Understanding bone examinations: Test types

Like other body tissues and organs, the bones can also get sick. The cause can be fractures or signs of wear, inflammation or cancer. Injuries and fractures are shared at a young age. With age, susceptibility to diseases such as osteoporosis and osteoarthritis increases. To find out what causes pain or restricted mobility, various bone examinations are available.

Understanding bone examinations: Test types

Before any imaging examinations or tests are made, the patient is usually interviewed (anamnesis) and physically examined. For a medical history, the doctor asks to describe complaints and requests, for example, the nature and location of pain and movement restrictions. Diseases in the past or the family, as well as information about workloads and personal lifestyles, can provide useful information. During the physical examination, the doctor examines the body without technical aids, for example, on deformity and mobility. If there is a suspicion of a specific problem, then various imaging tests and other tests may be considered.

X-ray

X-rays illuminate different parts of the body. Since different types of tissue transmit different amounts of radiation, specific structures can be imaged in this way. Due to their density, bones absorb almost all of the X-rays – they can, therefore, be recognized as white or gray contours on the X-ray image. Soft tissues like fat and muscle let almost all the radiation through – they look black in the X-ray.

Therefore, X-rays are particularly useful for imaging bones, but less well for soft tissue examination. Since X-ray examinations are always accompanied by radiation exposure, they should only be performed if they are medically necessary. Pregnant women should just be X-rayed in extreme emergency.

When is it used?

X-raying, for example, is used to detect or eliminate fractures, signs of wear, malpositions and the consequences of bone inflammation.

How does it go?

Before the examination, one is asked to undress the body section, which is x-rayed and to discard jewelry. Depending on which part of the body is x-rayed, the examination takes place while sitting, lying or standing. The body is located between the radiation source and the recorder during X-ray. Because of the radiation exposure, the sex organs, if possible, shielded with a lead apron. The medical staff usually protects themselves with a lead apron. The recording itself only takes a few seconds.

Computed tomography

Computed Tomography (CT) allows more accurate X-rays of the body. The X-rays are sent from different directions through the body. Also, not the entire examination region is irradiated at once, but only thin slices (“layers”).

From the many pieces of information in the individual images, the computer calculates a multi-dimensional cross-sectional illustration of the respective body region. A CT scan is associated with a significantly higher radiation exposure than a simple X-ray examination.

When is it used?

Computed tomography is used, for example, to see changes in the bones that are not or not recognizable on a classic X-ray image.

How does it go?

In this examination, one is pushed lying through an annular CT device. An x-ray source in the CT scanner rotates around the selected body region. Depending on the size of the area to be examined, the examination takes about 5 to 30 minutes.

Magnetic resonance imaging (magnetic resonance tomography)

Also in a magnetic resonance tomography, detailed sectional images of the body are created. However, no X-rays are used, but magnetic fields and radio waves. The procedure is therefore also called magnetic resonance imaging (MRI).

The magnetic resonance tomograph measures – somewhat merely said – the activity in the hydrogen atoms of the body. The signals thus measured are converted into image information and displayed on a computer as two- or three-dimensional images of bones, joints, and soft tissues.

Due to their high water content, soft tissues such as muscles, ligaments or articular cartilage can be evaluated particularly well in magnetic resonance imaging.

When is it used?

Magnetic resonance imaging is used, among other things, for diseases of the knee, shoulder or spine. For example, abrasions, ligament, and meniscal injuries, as well as inflammatory processes on the bones, should become visible.

How does it go?

Magnetic Resonance Imaging is a large, tube-like device containing individual coils that generate the magnetic fields and radio waves. For the examination, one must take place on a couch, which is then wholly or partially driven into a tube – depending on which body part is to be examined. There are loud knocking sounds during the measurements. For some people, the examination can be stressful because of the confined space and unusual noises. In total, magnetic resonance imaging can take about 15 to 30 minutes.

Patients with implants (such as a pacemaker) who do not tolerate magnetic fields should not be examined with an MRI scanner. In the meantime, some practices and hospitals also have open MRI scanners, which can be an alternative for people with claustrophobia or severe obesity.

