title: Ligamentous stabilizers against posterolateral rotatory instability of the elbow.
abstract: BACKGROUND
  The lateral ulnar collateral ligament, the entire lateral collateral ligament complex, and the overlying extensor muscles have all been suggested as key stabilizers against posterolateral rotatory instability of the elbow. The purpose of this investigation was to determine whether either an intact radial collateral ligament alone or an intact lateral ulnar collateral ligament alone is sufficient to prevent posterolateral rotatory instability when the annular ligament is intact.
  
  
  METHODS
  Sequential sectioning of the radial collateral and lateral ulnar collateral ligaments was performed in twelve fresh-frozen cadaveric upper extremities. At each stage of the sectioning protocol, a pivot shift test was performed with the arm in a vertical position. Passive elbow flexion was performed with the forearm maintained in either pronation or supination and the arm in the varus and valgus gravity-loaded orientations. An electromagnetic tracking device was used to quantify the internal-external rotation and varus-valgus angulation of the ulna with respect to the humerus.
  
  
  RESULTS
  Compared with the intact elbow, no differences in the magnitude of internal-external rotation or maximum varus-valgus laxity of the ulna were detected with only the radial collateral or lateral ulnar collateral ligament intact (p > 0.05). However, once the entire lateral collateral ligament was transected, significant increases in internal-external rotation (p = 0.0007) and maximum varus-valgus laxity (p < 0.0001) were measured. None of the pivot shift tests had a clinically positive result until the entire lateral collateral ligament was sectioned.
  
  
  CONCLUSIONS
  This study suggests that, when the annular ligament is intact, either the radial collateral ligament or the lateral ulnar collateral ligament can be transected without inducing posterolateral rotatory instability of the elbow.
authors.affiliation: Bioengineering Research Laboratory, Lawson Health Research Institute, Hand and Upper Limb Centre, St. Joseph's Health Care London, 268 Grosvenor Street, London, Ontario N6A 4L6, Canada.
authors.forename: C E
authors.initials: CE
authors.lastname: Dunning
authors.forename: Z D
authors.initials: ZD
authors.lastname: Zarzour
authors.forename: S D
authors.initials: SD
authors.lastname: Patterson
authors.forename: J A
authors.initials: JA
authors.lastname: Johnson
authors.forename: G J
authors.initials: GJ
authors.lastname: King
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D017885:Collateral Ligaments; D004551:Elbow Joint; D006801:Humans; D007593:Joint Instability / Q000473:pathology*; D008875:Middle Aged; D011884:Radius; D014457:Ulna