What proportion of isotope bone scans are positive in the diagnosis of suspected scaphoid fractures?

Abstract

Scaphoid fractures account for 60–80% of all wrist fractures. Approximately 16% are not detected on plain films and remain radiographically occult even on subsequent imaging, according to the literature. If repeated imaging exhibits no fracture in the continuing presence of symptoms (clinical scaphoid fracture) this poses a diagnostic dilemma. Isotope bone scans have then been used as a second line investigation. Our aim was to assess the proportion of positive bone scans in radiographically occult scaphoid fractures and to determine the timing of the scan in the sequence of events. A retrospective analysis was performed in 88 patients who attended our department over 27 months. All the patients were initially seen and had negative radiographs in the Accident & Emergency department and a second negative radiograph in the fracture clinic two weeks later. In the absence of radiographic fractures they were then referred for an isotope bone scan. Forty-four patients (50%) had normal bone scans. Nineteen patients (21.5%) had positive bone scans typical of scaphoid fractures. A further 19 patients (21.5%) had fractures of other wrist and distal forearm bones. Six patients (7%) had indeterminate scans. As the second radiograph remained unhelpful after the first negative radiograph we suggest that isotope bone scans should be performed after initial radiographs in these patients.