Biomechanical performance evaluation of S2AI combine with LC-2 screw for day II pelvic crescent fracture dislocation via finite element analysis

Plate fixation is a classic method for treating day II crescent fracture dislocation of the pelvic (CFDP). However, due to the advantages of minimally invasive techniques and reduced complications associated with internal fixation percutaneous cannulated screws have emerged as a promising alternative for treating Day II CFDP. In this study, we propose using an S₂AI screw combined with an LC-2 screw (S₂AI + LC-2) for the treatment of Day II CFDP. The aim of this study was to compare its biomechanical stability with that of two conventional fixation methods using finite element analysis (FEA). A finite element (FE) model of pelvic was developed and validated. Three fixation methods were applied: S₁ sacroiliac (SI) screws combined with LC-2 screw (S₁ + LC-2), S₁ and S₂ SI screws combined with LC-2 screw (S₁ + S₂ + LC-2), and S₂AI + LC-2. A 500 N load was applied, and the displacement of the crescent fracture fragments, the stress distribution of the implants, the displacement of the SI joint, and the maximum stress on the bone surrounding the screws were analyzed across the three FE models. After loading 500 N stress, the maximum displacement of the crescent fracture fragment and the maximum stress of bone around the implant in the S₂AI + LC-2 group were the smallest in three groups. The displacement of SI joint in S₂AI + LC-2 group was less than that in S₁ + LC-2 and S₁ + S₂ + LC-2 (P < 0.001). The maximum stress of implants in each group is smaller than the yield stress of titanium. The maximum stress of the bone around the screws at SI joint in all models lower than the yield strength of cortical bone. The maximum stress of the bone around LC-2 screws in all models lower than the yield strength of cancellous bone. The S₂AI + LC-2 group can achieve reliable stability of the SI joint, and the stress on the bone around the screw could be reduced. The S₂AI + LC-2 group has good biomechanical stability and can be considered as a new implant to treat Day II CFDP.