title: Biomechanical comparison of locked plating and spiral blade retrograde nailing of supracondylar femur fractures.
abstract: OBJECTIVE
  Biomechanical comparison between locked plating and retrograde nailing of supracondylar femur fractures with simulated postoperative weight-bearing.
  
  
  METHODS
  The Locking Condylar Plate (LCP) and Retrograde/Antegrade EX Femoral Nail (RAFN) were tested using 10 paired elderly cadaveric femurs, divided into Normal and Low Bone Mineral Density (BMD) groups, with a simulated AO/OTA type 33-A3 supracondylar femur fracture. Each specimen was subjected to 200,000 loading cycles in an attempt to simulate six weeks of postoperative recovery with full weight-bearing for an average individual. The construct's subsidence due to cyclic loading, and axial stiffness before and after the cyclic loading were measured and their correlation with BMD was studied. The two implants were compared in a paired study within each BMD group.
  
  
  RESULTS
  LCP constructs showed higher axial stiffness compared to RAFN for both Normal and Low BMD groups (80% and 57%, respectively). After cyclic loading, axial stiffness of both constructs decreased by 20% and RAFN constructs resulted in twice as much subsidence (1.9 ± 0.6mm). Two RAFN constructs with Low BMD failed after a few cycles whereas the matched pairs fixed with LCP failed after 70,000 cycles.
  
  
  CONCLUSIONS
  The RAFN constructs experienced greater subsidence and reduced axial stiffness compared to the LCP constructs. In Low BMD specimens, the RAFN constructs had a higher risk of failure.
authors.affiliation: Department of Mechanical Engineering, Temple University, Philadelphia, PA 19122, United States.
authors.forename: Soroush
authors.initials: S
authors.lastname: Assari
authors.forename: Alan
authors.initials: A
authors.lastname: Kaufmann
authors.forename: Kurosh
authors.initials: K
authors.lastname: Darvish
authors.forename: Jung
authors.initials: J
authors.lastname: Park
authors.forename: Jonathan
authors.initials: J
authors.lastname: Haw
authors.forename: Fayez
authors.initials: F
authors.lastname: Safadi
authors.forename: Saqib
authors.initials: S
authors.lastname: Rehman
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D015519:Bone Density; D001858:Bone Nails; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D005260:Female; D005264:Femoral Fractures / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D008297:Male; D013314:Stress, Mechanical; D016474:Weight-Bearing
keywords: Axial stiffness; Locking Condylar Plate; Postoperative weight-bearing; Retrograde/Antegrade Femoral Nail; Supracondylar femur fracture