Stability evaluation of anterior external fixation in patient with unstable pelvic ring fracture: a finite element analysis

The pelvic ring fractures (PRF) are commonly induced by the high-energy impact and will lead to unstable and sever injures. This study is aimed to explore the stability of anterior external fixation in treating pelvis fracture and evaluate the possibility for these kinds of patients to reduce bedridden time.A patient with Tile B3 pelvis fracture was chosen in the research and the corresponding digital model was reconstructed according to the CT images and 3D scanning. Four angles of pelvis under vertical compression were employed in the finite element (FE) analyses. The stress distribution and micro-motion displacement were calculated to validate the instability of pelvis.The stress applied on the pelvis was ranged from 4.296 to 8.364 MPa in all postures. The stress applied on pins was less than 7.011 MPa during reclining, and reached 28.29 MPa when standing. The micro-motion displacement in reclining posture was ranged from 0.005 to 0.087 mm. The value increased to more than 1mm in standing posture.It was safety for patients with pelvis fracture to sit vertical or recline on the bed during nursing or having treatment, but standing or walking will generate inappropriate micro-motion. The existence of external fixation can reduce the possibility of complications caused by long-term bedridden.