Biomechanical Comparison of Dynamic Hip Screw, Proximal Femoral Nail, Cannulated Screw, and Monoaxial External Fixation in the Treatment of Basicervical Femoral Neck Fractures

Abstract

PURPOSE OF THE STUDY The objective of this study was to establish relative fixation strengths of proximal femoral nail (PFN), dynamic hip screw (DHS), monolateral external fixator (EF), and cannulated screw (CS) in basicervical hip fracture model. MATERIAL AND METHODS The study involved four groups of implanted composite proximal femoral synthetic bones of eight specimens per group; nailing with PFN, DHS, fixation with three cannulated screws, and EF. 70˚ osteotomy was performed to simulate a Pauwels Type 3 basicervical fracture. Minimum preload of 100 N was applied before loading to failure. The constructs were subjected to cyclic loading with 16˚ to midline from 100 N to 1,000 N for 10,000 cycles at 3Hz. Axial loading was applied at 10 mm/min until failure. Failure load, failure mode, and displacement were documented. RESULTS Mean failure load was 2182.5 ± 377.9 N in PFN group, 2008.75 ± 278.4 N in DHS group, 1941.25 ± 171.6 N in EF group, and 1551.6 ± 236.2 N in CS group. Average displacement was 15.6 ± 4.5 mm, 15.5 ± 6.7 mm, 11.7 ± 1.9 mm, and 15 ± 1.7 mm, respectively. No significant difference was noted among groups for fixation strength except CS group. All CS constructs failed during cyclic loading. CONCLUSION Our findings suggest that PFN, DHS and EF achieved higher fixation strengths than CS in basicervical fracture. PFN has higher failure loads and possesses biomechanical benefits for fixation of unstable basicervical fractures compared with DHS and EF. Key words: basicervical fracture, internal fixation, biomechanics.