USE OF RADIOGRAPHY IN ACUTE KNEE INJURIES - NEED FOR CLINICAL DECISION RULES

Objectives: To study: 1) the efficiency of the current use of radiogra phy in acute knee injuries, 2) the: judgments and attitudes of experie nced clinicians in their use of knee radiography, and 3) the potential for decision rules to improve efficiency. Methods: This two-stage stu dy of adults with acute knee injuries involved: 1) a retrospective rev iew of all 1,967 patients seen over a 12-month period in the EDs of on e community and two teaching hospitals, and 2) a prospective survey of another 1,040 patients seen by attending emergency physicians. The pr ospective survey assessed each clinician's estimate of the probability of a knee or patella fracture, 120 patients were independently assess ed by two physicians.Results: Of the 1,967 patients seen in the first stage, 74.1% underwent radiography but only 5.2% were found to have fr actures. Of the 1,727 knee and patella radiographic series ordered, 92 .4% were negative for fracture. In the second stage, experienced physi cians predicted the probability of fracture to be 0 or 0.1 for 75.6% o f the patients. The kappa value for this response was 0.51 (95% CI 0.3 4 to 0.68). The physicians also indicated that they would have been co mfortable or very comfortable in not ordering radiography for 55.5% of the patients, The area under the receiver operating characteristic cu rve for the physicians' prediction of fracture was 0.87 (95% CI 0.82 t o 0.91), reflecting good discrimination between fracture and nonfractu re cases, Likelihood ratios for the physicians' prediction ranged from 0.09 at the 0 level to 42.9 at the 0.9-1.0 level. Conclusions: Emerge ncy physicians order radiography for most patients with acute knee inj uries, even though they can accurately discriminate between fracture a nd nonfracture cases and expect most of the radiographs to be normal. These findings suggest great potential for more efficient use of knee radiography, possibly through the use of a clinical decision rule.