title: A quantitative definition of scaphoid union: determining the inter-rater reliability of two techniques.
abstract: BACKGROUND
  Despite extensive literature supporting the use of computerized tomography (CT) scans in evaluating scaphoid fractures, there has not been a consensus on the methodology for defining and quantifying union. The purpose of this study was to test the inter-observer reliability of two methods of quantifying scaphoid union.
  
  
  METHODS
  The CT scans of 50 non-operatively treated scaphoid fractures were reviewed by four blinded observers. Each was asked to classify union into one of three categories, united, partially united, or tenuously united, based on their general impression. Each reviewer then carefully analyzed each CT slice and quantified union based on two methods, the mean percentage union and the weighted mean percentage union. The estimated percentage of scaphoid union for each scan was recorded, and inter-observer reliability for both methods was assessed using a Bland-Altman plot to calculate the 95% limits of agreement. Kappa statistic was used to measure the degree of agreement for the categorical assessment of union.
  
  
  RESULTS
  There was very little difference in the percentage of union calculated between the two methods (mean difference between the two methods was 1.2 ± 4.1%), with each reviewer demonstrating excellent agreement between the two methods based on the Bland-Altman plot. The kappa score indicated very good agreement (Κ = 0.80) between the consultant hand surgeon and the musculoskeletal radiologist, and good agreement (Κ = 0.62) between the consultant hand surgeon and the hand fellow for the categorical assessment of union.
  
  
  CONCLUSIONS
  This study describes two methods of quantifying and defining scaphoid union, both with a high inter-rater reliability. This indicates that either method can be reliably used, making it an important tool for both for clinical use and research purposes in future studies of scaphoid fractures, particularly those which are using union or time to union as their endpoint.
  
  
  METHODS
  Diagnostic, level III.
authors: Department of Surgery, Division of Orthopedic Surgery, Hand and Upper Limb Center, St, Joseph's Health Care, University of Western Ontario, London, Ontario, Canada. rgrewa@uwo.ca
authors: Ruby
authors: R
authors: Grewal
authors: Uri
authors: U
authors: Frakash
authors: Said
authors: S
authors: Osman
authors: Robert Y
authors: RY
authors: McMurtry
mesh_terms: D017102:Fracture Healing; D050723:Fractures, Bone / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy; D006801:Humans; D015588:Observer Variation; D015203:Reproducibility of Results; D021361:Scaphoid Bone / Q000000981:diagnostic imaging* / Q000293:injuries* / Q000473:pathology; D016037:Single-Blind Method; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome
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