Improved wrist fracture localization with digital overlay of bone scintigrams and radiographs

The diagnosis of scaphoid fracture is often difficult and of interest in traumatology. Because of the low sensitivity of repeated scaphoid radiographs, a bone scintigram is advocated and considered the gold standard. In this study, we tried to simplify the interpretation of the bone scintigram of hand and wrist in localizing the hot spot by the digital overlay of the radiograph and the bone scintigram, using a simple device, in patients after wrist trauma.

Twenty-one consecutive patients (22 wrists) with clinically-suspected scaphoid fracture and negative initial radiographs were included. The PA view of the wrist was obtained with the hand of the patient placed in an acrylic device with three lead markers. For the bone scan, a similar device was used with 57Co markers at the same positions. We called this device the "hand-fix." The PA radiograph was digitized with a videocamera and overlaid on the bone scan. Each bone scan was interpreted twice by each of three observers, one nuclear physician and two residents in nuclear medicine. The first interpretation was made without the digital overlay, and the second was made with the digital overlay.

The bone scintigrams were positive in the scaphoid, distal radius and in other carpal bones. Out of the 22 bone scans, Observer 1 judged 19 correctly, Observer 2 judged 16 correctly and Observer 3 judged 10 correctly without the digital overlay images. All three observers gave a correct localization in the 22 wrists using the digital overlay images.

The digital overlay of a radiograph and a bone scintigram, using the hand-fix, simplifies and improves interpreting and localizing the hot spot on bone scintigrams in patients with wrist injuries.