Since bones are very dense, they are easily seen, but soft tissue abnormalities are not easily detected. X-rays excel at identifying fractures, arthritis, and bone tumors, but are not particularly useful in evaluating tendon and ligament injuries, masses, and infection. X-ray of the toes in a diabetic patient with a deep skin wound, performed to evaluate for spread of infection to underlying bone. Bone destruction from infection can take up to two weeks to be detected by x-rays, and since bones overlap one other, it is often difficult to see each bone in its entirety. The injected radiotracer is bound to a molecule that seeks out areas of high bone turnover.
Increased radioactivity is detected at fractures, bone infections, and active arthritis.
Bone scans are very sensitive tests and are able to detect bone abnormalities weeks before they are visible on conventional x-rays. Since some patients who are suspected of having an infection may also have fracture or arthritis, this test may pose a diagnostic dilemma. It is therefore essential that x-rays are available when the test is being interpreted to assist in making an accurate diagnosis. This test reveals abnormalities related to the presence of large numbers of white blood cells, and is therefore fairly specific in diagnosing infection. Nuclear medicine tests are commonly used to diagnose bone infection, but MRI is becoming increasingly popular because of its ability to provide superior spatial resolution and anatomic depiction.