractures. This finding was made in females (p < 0.001 ) and males (p=0.02) and was consistent across all failure load quartiles. As a conclusion, femoral neck fractures were the most dominant at low fracture loads, while trochanteric fractures were more common at the high fracture
Oral Presentations
loads. The best predictor of fracture type appeared to be neck-shaft angle at all fracture load levels for both genders.
4592 Mo, 11:15-11:30 (P7) Differences in radius strength between male elite rock climbers and runners determined by FE analysis of bone in-vivo J. Kunecky 1,2, W. Kemmler 3, S. von Stengel 3, K. Engelke 3, B. van Rietbergen 1. 1Eindhoven University of Technology, Eindhoven, The
Netherlands, 2Czech Academy of Sciences, Prague, Czech Republic, 3University of Erlangen-NEtrnberg, Germany It is well known that active sportsmen can have site-specific increases in bone mass compared to a normal population. It is not well known, however, to what extent this increase in bone mass translates to an increase in bone strength. The goal of this study is to investigate if increased loading of the distal radius will result in increases in its density and strength by comparing the radii of two groups of male elite athletes: a group of rock climbers and a group of long distance runners. It is assumed that the climbers will load their radii much higher than normal whereas the runners, which are expected to load their radii in the normal range, are used as the control group. QCT scans (Siemens volume Zoom; 80 kVp, pitch 1,0.8 0.8 1 mm resolution) of the distal radius were made of the runners (N = 15) and climbers (N = 16) and these images were used to create patient-specific continuum finite element (FE) models. Linear elastic FE-analyses were performed to calculate the strains for loading conditions representing a fall on the outstretched hand and a strain-based failure criterion was used to predict the radius failure force. The pQCT scans were also used to determine BMC and BMD values of the modeled region. The FE-results indicate that the predicted failure load for the climbers group (average 2507 N) was 17% higher than the predicted failure load of the runners group (average 2142N) and this difference was significant (p<0.05). This difference was much larger than the difference in BMC (4.5% higher for climbers, not significant) but similar to the difference in BMD (17% higher for climbers, significant) of the selected distal region. These results suggest that active climbing training results in increased radial loading, density and strength and that BMD is a suitable predictor for the increase in strength.
4756 Mo, 11:30-11:45 (P7) The influence of CT parameters on Hounsfield units in cortical bone S. Pettersen 1,2, L. Nesje 3, B. Skallerud 1. 1Department of Structural
Engineering, Faculty of Engineering Science and Technology, Norwegian University of Science and Technology, Trondheim, Norway, 2Norwegian Orthopaedic Implant Research Unit, St. Olavs Hospital, Trondheim, Norway, 3Department of Radiotherapy, St. Olavs Hospital, Trondheim, Norway Many studies have tried to link elastic modulus of cortical bone to CT attenuation values [1,2] without finding any good correlation. The aim of this study was to see how the HU values in cortical bone are influenced by CT parameters such as peak voltage and X-ray tube current. Also, the results from three different multislice CT machines (Siemens Somatom 2-, 4- and 16-slice) were compared to check the repeatability of the results between the different machines. A piece of lamb femur in gelatine was scanned at different peak voltages (80-140 kV). X-ray tube current was tested at two different levels in the 4-slice machine at peak kV 140 - 9 5 mA (effective mAs 76) and 192 mA (effective mAs 153). No change was found when varying the X-ray tube current (HU192m A = 1.0 • HU95mA + 0.8, R 2 =0.996, n = 1905). Changing peak voltage had an effect on HU values in cortical bone. A relationship between HU values at different levels of peak voltage was found: HUi = a(PKV i, PKVj) • HUj, a(PKVi, PKVj):~ (PKVj/PKVi) °-61 , R 2 =0.957, n=22,860, p<0.001. The HU values at peak voltage 80kV were used to compare the results of the three CT machines. The HU values from the 16-slice machine tended to be 12% and 20% lower compared to the 2- and 4-slice machines, repectively. The HU values of the 4-slice were 10% higher compared to the 2-slice. The findings underline the importance of using proper CT phantoms with effective atomic number and densities in the range of bone when assessing material properties from CT scans. References [1] Rho et al., Relations of mechanical properties to density and CT numbers in human bone, Med. Eng. Phys. 1995. [2] Cuppone et al., Longitudinal Young's Modulus of Cortical Bone in the Midshaft of Human Femur and its Correlation with CT scanning Data, Calcif. Tissue Int. 2004.
