Radiographic detection of gravel in soft tissue

We sought to quantify the detectable size of varying compositions of gravel using a cadaveric chicken leg wound model and standard plain-film two-view radiographs.

We conducted a randomized, blinded, descriptive study with the assistance of faculty from the emergency medicine and radiology residency programs of a private urban teaching hospital. A standardized wound was created in each of 160 cadaver chicken legs. Zero, one, or two pieces of gravel of four differing compositions, ranging in size from .25 to 2.0 mm, were inserted into the wounds as determined with computer-generated randomization. The legs were then radiographically imaged (anteroposterior and lateral views). Three faculty physicians independently interpreted the radiographs to determine the number of foreign bodies and rated the ease of visibility. We calculated sensitivity, specificity, and interobserver reliability.

The accuracy with which gravel was detected ranged from an average of 97.7% for 2-mm and 1-mm particles to less than 75% for .5-mm and .25-mm particles. Visibility ratings were also lower for particles in the smaller ranges. Sensitivity was greater for the emergency physicians than for the radiologists, but their specificity was lower. Salt-and-pepper gravel was the most easily identified foreign body.

In this wound model, gravel particles of less than 1 mm were not accurately identified.