X-ray lumbar spine or L spine, LS spine or lower back X-ray
What is a Lumbar Spine X-ray?
It is a plain X-ray of the lower back, specifically of the five lumbar vertebrae that make up the lower (lumbar) spine, the sacrum and coccyx - which are the back part of the pelvis and tail bones.
One or more views can be requested; most commonly an "antero-posterior" picture is taken where you face the X-ray beam and the spine is shown from the front to the back, and a "lateral" picture where the X-ray beam comes from the side to show the side of the spine. Other oblique pictures may also be done, as well as pictures of the spine in different positions, i.e. bending over forwards or bending backwards.
What is the procedure commonly used for?
Lumbosacral spine X-rays are taken to investigate the presence of persistent ongoing pain in the spine, or numbness or weakness of the pelvis and legs. It is used to look for signs of arthritis, i.e. inflammation of the joints between the back bones, degeneration (breakdown due to ageing) of the discs between the bones of the spine or infections or tumours. Abnormal curvature of the spine like scoliosis and kyphosis can also be seen on X-rays.
After injury, X-rays are used to investigate dislocation or fracture of the back bones.
X-rays can also be done at an early age to investigate birth defects like spina bifida.
After surgery spine X-rays are used to assess changes in the spine caused by the surgery, and for post-surgical complications, e.g. infection, malalignment of bones or loosening, migration or failure of orthopaedic implants like joint replacement prostheses, plates, rods and screws.
How should I prepare?
Make sure you wear clothing that can be removed or pulled away from the back and waist. Remove all jewellery and braces, bandages or other objects that may be in the way.
How is the procedure performed?
After registering at the X-ray Department and spending some time in the waiting room, you will be led through to the X-ray room, which contains a bed and an X-ray machine. Your back will be exposed, and any jewellery or other metal objects like braces, splints removed (if possible) if they are in the way.
You will most likely be asked to stand up straight in front of the X-ray machine while the picture is taken. You will be positioned between the X-ray cassette, which is a flat plastic cassette that holds and protects the film, and the X-ray tube, which is the machine that produces the actual rays that will travel through your body onto the plate to form the X-ray image.
Newer X-ray departments may use digital machines. This means that the joint will be positioned on a flat panel sensor. A beam of light is used to help position the limb, cassette, and X-ray tube overhead.
The X-ray is then taken. This is painless and feels like having your photograph taken! Afterwards you may be asked to turn to the side so that a side view can be taken. You may also be asked to bend over forwards or extend your back, arching backwards, so that pictures may be taken from different angles.
If you are not able to stand, the procedure may be performed equally well if you lie flat on the X-ray table.
The greatest risk is to the pregnant patient. It is dangerous for the developing foetus to be exposed to X-rays, as this may cause abortion or serious birth defects. So, if you are pregnant or suspect that you may be pregnant, you should inform the X-ray department and the procedure will be postponed until after the birth, or once it is certain that you are not pregnant.
X-rays pose no immediate danger to one's health. There is also no clear evidence to suggest that average doses increase one's cancer risk. It is therefore considered to be entirely safe to have an X-ray taken.
What are the limitations of the procedure?
Different soft tissues like ligaments, tendons, cartilage, and discs in between the bones of the spine do not show up well on X-rays, therefore pain from or disease of these structures in the lumbosacral spine may not be detected. There may also be prolapsed discs or other pathologies pressing on the spinal cord or affecting the nerves coming from the spinal canal, causing pain, numbness or weakness in the pelvis or legs, that cannot be seen on a plain lumbosacral X-ray.
X-rays may sometimes miss small fractures of bone in the spine due to overlapping or blurring of shadows on the picture, or may sometimes incorrectly display a bone defect, lesion or fracture where there is none, once again due to overlapping shadows or "artefacts", which are false non-anatomical structures that can be present on the final X-ray image. This is caused by incorrect film handling or problems in processing - similar to those found in regular photography: dots, spot, lines and fingerprints!
A CT scan or MRI of the lumbar spine is often performed when your symptoms strongly suggest pathology - even if the lumbosacral X-rays are normal. This is because the lumbosacral spine is a complicated anatomical area and plain X-rays of the lumbosacral spine are of limited use.