title: Intramedullary screw fixation of Jones fractures.
abstract: BACKGROUND
  Jones fractures of the fifth metatarsal can be stabilized using intramedullary screw fixation techniques. A range of screw diameters from 4.5 mm to 6.5 mm can be used, but the optimal screw for this procedure has yet to be defined. In clinical practice, we have observed that failure is more likely when smaller diameter screws are used.
  
  
  METHODS
  Experimental Jones fractures were created in 23 pairs of human cadaver fifth metatarsals, which were fixed using either 5.0 mm or 6.5 mm screws. Fracture stiffness and pull-out strengths were measured for either screw type and their relationships with bone mineral density and medullary canal diameter were determined.
  
  
  RESULTS
  There was no significant difference in the bending stiffness of fractures stabilized with 5.0 mm and 6.5 mm screws; however, different mechanisms of failure were noted for either screw type. Poor thread purchase within the medullary canal was noted with the 5.0 mm screws, while excellent purchase was noted with 6.5 mm screws. Pull-out strength testing revealed significantly higher pullout strengths for the larger 6.5 mm screws. There was no significant difference in bone mineral density or medullary canal diameter between right and left metatarsals.
  
  
  CONCLUSIONS
  Fifth metatarsals can often accommodate a 6.5 mm screw for the stabilization of Jones fractures. Larger diameter screws did not result in greater fracture stiffness in our model, but did result in significantly greater pull-out strengths.
  
  
  CONCLUSIONS
  Larger diameter screws may be more appropriate for intramedullary screw fixation of Jones fractures.
authors.affiliation: Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: I P
authors.initials: IP
authors.lastname: Kelly
authors.forename: R R
authors.initials: RR
authors.lastname: Glisson
authors.forename: C
authors.initials: C
authors.lastname: Fink
authors.forename: M E
authors.initials: ME
authors.lastname: Easley
authors.forename: J A
authors.initials: JA
authors.lastname: Nunley
mesh_terms: D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation* / Q000379:methods; D050723:Fractures, Bone / Q000601:surgery*; D006801:Humans; D008682:Metatarsal Bones / Q000293:injuries* / Q000601:surgery; D011474:Prosthesis Design