Abstract:The use of bisphosphonates for osteoporosis patients has markedly decreased the incidence of femoral neck or trochanteric fractures. However, anti‐osteoporosis drugs have been reported to increase the incidence of atypical femoral fractures, which involve stress fractures in the subtrochanteric region or the proximal diaphysis. In this study, the morphological characteristics of the cortical bone in human femoral diaphysis samples were analyzed from individuals who lived before bisphosphonate drugs were availa… Show more
“…The same skeletons as those described in our previous study were used ( Imamura et al, 2019 ); among skeletal specimens of modern Japanese stored at Nagasaki University, 44 right femurs from females aged 31–87 years (mean age, 68.3 years) were examined. They were obtained from cadavers provided to the Nagasaki University School of Medicine for anatomical dissection by medical students between the 1950s and 1970s; most were voluntarily donated and from anonymous subjects.…”
Section: Methodsmentioning
confidence: 99%
“…The relationships between averaged morphological values and the biomechanical parameters of each zone were analyzed. The threshold values for the definition of the cortex were calculated as described in our previous study ( Imamura et al, 2019 ), and were assessed as follows: (i) all of the matrixes for the ten levels were pasted into one Microsoft Excel sheet, and (ii) a histogram was created based on a frequency table of CT values to calculate the mean CT value for the first peak (i.e., approximately −1000; mainly indicating the CT value of the surrounding air) and the CT value for the second peak (i.e., indicating the CT value of the bone itself). Fig.…”
Section: Methodsmentioning
confidence: 99%
“…Thus, cortical bone strongly contributes to the strength of the femur. Imamura et al focused on the morphology of the femoral diaphysis and, based on CT data, reported its cortical bone thickness, cross-sectional area (area of cortical bone in a cross-section), the cortical index, and periosteal border length in Japanese women and men before bisphosphonate drugs had been approved for treatment in order to obtain a more detailed understanding of the anatomical background of AFF ( Imamura et al, 2019 ). In women, age-related decreases were observed in cortical bone thickness, cross-sectional area, and the cortical index, and significant differences were noted in these morphological parameters between a younger group (<70 years) and older group (≥70 years).…”
The incidence of hip fractures is increasing in Japan and is high among women older than 70 years. While osteoporosis has been identified as one of the causative factors of fracture, atypical femoral fracture has emerged as a potential complication of bisphosphonate therapy. Atypical femoral fracture is prevalent among Asian women and has been attributed to morphological parameters. Age-related decreases in the morphological parameters of the femoral diaphysis, such as cortical bone thickness, cortical cross-sectional area, and the cortical index, were reported in Japanese women prior to bisphosphonate drugs being approved for treatment. Thus, in the present study, the relationships between biomechanical and morphological parameters were analyzed using a CT-based finite element method.
Finite element models were constructed from 44 femurs of Japanese women aged 31–87 years using CT data. Loading conditions were set as the single-leg configuration and biomechanical parameters, maximum and minimum principal stresses, Drucker-Prager equivalent stress, maximum and minimum strains, and strain energy density were calculated in 7 zones from the subtrochanteric region to distal diaphysis. Pearson's correlation coefficient test was performed to investigate relationships with morphological parameters.
While absolute stresses gradually decreased from the subtrochanteric region to distal diaphysis, absolute strains markedly declined in the proximal diaphysis and were maintained at the same levels as those in the distal regions. All types of stresses and minimum principal strain in the femoral diaphysis scored higher absolute values in the high-risk group (≥70 years, n = 28) than in the low-risk group (<70 years, n = 16) (p < 0.05). The distribution patterns of equivalent stress and strain energy density were similar to that of Young's modulus, except for the region of the linea aspera. All biomechanical parameters correlated with morphological parameters and correlation efficiencies, with the reciprocal of cortical bone thickness showing the strongest correlation.
The present results demonstrated that biomechanical parameters may be predicted by calculating the cortical bone thickness of femurs not treated with bisphosphonates. Furthermore, strain appeared to be repressed at a low level despite differences in stress intensities among the regions by bone remodeling. This remodeling is considered to be regulated by Wolff's law driven by equivalent stress and strain energy densities from the proximal to distal femur. The present results will promote further investigations on the contribution of morphological parameters in the femoral diaphysis to the onset of atypical femoral fracture.