Journal of Biomechanics 2006, Vol. 39 (Suppl 1)
(BL6, FVB, aging SAM/P6, Calcitonin- and src-deficient mice, total specimen number: n =94) were analyzed. Improved mechanical test conditions were achieved, since vertebral endplates were not transected and specimens were embedded in cement layers. Furthermore, the specimen-specific approach allowed an derivation of trabecular tissue characteristics (strength and stiffness), which correlated moderately with the tissue mineralization (R 2=0.44-0.64, power-law function). A strong correlation (R 2 = 0.99)was observed between individual morphometrical traits, such as BV/TV and trabecular architecture or BS/BV and trabecular thickness. Vertebral strength and stiffness were predicted (R 2 =0.85) using non-linear regression analysis allowing the identification of individual contribution from the cortical and trabecular structure, tissue, and architecture, independently of the mouse models analyzed. All mouse models exhibited individual skeletal phenotypes, while the aging SAM/P6 showed many similarities to senile osteoporosis and the src-deficient mouse exhibited a severe osteopetrotic phenotype. 6648 Mo, 09:30-09:45 (P5) Strain measurements in bovine cortical bone using X-ray imaging plate system K. Fujisaki, S. Tadano. Division of Human Mechanical Systems and Design,
Graduate School of Engineering, Hokkaido University, Sapporo, Japan A non-destructive measurement of strain is much important to investigate the mechanical state of bone tissue in vivo. Bone tissue is a composite material composed of HAp and collagen. As HAp is a crystalline structure, an X-ray diffraction method is available to measure the lattice strain of HAp crystals. Authors have proposed a method to measure the lattice strain of HAp with low degree of crystallinity in the bone tissue. The relationship between the macroscopic bone tissue strain and lattice strain of HAp was investigated under tensile loading. The bone tissue strain could be estimated from the lattice strains of HAp. In these measurements, a scintillation counter was used to obtain a strain at the loading direction. It is difficult to measure concurrently the strains at the several directions using the counter scanning system. In this work, X-ray imaging plate system was innovated to measure the lattice strains of HAp in various directions. In this experiment, the strip specimens were cut from cortical region in a shaft of bovine femur. When a simple tensile loading was applied to the specimen, the diffracted X-ray pattern was detected in the X-ray transmitted side. The crystal orientation of HAp was confirmed from the diffracted X-ray pattern of (002) plane detected on the imaging plate. The lattice strains of (211) plane were obtained from the patterns at the non-strained and strained state. The lattice strain was lower value than the bone tissue strain and increased linearly with the bone tissue strain at the loading direction. The two dimensional distribution of lattice strains was obtained from the patterns. The difference of the strains between the tensile or compressive side was clearly shown on the microscopic scale of HAp crystal lattice. 6541 Mo, 11:00-11:15 (PT) Cervical hip fractures predominate at low fracture loads P. Pulkkinen 1, F. Eckstein 2,3, E.-M. LochmLiller 2, V. Kuhn 2,4, T. J~ms~ 1.
1Department of Medical Technology, University of Oulu, Oulu, Finland, 2Ludwig-Maximilians-Universit~t, MEmchen, Germany, 3paracelsus Medical Private University, Salzburg, Austria, 4Medical University, Innsbruck, Austria Bone geometry has been shown to be a risk factor for osteoporotic fractures, being different in cervical and trochanteric hip fractures. However, the determinants of fracture types at different levels of fracture load are not known. The aim of the present study was to investigate the incidence of cervical and trochanteric fractures at different fracture load levels and to find the geometry and BMD determinants for the fracture type. The sample comprised left femurs of 140 cadavers (77 females, mean age 81.7, 63 males, mean age 79.1). The bones were radiographed and a set of geometrical parameters was determined from the digitized X-rays. BMD was measured in vitro using a standard DXA scanner. The femurs were mechanically tested in a side impact configuration. After the mechanical test, the fracture patterns were classified into cervical and trochanteric. The statistics was performed at fracture load quartiles. The overall proportion of cervical fractures was higher in females (74%) than in males (49%) (p=0.002). The fracture type distribution differed significantly across load quartiles in females (p=0.025), but not in males (p=0.205). At the lowest load quartiles, 94.7% of fractures in female and 62.5% in male were femoral neck fractures. At the highest quartiles, in contrast, only 52.6% of fractures in female and 33.3% in male were cervical fractures. Neck-shaft angle was the best predictor of fracture type, with higher values in subjects with cervical fractures. This finding was made in females (p < 0.001 ) and males (p=0.02) and was consistent across all failure load quartiles. As a conclusion, femoral neck fractures were the most dominant at low fracture loads, while trochanteric fractures were more common at the high fracture
Oral Presentations
loads. The best predictor of fracture type appeared to be neck-shaft angle at all fracture load levels for both genders.
