title: Complex varus elbow instability: a terrible triad model.
abstract: OBJECTIVE
  The terrible triad is a debilitating injury that involves elbow dislocation with injury to the lateral collateral ligament (LCL) complex, the radial head, and the coronoid process. This study investigated the role of these components in varus stability of the elbow.
  
  
  METHODS
  We investigated the role of these components in varus stability of the elbow using 10 cadaveric fresh frozen upper extremities. The testing order allowed each of four states to be tested (intact, LCL complex deficient or repaired, radial head resected or replaced) at two flexion angles and multiple coronoid resection levels. Values for restraining load (newtons [N]) at 1.5 cm of varus displacement were obtained on a materials testing machine.
  
  
  RESULTS
  Beyond a 50% loss of the coronoid process, neither repair of the LCL nor replacing the radial head alone resulted in a statistically significant increase in varus stability. For a loss of the coronoid process between 67-75%, repair of the LCL and replacement of the radial head showed improved stability over repair alone, or radial head replacement alone. For loss of the coronoid beyond 75%, even repair of the LCL and replacement of the radial head did not improve varus stability of the elbow.
  
  
  CONCLUSIONS
  These findings provide a biomechanical basis for aggressive treatment of coronoid fractures as a component of the terrible triad injury.
  
  
  METHODS
  Basic science study.
authors.affiliation: Department of Orthopaedic Surgery and Biomedical Engineering, Orthopaedic Research Laboratory, Virginia Commonwealth University, Richmond, VA 23298-0694, USA.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Fern
authors.forename: John R
authors.initials: JR
authors.lastname: Owen
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Ordyna
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Wayne
authors.forename: N Douglas
authors.initials: ND
authors.lastname: Boardman
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D017885:Collateral Ligaments / Q000293:injuries*; D006801:Humans; D004204:Joint Dislocations / Q000150:complications*; D007593:Joint Instability / Q000209:etiology*; D008875:Middle Aged; D011884:Radius / Q000293:injuries*; D000092464:Elbow Injuries