Abstract: BACKGROUND: Bone mineral density is the clinical gold standard for determining bone strength, but bone mineral density is less sensitive to changes in bone mass, with large changes in bone mineral density only occurring when bone mass is significantly reduced, so bone mineral density has limited ability to predict changes in bone strength and fracture risk.  
OBJECTIVE: A model of the normal and osteoporotic hip joint was developed to analyze the stresses and deformation in the hip of normal and osteoporotic patients under single-leg standing conditions.
METHODS: A healthy adult female volunteer at the age of 36 years was selected as the study subject. The CT data of the hip joint of this volunteer were obtained and saved in DICOM format. The hip joint model was reconstructed in three dimensions, and the material properties were assigned by the gray value assignment method to obtain the normal and osteoporotic hip joint models according to the empirical formula. The same boundary conditions and loads were set to simulate the stresses and deformation in the normal and osteoporotic hip joints in the single-leg standing position.  
RESULTS AND CONCLUSION: (1) In the finite element model of the normal and osteoporotic hip, the stress distribution was more concentrated in the medial region of the femoral neck. (2) In the hip bone, the stress distribution was mainly concentrated in the upper part of the acetabulum. (3) The stress peaks in the medial femoral neck and upper acetabulum were larger in the normal hip model than in the osteoporotic hip model, probably due to the reduced bone strength of the osteoporotic bone. (4) The peak Von Mises of both normal and osteoporotic hip models were concentrated on the medial femoral neck, and the peak Von Mises of the hip bone was smaller, indicating that the overall effect of osteoporosis on hip bone stresses was relatively small. (5) In terms of deformation in the single-leg standing position, the maximum deformation in the normal hip model was located at the acetabulum and femoral head, and the maximum deformation was located at the upper part of the greater trochanter of the femur. (6) It is suggested that the finite element analysis method to model the values of parameters related to bone tissue in osteoporosis may improve clinical prediction of bone strength changes and fracture risk. It is explained from the biomechanical view that the intertrochanteric femur and femoral neck are good sites for osteoporotic hip fractures.

Key words: hip joint, osteoporosis, gray value assignment method, stress, deformation, finite element