Biomechanical Evaluation of Screw Fixation With and Without Physeal Crossing in Delbet Type 2 Pediatric Femoral Neck Fractures

Background: The aim of this biomechanical study was to compare the stability of by standard cannulated screws that either cross or do not cross the physis following the fixation of a simulated Delbet type 2 fracture in a paediatric femur model. Methods: Twelve synthetic paediatric femoral bone models were randomly divided into two groups (A and B). A computed tomography was performed on one of the bones, and guides were designed to simulate a vertically unstable Delbet type 2 fracture and to send the screws. After osteotomy, in group A, the screws crossed the physis, and in group B, the screws did not cross the physis. To avoid stress below the osteotomy line during axial loading in the experiment, a 30 degree wedge was removed. The prepared samples were fixed to the platform in at 5 degrees of valgus with 2 cm of the inferior part of the shaft exposed. The experiment was continued until a displacement of 5 mm was reached. A displacement of 5 mm was considered the failure load. Results: Force differences between the two groups were analysed for each displacement level. The tests revealed no statistically significant difference between groups A and B in the forces corresponding to displacement levels of 1, 2, 3, 4 and 5 mm. Conclusion: While screws penetrating the physis provided greater resistance in Delbet type 2 fractures, this difference was not statistically significant. In transcervical paediatric femoral neck fractures, the use of screws that do not cross the physis after reduction and the use of external fixation such as a spica cast, if the child's size allows, may contribute to the initial stability of the fracture.