Biomechanical comparison of locking femoral neck plate versus cannulated screws with or without a medial buttress plate in Pauwels type 3 femoral neck fractures.

Abstract

The aim of this study was to evaluate whether the locking femoral neck plate (LFNP) can be an alternative fixation method to the cannulated screws with a medial buttress plate. For this purpose, we compared biomechanically the LFNP and cannulated screws with or without a medial buttress plate in Pauwels type 3 femoral neck fractures. A vertical fracture model was created at an 80-degree angle to the femoral neck in 28 synthetic bone models. The models were randomly divided into 4 groups, each containing 7 bones each. The bone fracture models were fixed with 3 parallel cannulated screws in group 1, 3 parallel cannulated screws combined with a medial buttress plate in group 2, LFNP in group 3, LFNP combined with a medial buttress plate in group 4. The stability of the specimens was tested biomechanically at a 7° valgus inclination to simulate normal 2-legged weight-bearing through an anatomical femur. The forces corresponding to 0.5 mm, 1 mm, 1.5 mm, and 2 mm displacement and failure loads were calculated in all groups. The axial load values corresponding to 4 di!erent fracture displacements and the failure load values of the groups were compared, group 1 was significantly weaker (P < .05 for each) while group 4 was significantly stronger (P < .05 for each) compared to the other groups. There was no statistically significant di!erence between group 2 and group 3 (P > .05 for each). The results of this biomechanical study showed that the LFNP fixation system provided su"cient biomechanical stability for unstable Pauwels type 3 femoral neck fractures. The biomechanical performance of LFNP was similar to that of cannulated screws with medial buttress plate and better than that of cannulated screws alone. This suggests that LFNP can be a promising stable alternative fixation method to cannulated screws with a medial buttress plate in unstable femoral neck fractures.