Sensitivity and specificity of ultrasound in the diagnosis of foreign bodies in the hand.

High-resolution ultrasound is capable of detecting foreign bodies of practically any composition. The purpose of this study was to determine in a controlled manner the sensitivity and specificity of ultrasound in the diagnosis of foreign bodies in the hand. Each of 15 fresh-frozen cadaver hands was divided into 21 standardized sites for potential foreign body insertion. Foreign bodies consisted of two sizes of three different materials (wood, glass, and metal). Foreign bodies were randomly assigned to 50% of the available sites. The empty sites served as controls. All hands were scanned by a single radiologist using high-resolution ultrasound at a frequency of 10 MHz. The radiologist was unaware of which specimens contained foreign bodies. Of the 166 foreign bodies inserted in total, 156 were detected by ultrasound. Ten sites were falsely analyzed as negative, for a sensitivity of 94%. There was one false positive result and 148 true negatives. The specificity was therefore 99%. The high specificity of ultrasound allows foreign body presence to be confirmed given a positive result. A combination of ultrasound and x-ray films should allow for diagnosis and localization of virtually all foreign bodies in the hand.