title: Intramedullary fixation of unstable intertrochanteric hip fractures: one or two lag screws.
abstract: OBJECTIVE
  To compare the screw sliding characteristics and biomechanical stability of four-part intertrochanteric hip fractures stabilized with an intramedullary nail using either one large-diameter lag screw (intramedullary hip screw [IMHS]; Smith & Nephew, Memphis, TN) or two small-diameter lag screws (trochanteric antegrade nail [TAN]; Smith & Nephew, Memphis, TN).
  
  
  METHODS
  Laboratory investigation using eight matched pairs of cadaveric human femurs with simulated, unstable intertrochanteric hip fractures.
  
  
  METHODS
  One femur of each matched pair was stabilized with an IMHS intramedullary nail, and the other was stabilized with a TAN intramedullary nail. Femurs were statically, then cyclically loaded on a servohydraulic materials testing machine. Finally, all specimens were loaded to failure.
  
  
  METHODS
  Screw sliding and inferior and lateral head displacements were measured for applied static loads from 500N to 1250N. The same measurements were obtained before and after cyclically loading the specimens at 1250N. Ultimate failure strength of the implant constructs also was determined.
  
  
  RESULTS
  There was no significant difference between the TAN and IMHS in static or cyclical loading with respect to screw sliding or inferior and lateral head displacements. There was a statistically significant difference (P < 0.02) in failure strength, with the IMHS construct failing at an average of 2162N and the TAN construct failing at an average of 3238N.
  
  
  CONCLUSIONS
  The two constructs showed equivalent rigidity and stability in all parameters assessed in elastic and cyclical tests. The TAN had a greater ultimate failure load.
authors.affiliation: Department of Orthopaedic Surgery, NYU-Hospital for Joint Diseases, 301 East 17th Street, New York, NY 10003, USA.
authors.forename: Erik N
authors.initials: EN
authors.lastname: Kubiak
authors.forename: Mathew
authors.initials: M
authors.lastname: Bong
authors.forename: Samuel S
authors.initials: SS
authors.lastname: Park
authors.forename: Fred
authors.initials: F
authors.lastname: Kummer
authors.forename: Kenneth
authors.initials: K
authors.lastname: Egol
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Koval
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D001863:Bone Screws; D005260:Female; D005594:Fracture Fixation, Intramedullary / Q000379:methods*; D006620:Hip Fractures / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged