What is a Hand X-ray?
It is a plain X-ray of one or both hands. Usually the entire hand including the wrist is shown, and often both hands are imaged together, as assessment of both hands is usually necessary when searching for disease.
If closer attention needs to be paid to a certain finger or joint, e.g. injury or foreign body, then a finger can be imaged on its own.
What is the procedure commonly used for?
Hand X-rays are performed to look for joint diseases, which present as constant pain in a single or multiple joints, visible deformity or joint changes, redness or swelling, as well as a decrease in joint function, e.g. inability to fully extend or bend a joint in the hand.
X-ray of the hands is a very valuable investigation in rheumatology, i.e. the specialty dealing with chronic joint diseases. Joint diseases affecting the hand and other joints in the body may be identified by individual features such as joint space narrowing, erosions, new bone formation, dislocation and deformity, which may be diagnostic of a specific joint disease. In chronic diseases such as rheumatoid arthritis, the presence of erosions on the hand X-ray gives a valuable measure of disease progression and response to therapy.
X-rays of the hands can be used to assess tumours or search for infection of joints and bones.
X-rays are frequently used after orthopaedic surgery to assess changes in the joint and to look for complications after the surgery, e.g. infection, malalignment of bones or loosening, migration or failure of orthopaedic implants like joint replacement prostheses, plates, rods and screws.
Hand X-rays are used in newborns and infants if skeletal birth defects or bone abnormalities affecting bones and joints like achondroplasia or osteogenesis imperfecta are suspected.
How should I prepare?
Make sure you wear clothing that can be removed or pulled away from the hands. Remove all jewellery and other devices like bandages, splints or braces.
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 has a bed and an X-ray machine. Your hands are exposed from under the clothing and any jewellery or other metal objects like braces, splints removed (if possible), especially if they are in the way. The hands are positioned between the X-ray cassette, 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, which means that the joint is positioned on a flat panel sensor. A beam of light is used to help position the limb, cassette, and X-ray tube overhead.
The image is then taken, which is painless and feels the same as having your photograph taken! Afterwards the hands may be repositioned to take X-rays from different positions or angles.
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 can be postponed to a later date after the birth, or once it is certain that you are not pregnant.
Taking an X-ray picture poses no immediate risk to your health. There is no clear evidence that X-rays in average doses increase one’s risk for cancer - therefore the procedure is considered to be entirely safe.
What are the limitations of the procedure?
Different soft tissues like ligaments, tendons, cartilage, synovial or bursal membranes do not show up well on X-rays, therefore pain from or disease of these structures may not be easy to detect. Cartilage thickness (joint space) and osteoarthritis progression may be estimated from an X-ray, but once again the actual cartilage cannot be seen.
X-rays may sometimes miss small fractures of bone due to overlapping or blurring of shadows on the X-ray picture, or may sometimes incorrectly display a bone defect, lesion or fracture where there is none. This once again due to overlapping shadows or artefacts, which are false non-anatomical structures that can be present on the final X-ray image. It is caused by incorrect film handling or problems in processing, similar to those found in photography: dots, spot, lines and fingerprints!