By now you’ve likely seen parts one, two and three. Moving in a logical direction part four will focus on imaging, As you’d imagine, radiographic studies are supremely important in the diagnosis of osteo. Let’s take a look by modality shall we?
Plain films
The bottom line is that it can take up to 2-3 weeks for the typical osteo to show up on plain films, though it could be as soon as 5-7 days in childen. Nonetheless, you should get films on initial evaluation, as this will help you rule out fractures (pathologic or otherwise) or Ewing’s sarcoma. The characteristic appearance is called the “rat bite” lesion, as seen below. Osteo needs to extend 1 cm and compromise 30 to 50% of bone content to produce changes in plain radiographs.
Bone scan and CT
osteo of the femur on bone scan
Now we’re talking. Ideally, CT is a sensitive study, but the radiation exposure can be significant. Bone scan approaches an accuracy of 90% and can be especially useful in long bone disease where the precise location is not able to be determined based on exam alone. In patients in who sedation for MRI is contraindicated, or MRI unavailable altogether bone scan is an excellent choice.
MRI
MRI, if available, is the ideal study for the precise diagnosis of osteomyelitis. It has the added benefit of showing surrounding tissue involvement especially in cases that are hard to differentiate. Of course, younger patients
may need to be sedated, which can be a big deal.
Recommendations
In any case where osteo is suspected you should get plain XRays as they can help rule out pathologic fractures, Ewing’s sarcoma and may show findings as early as 5-7 days in children. If available an MRI would be the best diagnostic study – though it may require sedation.
