title: Biomechanical analysis of augmented plate fixation for the treatment of vertical shear femoral neck fractures.
abstract: OBJECTIVE
  To compare the strength of augmented versus nonaugmented fixation techniques for stabilizing vertical shear femoral neck fractures.
  
  
  METHODS
  Two surgical screw constructs were tested with and without augmentation using 40 composite femurs: (1) 7.3-mm cannulated screws placed in an inverted triangular configuration and (2) 135-degree dynamic hip screw (DHS). The augmentation consisted of a 2.7-mm locking plate placed on the anterior-inferior femoral neck. Specimens in all 4 groups were tested with load to failure, while failure loads, energy absorbed to failure, and axial stiffness were determined. These data were then analyzed using a two-way (construct × augmentation) analysis of variance.
  
  
  RESULTS
  There was no statistically significant interaction between screw construct and augmentation for load to failure (P = 0.11). Augmentation with the 2.7-mm locking plate increased failure loads in both constructs on average by 83% (2409 vs. 4417 N, P < 0.01). Femurs instrumented with cannulated screws had 26% higher loads to failure than those instrumented with DHS (3879 vs. 3087 N, P < 0.01). On average, the augmentation increased energy absorbed to failure by 183% and constructs' stiffness by 35%.
  
  
  CONCLUSIONS
  The strength of surgical repairs of the vertical shear femoral neck fractures can be significantly augmented with the 2.7-mm locking plate. The construct with the cannulated screws was significantly stronger than the DHS construct.
authors: *MSU Center for Orthopedic Research, College of Osteopathic Medicine, Michigan State University, East Lansing, MI; †Eastern Oklahoma Orthopedic Center, Tulsa, OK; ‡St. Clair Orthopaedics and Sports Medicine, St. Clair Shores, MI; and §OrthoIndy, Indianapolis, IN.
authors: Sarat C
authors: SC
authors: Kunapuli
authors: Matthew J
authors: MJ
authors: Schramski
authors: Angela S
authors: AS
authors: Lee
authors: John M
authors: JM
authors: Popovich
authors: Jacek
authors: J
authors: Cholewicki
authors: N Peter
authors: NP
authors: Reeves
authors: Renn J
authors: RJ
authors: Crichlow
mesh_terms: D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D005265:Femoral Neck Fractures / Q000503:physiopathology* / Q000601:surgery; D005593:Fracture Fixation, Internal / Q000295:instrumentation; D006801:Humans; D008953:Models, Anatomic