title: Analysis of the influence of bone fragment displacement in long bone fractures on interfragmentary contact surface.
abstract: BACKGROUND
  The aim of the study was to validate the impact of angular and lateral displacements of bone fragments on the interfragmentary contact surface. Mathematical analysis was performed in a model of transverse fracture of long bone shaft treated as a tubular structure with a diameter of 42 mm. We performed our calculations for cortical thickness of 4, 6 and 8 mm.
  
  
  METHODS
  Displacements to the side were analyzed within a range from 0 to a half of bone diameter (21 mm), and angular displacements within a 0-18 degree range. Acquired results were related to the contact area of a non-displaced fracture.
  
  
  RESULTS
  Lateral displacement of bone fragments equal to the width of bone's cortical layer (4, 6 and 8 mm) leads to a decrease in interfragmentary contact area to 48.6%, 51.3% and 54.6%, while displacement equal to a half of bone's diameter--to 7.9%, 20.1% and 28.4% of the contact area in an anatomically reduced fracture for cortical thickness values of 4, 6 and 8 mm respectively. Interfragmentary contact area equal to 80% of anatomically reduced fracture is achieved for displacements of 1.5 mm, 2.4 mm and 3.5 mm, corresponding to 3.6%, 5.7% and 8.3% of bone diameter, and to 37.5%, 40% and 42.5% of its cortical thickness (4, 6 and 8 mm, respectively). Angular displacement of less than 2.5 degrees did not affect the interfragmentary contact area, decreasing rapidly to reach values of 66.1%, 76.1% and 81.1% of anatomically reduced fractures at 3.3-degree angulation (values given for cortical thickness of 4, 6 and 8 mm, respectively).
  
  
  CONCLUSIONS
  Obtained results indicate pronounced loss of contact surface between bone fragments during their displacement to the side and for angular displacements greater than 2.5 degrees. Moreover, bone fragments contact surface decreases with reduction of cortical thickness. In conclusion, it is necessary to reduce a fracture as precisely as possible, particularly in case of bone atrophy.
authors.affiliation: Chair and Department of Orthopaedics and Traumatology of the Locomotor System, Medical University of Warsaw, Warsaw, Poland. 501167475@orange.pl
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Szczęsny
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005264:Femoral Fractures / Q000503:physiopathology*; D005593:Fracture Fixation, Internal / Q000379:methods; D018460:Fractures, Comminuted / Q000503:physiopathology*; D006801:Humans; D008954:Models, Biological; D013314:Stress, Mechanical; D013499:Surface Properties; D014143:Traction