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 or dislocation.
Several other imaging techniques are available that offer additional information. These techniques, which include radionuclide bone scanning, ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and fluoroscopy, are valuable in the evaluation of certain acute musculoskeletal disorders. These studies and the clinical situations in which they are useful are discussed in this chapter.
In radionuclide skeletal imaging, bone-seeking isotopes are administered to the patient intravenously and allowed to localize within the skeleton. The photon energy emitted is then recorded in three phases using a gamma camera: at the time of administration of the radiopharmaceutical, in the first few minutes after injection, and 3–6 hours later. Numerous isotopes have been used for this purpose in the past. Currently, clinical bone scanning chiefly employs technetium-99 complexed with organic phosphates. These compounds combine a low absorbed radiation dosage with high-resolution images of the skeleton, which are recorded 2 to 3 hours after injection of the isotope.
The bone scan is an extremely sensitive, but fairly nonspecific tool for detecting a broad range of skeletal and soft-tissue abnormalities. The pathophysiologic basis of the technique is complex but depends on localized differences in blood flow, capillary permeability, and metabolic activity that accompany any injury, infection, repair process, or growth of bone tissue. These processes cause increased uptake of isotope, resulting in “hot spots” on the scan. Comparison of the affected and nonaffected sides is generally used to detect differences in uptake.
Applications of the radionuclide bone scan in the evaluation of acute extremity complaints can be divided into traumatic and nontraumatic categories, as seen in Table 5–1.
Table 5–1. Applications of the Radionuclide Bone Scan in the Evaluation of Acute Extremity Complaints |Favorite Table|Download (.pdf)
Table 5–1. Applications of the Radionuclide Bone Scan in the Evaluation of Acute Extremity Complaints
|1. Anatomically difficult locations|
|2. Occult fractures (nondisplaced or stress fractures)|
|B. Traumatic osteonecrosis without fracture|
|B. Tumor (primary or metastatic)|
|C. Occult fractures|
|D. Hip pain|
|1. Adults: Aseptic necrosis, arthritis, transient osteoporosis, occult femoral neck fracture|
|2. Children: Transient synovitis, arthritis, Legg–Perthes disease|
Some of the subtle problems that can be identified with this process are occult fractures, facet arthritis, and even difficult-to-diagnose inflammatory conditions that may not be clearly evident or may ...