title: Internal fixation of femoral neck fractures with posterior comminution: a biomechanical comparison of DHS® and Intertan nail®.
abstract: OBJECTIVE
  Internal fixation is a therapeutic mainstay for treatment of undisplaced femoral neck fractures and fractures without posterior comminution. The best treatment for unstable and comminuted fractures, however, remains controversial, especially in older patients. The present study was designed to assess the utility of the Intertan Nail® (IT) for stabilization of comminuted Pauwels type III fractures compared to dynamic hips screw (DHS).
  
  
  METHODS
  Randomized on the basis of bone mineral density, 32 human femurs were assigned to four groups. Pauwels type III fractures were osteomized with a custom-made saw guide. In 16 specimens the posteromedial support was removed and all femurs were instrumented with an IT or a DHS. All constructs were tested with nondestructive axial loading to 700N, cyclical compression to 1,400N (10,000 cycles), and loading to failure. Outcome measures included number of survived cycles, mechanical stiffness, head displacement and load to failure.
  
  
  RESULTS
  Postoperative mechanical stiffness and stiffness after cyclical loading were significantly reduced in all constructs regardless of the presence of a comminution defect (p = 0.02). Specimens stabilized with the IT had a lower construct displacement (IT, 8.5 ± 0.5 mm vs. DHS, 14.5 ± 2.2 mm; p = 0.007) and sustained higher failure loads (IT, 4929 ± 419 N vs. DHS, 3505 ± 453 N; p = 0.036) than the DHS constructs.
  
  
  CONCLUSIONS
  In comminuted Pauwels type III fractures, the fixation with the IT provided sufficient postoperative mechanical strength, comparable rate of femoral head displacement, and a similar tolerance of physiological loads compared to fractures without comminution. The absence of the posteromedial support in comminuted fractures tended to reduce the failure load regardless of the fixation method.
authors.affiliation: Department of Trauma, Hand and Reconstructive Surgery, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany. mrupprec@uke.uni-hamburg.de
authors.forename: Martin
authors.initials: M
authors.lastname: Rupprecht
authors.forename: Lars
authors.initials: L
authors.lastname: Grossterlinden
authors.forename: Kai
authors.initials: K
authors.lastname: Sellenschloh
authors.forename: Michael
authors.initials: M
authors.lastname: Hoffmann
authors.forename: Klaus
authors.initials: K
authors.lastname: Püschel
authors.forename: Michael
authors.initials: M
authors.lastname: Morlock
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Rueger
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lehmann
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D001858:Bone Nails; D001863:Bone Screws; D002102:Cadaver; D019544:Equipment Failure Analysis; D005260:Female; D005265:Femoral Neck Fractures / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000379:methods*; D018460:Fractures, Comminuted / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology