ULTRASOUND VERSUS RADIOGRAPHY IN THE DETECTION OF SOFT-TISSUE FOREIGN-BODIES

Study objective: To determine the usefulness of ultrasound and radiogr aphy in detecting foreign bodies in soft-tissue models closely duplica ting puncture-wound trauma and hand anatomy. Methods: In this randomiz ed, blinded descriptive study, two radiologists independently evaluate d 120 chicken thighs for foreign bodies with the use of standard two-v iew radiography and 7.5-MHz transducer ultrasonography. All chicken th ighs were manipulated with hemostats to ensure uniform tissue damage. In 60 thighs, one foreign body had been inserted (10 each: gravel, met al, glass, cactus spine, wood, and plastic). Results: The sensitivity of ultrasound in detecting gravel was 40%, that for metal was 45%, tha t for glass was 50%, that for cactus spine was 30%, that for wood was 50%, and that for plastic was 40%. The overall sensitivity, specificit y, and false-negative and false-positive rates for ultrasound were 43% , 70%, 50%, and 30%, respectively. No individual foreign body had an u ltrasound detection rate of 50%. Radiography detected foreign bodies g enerally considered radiopaque (gravel, glass, metal) 98% of the time, but it never detected bodies considered radiolucent (wood, plastic, c actus spine). The false-negative and false-positive rates for radiogra phy were 50% and 1.6%, respectively. Conclusion: Ultrasound detection of foreign bodies by skilled operators in this animal model revealed p oor sensitivity and specificity. Radiographic detection was highly sen sitive for foreign bodies considered radiopaque. Our data suggest that ultrasound should not be relied on to rule out the po retained foreig n body in the distal extremities.