Occult fracture
An occult fracture is a broken bone (fracture) that cannot or cannot be seen directly on a normal X-ray . In some cases indirect signs of a fracture can indicate the presence of a fracture, in other cases the fracture cannot be identified at all on the basis of the X-ray image alone. If there is a suspicion - for example, due to severe pain - magnetic resonance imaging (MRI) or computed tomography (CT) can show or rule out the break in most cases . In patients for whom z. B. MRI is not an option because of a pacemaker , a skeletal scintigraphy can also be performed to detect a fracture.
An initially occult fracture can also become visible in x-rays taken days or weeks later. The body's reactions to the bone fracture then appear, such as a reduction in bone density at the fracture gap due to resorption or thickening or calcification of the periosteum as part of the healing of the fracture . In the most unfavorable case, the bone fragments are shifted relative to one another so that the fracture gap becomes directly visible.
Investigation methods
Computed Tomography
Even if excellent spatial resolution can be achieved with modern computed tomography, the detection of an unshifted fracture is not always possible, especially on the trunk ( spine ) due to the disturbing scattered radiation , in patients with osteoporosis with little mineral bone substance and in already pre-existing, older fractures, as a result of which the bone no longer has its original anatomical shape. Nevertheless, because of its superimposition-free display, computed tomography is superior to conventional x-rays.
Magnetic resonance imaging
Magnetic resonance imaging is capable of very sensitive one edema represent the bone marrow. Since such edema occurs with practically every fresh bone fracture, an injury to the bone can be recognized even if the mineral trabeculae, i.e. what is shown in the X-ray, are not interrupted or displaced by a fracture.
Skeletal scintigraphy
Skeletal scintigraphy is not part of the primary diagnosis of acute trauma. After initial treatment of a polytrauma patient, the examination can be used to identify undetected fractures. The examination can also be helpful in the event of persistent symptoms without evidence of a fracture in the X-ray. Scintigraphy has the following advantages in the search for occult fractures: the whole body can be imaged, there is a high sensitivity for pathological processes and the costs are low. The disadvantages are: the examination is not positive immediately after the trauma and radiation exposure must be taken into account. The effective dose is typically at a applied activity of 500 MBq 99m TC - HDP about 2.9 mSv . This examination is contraindicated in pregnant and breastfeeding women .
After a fracture, there is an increase in bone metabolism in the affected area within a few days. The effect occurs later when bone metabolism in the affected bone is low. In old patients, therefore, there can be a week between the trauma and the scintigraphically recognizable increase in bone metabolism.
If the examination is carried out as a so-called three-phase scintigraphy (1st bolus phase, see radionuclide angiography , 2nd soft tissue phase a few minutes after the injection and 3rd mineralization phase about two to five hours after injection), a fresh fracture already shows an accumulation in the first two phases. Enrichments in the mineralization phase can still be detectable in the area of old fractures after months or years.
swell
- K. Bohndorf, H. Imhof: Radiological diagnosis of bones and joints . Thieme, Stuttgart / New York 1998, ISBN 3-13-110982-3 .
- W. Römer, T. Kuwert: Skeletal system. In: T. Kuwert, F. Grünwald, U. Haberkorn, T. Krause: Nuclear medicine. Stuttgart / New York 2008, ISBN 978-3-13-118504-4 .
Individual evidence
- ^ W. Sonnenschein, A. Bockisch: Radiation protection. In: T. Kuwert, F. Grünwald, U. Haberkorn, T. Krause: Nuclear medicine. Stuttgart / New York 2008, ISBN 978-3-13-118504-4 .