“…The same skeletons as those described in our previous study were used ( Imamura et al, 2019 ); among skeletal specimens of modern Japanese stored at Nagasaki University, 44 right femurs from females aged 31–87 years (mean age, 68.3 years) were examined. They were obtained from cadavers provided to the Nagasaki University School of Medicine for anatomical dissection by medical students between the 1950s and 1970s; most were voluntarily donated and from anonymous subjects.…”
Section: Methodsmentioning
confidence: 99%
“…The relationships between averaged morphological values and the biomechanical parameters of each zone were analyzed. The threshold values for the definition of the cortex were calculated as described in our previous study ( Imamura et al, 2019 ), and were assessed as follows: (i) all of the matrixes for the ten levels were pasted into one Microsoft Excel sheet, and (ii) a histogram was created based on a frequency table of CT values to calculate the mean CT value for the first peak (i.e., approximately −1000; mainly indicating the CT value of the surrounding air) and the CT value for the second peak (i.e., indicating the CT value of the bone itself). Fig.…”
Section: Methodsmentioning
confidence: 99%
“…Thus, cortical bone strongly contributes to the strength of the femur. Imamura et al focused on the morphology of the femoral diaphysis and, based on CT data, reported its cortical bone thickness, cross-sectional area (area of cortical bone in a cross-section), the cortical index, and periosteal border length in Japanese women and men before bisphosphonate drugs had been approved for treatment in order to obtain a more detailed understanding of the anatomical background of AFF ( Imamura et al, 2019 ). In women, age-related decreases were observed in cortical bone thickness, cross-sectional area, and the cortical index, and significant differences were noted in these morphological parameters between a younger group (<70 years) and older group (≥70 years).…”
The incidence of hip fractures is increasing in Japan and is high among women older than 70 years. While osteoporosis has been identified as one of the causative factors of fracture, atypical femoral fracture has emerged as a potential complication of bisphosphonate therapy. Atypical femoral fracture is prevalent among Asian women and has been attributed to morphological parameters. Age-related decreases in the morphological parameters of the femoral diaphysis, such as cortical bone thickness, cortical cross-sectional area, and the cortical index, were reported in Japanese women prior to bisphosphonate drugs being approved for treatment. Thus, in the present study, the relationships between biomechanical and morphological parameters were analyzed using a CT-based finite element method.
Finite element models were constructed from 44 femurs of Japanese women aged 31–87 years using CT data. Loading conditions were set as the single-leg configuration and biomechanical parameters, maximum and minimum principal stresses, Drucker-Prager equivalent stress, maximum and minimum strains, and strain energy density were calculated in 7 zones from the subtrochanteric region to distal diaphysis. Pearson's correlation coefficient test was performed to investigate relationships with morphological parameters.
While absolute stresses gradually decreased from the subtrochanteric region to distal diaphysis, absolute strains markedly declined in the proximal diaphysis and were maintained at the same levels as those in the distal regions. All types of stresses and minimum principal strain in the femoral diaphysis scored higher absolute values in the high-risk group (≥70 years, n = 28) than in the low-risk group (<70 years, n = 16) (p < 0.05). The distribution patterns of equivalent stress and strain energy density were similar to that of Young's modulus, except for the region of the linea aspera. All biomechanical parameters correlated with morphological parameters and correlation efficiencies, with the reciprocal of cortical bone thickness showing the strongest correlation.
The present results demonstrated that biomechanical parameters may be predicted by calculating the cortical bone thickness of femurs not treated with bisphosphonates. Furthermore, strain appeared to be repressed at a low level despite differences in stress intensities among the regions by bone remodeling. This remodeling is considered to be regulated by Wolff's law driven by equivalent stress and strain energy densities from the proximal to distal femur. The present results will promote further investigations on the contribution of morphological parameters in the femoral diaphysis to the onset of atypical femoral fracture.
