Chapter 7. Imaging Studies in Orthopaedics

At the completion of this chapter, the reader will be able to:

1. List the various imaging studies available.

2. Discuss the advantages and disadvantages of each of the imaging studies.

3. Describe how the various musculoskeletal tissues are depicted in imaging studies.

4. Understand the strengths and weaknesses of each of the imaging studies.

5. Outline the rationale for the choice of one imaging technique versus another.

6. Describe how the results from imaging studies may help in the clinical decision-making process.

For health-care professionals involved in the primary management of neuromusculoskeletal disorders, diagnostic imaging is an essential tool. The availability of diagnostic images to physical therapists greatly depends on the practice setting. For example, physical therapists in the United States army, with primary-care physical therapy provided with credentials, have had privileges for ordering diagnostic imaging procedures since the early 1970s.1 Although, outside of the United States military health system, the ordering of imaging studies is not within the scope of physical therapy practice, clinicians frequently request or receive imaging study reports. Although the interpretation of diagnostic images is always the responsibility of the radiologist, it is important for the clinician to know what importance to attach to these reports, and the strengths and weaknesses of the various techniques that image bone and soft tissues, such as muscle, fat, tendon, cartilage, and ligament. In general, imaging tests have a high sensitivity (few false negatives) but low specificity (high false-positive rate), so are thus used in the clinical decision-making process to test a hypothesis but should not be used in isolation. In addition, imaging studies are expensive and somewhat more invasive compared to a physical examination, so the clinician must weigh the relative value of recommending an imaging study in relation to the working hypothesis. For example, when there is little likelihood that imaging will reveal anything that will change the course of treatment, the tests should be considered unnecessary.1 In addition, the clinician needs to understand that the results of an imaging study may not correlate with the results of the physical examination. Although imaging may provide evidence of pathology, the mere presence of the abnormality may or may not be relevant to the presenting signs and symptoms. In such situations, the clinician should place no more or less weight on the imaging than on other aspects of the decision-making process.

In 1895, Wilhelm Conrad Röentgen was experimenting with a type of electrical tube that produced an electrical discharge when a high voltage current was passed through it.2 When Röentgen shielded the tube with heavy black cardboard, he noticed that a fluorescent screen a few feet away lit up and glowed indicating that some form of energy was passing through the tube. Further experiments led Röentgen to discover that these energy waves could reliably reproduce images of the human skeleton on a glass photographic plate.2 Röentgen named these energy waves x-rays because “x” was the unknown quantity in a ...