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Radiography

Conventional radiography is the most commonly used imaging technique to evaluate the joints of the musculoskeletal system. This technique should always be the first imaging study performed in a patient suspected of having joint problems. Radiography has the following important advantages: It is almost universally available, is relatively inexpensive compared to other imaging studies and delivers only a small radiation dose to the patient. When possible, orthogonal projections should be obtained, meaning two images of the joint that are perpendicular to each other (usually a frontal projection in either in the anteroposterior [AP] or posteroanterior [PA] directions and a lateral). In some instances oblique images may also be obtained, depending on the preferences of the referring physician or radiologist or the clinical situation. In certain instances it may also be important to obtain images of the joint proximal and distal to the injury. Examples of this include the forearm and lower leg (paired bones), as the joints proximal and distal are often injured. Because conventional radiography uses ionizing radiation, it should be used judiciously, especially in pediatric patients and pregnant women.

Historically, radiographic images were printed on film. However, with widespread adoption of PACS (picture archiving and communications system), images can be electronically processed and viewed on computer work screens. These images then can be transmitted anywhere electronically via the Internet.

Conventional Tomography

Conventional tomography is mentioned mainly for historical interest. High radiation dose, relatively poor image resolution, and imaging that is only possible in one plane were its major disadvantages. The technique has been almost totally replaced by other imaging tests, especially computed tomographic (CT) and magnetic resonance (MR) imaging. Orthopantograms are one of the few remaining vestiges of this imaging technique.

Arthrography

Arthrography is a technique in which contrast is injected into the joint using fluoroscopic guidance. The joint is then imaged using radiography, CT, or MR imaging or a combination of these techniques. The injected contrast may be an iodine-containing water-soluble compound (eg, Conray), subsequently imaged with radiography or CT (Figure 7-1). Alternatively, a paramagnetic compound (eg, gadolinium pentazocine) may be injected and imaged with MRI. MR arthrographic images of the joint may also be performed after intravenous injection of the paramagnetic contrast agent, although this technique does not distend the joint, and thereby is not used commonly today. MR arthrography is mainly used to evaluate the labrum of the hip or glenohumeral joint (Figure 7-2) but is also useful in the evaluation of the structures of the wrist and elbow joints. CT arthrography, and less commonly conventional arthrography can be useful in patients who cannot undergo, or have contraindications to, MR imaging (Figure 7-3).

Figure 7-1.

Contrast arthrogram with plain radiograph: AP wrist arthrogram view obtained after injection of contrast ...

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