Bone density measurement (osteodensitometry)

In a bone density measurement, the mineral salt content of the bones is determined. From these results, conclusions can be drawn on the fracture strength of the bone. Most bone density is examined with a particular X-ray method, the DEXA or DXA (abbreviated to the English term “Dual Energy X-Ray Absorptiometry”). As a rule, weak X-rays are directed from below through the bones of the spinal column and the femoral neck.

For people with severe signs of wear on the spine, only thigh measurements are made; for people with artificial hip joints, only measures of the needle. The radiation exposure of the DEXA is lower than with a normal radiograph and much lower than with computerized tomography.

Osteodensitometry does not produce an X-ray but measures how much the bones attenuate X-rays. The more porous and fragile the bones are, the more x-rays they penetrate. The number of X-rays that penetrate the bone is converted to a measure that compares the current bone density value with that of young, healthy adults. This measure is called a T-score.

A T-score of -1 is considered normal, a T-score of -1 to -2.5 is deemed to be low. According to the relevant recommendations, osteoporosis is referred to when the T-score is equal to or less than -2.5.

Sometimes bone density measurements on the heel are made by ultrasound or computed tomography (CT). However, there are not enough essential studies to assess whether these methods are better or worse than DEXA. Also, computed tomography, as already mentioned, is associated with significantly higher radiation exposure.

When is it used?

A bone density measurement can be used to determine if someone has osteoporosis and how high the risk of bone fracture is. It is also used to monitor the course of treatment.

How is the examination performed?

For a DEXA, lie flat on your back. To measure the spine, the legs are bent at a 90-degree angle and stored high. To measure the upper neck, the legs are stretched flat.

Under the couch is the radiation source from which the X-rays emanate. A measuring arm then moves over the body and measures how the body absorbs many X-rays. The examination takes about 5 to 10 minutes.

Bone scintigraphy

Bone scintigraphy (skeletal scintigraphy) provides a pictorial representation of the metabolism in the bones. To get an accurate picture, the subjects are previously injected with a weakly radioactive substance. The dangerous material accumulates in the bone and improves the appearance of the different structures on the examination image. For example, cancer metastases or inflammatory sites often store the material more strongly than healthy tissue, which makes them recognizable on the image. The investigation also brings a radiation burden with it.

When is it used?

The metabolism in the bones changes, for example, with a growing tumor and inflammation in the bones. Therefore, bone scintigraphy is used in cases of a suspected disease, sometimes with poorly healing bone fractures.

How does it go?

As preparation, the radioactive substance is injected into a vein. Then you wait a few hours until the element has spread throughout the body. After this waiting period, a picture of the body is taken with a particular camera. For that, one lies down, and the camera moves over the body.

Bone biopsy and bone marrow biopsy

In a bone biopsy, the doctor uses a fine needle to remove some tissue from the bone with the aim of identifying specific pathological changes. In a bone marrow biopsy, the sample is taken from the bone marrow inside the bone.

When is it used?

A bone biopsy is used among other things in the study of tumors, inflammation, and disorders of bone structure such as osteoporosis. Bone marrow biopsy may be considered in cases of the suspected hemorrhagic disease, such as suspected anemia.

How does it go?

As preparation, the skin area above the bone is locally, and then a small incision is made, through which the biopsy needle is inserted. In a bone, biopsy tissue is often taken from the pelvic bone, but also the knee or thigh bone. In a bone marrow biopsy, the specimen is usually made from the iliac crest or sternum. The sample is then examined in the laboratory.

Blood tests

Blood levels are also used to identify certain bone diseases. For example, a blood test may be performed in cases of suspected osteoporosis to identify risk factors and prevent other diseases. The height of the calcium level, for example, should show if someone takes enough calcium. It does not say anything about how much calcium is in the bones. Significant is also the blood value “Alkaline Phosphatase.” This is a protein that is elevated in certain bone diseases.

Other blood levels may indicate inflammation, tumors or metabolic diseases that may affect the condition of the bones.


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