title: Hybrid external fixation of the proximal tibia: strategies to improve frame stability.
abstract: OBJECTIVE
  To determine the specific frame construction strategies that can increase the stability of hybrid (ring with tensioned wires proximally connected by bars to half-pins distally) external fixation of proximal tibia fractures. DESIGN Repeated measures biomechanical testing.
  
  
  METHODS
  Laboratory.
  
  
  METHODS
  Composite fiberglass tibias.
  
  
  METHODS
  Using the Heidelberg and Ilizarov systems, external fixators were tested on composite fiberglass tibias with a 1-cm proximal osteotomy (OTA fracture classification 41-A3.3) in seven frame configurations: unilateral frames with 5-mm diameter half-pins and 6-mm diameter half-pins; hybrid (as described above), with and without a 6-mm anterior proximal half-pin; a "box" hybrid (additional ring group distal to the fracture connected by symmetrically spaced bars to the proximal rings) with and without an anterior, proximal half-pin; and a full, four-ring configuration. Each configuration was loaded in four positions (central, medial, posterior, and posteromedial).
  
  
  METHODS
  Displacement at point of loading of proximal fragment.
  
  
  RESULTS
  The "box" hybrid was stiffer than the standard hybrid for all loading positions. The addition of an anterior half-pin stiffened the standard hybrid and the "box" hybrid.
  
  
  CONCLUSIONS
  The most dramatic improvements in the stability of hybrid frames used for proximal tibial fractures result from addition of an anterior, proximal half-pin.
authors.affiliation: Department of Orthopaedic Surgery, University of Lousville, Lousville, Kentucky 40202, USA. craig.roberts@lousville.edu
authors.forename: Craig S
authors.initials: CS
authors.lastname: Roberts
authors.forename: James C
authors.initials: JC
authors.lastname: Dodds
authors.forename: Kelvin
authors.initials: K
authors.lastname: Perry
authors.forename: Dennis
authors.initials: D
authors.lastname: Beck
authors.forename: David
authors.initials: D
authors.lastname: Seligson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Voor
mesh_terms: D001696:Biomechanical Phenomena; D004867:Equipment Design; D016267:External Fixators; D013978:Tibial Fractures / Q000601:surgery*