BEWARE OF THE NORMAL X-RAY
Dr Ruth Highet - Sports Physician

Shortcomings of x-rays

All too often in sports medicine, one sees patients who give a history very suggestive of a bony injury whom have been x-rayed and discharged with a diagnosis of NBI (No Bony Injury). Months after their episode of trauma they still have pain and swelling and have been unable to get back to their sporting activity.

The patient has usually been told that they have simply "sprained their ligaments".

Athletes do need to be aware that x-rays, particularly at the time of the injury and particularly in joints such as the ankle, frequently miss fractures. In fact, any athlete who is still limping from an "ankle sprain" a week after their initial injury, with profuse swelling of the ankle and foot, and pain over the front or the back of the ankle rather than just the outer aspect, should assume they have a fracture till proven otherwise.

What other investigations can be done?

A bone scan is often used these days to make the diagnosis of bony injury where x-rays are normal but the history and examination findings suggest otherwise. This requires an injection of a radio isotope dye into the arm which is then taken around the body by the blood stream. Areas of increased bone activity that occur in healing fractures, bone infections and other bone problems will show up as "hot spots" on the bone scan. This allows the diagnosis of a bony injury to be made and to localise the particular bone involved.

Sometimes specific types of imaging (CAT or MRI scans) of the particular area are performed to assess the extent of the damage to the bony and cartilaginous surfaces. This may allow us to see bony fractures which have become unstable and formed loose bodies in the past. These may require removal via an arthroscope. The arthroscope is a small telescope inserted into the joint space allowing assessment of the joint surfaces. Any bony or cartilaginous debris or chronically inflamed joint lining (chronic synovitis), can be removed or treated through the arthroscope.

"Stress" fractures which occur from repetitive overuse (bone stress) over a period of time (rather than a one-off acute injury) are a commonly occurring sports injury. Depending on the bone involved, they may fail to show up at all on plain x-rays. If they do, they won't appear on x-ray for at least three to four weeks after their onset. A bone scan will be positive however within 24 hours of the onset of a stress fracture and will very clearly localise the specific bone involved. Early diagnosis of these stress fractures will allow appropriate treatment. This usually means temporarily removing the athlete from their provocative activity and embarking on an appropriate rehabilitation programme before the stress "crack" in the bone becomes anything more major.

Ultrasound scans are also used more and more these days to help determine the nature of soft tissue injuries such as acute or chronic Achilles (bottom of calf), patella (front of knee), tendon injuries and rotator cuff tears in the shoulder. These are a relatively inexpensive form of investigation but can provide very useful information with regard to diagnosis and severity of injury. Their usefulness is highly operator dependent i.e. dependent on the skills and knowledge of the radiographer performing them.

The most advanced (and expensive) form of imaging used in sports medicine is the MRI scan. MRI (Magnetic Resonance Imaging) gives the best pictures of the soft tissues available and allows us to see the precise anatomy of muscles and tendons, nerves and blood vessels, amount of fluid in joints as well as bony architecture. It even allows us to see "bruises" in bones which may not be picked up by any other type of imaging. Another of the major pluses of MRI, is that it doesn't involve any radiation.

Conclusion

In summary, if you're still hobbling around on your sore ankle with severe swelling and a lot of pain more than a week after your injury then it's "high on the cards" that either an ankle fracture has been missed on plain x-ray or that significant soft tissue damage to the tendons, ligaments, or cartilage in and around the ankle has occurred. These days there are much more sensitive tools for diagnosis than plain x-rays and a correct diagnosis achieved through examination, and sometimes these other forms of imaging may result in appropriate early management and a much more rapid return to normal activities.