“…The direct relationship between the mechanical properties of specific skeletal regions and their intrinsic architecture has been described by several reports (Hernandez et al, 2006; Imamura et al, 2019; Liu et al, 2010; Ramchand & Seeman, 2018). In particular, cortical bone and its microstructural bone remodelling, as well as the cortical porosity (Ct.Po) and the cortical thickness (Ct.Th), have significant importance for osteoporotic bone loss and mechanical stability (Bala et al, 2014; Imamura et al, 2019; Ohlsson et al, 2017; Zebaze et al, 2019). Microstructural differences offer the opportunity to identify individuals in groups with comparable bone mineral density (BMD) who are at risk for a low‐energy trauma fracture (Nishiyama et al, 2012; Skedros et al, 2016; Vico et al, 2008).…”
Section: Introductionmentioning
confidence: 85%
“…The trabecularization of the cortex was a prominent feature observed in osteoporotic bone when compared to normal bone. A more detailed histological assessment of the periosteal, central and the endosteal regions further enabled identification of osteons at rest and those actively remodelling (Crane et al, 2019; Imamura et al, 2019). In our study, the definition of the two groups of osteons, those at rest and those actively remodelling, was based on arbitrarily defined intervals for the inner osteon diameter (Figure 4).…”
Cortical bone and its microstructure are crucial for bone strength, especially at the long bone diaphysis. However, it is still not well‐defined how imaging procedures can be used as predictive tools for mechanical bone properties. This study evaluated the capability of several high‐resolution imaging techniques to capture cortical bone morphology and assessed the correlation with the bone's mechanical properties. The microstructural properties (cortical thickness [Ct.Th], porosity [Ct.Po], area [Ct.Ar]) of 11 female tibial diaphysis (40–90 years) were evaluated by dual‐energy X‐ray absorptiometry (DXA), high‐resolution peripheral‐quantitative‐computed‐tomography (HR‐pQCT), micro‐CT (μCT) and histomorphometry. Stiffness and maximal torque to failure were determined by mechanical testing. T‐Scores determined by DXA ranged from 0.6 to −5.6 and a lower T‐Score was associated with a decrease in Ct.Th (p ≤ 0.001) while the Ct.Po (p ≤ 0.007) increased, and this relationship was independent of the imaging method. With decreasing T‐Score, histology showed an increase in Ct.Po from the endosteal to the periosteal side (p = 0.001) and an exponential increase in the ratio of osteons at rest to those after remodelling. However, compared to histomorphometry, HR‐pQCT and μCT underestimated Ct.Po and Ct.Th. A lower T‐Score was also associated with significantly reduced stiffness (p = 0.031) and maximal torque (p = 0.006). Improving the accuracy of Ct.Po and Ct.Th did not improve prediction of the mechanical properties, which was most closely related to geometry (Ct.Ar). The ex‐vivo evaluation of mechanical properties correlated with all imaging modalities, with Ct.Th and Ct.Po highly correlated with the T‐Score of the tibial diaphysis. Cortical microstructural changes were underestimated with the lower resolution of HR‐pQCT and μCT compared to the histological ‘gold standard’. The increased accuracy did not result in an improved prediction for local bone strength in this study, which however might be related to the limited number of specimens and thus needs to be evaluated in a larger collective.
Age‐related changes in human trabecular bone and cortical bone are known to vary. Although the porosity of cortical bone has been suggested to increase the risk of bone fracture, most of the currently available instruments for osteoporosis testing target trabecular bone. In this study, we evaluated cortical bone density using clinical computed tomography (CT) and compared the reliability of the cortical bone density index (CDI) with that of a polished male femoral bone from the same region. CDI images revealed that the porous area of cortical bone was extended in low CDI values. Moreover, this method was used to semi‐quantitatively evaluate the cortical bones of the diaphysis of male femur specimens (n = 46). We found that there was a significant relationship (r = 0.70, p < 0.01) between the value of the cortical index (the ratio of cortical bone area to the cross‐sectional area of the femoral diaphysis) and the average of CDI in the low signal area. Our findings suggest that the smaller the cortical bone occupancy, the more areas of consequential bone density loss were present. This may be the first step toward using clinical CT to assess cortical bone density.
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