title: Intraoperative fluoroscopic assessment of proper prosthetic radial head height.
abstract: BACKGROUND
  Selecting a properly sized radial head prosthesis is imperative during radial head replacement. Although there has been much emphasis on avoiding overlengthening of the radius, little has been studied about how to avoid shortening. The purpose of this study was to characterize how a radial head replacement appears on intraoperative fluoroscopy depending on the height of the prosthetic radial head.
  
  
  METHODS
  Articular cartilage thickness of the radial head was measured in 9 cadaveric elbows. Radial head replacement was performed in each specimen with 4 different prosthetic head heights: 4 mm and 2 mm shortening, anatomic, and 2 mm overlengthening. Anteroposterior fluoroscopic images were obtained for each head height, and the prosthetic radial head height was measured at 3 forearm positions (supination, neutral, and pronation) using the subchondral bone of the lateral edge of the coronoid at the reference point.
  
  
  RESULTS
  The mean cartilage thickness of the radial head was 1.3 ± 0.4 mm. The prosthetic radial head appeared 2.2 ± 0.4 mm more proximal than the subchondral bone of the coronoid lateral edge in anteroposterior radiographs when the articular surface of the prosthesis was completely even with the coronoid articular surface. Unlike the native radial head, a prosthetic radial head showed a significant change of height with different forearm rotation (P < .001).
  
  
  CONCLUSIONS
  This study found that a perfectly anatomic radial head replacement appears overlengthened by approximately 2 mm in intraoperative radiographs. This finding can be useful in guiding the appropriate height of a prosthetic radial head.
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Milton S. Hershey Medical Center, Hershey, PA, USA. Electronic address: hkim2@hmc.psu.edu.
authors.forename: H Mike
authors.initials: HM
authors.lastname: Kim
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Milton S. Hershey Medical Center, Hershey, PA, USA.
authors.forename: Evan P
authors.initials: EP
authors.lastname: Roush
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Milton S. Hershey Medical Center, Hershey, PA, USA.
authors.forename: Casey
authors.initials: C
authors.lastname: Kiser
mesh_terms: D000328:Adult; D057929:Arthroplasty, Replacement, Elbow; D002102:Cadaver; D002358:Cartilage, Articular / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D004551:Elbow Joint / Q000601:surgery; D058569:Elbow Prosthesis; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D007430:Intraoperative Care; D008297:Male; D008875:Middle Aged; D017755:Prosthesis Fitting; D011884:Radius / Q000000981:diagnostic imaging* / Q000601:surgery; D011885:Radius Fractures / Q000601:surgery
keywords: Intraoperative fluoroscopy of prosthetic radial head; joint mechanics; prosthetic radial head; radial head fracture; radial head height; radial head replacement