What It Is

A femur X-ray is a safe and painless test that uses a small amount of radiation to make an image of a person's upper leg (the area between the hip and knee). During the examination, an X-ray machine sends a beam of radiation through the upper leg, and an image is recorded on special film or a computer. This image shows the soft tissues and the bone in the upper leg, which is called the femur.

The X-ray image is black and white. Dense body parts that block the passage of the X-ray beam through the body, such as bones, appear white on the X-ray image. Softer body tissues, such as the skin and muscles, allow the X-ray beams to pass through them and appear darker. An X-ray technician takes the X-rays. Two pictures of the femur are usually taken: one from the front (AP, or anteroposterior view) and one from the side (lateral view).

Why It's Done

A femur X-ray can help find the cause of symptoms such as pain, limp, tenderness, swelling, or deformity of the upper leg. It can detect a broken bone, and after a broken bone has been set, it can help determine whether the bone is in satisfactory alignment.

If surgery of the upper leg is required, an X-ray may be taken to plan for the surgery and to assess the results of the operation. Also, an X-ray can help detect cysts, tumors, or other diseases in the bone, including later stages of bone infections.

Preparation

A femur X-ray doesn't require any special preparation. Your child may be asked to remove some clothing, jewelry, or any metal objects that might interfere with the image.

If your daughter is pregnant, it's important to tell the X-ray technician or her doctor. X-rays are usually avoided during pregnancy because there's a small chance the radiation may harm the developing baby. But if the X-ray is necessary, precautions can be taken to protect the fetus.

Procedure

Although the procedure may take about 15 minutes or longer, actual exposure to radiation is usually less than a second.

Your child will be asked to enter a special room that will most likely contain a table and a large X-ray machine hanging from the ceiling. Parents are usually able to accompany their child to provide reassurance. If you stay in the room while the X-ray is being done, you'll be asked to wear a lead apron to protect certain parts of your body. Your child's reproductive organs will also be protected with a lead shield.

If your child is in the hospital and can't easily be brought to the radiology department, a portable X-ray machine can be brought to the bedside. Portable X-rays are sometimes used in emergency departments, intensive care units (ICUs), and operating rooms.

The technician or radiologist will position your child (either lying or standing), then step behind a wall or into an adjoining room to operate the machine. Two X-rays are usually taken (from the front and side), so the technician will return to reposition the leg for each X-ray.

Older children will be asked to stay still for a couple of seconds while the X-ray is taken; infants may require gentle restraint. Keeping the leg still is important to prevent blurring of the X-ray image.

What to Expect

Your child won't feel anything as the X-rays are taken. The X-ray room may feel cool due to air conditioning used to maintain the equipment.

The positions required for the X-rays may feel uncomfortable, but they need to be held for only a few seconds. If your child has an injury and can't stay in a required position, the technician might be able to find another position that's easier. Babies often cry in the X-ray room, especially if they're restrained, but this won't interfere with the procedure.

After the X-rays are taken, you and your child will be asked to wait a few minutes while the images are processed. If they are blurred or unclear, the X-rays may need to be redone.

Getting the Results

The X-rays will be looked at by a radiologist (a doctor who's specially trained in reading and interpreting X-ray images). The radiologist will send a report to your doctor, who will discuss the results with you and explain what they mean.

In an emergency, the results of an X-ray can be available quickly. Otherwise, results are usually ready in 1-2 days. In most cases, results can't be given directly to the patient or family at the time of the test.

Risks

In general, X-rays are very safe. Although there's some risk to the body with any exposure to radiation, the amount of radiation used in a femur X-ray is small and not considered dangerous. It's important to know that radiologists use the minimum amount of radiation required to get the best results.

Developing babies are more sensitive to radiation and are at greater risk for harm, so if your daughter is pregnant, make sure to inform her doctor and the X-ray technician.

Helping Your Child

You can help your young child prepare for a femur X-ray by explaining the test in simple terms before the procedure. It may help to explain that getting an X-ray is like posing for a picture.

You can describe the room and the equipment that will be used, and reassure your child that you'll be right there for support. For older kids, be sure to explain the importance of keeping still while the X-ray is taken so it won't have to be repeated.

If You Have Questions

If you have questions about why the femur X-ray is needed, speak with your doctor. You can also talk to the X-ray technician before the procedure.

Reviewed by: Yamini Durani, MD
Date reviewed: August 2011