Low modulus titanium alloy plating for femoral shaft fractures: A finite element analysis

Abstract

Objective To investigate the effects of internal plating with high and low moduli of elasticity on the stress and its distribution on the femoral shaft fracture. Methods A femur from a normal Chinese adult male was scanned by 64-detector row helical CT at 0. 5 mm interval. The CT images were used to establish a finite element model of the femur by software. The mid-femoral fracture was simulated in the model and fixated by eight-hole plates of Ti-6Al-4V (high modulus group, E = 110 GPa) and of Ti2448 (low modulus group, E = 30 GPa). When the femur was in axial compression, flexion and torsion loads, the stress and its distribution on the bone fracture site were analyzed to compare the biomechanics of the plates with high and low moduli. Results Under axial compression load, the contact stress between fracture ends in the low modulus group was larger than that in the high modulus group, while the max stress at the hole (11.47MPa) was smaller than that in the high modulus group (13.89 MPa) . Under four-point bending load, the contact stress in the low modulus group was still larger, while the bending movement was smaller. Under the torsion load, stress on the femur was well-distributed in both groups, but the max stress at the hole in the low modulus group (11.47 MPa) was smaller than that in the high modulus group (31.24 MPa). Conclusions Under internal fixation by plates of low modulus, the stress stimulus at the fracture site may be increased,while the stress concentrated at the hole may be decreased. The stress shielding of the low modulus plate may also be modified. Key words: Femoral fractures; Bone plates; Finite element analysis; Fracture fixation, internal; Modulus of elasticity