CAN A DAY-4 BONE-SCAN ACCURATELY DETERMINE THE PRESENCE OR ABSENCE OFSCAPHOID FRACTURE

Study objective: To evaluate the accuracy of day 4 bone scans in predi cting the presence or absence of fracture in patients with ''clinical scaphoid fracture.'' Design: Prospective sensitiviy study of ED patien ts with clinical scaphoid fractures. Each patient was immobilized in a thumb spica cast and had day 4 bone scans of both wrists and hands. B linded day 4 bone scan results were ultimately compared with the diagn osis on day 14 when patients returned for repeat clinical examination and radiographs. In cases of equivocal radiographic or clinical examin ation results, a day 14 bone scan was performed. Setting: Two tertiary care teaching hospital emergency departments. Participants: All ED pa tients older than 16 years with the diagnosis of clinical scaphoid fra cture were eligible. Results: Ninety-nine patients were enrolled and s uccessfully completed the study protocol from October 1990 through Nov ember 1992. One patient bad bilateral injury, for a total of 100 compl eted studies. Day 4 bone scans were 100% sensitive and 92% specific, f or a positive predictive value of 65%, a negative predictive value of 100%, and accuracy of 93% (95% confidence interval, 88% to 98%). Many other types of fractures were identified on the day 4 scans, including those of the triquetra, distal radius, capitate, hamate, trapezoid, t rapezium, acid metacarpals. Conclusion: Day 4 bone scans are an accura te means of ruling out scaphoid fracture. However, because of a signif icant number of false-positive scans at day 4, they do not reliably co nfirm the diagnosis of scaphoid fracture. The bone scans also permitte d identification of several other wrist fractures that had not been ra diographically apparent.