4592 Mo, 11:15-11:30 (P7) Differences in radius strength between male elite rock climbers and runners determined by FE analysis of bone in-vivo J. Kunecky 1,2, W. Kemmler 3, S. von Stengel 3, K. Engelke 3, B. van Rietbergen 1. 1Eindhoven University of Technology, Eindhoven, The
Netherlands, 2Czech Academy of Sciences, Prague, Czech Republic, 3University of Erlangen-NEtrnberg, Germany It is well known that active sportsmen can have site-specific increases in bone mass compared to a normal population. It is not well known, however, to what extent this increase in bone mass translates to an increase in bone strength. The goal of this study is to investigate if increased loading of the distal radius will result in increases in its density and strength by comparing the radii of two groups of male elite athletes: a group of rock climbers and a group of long distance runners. It is assumed that the climbers will load their radii much higher than normal whereas the runners, which are expected to load their radii in the normal range, are used as the control group. QCT scans (Siemens volume Zoom; 80 kVp, pitch 1,0.8 0.8 1 mm resolution) of the distal radius were made of the runners (N = 15) and climbers (N = 16) and these images were used to create patient-specific continuum finite element (FE) models. Linear elastic FE-analyses were performed to calculate the strains for loading conditions representing a fall on the outstretched hand and a strain-based failure criterion was used to predict the radius failure force. The pQCT scans were also used to determine BMC and BMD values of the modeled region. The FE-results indicate that the predicted failure load for the climbers group (average 2507 N) was 17% higher than the predicted failure load of the runners group (average 2142N) and this difference was significant (p<0.05). This difference was much larger than the difference in BMC (4.5% higher for climbers, not significant) but similar to the difference in BMD (17% higher for climbers, significant) of the selected distal region. These results suggest that active climbing training results in increased radial loading, density and strength and that BMD is a suitable predictor for the increase in strength.
4756 Mo, 11:30-11:45 (P7) The influence of CT parameters on Hounsfield units in cortical bone S. Pettersen 1,2, L. Nesje 3, B. Skallerud 1. 1Department of Structural
Engineering, Faculty of Engineering Science and Technology, Norwegian University of Science and Technology, Trondheim, Norway, 2Norwegian Orthopaedic Implant Research Unit, St. Olavs Hospital, Trondheim, Norway, 3Department of Radiotherapy, St. Olavs Hospital, Trondheim, Norway Many studies have tried to link elastic modulus of cortical bone to CT attenuation values [1,2] without finding any good correlation. The aim of this study was to see how the HU values in cortical bone are influenced by CT parameters such as peak voltage and X-ray tube current. Also, the results from three different multislice CT machines (Siemens Somatom 2-, 4- and 16-slice) were compared to check the repeatability of the results between the different machines. A piece of lamb femur in gelatine was scanned at different peak voltages (80-140 kV). X-ray tube current was tested at two different levels in the 4-slice machine at peak kV 140 - 9 5 mA (effective mAs 76) and 192 mA (effective mAs 153). No change was found when varying the X-ray tube current (HU192m A = 1.0 • HU95mA + 0.8, R 2 =0.996, n = 1905). Changing peak voltage had an effect on HU values in cortical bone. A relationship between HU values at different levels of peak voltage was found: HUi = a(PKV i, PKVj) • HUj, a(PKVi, PKVj):~ (PKVj/PKVi) °-61 , R 2 =0.957, n=22,860, p<0.001. The HU values at peak voltage 80kV were used to compare the results of the three CT machines. The HU values from the 16-slice machine tended to be 12% and 20% lower compared to the 2- and 4-slice machines, repectively. The HU values of the 4-slice were 10% higher compared to the 2-slice. The findings underline the importance of using proper CT phantoms with effective atomic number and densities in the range of bone when assessing material properties from CT scans. References [1] Rho et al., Relations of mechanical properties to density and CT numbers in human bone, Med. Eng. Phys. 1995. [2] Cuppone et al., Longitudinal Young's Modulus of Cortical Bone in the Midshaft of Human Femur and its Correlation with CT scanning Data, Calcif. Tissue Int. 2004.