Key Insights On Managing Infected Diabetic Ulcers

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Here is a severe polymicrobial diabetic foot infection with MRSA as the primary pathogenic organism. Anthony F. Cutrona, MD, says MRSA accounts for 65 percent of Staph aureus cases at his facility.
For the majority of pedal osteomyelitis, Lawrence Karlock, DPM, says he usually relies on standard radiographs as well as probe to bone tests. (Photo courtesy of Dr. Karlock.)
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Author(s): 
Clinical Editor: Lawrence Karlock, DPM

Q: In the workup of possible pedal osteomyelitis, what imaging modalities do you prefer to use and why?
A:
Drs. Brill and Karlock prefer magnetic resonance imaging (MRI) when they suspect osteomyelitis. Unless plain radiographs unequivocally demonstrate osteomyelitis, Dr. Brill says he prefers MRI because it is noninvasive and “has a fairly reliable sensitivity and specificity.” However, he warns there is a 10 to 20 percent false positive finding with MRIs, which he says is most likely due to neuropathic changes in bone.
For the majority of pedal osteomyelitis, Dr. Karlock says he “usually relies” on standard radiographs as well as probe to bone tests. Dr. Cutrona agrees, noting that changes in serial plain X-rays should enable one to make the diagnosis. Dr. Karlock says he occasionally uses the Tc99 bone scan to rule out osteomyelitis. If he is dealing with a deep wound and wants to determine whether it is a soft tissue infection or osteomyelitis, Dr. Karlock says he will order the Tc99 to confirm there is no bony infection in the foot. He emphasizes this is not commonplace in his practice.
Bone scans and the white blood cell tag in the scans seem to be unreliable in assessing patients with diabetes, according to Dr. Cutrona, who cites false positive and negatives in the range of 60 percent. He says these tests are “very expensive,” and for about the the same cost, one can obtain good anatomical resolution either by CT scan or MRI. Dr. Karlock agrees, noting that he usually does not order multiple tests and/or scans in this clinical setting.
“I have found that ordering all these tests can actually become more confusing and lead you down the wrong path,” cautions Dr. Karlock.
In summary, Dr. Cutrona emphasizes the importance of diagnosing osteomyelitis on both a clinical basis as well as through laboratory data, radiographic data and, if possible, a biopsy.

Dr. Brill practices at the Limb Salvage Center at the BrillStone Building and is President of the BrillStone Corporation in Dallas. He is a Fellow of the American College of Foot and Ankle Surgeons and is also a consultant in wound care and reconstructive foot and ankle surgery at the Wound Care Clinic at Presbyterian Hospital in Dallas.

Dr. Cutrona is the Director of the Infectious Disease Section of the St. Elizabeth Health Center in Youngstown, Ohio.

Dr. Karlock (pictured) is a Fellow of the American College of Foot and Ankle Surgeons and practices in Austintown, Ohio. He is a member of the Editorial Advisory Board for WOUNDS, a Compendium of Clinical Research and Practice.

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