X-rays are usually the first imaging test done on children with hip pain of an unknown cause. There may be a fracture, tumor, or dislocation causing the painful symptoms. These kinds of problems show up readily on X-rays.
But when the X-ray appears normal, the physician must decide on the next step. This could be an ultrasound, CT scan, nuclear testing, or some other imaging test. In this report, each of these options is tested and reviewed for results.
Ultrasound is noninvasive and may be done after X-rays. The images produced by the sound waves help look for effusion (swelling) within the hip. Effusion suggests a hip infection.
At this point, the physician may aspirate the fluid. A long, thin needle is inserted into the pocket of fluid and a sample is withdrawn. Lab tests of the fluid can reveal the presence of infection.
In this study, 23 cases of suspected pelvic osteomyelitis were reviewed. Osteomyelitis is a bone infection caused by bacteria. Within the first four days of symptoms, X-rays were taken of everyone. Radiographic findings this early were negative. Lab tests were also done but blood cultures were only positive for three patients.
According to the results of this study, magnetic resonance imaging (MRI) may be the next best test to order to identify osteomyelitis. Early evidence of inflammation of the soft tissues and an abnormal bone marrow signal can lead to the diagnosis.
None of the MRIs in this group of patients were normal. There was always something to suggest soft tissue inflammation and bone marrow edema. MRIs enhanced by dye showed even greater soft tissue findings. Collections of fluid called phlegmons were often described.
MRIs of this patient group were also able to show distinct anatomical patterns within the pelvic area. Sometimes it was the sacroiliac joint that was involved.
In other cases, osteomyelitis was focused in the pubic symphysis. This is the area where the pelvic bones on both sides meet in the middle at the front of the pubic area. MRI also showed patterns affecting the growth plates of the pelvic bones.
The authors conclude by saying that MRIs speed up the diagnosis of pelvic osteomyelitis in children and teenagers. Any physician who suspects this problem may want to bypass the ultrasound, CT scan, and scintigraphy and go right to an MRI. This can save time and money in the long run.