title: The effect of the orientation of the noncircular radial head on elbow kinematics.
abstract: OBJECTIVE
  The objective of this study was to identify the effect of radial head shape and orientation on elbow kinematics in the otherwise intact elbow.
  
  
  METHODS
  Biomechanical study, analyzing simulated active motion of cadaveric arms.
  
  
  BACKGROUND
  A discrepancy exists between the noncircular anatomy of the radial head and radial head prostheses. The effect of radial head shape is unknown.
  
  
  METHODS
  Kinematic effects of radial head shape were tested in six fresh-frozen upper extremities. A custom-made native radial head prosthesis was used to simulate altered shape conditions, by rotating the radial head 90 degrees. Three-dimensional spatial orientation of the ulna was recorded, during simulated active motion. A three factor ANOVA was used to compare (a) nominal and 90 degrees oriented conditions, (b) throughout the flexion arc (c) in three forearm positions (P < 0.05). Post-hoc Tukey tests were done to assess significance.
  
  
  RESULTS
  No significant effect of altering radial head shape was found on total ulnohumeral laxity and angulation during gravity valgus stress. We did find a significant effect on total ulnar axial rotation and rotation during gravity valgus stress.
  
  
  CONCLUSIONS
  The outer shape of the radial head seems to change rotation of the ulna during flexion-extension in an otherwise intact elbow.
  
  
  CONCLUSIONS
  The shape of the radial head effects intact elbow kinematics. Clinical importance of this finding is clear. If a sub-optimally placed radial head prosthesis were to be used in an otherwise intact elbow, the elbow could be at risk for early ulnohumeral arthritis.
authors.affiliation: Mayo Clinic Rochestor, Orthopedic Biomechanics Laboratory, 200 First Street, S.W., Rochester, MN 55902, USA.
authors.forename: R P
authors.initials: RP
authors.lastname: van Riet
authors.forename: F
authors.initials: F
authors.lastname: Van Glabbeek
authors.forename: J A
authors.initials: JA
authors.lastname: Baumfeld
authors.forename: P G
authors.initials: PG
authors.lastname: Neale
authors.forename: B F
authors.initials: BF
authors.lastname: Morrey
authors.forename: S W
authors.initials: SW
authors.lastname: O'Driscoll
authors.forename: K-N
authors.initials: KN
authors.lastname: An
mesh_terms: D001696:Biomechanical Phenomena / Q000379:methods; D002102:Cadaver; D004551:Elbow Joint / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D009068:Movement / Q000502:physiology*; D011884:Radius / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation