A sensitive method of measuring bone activity is the radionuclide bone scan. A diphosphonate ester compound, labeled with technetium 99m, is injected intravenously. The half-life distribution of these tracers from the vascular to the extravascular spaces is two to four minutes. By three hours time, about 35 percent of the tracer has been excreted by the kidney, 30-40 percent has been absorbed by bone, 10-15 percent is in other tissues, and about 5 percent remains in the blood.
Photons of energy are given off by the tracer and are recorded by a gamma camera. Newer systems allow a larger field of view so that whole body scans are able to provide excellent images and may be preferable to limited regional studies for practical reasons.
Scintigraphy, a more formal name for bone scanning, using technetium 99m methylene diphosphonate (MDP) will reveal a variety of non-osseous disorders, including neoplastic, hormonal, inflammatory, ischemic, traumatic, and excretory. Soft tissue Tc99m MDP uptake can be observed in benign conditions, such as tumoral calcinosis or myositis ossificans, and in malignant conditions, such as sarcomas, adenocarcinomas, and metastases. Moreover, tissue damage (which may be due to inflammation, physical injury, or infection), generally results in localized hyperemia, edema, or calcium (and hemosiderin) deposition. These can also be visualized with scintigraphy.1
For deeper structures, single photon emission computed tomography (SPECT) can produce increased image contrast and improve spacial resolution.2 Limitations to imaging the cervical spine with SPECT include decreased resolution, as a result of the relatively low bone mass of the cervical spine, and the relatively large radius of rotation necessitated by the mass of the shoulders. Despite such limitations, a recent report reveals the usefulness of cervical SPECT in trauma cases; the authors were able to make the diagnosis of occult fractures not seen with conventional plain film, demonstrate periosteal injury, differentiate radiographic abnormalities from healed fractures, and identify active posttraumatic osteoarthritis superimposed on chronic degenerative disease.3 Their proposed algorithm for the diagnosis of cervical spine injury after trauma is presented in Figure 1.
| Figure 1 | Neck Trauma | |||
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__________________ | Cervical spine series | _________________ | ||
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Negative fracture | | | Positive acute fracture | ||
Positive DDD(?) fracture | ||||
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Persistent pain | Flexion/extension films | --Unstable-- | CT | |
| | | | | | ||
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| | Stable | | | ||
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| | Persistent pain | Neurosurgery | ||
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SPECT | SPECT | | | ||
______ | ______ | _______ | _____ | | |
| | | | | | | | | |
| Positive | Negative | Positive | Negative | | |
| | | | | | | | Consider Bone SPECT |
| | | | | | | | |
| Consider CT, immobilization | Conservative treatment | CT | Conservative treatment | |
In a similar comparative study,5 this time for low back pain, SPECT was shown to be superior to both plain film radiology and CT in the identification of lesions. Eighty percent of the SPECT visualized lesions were seen on CT, but only 37 percent were seen on plain film studies. Another report suggests that SPECT may be more likely than CT to correlate with clinical findings in cases of spondylosis.6
About 90 percent of fractures will appear normal on bone scan within two years. They can be detected within hours of injury in the majority of cases. The occasional exception to this rule is in hip fractures in the elderly.
In many cases, bone scan can detect bone injuries which are too subtle for plain film radiography or CT -- modalities that detect fracture on the basis of absolute loss of bone crystal. Below is the list of the conditions detectable with scintigraphy.
Conditions Detectable with Radionuclide Imaging:
Many relevant diagnostic signs are not performed deliberately by the examiner or by the patient at the examiner’s direction. They are observed as the patient reacts to their condition. Fortin’s finger sign, Minor’s sign, and Vanzetti’s sign are three examples of this principle.
On Feb. 1, 2024, two more legislators – John R. Carter (R-Texas) and Robert “Bob” Good (R-Va.) – co-sponsored the Chiropractic Medicare Coverage Modernization Act of 2023, bringing the co-sponsor total to 155, two more than the total achieved over the entire two-year congressional cycle in which identical legislation last appeared (2021-22).
While working at the Lovelace Medical Center in Albuquerque, N.M., one of the primary care physicians stated that imaging every patient prior to receiving chiropractic was not medically necessary. It was at that point I reconsidered the need for the imaging of every patient to avoid malpractice.
