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If you can believe this, our seven-year-old daughter actually dislocated her hip playing softball (she slid into someone standing at home plate). The X-ray department took an X-ray but the radiologist refused to do an MRI (as suggested by another person evaluating our daughter). The radiologist said there's nothing there but cartilage and it wasn't "medically necessary." Is that true?
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There is some debate about what type of imaging studies are useful, needed, and helpful in diagnosing acute traumatic hip injuries in children. Age and gender (boys versus girls) are two important variables and we'll explain why here in a minute.
Children and young teens active in sports training and competition who have not completed their growth will need some special consideration when being evaluated because the bones are not fully formed yet.
For example, when the hip socket (known as the acetabulum) is still more cartilage than bone, X-rays may falsely show what looks like a rotated angle of the hip. It is easy to mistake the hip pain as coming from a problem known as femoroacetabular impingement when that's not it at all.
In another example, X-rays and CT scans looking for a fracture of the backside of the acetabulum may not show a torn labrum (fibrous rim of cartilage around the hip socket) or a loose piece of cartilage in the joint. Only an MRI will show that.
So when should an X-ray versus CT scan versus MRI be ordered for a child with hip pain associated with trauma (accident, injury, or sports overuse)? Recently, a group of orthopedic surgeons from the Hospital for Special Surgery in New York City did a study to sort this out.
They found medical records for 180 patients between the ages of four and 15 with hip pain who were evaluated by X-ray and MRI. They compared the findings and results. In the process of collecting this information, they were able to determine the order, speed, and age(s) at which the backside and rim of the acetabulum (hip socket) develops.
They found that the posterior (back) wall of the hip socket (acetabulum) develops in four distinct phases. At first (in the young child before age eight), the acetabulum is made up of 100 per cent cartilage. Around age eight or nine, the cartilage starts to turn to bone. That process is called ossification. MRI images showed a cobblestone formation with islands of bone ringed by areas of cartilage.
By age 12 or 13, the three bones (ilium, ischium, pubis) that join together to form the acetabulum have met together and fused. At this point, there is still a rim of bone forming (ossification) around the upper back (posterior) portion of the acetabulum. This is referred to as the posterior rim sign. The final step is closure of the cartilage between the three bones called the triradiate cartilage. This last phase occurs in girls by age 12 and in boys by age 14.
If a surgeon needs to know the shape and developmental phase of the acetabulum before that final phase (before closure of the triradiate cartilage), then an MRI (not X-rays or CT scans) will be needed. Children younger than eight won't need an MRI since it is known the socket is all cartilage. Children between nine and 14 must be evaluated on an individual basis keeping their gender in mind (girls complete the fusion process at a younger age than boys).
The authors of this study suggest surgeons should NOT rely on anything but MRIs when evaluating the hip socket in older children and young teens who do not have a fully closed triradiate cartilage. The radiologist is correct that your daughter probably doesn't need an MRI at this time for the reason stated.
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*Disclaimer:*The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic. |
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