Back Tests: Diagnosing Back Pain

Tests: What Do They Really Show?
Do patients and doctor alike put too much faith in medical tests, or are the tests available to us sophisticated enough to tell us what is really wrong with our bodies. Today, the most common diagnostic tests used to determine the cause of back pain include X-Rays, CT Scan, MRI, Ultrasounds, and Dynamic Radiographic Computerized Analysis. Each of these tests will give doctors a lot of information about the anatomy of the body, and possible pathology. Each of these tests have their own strengths and weaknesses, in relation to costs, risks, and diagnostic quality. Some tests are better than others for imaging certain parts of the body and assessing for certain joint problems or neurologic disorders. In most cases, one or more of these tests will provide doctors with useful diagnostic information to supplement the observations that were made during the physical examination. It should be noted, however, two important facts:
  • In many cases, a patient may be successfully treated for back pain without the cause of the condition ever being diagnosed.
  • In many cases, doctors are never successful in finding the main pain generator even after an extensive battery of diagnostic tests. This is the theory behind situations in which a patient has continued back pain ever after treatments such as physical therapy and back surgery were believed to have fixed the physical problem. The main pain generator is the term given to the structure in the spine or musculoskeletal system that is damaged, causing the pain symptoms. When the pain generator has been repaired or removed, though back surgery, and the pain continued, many times doctors determine that that site was not the cause of the pain, in spite of the observable pathology. That being said, these back tests all have their strengths as diagnostic resources for determining the cause of back pain. Let's look at a more detailed account of how each one works, and how they give us a better window into the structure and function of our bodies.

X-Rays: X-Rays are the most common test used to determine if a bone has been injured or fractured. X-Rays have been in regular use in orthopedic diagnostics for over 120 years now, while the other tests are relatively new (last 50 years). Here's a brief description in how these tests work. X-Ray photons shoot from an X-Ray tube, they go through the patient, and hit an image receptor behind the patient. Some X-rays pass all the way through the patient without being stopped. Some of the X-Rays are absorbed by the body, especially the bones and muscle which are much denser than other tissues, such as the joints and internal organs. At the image receptor, the image will show up as black where the X-Rays have passed through the patient, and the image will show up whiter in the areas in which the X-Rays have been absorbed by the body. The images will also be various shades of grey in areas where some X-Rays have been absorbed, and others have passed through the patient. Overall, an image representing the internal structure of the body will develop as a result of these contrasts of blacks, whites, and grays. Most of all, X-Rays show good detail of the bones and the joint spaces in between the bones. These X-Rays are good at showing information about bone density, bone fractures, and misalignments of the bone structure (e.g. scoliosis, spondylolisthesis).

X-Rays are not as good at showing the detail of soft tissue and specific pathology related to the soft tissue. For example, a lumbar spine X-Ray will show us good detail of the vertebrae (vertebral bones) as well as the amount of space between these spinal bones. In the event that a patient has degenerative disc disease, the X-Rays will present vertebrae without very little spacing between one another, This lack of separation between the vertebrae is indicative of degenerative disc disease.

But what does degenerative disc disease mean, and how do we know what caused it? And how do we even know is this spinal condition is the cause of our back pain? Degenerative disc disease simply means the loss of volume or size of the intervertebral discs. This condition may or may not be the cause of back pain. Without other more sophisticated testing, it is somewhat difficult to know if the degenerative changes observed on X-Rays are the cause of the patient's pain. What causes the pain most often, in relation to this disease, is when a hole forms in the outer membrane of the disc, and the inner material is ejected outwards, pressing into the spinal nerves. To determine if this is the case, MRI tests are usually ordered, which show much much better detail of the soft tissues and spinal nerves of the body.