Our results suggested that using new configuration of an OCCS plus two HCCSs improved the outcome of vertical femoral neck fractures (FNF) patients compared to those using OCCS alone, which provides a new choice for treatment of FNF.

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Purpose The purpose of this study is to verify whether the headless cannulated compression screw (HCCS) has higher biomechanical stability than the ordinary cannulated compression screw (OCCS) in the treatment of vertical femoral neck fractures. Materials and Methods 30 synthetic femur models were equally divided into 2 groups, with 50°, 60°, and 70° Pauwels angle of femoral neck fracture, under 3D printed guiding plates and C-arm fluoroscopic guidance. The femur molds were fixed with three parallel OCCSs as OCCS group and three parallel HCCSs as HCCS group. All specimens were tested for compressive strength and maximum load to failure with a loading rate of 2 mm/min. Results The result showed that there was no significant difference with the compressive strength in the Pauwels angle of 50° and 60°. However, we observed that the maximum load to failure with the Pauwels angle of 50°, 60°, and 70° and the compressive strength with 70° of HCCS group showed better performance than the OCCS group. Conclusion HCCS performs with better biomechanical stability than OCCS in the treatment of vertical femoral neck fracture, especially with the Pauwels angle of 70°.

Purpose. To verify the biomechanical importance with respect to the integrity of posteromedial cortex of femoral neck fracture (FNF) and demonstrate whether the modified fixation of cannulated screws (CSs) could increase the biomechanical strength. Methods. A total of 24 left artificial femurs were randomly divided into three groups. The osteotomy was made in the center of the femoral neck at a 20° angle to the shaft axial. The posteromedial cortices of femoral neck were removed in groups B and C. In group A, 8 femurs with intact posteromedial cortex were fixed with three parallel partial thread screws (PTSs), forming a standard triangle. In group B, the femurs were stabilized with the same fixation of CSs like group A. In group C, two inferior PTSs were replaced by two fully thread screws (FTSs). Results. The lower A-P and axial stiffness and load to failure along with higher axial displacement were found in group B compared with group A (p≤0.001 for all). Between groups B and C, the modified fixation of CSs increased A-P and axial stiffness and load to failure and reduced the axial displacement (p≤0.001 for all). Conclusions. We verified that the comminuted posteromedial cortex affected the biomechanical strength adversely and resulted in higher displacement. The modified fixation of CSs characterized by two inferior FTSs could improve the biomechanical performance and buttress the femoral head fragment better.