title: Comparative study of the pullout strength of the 2.4-mm AO locking screw, 2.0-mm AO cortical screw and Herbert screw in sawbones: a biomechanical study.
abstract: BACKGROUND
  Headless screw is a standard implant for an osteochondral fragment fixation. With a threaded design, the screw head can be buried under the articular cartilage to prevent a post-traumatic arthritis. However, the screw is expensive and maybe not available in the emergency situation. The 2.4-mm AO locking screw also has a threaded head which is able to advance underneath the cartilage. This has been usedfor fixation of the osteochondal fracture clinically. We compared the pullout strength of 2.4-mm AO locking screw with those ofHerbert screw and 2.0-mm AO cortical screw.
  
  
  METHODS
  The studies pemformed by using Instron 4502 to measure the pullout strength in 12 models for each type of the screw. The pullout strength of the 2.4-mm AO locking screw from a corticocancellous bone model was compared with the pullout strength of the Herbert screw from a cancellous bone model and the 2.0-mm AO cortical screw ifom the corticocancellous bone model. The differences in pullout strength between the 2.4-mm AO locking screw and the other two screws were determined by independent t-test.
  
  
  RESULTS
  The pullout strength of the 2.4-mm AO locking screw, Herbert screw and 2.0-mm AO cortical screw were 143.49+46.18 N, 72.83 +/- 16.64 N, and 80.38 +/- 1.42 N, respectively. The pullout strength of2.4-mm AO locking screw was signi2ficantly higher than those ofHerbert screw and 2.0-mm AO cortical screw (p<0.001).
  
  
  CONCLUSIONS
  According to the recent biomechanical study, the 2.4-mm AO locking screw in the corticocancellous bone model had pullout strength higher than the Herbert screw in the cancellous bone model and the 2.0-mm AO cortical screw in corticocancellous bone model. The 2.4-mm AO locking screw may use instead of headless screw for intra-articular fixation in a specific situation, such as when the headless screw is unavailable.
authors.forename: Arkaphat
authors.initials: A
authors.lastname: Kosiyatrakul
authors.forename: Soon
authors.initials: S
authors.lastname: Sompan
authors.forename: Suriya
authors.initials: S
authors.lastname: Luenam
mesh_terms: D001696:Biomechanical Phenomena; D001863:Bone Screws; D005592:Fracture Fixation / Q000295:instrumentation*; D006801:Humans; D008954:Models, Biological