Reduced cortical bone thickness increases stress and strain in the female femoral diaphysis analyzed by a CT-based finite element method: Implications for the anatomical background of fatigue fracture of the femur

Abstract

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.

Biomechanical Stress Analysis of Platform Switch Implants of Varying Diameters on Different Densities of Bone

“…The results also indicate greater bone strain values on the buccal cortical plate as compared to the lingual cortical plate irrespective of the implant diameter and density of bone. This is may be due to the fact that buccal cortical plate is relatively thinner when compared to the lingual cortical plate [ 16 ]. The results also indicate greater bone strain values in the D2 type of bone as compared to the D3 type of bone.…”

Application of Methods for a Morphological Analysis of the Femoral Diaphysis Based on Clinical CT Images to Prehistoric Human Bone: Comparison of Modern Japanese and Jomon Populations from Hegi Cave, Oita, Japan

“…However, as our previous studies have shown, the trends of age-related changes were different for diaphyseal peripheral border length and thickness of cortical bone. On the other hand, the thickness of cortical bone not peripheral border length was strongly correlated with the stress and strain applied to the femur with one-legged standing configuration estimated with the finite element method [ 11 ], suggesting that external measurement of femoral morphology alone is insufficient to estimate its function and that it is essential to analyze its internal structure. For this reason, many analyses have been performed using CT [ 24 – 26 ], but measurement conditions must be uniform to compare results among different populations.…”

“…Mean cortical bone thickness in each cross-section was also larger in Initial/Early and Late Jomon femurs than in modern femurs, both before and after standardization by diaphyseal length. A previous study reported that the mean thickness of the diaphysis in modern skeletal specimens correlated with the stresses and strains applied to the diaphysis during a one-legged stance [ 11 ]. Furthermore, mean thickness values were high in Jomon humans, indicating that their femurs were highly resistant to force, particularly that applied along the bone axis.…”

“…This analysis revealed marked diversity in the morphology of cortical bone and also showed that the area of cortical bone, CI, and cortical bone thickness were affected by sex and age. We previously demonstrated that bone morphology correlated with mechanical functions by comparing these quantitative values to the findings of a finite element analysis using a 3D model constructed from CT images [ 11 ]. In addition to the estimation of disease risk, bone morphology has been considered to reflect the living environment of adults [ 12 – 14 ] based on Wolff's law that bone morphology changes to adapt to a given load [ 15 ].…”

The Effect of Humanized Nursing Intervention Guided by Computed Tomography Images on Elderly Patients Undergoing Anesthesia for Femur Intertrochanteric Fractures under Intelligent Reconstruction Algorithm

“…After FIF, it often causes hip pain, swelling, deformity, and limitation of movement [ 3 – 5 ]. If FIF is treated nonsurgically, it has many complications, and it is prone to complications such as pressure ulcers, lung infections, urinary tract infections, and deep vein thrombosis of the lower extremities, which can easily endanger the lives of patients [ 6 ]. Therefore, if the patient has no obvious surgical contraindications, for FIF, surgical treatment is recommended to stabilize the fracture end, shorten the patient's bedtime, and reduce the complications of the patient's bed [ 7 , 8 ].…”