title: Fixation properties of a biodegradable "free-form" osteosynthesis plate with screws with cut-off screw heads: biomechanical evaluation over 26 weeks.
abstract: OBJECTIVE
  The aim of this study was to compare the postoperative fixation properties of a biodegradable osteosynthesis "free-form" plate achieved with countersunk screws with those provided by screws with cut-off screw heads.
  
  
  METHODS
  Acrylic pipes were fixed together to simulate fracture fixation for tensile testing. Additional plates were fixed to a polyurethane block with a single screw for plate-screw pullout testing. Specimens were incubated in phosphate buffer solution at 37 degrees C, and testing was conducted at various time points during hydrolytic degradation of 26 weeks. In both tests the specimens were loaded at a speed of 5 mm/min until failure. The yield load, maximum load, and stiffness were recorded, and failure mode was visually determined.
  
  
  RESULTS
  Both countersunk screws and screws with cut-off screw heads provided similar plate fixation properties over degradation time.
  
  
  CONCLUSIONS
  According to these results, fixation of the biodegradable osteosynthesis free-form plate with screws with cut-off screw heads seems to be feasible.
authors.affiliation: Department of Physics, Faculty of Natural and Environmental Sciences, University of Kuopio, Kuopio, Finland.
authors.forename: Petteri
authors.initials: P
authors.lastname: Väänänen
authors.forename: Janne T
authors.initials: JT
authors.lastname: Nurmi
authors.forename: Reijo
authors.initials: R
authors.lastname: Lappalainen
authors.forename: Siegfried
authors.initials: S
authors.lastname: Jank
mesh_terms: D020341:Absorbable Implants; D001860:Bone Plates; D001863:Bone Screws; D003799:Dental Stress Analysis; D004867:Equipment Design; D005147:Facial Bones / Q000601:surgery; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006868:Hydrolysis; D019248:Jaw Fixation Techniques / Q000295:instrumentation*; D013718:Tensile Strength