title: Mechanical comparison of a distal femoral side plate and a retrograde intramedullary nail.
abstract: OBJECTIVE
  To compare quantitatively the axial and torsional stiffness of a retrograde intramedullary nail and a fixed angle screw side plate in treating a supracondylar femur fracture in osteopenic femora. To determine the modes of failure of an intramedullary nail and a side plate under axial loading.
  
  
  METHODS
  Matched pair cadaveric study.
  
  
  METHODS
  Orthopaedic biomechanics laboratory.
  
  
  METHODS
  Eleven matched pairs of preserved human femora were selected. The cadaveric specimens were harvested from relatively elderly donors with an average age of 75.6 years, which represents the principal population at risk for poor fracture fixation.
  
  
  METHODS
  The eleven matched pairs were osteotomized to simulate segmental structural defects in the supracondylar region. One femur of each matched pair was fixed with an intramedullary nail, and the contralateral femur was fixed with a side plate.
  
  
  METHODS
  Axial and torsional stiffness values. Axial modes of failure.
  
  
  RESULTS
  The intramedullary nail axial stiffness was 14 percent (p = 0.04) less and torsional stiffness was 17 percent (p = 0.05) less than that provided by the side plate. The axial failure of the intramedullary nail occurred distally, allowing the hardware to protrude into the articular space. The side plate also failed distally by displacing the condylar screw into a varus angulation.
  
  
  CONCLUSIONS
  The mechanical advantages favor the use of the side plate if fixation stiffness is essential. The axial mode of failure occurs distally for both fixation devices.
authors.affiliation: Finger Lakes Orthopaedic Surgery, Elmira, New York, USA.
authors.forename: R W
authors.initials: RW
authors.lastname: Meyer
authors.forename: N A
authors.initials: NA
authors.lastname: Plaxton
authors.forename: P D
authors.initials: PD
authors.lastname: Postak
authors.forename: A
authors.initials: A
authors.lastname: Gilmore
authors.forename: M I
authors.initials: MI
authors.lastname: Froimson
authors.forename: A S
authors.initials: AS
authors.lastname: Greenwald
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001858:Bone Nails / Q000592:standards*; D001860:Bone Plates / Q000592:standards*; D002102:Cadaver; D019245:Compressive Strength; D004548:Elasticity; D004867:Equipment Design; D005260:Female; D005264:Femoral Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation*; D018460:Fractures, Comminuted / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D011859:Radiography; D013718:Tensile Strength; D014102:Torsion Abnormality; D016474:Weight-Bearing