Large loose bodies are well seen with MRI, especially when an effusion is present (Fig. 4.10).43 Small loose bodies may be more difficult to detect and differentiate from other foci of signal void on MRI, such as thickened synovium (Fig. 4.11). Air bubbles also may mimic loose bodies on MRI.44 Small air bubbles may arise naturally from vacuum phenomenon or may be introduced iatro-genically during aspiration or injection of fluid. Vacuum phenomenon is unusual in the elbow joint, whereas small bubbles are commonly seen with MR arthrography. Even with good arthrographic technique, it is not uncommon to inject several small air bubbles into the joint that may mimic loose bodies on MRI. These air bubbles can be recognized by a characteristic margin of high signal adjacent to the signal void, which is due to a magnetic susceptibility artifact and is not found along the margins of a real loose body. A similar appearance of multiple foci of magnetic susceptibility artifact also may be seen at the site of micrometallic deposition associated with previous
FIGURE 4.9. Osteochondritis dissecans (OCD) in an 11-year-old female gymnast. (A) Plain X-ray reveals a small lucency in the capitellum (arrow). (B) T1-weighted axial image reveals a small focus of OCD in the anterior aspect of the capitellum (arrow). (C) T1-weighted axial image obtained after IV administration of gadolinium reveals enhancement of thickened irregular synovium (curved arrows) compatible with synovitis. Enhancing granulation tissue is seen highlighting the overlying osteochondral defect (arrow).
surgery. These foci of magnetic susceptibility artifact are most prominent on gradient-echo T2*-weighted images.
Noncalcified chondral loose bodies cannot be visualized on CT or radiographs; however, they can be identified with MRI. Calcified loose bodies are very conspicuous on MRI, especially with gradient-echo T2*-weighted sequences. Calcified loose bodies may appear slightly larger than their actual size on gradient-echo T2*-weighted images as a result of magnetic susceptibility effects that are normally dampened by the 180° refocusing pulse on spin-echo images.
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Everything you wanted to know about. How To Cure Tennis Elbow. Are you an athlete who suffers from tennis elbow? Contrary to popular opinion, most people who suffer from tennis elbow do not even play tennis. They get this condition, which is a torn tendon in the elbow, from the strain of using the same motions with the arm, repeatedly. If you have tennis elbow, you understand how the pain can disrupt your day.