LAUSR

Objective Day type II crescent fracture–dislocation is a subtype of pelvic lateral compression injury. At present, there is still a controversy on the operative approach and fixation technique. We have put forward closed reduction and percutaneous crossed screws fixation for treating type-II crescent fracture–dislocation. Finite element analysis is used to compare the biomechanical properties between percutaneous crossed screws and other internal fixations. Methods A three-dimensional finite element model of Day type-II crescent fracture–dislocation was simulated using 5 implants, including double anterior plates (Model A), one posterior plate and one iliac screw (Model B), one sacroiliac joint screw (Model C), crossed one iliac screw and one sacroiliac joint screw (Model D), and crossed two iliac screws and one sacroiliac joint screw (Model E). 600-N stress was applied to S1 vertebral end-plate. To evaluate the biomechanical properties, the stress distribution and displacement distribution of the pelvis, stress distribution of the crescent fragment and stress distribution of plate and cannulated screw were recorded and analyzed. Results Under the loading of 600N, the maximum pelvic displacements in the finite element model were compared as follows: model E (0.070 mm), model D (0.071 mm), model A (0.080 mm), model C (0.096 mm), and model B (0.112 mm). The maximum displacements of crescent fragment were compared as follows: model E (0.018 mm), model B (0.022 mm), model D (0.023 mm), model A (0.030 mm), and model C (0.043 mm). The maximum stress of all implants were compared as follows: model D (90.01 Mpa), model E (81.60 Mpa), model C (69.07 Mpa), model A (56.51 Mpa), model B (18.29 Mpa). Model E and model D could provide better mechanical support for whole pelvic. Conclusions With sufficient biomechanical stability and minimally invasive advantage, percutaneous crossed screw fixation is a recommended treatment for Day Type-II Crescent Fracture–dislocation. It is recommended to fix crescent fracture fragment and sacroiliac joint simultaneously during the operation. If it is difficult to fix the both position, the sacroiliac joint is preferentially fixed. The translational potential of this article There is a controversy on the operative approach and fixation technique of Day type-II crescent fracture–dislocation. This article proves that percutaneous crossed screw fixation is a recommended treatment for Day type-II crescent fracture–dislocation by finite element analysis.