A Comparison of Plain Radiographs and Computed Tomography for Determining Canal Diameter of the Distal Phalanx.

Abstract

To compare plain radiographs and computed tomography (CT) when determining the narrowest diameter of the medullary canal of the distal phalanx. A database review identified 48 patients (23 male, 25 female) who underwent a CT scan of the hand and plain radiographs of the same hand. Using digital imaging software, the smallest diameter of the medullary canal was measured for each finger (index, middle, ring, little) on CT and on radiographs. The narrowest diameter of the medullary canal was measured on the axial CT and lateral hand radiograph at the transition between the tuft and the distal phalanx shaft. The mean narrowest diameters on plain radiographs for the index, middle, ring, and little fingers were 1.4 mm, 1.4 mm, 1.4 mm, and 1.1 mm, respectively. The mean diameters on CT were 1.2 mm, 1.3 mm, 1.2 mm, and 1.0 mm, respectively. Men had larger medullary canal dimensions (1.5-1.7 mm) than women (0.8-1.2 mm). The differences in canal diameter measurements between plain radiograph and CT were small and likely clinically insignificant. Lateral radiographs can be used for preoperative planning when estimating the size of the distal phalanx intramedullary canal.