Chapter 5: Special Imaging Techniques

Plain radiographs are a sufficient adjunct to the history and physical examination for the evaluation of most acute extremity complaints. It must be stressed that this statement is true assuming that the quality of views is adequate. A minimum of two perpendicular views are required to adequately visualize and describe fractures. Oblique views are commonly included when imaging the wrist, hand, ankle, and foot. In addition, radiographs of the joints above and below a fracture should be considered to exclude the presence of a subluxation, dislocation, or a second fracture.

Several other imaging techniques exist that offer additional information not readily available when imaging with plain radiography. These techniques, which include ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and fluoroscopy, may be used in conjunction with plain radiographs and may be superior to plain radiographs for certain musculoskeletal disorders. These studies and the clinical situations in which they are useful are discussed in this chapter.

Ultrasound

Ultrasonography is gaining an increasing role within the specialty of emergency medicine, and this role continues to grow for orthopedic conditions. Soft tissue and musculoskeletal ultrasound is now recognized as one of the eleven core emergency ultrasound applications.¹ This modality offers several advantages over traditional imaging methods including the ability to perform dynamic imaging of the affected body part, the ability to easily compare findings on the affected side with those on the unaffected side, and the lack of exposure to the harmful effects of radiation. The last advantage mentioned is particularly important when evaluating the pediatric population who are more susceptible to ionizing radiation, which is delivered in large doses with imaging techniques such as CT.^2,3

Common musculoskeletal ultrasound applications in the emergency department (ED) include tendon evaluation, muscle evaluation, joint evaluation for effusion, foreign body identification, and procedural guidance.^4–6 There are several studies documenting the usefulness of ultrasound in trauma, especially with regard to the evaluation of bony trauma. It may be used in conjunction with plain radiographs to evaluate for fractures and may even be superior to plain radiographs in certain types of fractures, including rib and scaphoid fractures (Fig. 5–1).^7–9 In addition, recent research has also suggested that this modality is useful in diagnosing extremity fractures in military or sideline settings where other imaging capabilities are not readily available.^10–11 This role of ultrasound in the acute setting is also expanding to include evaluation of musculoskeletal infections. The localization of soft-tissue collections by ultrasound helps narrow the differential diagnosis based on the finding of fluid in the dermis, joint, bursa, or muscle. For this reason, ultrasound can be used to detect simple abscesses, pyomyositis, septic bursitis and tenosynovitis, joint effusions, and subperiosteal fluid associated with osteomyelitis.¹²