title: Computational modelling of long bone fractures fixed with locking plates - How can the risk of implant failure be reduced?
abstract: OBJECTIVE
  The Locking Compression Plate (LCP) is part of a new plate generation requiring an adapted surgical technique and new thinking about commonly used concepts of internal fixation using plates. Knowledge of the fixation stability provided by these new plates is very limited and clarification is still necessary to determine how the mechanical stability and the risk of implant failure can best be controlled.
  
  
  METHODS
  Upon validation, a finite element model of an LCP attached to a cylinder was developed to simulate and analyse the biomechanics of a transverse long bone fracture fixed with a locking plate. Of special interest were the factors influencing the mechanical conditions at the fracture site, the control of interfragmentary movement and implant failure.
  
  
  RESULTS
  Several factors were shown to influence stability in compression. Increasing translation and/or fracture angle post fixation reduced construct stability. Axial stiffness was also influenced by the working length and plate-bone distance. The fracture gap had no effect on the construct stability when no bone contact occurred during loading. Stress analysis of the LCP demonstrated that the maximum Von Mises stresses were found in the innermost screws at the screw-head junction.
  
  
  CONCLUSIONS
  For the clinical use of the LCP as a locked internal fixator in fractures with an interfragmentary gap of 1 mm, at least two to four plate holes near the fracture gap should be omitted to allow fracture motion and bone contact to occur. This will also achieve a larger area of stress distribution on the plate and reduce the likelihood of fatigue failure due to cyclic loading.
authors.affiliation: Cappagh National Orthopaedic Hospital, Finglas, Dublin, Ireland.
authors.forename: M
authors.initials: M
authors.lastname: Nassiri
authors.affiliation: School of Mechanical Engineering, Dublin City University, Dublin, Ireland.
authors.forename: B
authors.initials: B
authors.lastname: Macdonald
authors.affiliation: Cappagh National Orthopaedic Hospital, Finglas, Dublin, Ireland.
authors.forename: J M
authors.initials: JM
authors.lastname: O'Byrne
keywords: Failure; Fracture; Locking; Modeling; Plate