title: The effect of prosthetic radial head geometry on the distribution and magnitude of radiocapitellar joint contact pressures.
abstract: OBJECTIVE
  To determine if radiocapitellar contact pressures would be elevated with nonanatomical (circular) prostheses over those mimicking native anatomy and if such pressures would be related to the depth and contour of the articular dish and to the pattern of prosthetic articulation against the lateral trochlear ridge.
  
  
  METHODS
  Three commercially available circular radial head designs were compared with an anatomical radial head and 2 modified anatomical prototype radial head designs in 10 cadaveric specimens. Each prosthesis and specimen combination was loaded in neutral rotation and maximal extension with a custom testing apparatus while measuring contact areas and pressures using thin-film pressure sensors.
  
  
  RESULTS
  Anatomical radial head prototype 2 had similar radiocapitellar contact areas and mean pressures as the native radial head; all other designs showed significant decreases in contact area and increased mean pressures. Peak contact pressures were also measured and were significantly elevated with all prostheses tested. Anatomical designs are statistically more likely to mimic normal contact with the lateral trochlear ridge and its adjacent sulcus than circular prostheses. They are also significantly less likely to have contact pressures above the 5 MPa threshold that is thought to be harmful to cartilage. The depth of the articular dish had a significant effect on contact area and pressure.
  
  
  CONCLUSIONS
  Commercially available radial head prostheses demonstrated reduced radiocapitellar contact areas and elevated contact pressures during compressive loading. These were significantly greater with symmetrical circular prostheses than with asymmetrical elliptical designs. The prosthesis that best mimicked native contact behavior was the anatomical radial head prototype 2 owing to its design for articulating with the capitellum, the lateral trochlear ridge, and the sulcus between.
  
  
  CONCLUSIONS
  Because radial head prostheses have the potential to cause capitellar erosion or arthritic change, those with lower contact pressures may lead to fewer such complications.
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Bachman
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.
authors.forename: Sutee
authors.initials: S
authors.lastname: Thaveepunsan
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.
authors.forename: Sangeun
authors.initials: S
authors.lastname: Park
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.
authors.forename: James S
authors.initials: JS
authors.lastname: Fitzsimmons
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.
authors.forename: Kai-Nan
authors.initials: KN
authors.lastname: An
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN. Electronic address: odriscoll.shawn@mayo.edu.
authors.forename: Shawn W
authors.initials: SW
authors.lastname: O'Driscoll
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology*; D004551:Elbow Joint / Q000503:physiopathology* / Q000601:surgery*; D058569:Elbow Prosthesis; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D011312:Pressure; D011474:Prosthesis Design; D011884:Radius / Q000503:physiopathology* / Q000601:surgery*; D014160:Transducers, Pressure; D016474:Weight-Bearing / Q000502:physiology
keywords: Radial head replacement; arthroplasty; biomechanics; contact area; contact pressure