title: Measurements of the ispilateral capitellum can reliably predict the diameter of the radial head.
abstract: BACKGROUND
  There is no validated method to determine the correct diameter of a radial head implant when the radial head is too comminuted to function as a template or during revision surgery when the radial head has been previously excised. The purpose of this study was to determine if ipsilateral capitellar dimensions could be used to predict the diameter of the radial head; and hence to assist with implant selection.
  
  
  METHODS
  Computer tomography scans of 50 normal elbows were used to generate 3D models. Measurements of the radial head included the maximum (Dmax) and minimum (Dmin) outer diameters and the maximum (Dishmax) and minimum (Dishmin) articular dish diameters. Measurements of the humerus included the width of the capitellum (CAPwidth), and the width from the lateral aspect of the capitellum to the lateral trochlear ridge (CAP-TROCHridge). Relationships were determined with Pearson bivariate coefficients.
  
  
  RESULTS
  The mean radial head dimensions were Dmax = 24.7 ± 2.3 mm, Dmin = 23.5 ± 2.3 mm, Dishmax = 18.2 ± 1.9 mm and Dishmin = 16.8 ± 1.7 mm. The mean capitellar measurements were CAPwidth (18.4 ± 1.4 mm) and CAP-TROCHridge (23.0 ± 2.1 mm). The most significant correlations were found between Dmax and CAP-TROCHridge (R = .90, P < .001) and Dmin and CAP-TROCHridge (R = .90, P < .001).
  
  
  CONCLUSIONS
  Radiologic measurements of the capitellum are useful in the estimation of native radial head diameter. The CAP-TROCHridge measurement was very strongly correlated with both the maximum and minimum diameters of the radial head. This suggests that CAP-TROCHridge may be useful to accurately predict the native radial head diameter. These morphological relationships were plotted to produce an implant selection chart for radial head sizing applicable to any implant system.
  
  
  METHODS
  Basic science, anatomy study, CT imaging.
authors.affiliation: The Bioengineering Laboratory, Hand and Upper Limb Centre, St Joseph's Health Care, University of Western Ontario, London, ON, Canada.
authors.forename: Alexandre E
authors.initials: AE
authors.lastname: Leclerc
authors.forename: Simon
authors.initials: S
authors.lastname: Deluce
authors.forename: Louis
authors.initials: L
authors.lastname: Ferreira
authors.forename: Sagar
authors.initials: S
authors.lastname: Desai
authors.forename: Graham J W
authors.initials: GJ
authors.lastname: King
authors.forename: George S
authors.initials: GS
authors.lastname: Athwal
mesh_terms: D002102:Cadaver; D004551:Elbow Joint / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D006811:Humerus / Q000000981:diagnostic imaging*; D007595:Joint Prosthesis; D008297:Male; D008954:Models, Biological; D011884:Radius / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed
keywords: Anatomy Study; Basic Science; CT Imaging; Radial head fracture; elbow fracture; implant sizing; radial head arthroplasty; terrible triad; trauma