Validity of conventional radiography in determining scaphoid waist fracture displacement

Objective: This study examines interpreter accuracy and interobserver agreement in evaluating conventional radiographs for scaphoid waist fracture displacement. Methods: Six fresh-frozen cadaver arms were obtained transected above the elbow. A waist fracture was created in each scaphoid. In a random fashion, three of the fractures were displaced 1 mm in the radial-ulnar plane, whereas the other three were reapproximated to anatomic position before all fractures were stabilized with radiolucent adhesive glue. A three-view conventional radiography series consisting of a posterior-anterior, lateral, and ulnar-deviated elongated scaphoid view was obtained for each wrist. Each radiograph was then presented in the same sequence for interpretation to six independent observers: two hand surgeons, two musculoskeletal radiologists, and two senior orthopaedic surgery residents who were all blinded to the actual fracture pattern. Results: In 14 of the 18 (78%) displaced fracture radiographic series, the interpreters correctly recognized displacement being present. However, displacement was also reported in six of the 18 (33%) nondisplaced fracture series. The estimated overall accuracy of all readings for distinguishing between displaced and nondisplaced fractures was 72%. Of the 90 total possible pairwise agreements between interpreters regarding fracture displacement, there were 54 actual agreements (60%), and kappa was estimated to be 0.31. Taken together, these two measures of agreement can be interpreted as indicating poor to moderate agreement. Conclusion: Our results suggest that conventional radiography is not reliable in determining 1-mm scaphoid waist fracture displacement in the radioulnar plane and also indicated a lack of strong interobserver agreement.