Determination of Optimum Volumetric Area Projection for Cannulated Screw Internal Fixation of Femoral Neck Fractures in Porcine Animal Models

Abstract

Femoral neck fractures not only carry a higher mortality rate amongst elderly individuals, they also pose a significant social and economic burden as a result of perioperative and postoperative costs. Depending on the severity of fracture and patient candidacy, orthopedic surgeons may opt for joint arthroplasty or open reduction internal fixation methods such as percutaneous cannulated screw fixation (PCSF). There is currently no general consensus on the optimum screw configuration for femoral neck internal fixation using the PCSF method. This research aims to investigate the biomechanical stability of three-screw and four-screw configurations of either prismatic or pyramidal volumetric projections in porcine animal models, evaluating the maximum axial load and shear stress sustained prior to failure of bone as a material to provide conclusive data to improve fracture fixation longevity and patient quality of life following surgery. Thirty two porcine femora were cleaned of soft tissue, measured, and potted in epoxy resin prior to fracture generation and fixation. Testing protocols involved ramp, cyclic fatigue, and failure testing to obtain data on maximum axial force and failure shear forces. Rectangular base pyramids configurations sustained the highest maximum axial force on average prior to failure, followed by rectangular base prism, triangular base prism, and triangular base pyramid configurations. Shear stress data revealed that the rectangular base prism configuration sustained the most shear stress prior to failure, followed in descending order by the rectangular base pyramid, triangular base prism, and triangular base pyramid configurations. Single factor ANOVA analysis of the maximum axial force and maximum shear stress found a p value of p < 0.119 and p < 0.256, respectively, and unpaired t test data for the same parameters revealed no statistical significance between any sets of the groups. For future studies, it should be expected that a control group is established to provide baseline data for comparison, experimental groups have a sample size of at least 30 specimens, and analysis of failure rate of each configuration to make definitive conclusions regarding the biomechanical stability of triangular base pyramid, triangular base prism, rectangular base pyramid, and rectangular base prism percutaneous cannulated screw fixation methods.