Finite element analysis of the hip with different material assignment properties Guo Sutong1,Feng Dehong1 , Guo Yu1, Wang Ling1, Ding Yujian1, Liu Yi1, Qian Zhengying2,Li Mingyang3 (1 Department of Orthopaedics, Wuxi People's Hospital, Nanjing Medical University, Wuxi 214000, Jiangsu Province; 2 Medical Engineering Division, Wuxi People's Hospital, Nanjing Medical University, Wuxi 214000, Jiangsu Province; 3 Beijing Zhongnuo Hengkang Biotechnology Company Limited, Changping District, Beijing 102299, China) Abstract Objective To investigate the effects of three different modelling approaches on the biomechanical properties of the finite element model of the hip joint and to investigate a more realistic method of assigning material properties to the hip joint. Methods A three-dimensional reconstruction of the hip joint model was carried out, and the material parameters were assigned using the dermal- cancellous bone assignment method, the homogeneous assignment method and the gray value assignment method respectively, and the same boundary conditions and loads were set to compare the hip joint stresses and strains in the 3 groups of models. Results The stresses in the three different modelling approaches were concentrated in the medial femoral neck, with peak Von Mises stresses of 11.04 MPa, 3.91 MPa and 4.25 MPa for the cortical bone and cancellous bone assignment method, the homogeneous assignment method and the gray value assignment method, respectively. The maximum strain in the hip joint cortical bone and cancellous assignment model is at the upper part of the greater trochanter, with a peak strain of 0.27 mm at the acetabulum and femoral head. the maximum strain in the homogeneous material assignment model and the gray value assignment model is at the acetabulum and femoral head, with peak strains of 0.11 mm and 0.12 mm respectively. Conclusion The gradient assignment based on the gray value of the hip CT data makes the material property distribution of the hip model closer to the real material properties of the bone. Keywords: hip joint; cortical bone and cancellous bone assignment method; homogeneous assignment method; gray value assignment method