Acute knee trauma: how many plain film views are necessary for the initial examination?

OBJECTIVE: To determine whether anteroposterior (AP) and lateral views of the knee are equivalent to four views in acute fracture detection.

DESIGN: Three musculoskeletal radiologists retrospectively interpreted the plain film knee examinations of each patient, establishing ground truth for the presence or absence of a fracture. Cases were presented to four masked senior radiology residents twice--once as a two-view study and again as a four-view study--with 4 weeks separating the two reading sessions to minimize recall bias. Sensitivity, specificity, and diagnostic performance were calculated.

PATIENTS: Ninety-two patients presenting to the emergency department with acute knee trauma were evaluated with at least a four-view plain film examination.

RESULTS AND CONCLUSIONS: Mean sensitivity for fracture detection using four views (85%) was significantly higher than that using two views (79%). Mean specificity and receiver operating characteristic curve areas were not significantly different using two or four views. Four views are more sensitive than AP and lateral views alone in detection of acute knee fracture.