title: The change in energy absorbed post removal of metalwork in a simulated paediatric long bone fracture.
abstract: OBJECTIVE
  The surgical treatment of paediatric fractures is increasing. Open reduction and internal fixation (ORIF) with plates and screws is long established, whilst the use of elastic stable intramedullary nailing (ESIN) has become increasingly popular. This study quantifies, in terms of the energy required to produce a fracture, the biomechanical sequelae of both techniques post removal of metalwork, to provide clinicians with evidence to guide post-operative advice.
  
  
  METHODS
  An immature bovine model was adopted to ascertain whether these techniques exposed the bone to a greater re-fracture risk following removal of the device. Bones were prepared to reflect ORIF or ESIN techniques, or prepared intact for the acquisition of control data. Each bone was tested to failure at 90 °/s, with the absorbed energy then being calculated to determine the relative difference between each technique and versus control data. Data describing peak shear stress and torque were recorded.
  
  
  RESULTS
  Absorbed energy was reduced by 47 % in the ORIF group compared to both the control (p = 0.011) and ESIN (p = 0.018) groups. The peak shear stress and torque were also significantly different. All ORIF bones failed through drill holes, suggesting stress localisation around the defects.
  
  
  CONCLUSIONS
  This study suggests that there is a significantly higher re-fracture risk following the removal of ORIF plates when compared to both ESIN and the control environment. Whilst this may reflect the intuitive view of many clinicians, this study provides a quantitative value of the reduction in strength and should help clinicians to appropriately caution patients and parents prior to surgery.
authors.affiliation: Trauma Biomechanics Research Group, Institute of Medical Engineering and Medical Physics, Cardiff University, Queen's Building, The Parade, Cardiff, CF24 3AA, UK, alanjhowieson@hotmail.com.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Howieson
authors.forename: Michael D
authors.initials: MD
authors.lastname: Jones
authors.forename: Peter S
authors.initials: PS
authors.lastname: Theobald