Dynamic hip screw and Gamma nail fixation repair unstable intertrochanteric fracture:a three-dimensional finite element analysis / 中国组织工程研究

ABSTRACT

BACKGROUND:For unstable intertrochanteric fracture repair, there are two viewsextramedul ary fixation or intramedul ary fixation. Theoretical y, intramedul ary fixation is in line with the principles of minimal y invasive, more mechanical and biological advantages. However, evidence-based medicine and related studies have shown that compared with the extramedul ary fixation, intramedul ary fixation did not reflect the proper theoretical advantage. OBJECTIVE:To compare the biomechanical performance of two kinds of internal fixation systemsdynamic hip screw and Gamma nail which commonly used in repair of intertrochanteric fractures by finite element method, and to evaluate the advantages and disadvantages of dynamic hip screw and Gamma nail in treatment of unstable intertrochanteric fracture. METHODS:Three-dimensional finite element model of human femur unstable intertrochanteric fractures (31-A2;AO fracture classification), and the three-dimensional finite element models of dynamic hip screw and Gamma nail were established respectively, and were fixed according to the requirement of orthopedic surgery. The reference load which the joint bearing was at the peak time in adult step state period with the body mass of 700 N was stimulated. The stress distribution of bone, bone-internal fixation model, nail or screw, the strain and deformation of fracture location on the surface of the bone and bone-internal fixation model, the stress distribution along the femur and the loading transfer condition along the internal fixator and the like were analyzed. RESULTS AND CONCLUSION:Dynamic hip screw and Gamma nail have good sliding compression features which could make the continuous and dynamical y axial compression of the fractured section. Under the load conditions, the displacement value of dynamic hip screw was larger. In the treatment of unstable intertrochanteric fracture, Gamma nail was stronger than dynamic hip screw. Two kinds of internal fixations al make the bearing load of the proximal femur reduce. In the treatment of 31-A2 type unstable intertrochanteric fractures, we should choose dynamic hip screw for fixation if the femoral calcar was not seriously crushed, little defect or no defects and can immediately rebuild the stability of femoral calcar during operation, otherwise, stronger internal fixation, namely Gamma nail fixation should be chosen.