title: Influence of radial head prosthetic design on radiocapitellar joint contact mechanics.
abstract: OBJECTIVE
  Our aim was to test whether anatomically designed metallic radial head implants could better reproduce native radiocapitellar contact pressure and areas than nonanatomic implants.
  
  
  METHODS
  The distal humerus and proximal radius from 6 cadaveric upper extremities were serially tested in supination with 100 N of compression force at 4 angles of flexion (0°, 30°, 60°, and 90°). By use of a thin flexible pressure transducer, contact pressures and areas were measured for the native radial head, an anatomic implant, a nonanatomic circular monopolar implant, and a bipolar nonanatomic implant. The data (mean contact pressure and mean contact area) were modeled using a 2-factor repeated-measures analysis of variance with P ≤ .05 considered to be significant.
  
  
  RESULTS
  The mean contact areas for the prosthetic radial heads were significantly less than those seen with the intact radial heads at every angle tested (P < .01). The mean contact pressures increased significantly with all prosthetic radial head types as compared with the native head. The mean contact pressures increased by 29% with the anatomic prosthesis, 230% with the monopolar prosthesis, and 220% with the bipolar prosthesis. Peak pressures of more than 5 MPa were more commonly observed with both the monopolar and bipolar prostheses than with the anatomic or native radial heads.
  
  
  CONCLUSIONS
  The geometry of radial head implants strongly influences their contact characteristics. In a direct radius-to-capitellum axial loading experiment, an anatomically designed radial head prosthesis had lower and more evenly distributed contact pressures than the nonanatomic implants that were tested.
authors.affiliation: Department of Orthopaedics, Biomechanics Laboratory, Mayo Clinic, Rochester, MN, USA.
authors.forename: Dipit
authors.initials: D
authors.lastname: Sahu
authors.affiliation: Department of Orthopaedics, Biomechanics Laboratory, Mayo Clinic, Rochester, MN, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Holmes
authors.affiliation: Department of Orthopaedics, Biomechanics Laboratory, Mayo Clinic, Rochester, MN, USA.
authors.forename: James S
authors.initials: JS
authors.lastname: Fitzsimmons
authors.affiliation: Department of Orthopaedics, Biomechanics Laboratory, Mayo Clinic, Rochester, MN, USA.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Thoreson
authors.affiliation: Department of Orthopaedics, Biomechanics Laboratory, Mayo Clinic, Rochester, MN, USA.
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Berglund
authors.affiliation: Department of Orthopaedics, Biomechanics Laboratory, Mayo Clinic, Rochester, MN, USA.
authors.forename: Kai-Nan
authors.initials: KN
authors.lastname: An
authors.affiliation: Department of Orthopaedics, Biomechanics Laboratory, Mayo Clinic, Rochester, MN, USA. Electronic address: odriscoll.shawn@mayo.edu.
authors.forename: Shawn W
authors.initials: SW
authors.lastname: O'Driscoll
mesh_terms: D000368:Aged; D002102:Cadaver; D004551:Elbow Joint / Q000502:physiology*; D058569:Elbow Prosthesis; D005260:Female; D006801:Humans; D006811:Humerus / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011884:Radius / Q000502:physiology*; D016059:Range of Motion, Articular
keywords: Contact pressure; anatomic radial head implant; circular radial head implant; contact area; prosthesis; radial head