A Finite Element Analysis of Internal Fixations for U-Shaped Sacral Fracture

Research Purpose: To compare the stability of sacral fracture fixation with three kinds of internal fixations by using finite element method. Proposed Methods: The L4-L5 and pelvic models were intercepted from previously established and validated complete lumbar pelvic model and modified to simulate the U-shaped sacral fracture model, and fixed using the following three fixation methods. (1) screw with S1S2 passed through, (2) L4L5 pedicle screw + screw for wing of ilium, (3) L4L5 pedicle screw + screw with S1 passed through + screw for wing of ilium. A 500N force was applied for point of action where is in central position of L4 superior end-plate and coupled with superior end-plate surface, then compared the stress, strain and fracture gap separation value of different fixation methods. Results: There is no significant difference on fracture gap separation value and strain on fracture surface in above three fixation methods, however the maximum stress (101.1MPa) produced by the first fixation method is less than the one (291.1MPa) produced by the second method and the one (197.1MPa) produced by the third fixation method. Conclusions: For U-shaped sacral fracture, the prior adoption is the first fixation method to make fix.