We have all been in this situation: patient with diabetes and neuropathy presenting with a red hot swollen rocker bottom foot with a plantar draining ulcer which happens to probe deep and close to bone. Because the clinical presentation of both entities are relatively similar, we often rely on additional information from imaging modalities hoping to give us distinction between the two pathologies. Of course, the standard is histologic diagnosis with bone biopsy. But if this was not available, is there an imaging tool that can provide enough information distinguishing osteomyelitis from Charcot?

The problem with the "gold standard" biopsy is that it has never been tested itself. It might actually be difficult to obtain a uncontaminated specimen of bone in the presence of a wound. MRI can not distinguish OM from Charcot changes in the bone and you must rely upon "secondary signs". Secondary signs are keeping in mind that Charcot foot usually affect more than one bone, OM usually only one bone. Charcot usually affects the midfoot, OM more commonly the forefoot. And perhaps most importantly, OM rarely occurs without the presence of an open wound or tract to bone. My test of choice when differentiating between Charcot and OM is the WBC-labeled bone scan. See our article Rogers LC, Bevilacqua NJ. Imaging of the Charcot Foot. Clin Pod Med Surg. Apr 2008 for a more detailed synopsis.

An issue that maybe encountered is false positives with Indium111 for osteomyelitis with concomitant charcot as Indium will accumulate in the reparative phases of charcot process.  May consider bone marrow imaging with sulfur colloid with indium111 instead.  Sulfur colloid will only accumulate in areas of reticulendotheliocytes (marrow).  In the presence of infection, sulfur colloid will not accumulate in infarcted infected marrow.  If the Indium accumulates in this area of absent sulfur colloid tracer, it is call spatially inconguent and more accurate for the diagnosis of osteomyelitis.  Palestro has performed a majority of this work in the 90's.