title: Fracture site motion with Ilizarov and "hybrid" external fixation.
abstract: OBJECTIVE
  To evaluate differences in fracture site motion by using different external fixators.
  
  
  METHODS
  A wooden dowel was used to simulate a long bone with a transverse diaphyseal fracture. Ilizarov, "hybrid," and strutaugmented "hybrid" external fixation was used to stabilize the "fracture." The wooden dowel was subjected to separate axial, four-point bending, and torsional loads. Fracture site motion in the axial plane, off-axis motion (shear and bending), and rotation were measured.
  
  
  METHODS
  All mechanical testing was performed with a sevohydraulic test frame (MTS Systems, Minneapolis, MN, U.S.A.). Fracture site motion was measured with an interfragment motion device developed in this laboratory.
  
  
  METHODS
  Comparison was made between a traditional fourring Ilizarov fixator, a "hybrid" fixator using rings and threaded pins attached by a unilateral aluminum bar, and a "hybrid" fixator augmented with a V-shaped strut.
  
  
  METHODS
  Load-deformation behavior in axial displacement, shear displacement, and bending displacement were compared between the different configurations under identical conditions of axial loading, torsional loading, and four-point bending. In torsional loading, rotational displacement was also measured.
  
  
  RESULTS
  The Ilizarov configuration allowed significantly less off-axis fracture site motion in all loading modes than either "hybrid" configuration while still allowing axial compression of the fracture ends.
  
  
  CONCLUSIONS
  In a completely unstable fracture with poor bone apposition, the mechanical behavior of a four-ring Ilizarov external fixator is superior to the mechanical behavior of a unilateral "hybrid" frame.
authors.affiliation: Department of Orthopaedic Surgery, University of Louisville, Kentucky 40202, USA.
authors.forename: C
authors.initials: C
authors.lastname: Khalily
authors.forename: M J
authors.initials: MJ
authors.lastname: Voor
authors.forename: D
authors.initials: D
authors.lastname: Seligson
mesh_terms: D001696:Biomechanical Phenomena; D016267:External Fixators; D005592:Fracture Fixation; D050723:Fractures, Bone / Q000601:surgery*; D009038:Motion