A new pediatric femoral neck system for pediatric femoral neck fractures with a free fracture fragment: a biomechanical analysis / 中华创伤骨科杂志

ABSTRACT

Objective:To investigate the biomechanical properties of a new pediatric femoral neck system in the fixation of pediatric femoral neck fractures with a free fracture fragment.Methods:Ten Sawbones model bones were randomly divided into 2 even groups ( n=5), all of which were made into Delbet Type Ⅱ femoral neck fractures with a Pauwels angle of 70°. A free bone block was removed from the bottom at the proximal end of the fracture to simulate a femoral neck fracture with a free fragment. Group A were fixed with traditional inverted triangle cannulated screws, and group B with a new pediatric femoral neck system. After the 2 groups of specimens were placed on a biomechanical testing machine, each specimen was subjected to a static axial compression test, an anti-torsion test and a cyclic load test in turn. The biomechanical results were compared between groups A and B in aspects of axial compression stiffness, torsional stiffness and maximum displacement difference. Results:The axial compression stiffness [(321.718±5.770) N/mm] and torsional rigidity [(1.448±0.079) N·m/°] in group B were significantly higher than those in group A [(266.722±4.788) N/mm and (1.282±0.023) N·m/°] ( P<0.05). The maximum displacement difference in the cyclic load test in group B [(0.063±0.038) mm] was also significantly smaller than that in group A [(0.117±0.056) mm] ( P<0.05). Conclusion:In fixation of pediatric femoral neck fractures with a free fracture fragment, the new pediatric femoral neck system can lead to better biomechanical stability than the traditional inverted triangle cannulated screws.