Three-dimensional Images Observation And Mechanical Characteristics Of Pauwels Type Ⅲ Femoral Neck Fracture In Young Adults

Background Pauwels classification,which categorizes types of femoral neck fractures,cannot fully reflect the three-dimensional characteristics of this injury.The purpose of our study was to determine the morphological characteristics of Pauwels Ⅲ fractures through computed tomography image analysis and to summarize the relevant biomechanical characteristics of different morphological fractures.Methods A total of 209 patients diagnosed with Pauwels type Ⅲ femoral neck fractures were retrospectively reviewed.Fracture reduction was simulated based on mirror symmetry of the bilateral femur by Mimics.The fracture angle was measured and subtypes were defined.Models of various subtype femoral neck fractures were reconstructed and fixed by four instruments: three cannulated compression screws,four cannulated screws,a dynamic hip screw,and a buttress plate combined with CCS.Biomechanical characteristics were compared by finite element analysis and validated using a biomechanical experiment,which was performed on a cadaveric sample.Results Pauwels Ⅲ femoral neck fractures can be divided into three subtypes: anterior,posterior,and classical.The proportion of three subtypes was 28.71%,67.46%,and 3.82%,respectively.The anterior subtype showed the lowest axial stiffness but highest implant and bone stress.The buttress model exhibited the highest stiffness and stress level,followed by DHS,FCS,and CCS.High stress was concentrated on the screw-bone interface and screw-plate connections.Conclusion Posterior fractures account for most of the Pauwels Ⅲ femoral neck fractures.The anterior subtype showed the lowest stiffness,which should be considered for treatment.Biomechanical differences across the three subtypes of Pauwels Ⅲ femoral neck fractures provides insight for the high failure rates and for choice of fixation implants.