Finite Element Modeling of Proximal Femur with Quantifiable Weight-Bearing Area in Standing Position

Abstract

Background: The positional distribution and size of the weight-bearing area of femoral head in the standing position as well as the direct active surface of joint force can directly affect the result of finite element (FE) stress analysis, however in most studies related separate FE models of femur, the division of this area is vague, imprecise and un-individualized. The purpose of this study was to quantify the positional distribution and size of the weight-bearing area of femoral head in standing position by a set of simple methods, to realize individualized reconstruction of proximal femur FE model. Methods: Five adult volunteers were recruited for X-ray and CT examination in the same simulated bipedal standing position with a specialized patented device. We extracted these image data, calculated the 2D weight-bearing area on X-ray image, reconstructed the 3D model of proximal femur based on CT data, and registered them to realize the 2D weight-bearing area to 3D transformation as the quantified weight-bearing surface. One of the 3D models of proximal femur was randomly selected for finite element analysis (FEA), and we defined three different loading surfaces, and compared their FEA results. Results: A total of 10 weight-bearing surfaces in 5 volunteers were constructed, they were mainly distributed on the dome and anterolateral of femoral head with crescent shape, in the range of 1,218.63mm2 - 1,871.06mm2. The results of FEA showed stress magnitude and distribution in proximal femur FE models among three different loading conditions were significant differences, the loading case with quantized weight-bearing area was more in accordance with the physical phenomenon of the hip. Conclusion: This study confirmed an effective FE modeling method of proximal femur, which can quantify weight-bearing area to define more reasonable load surface setting without increasing the actual modeling difficulty. Funding Statement: This study was supported by grants from the National Natural Science Foundation of China (Grant No. 81873327), Natural Science Foundation of Guangdong (Grant No. 2015A030313353), Scientific Research Project of Chinese Medicine of Guangdong (Grant No. 20191116) and Excellent Doctoral Dissertation Incubation Grant of First Clinical School of Guangzhou University of Chinese Medicine (Grant No. YB201802). Declaration of Interests: The authors declare no conflict of interest. Ethics Approval Statement: This study was conducted in agreement with the Declaration of Helsinki and its later amendments or comparable ethical standards and had been approved by the ethics board of The First Affiliated Hospital of Guangzhou University of Chinese Medicine (No: Y《2019》118).