Institute of Biomedical Engineering, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin (300192), China;Department of Digital Bone Science, Tianjin Hospital, Tianjin University, Tianjin University, Tianjin 300050, China
Abstract:
Objective To explore the biomechanical properties of different internal fixation for Pauwels III femoral neck fracture and their clinical implications. Methods The three-dimensional digital model of the femur from a heathy male volunteer was reconstructed. The femur was modelled to Pauwels III femoral neck fracture and the models of different fixations were assembled. The 3D finite element models of the femur and five internal fixations were established, in which axial stresses of 1400 N were loaded. We measured and compared respectively the von Mises stress and displacement distributions in different fixations and on the femurs fixated by the five implants, as well as the stress and displacement peak values. Results The stress on the implant and femur were mainly located on the femoral neck and femoral shaft, and the stress increased near the fracture line. The displacement of the internal fixation mainly distributed on the screw tip inside the femoral head. The displacement of the femur is concentrated on the top of the femoral head, where the stress loaded. Among the five internal fixations, four cannulated screws had the minimum peak stress (135.3 MPa). Locking compression plate had the maximum peak stress (405.9 MPa) and the minimum peak displacement (12.3 mm). The maximum peak displacement (18.8 mm) was founded on the three cannulated screws. The minimum peak stress (36.8 MPa) of femur appeared when three cannulated screws fixed, as well as the maximum peak displacement (19.3 mm). Meanwhile the maximum peak stress (104.6 MPa) and the minimum peak displacement (12.6 mm) of femur appeared when locking compression plate fixed. Conclusion Locking compression plate has the most stability in five internal fixations, but at the same time the femur and internal fixation will bear greater pressures and shear forces. In addition, dynamic hip screw has an advantage in promoting fracture healing in the short term, however intramedullary nail is better for long-term fixation.
