title: Validation of the contralateral side as reference for selecting radial head implant sizes.
abstract: OBJECTIVE
  In arthroplasty of comminuted radial head fractures, the contralateral radial head diameter can be used as reference for implant selection. However, potential bilateral asymmetry may result in a mismatch of the implant with the native bone. Therefore, our purpose was to evaluate anatomical right-to-left differences of radial head diameters. We also compared conventional two-dimensional (2D) with three-dimensional (3D) measurements.
  
  
  METHODS
  We used bilateral CT-scans from 25 intact proximal radius pairs of right-handed adult subjects to obtain 50 3D radial head models. After contralateral matching, diameters were calculated using a 3D-based method using an automated circle-fit in standardized cross-sections at the widest level midway through the radial head. The 3D-based diameters were compared to orthogonal line measurements in standard axial CT-slices.
  
  
  RESULTS
  Three-dimensional analysis yielded a radial head diameter of 23.0 ± 1.7 mm. The dominant right side was significantly wider, with right-to-left differences of 0.2 ± 0.4 mm, with a maximum of 0.9 mm. The 2D-based diameter was 22.9 ± 1.7 mm, which was 0.1 ± 0.3 mm smaller compared to corresponding 3D-based diameter.
  
  
  CONCLUSIONS
  In healthy radial heads, the diameter was biased to the dominant right side, but individual differences were not larger than 1 mm. Compared to implant designs, in which diameter increments are usually 2 mm, this right-bias is not clinically relevant, as it would not affect implant selection. Therefore, the contralateral side can be considered a suitable reference. In clinical practice, the surgeon could estimate this diameter using standard axial CT slices, since its difference with the 3D-based evaluation was also relatively small compared to implant sizing increments.
authors.affiliation: Department of Plastic, Reconstructive, and Hand Surgery, Academic Medical Center, University of Amsterdam, Room G4-226, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands. paultenberg@hotmail.com.
authors.forename: Paul W L
authors.initials: PW
authors.lastname: Ten Berg
authors.affiliation: Department of Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Johannes G G
authors.initials: JG
authors.lastname: Dobbe
authors.affiliation: Department of Orthopaedics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Gerhard
authors.initials: G
authors.lastname: van Wolfswinkel
authors.affiliation: Department of Plastic, Reconstructive, and Hand Surgery, Academic Medical Center, University of Amsterdam, Room G4-226, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
authors.forename: Simon D
authors.initials: SD
authors.lastname: Strackee
authors.affiliation: Department of Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.|Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Geert J
authors.initials: GJ
authors.lastname: Streekstra
mesh_terms: D000328:Adult; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D019736:Prostheses and Implants; D011884:Radius / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Proximal radius; Radial head; Radial head arthroplasty; Radial head fracture; Radial head implant