Occult fractures

Occult fractures. Occult fractures, by definition, are not seen on the plain films. If you ever suspect a fracture, you always start with a plain film. They are the least expensive, most cost effective and most helpful study if they are positive. If they are negative and your clinical suspicion remains high, like our nice little osteoporotic lady with severe right hip pain that we did last Friday who had two pelvic fractures of the sacroiliac joint and then in through the sacrum, you need to go on and do a bone scan.

Osteomyelitis. Typically this is the diabetic patient with a lovely ulcer that’s just eroding through the skin and pretty much down to the bone and you’re trying to decide if all they have is a cellulitis or if they actually also have osteomyelitis and need a longer term of intravenous antibiotics.
Once you get into what I like to consider traumatized bone, like the diabetic foot, someone who can have some pretty bad neuropathic changes (Charcot joints), your specificity of your bone scan will decrease. Then we may well need to recommend additional imaging, for example, with a labeled white blood cell study. If those white blood cells are only in the soft tissues it’s cellulitis. If they are nice and focal right there in the bone, that’s going to be an osteomyelitis.
If it’s untraumatized bone, let’s say it’s the honeymooner that stepped on a sea urchin spine in Hawaii five weeks ago and has persistent foot pain even though you don’t see any definite abnormalities on the outside, then the sensitivity and specificity for bone scanning is about 95%. So it’s really very good in untraumatized bone.
Painful joint prostheses. This is generally someone who has had a joint replaced. Usually they have an initial improvement in their pain in that joint and then it starts to deteriorate again. It can be much later. The incidence of loosening in prosthetic joints is actually quite high. I don’t want to quote a number but it is significant. So, again, bone scans can be very helpful there. If you’re doing the bone scan very close to the surgery, then we can get some false positives or we can be a little wishy-washy on the interpretation saying, “Post surgical changes. Maybe osteomyelitis”. Then, again, we might ask for a white blood cell study in that case.
Hip pain. The main thing that makes it important for you to do a bone scan early in hip pain is if you’re worried about aseptic necrosis. You want to get these people prior to irreversible changes and do surgery and hopefully reestablish the blood flow to that hip.

Osteomyelitis and septic arthritis are often in the differential diagnosis in children or in infants with hip pain or who are refusing to bear weight on an extremity. Again, you need to rule out aseptic necrosis very early on. Early on, the plain films in aseptic necrosis are going to be normal because it’s going to take quite some time before the bone loses enough calcium and starts to collapse. Those are the findings that you will see on the plain films.

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