title: Bicortical screw fixation provides superior biomechanical stability but devastating failure modes in periprosthetic femur fracture care using locking plates.
abstract: OBJECTIVE
  The incidence of periprosthetic fractures is inevitably increasing. Sufficient stabilisation and proper screw placement next to large-volume implants remains difficult. Modern locking plates allow polyaxial, thus bicortical, screw placement around a prosthetic stem. This study analysed the biomechanical properties of different screw configurations in a locking plate construct of a periprosthetic femoral fracture model.
  
  
  METHODS
  A total of 20 Sawbones were used to stabilise a Vancouver-B1 femoral fracture with a locking plate using either four monocortical screws or three bicortical screws for proximal fixation. These were loaded with an increasing axial compression until failure.
  
  
  RESULTS
  Bicortical screw purchase was significantly superior to monocortical regarding load to failure (1,510 N ± 284 N versus 2,350 N ± 212 N, p < 0.001) and maximal number of cycles (6803 ± 760 versus 4041 ± 923, p < 0.001). However, the mode of failure in the bicortical group was a severe comminuted fracture pattern as opposed to the monocortical group in which a pull-out of the screws without further damage to the bone was observed.
  
  
  CONCLUSIONS
  Bicortical screw placement enhances the primary stability in treating periprosthetic femoral fractures. Notably, the mode of failure may limit the salvage options in case of revision surgery.
authors.affiliation: Centre for Musculoskeletal Surgery, Charité - University Medicine Berlin, Augustenburger Platz 1, 13353, Berlin, Germany, clemens.gwinner@charite.de.
authors.forename: Clemens
authors.initials: C
authors.lastname: Gwinner
authors.forename: Sven
authors.initials: S
authors.lastname: Märdian
authors.forename: Tobias
authors.initials: T
authors.lastname: Dröge
authors.forename: Martin
authors.initials: M
authors.lastname: Schulze
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Raschke
authors.forename: Richard
authors.initials: R
authors.lastname: Stange
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws / Q000009:adverse effects*; D005264:Femoral Fractures / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000009:adverse effects* / Q000295:instrumentation; D018460:Fractures, Comminuted / Q000209:etiology / Q000601:surgery; D006801:Humans; D008953:Models, Anatomic; D057068:Periprosthetic Fractures / Q000601:surgery*; D011475:Prosthesis Failure; D012086:Reoperation