Cath Lab Digest

By Brian McCurdy, Senior Editor

   Given that osteomyelitis can have serious consequences in the diabetic foot, a recently published study online in Diabetes Research and Clinical Practice identifies several risk factors that may facilitate earlier diagnosis of bone infection.

   Researchers studied 1,666 patients with diabetes from two large primary care facilities in south Texas. They defined osteomyelitis as a positive culture from a bone specimen. Over a mean follow-up period of 27.2 months, 151 patients developed foot infections and 30 of these patients had osteomyelitis, according to the study. Furthermore, the study says of the 50 patients who underwent lower extremity amputations, half had osteomyelitis, 44 percent had a soft tissue infection and 6 percent had no clinical evidence of infection.

   The researchers note that independent risk factors for osteomyelitis included wounds extending to bone or joint, previous history of a wound, and recurrent or multiple wounds during the study. The authors believe their study is the first to identify specific history and physical findings that are significantly associated with the presence of osteomyelitis.

Assessing The Value Of The Probe To Bone Test And Bone Cultures

   Three of the study authors note the probe to bone test is easy and inexpensive to perform, although they do cite some disadvantages. Lead study author Lawrence Lavery, DPM, notes that the test can lead to false positives and adds that wound depth is not the only factor to consider when diagnosing bone infection.

   Co-author Benjamin Lipsky, MD, says the most common mistakes in probe to bone tests are failing to debride the wound before probing and using a non-metallic device for the test.

   Co-author David Armstrong, DPM, PhD, says the setting in which one performs the test affects the efficacy of the test.

    “If one is in a setting like a referral-based inpatient unit, where there is a lot of osteomyelitis, then probing is a pretty good test even by itself. If one is in an outpatient office where the rate of bone infection is lower, then probing is not as accurate by itself,” says Dr. Armstrong, who is affiliated with the Department of Surgery at the Southern Arizona Limb Salvage Alliance (SALSA) at the University of Arizona College of Medicine in Tucson, Ariz.

   Drs. Lavery and Lipsky cite the efficacy of positive bone cultures. A bone biopsy provides “the most definitive diagnosis” of the cause of a bone lesion, according to Dr. Lipsky, a Professor of Medicine at the University of Washington School of Medicine. He says it is the only method of ascertaining the causative organism and its susceptibility to antibiotics, which is the key to determining which antibiotics, if any, one should use for treatment.

   Dr. Lavery, a Professor in the Department of Surgery at the Texas A&M Health Science Center College of Medicine, says bone cultures are not difficult to obtain and positive cultures will point to which organisms to treat.

   Where should further research into this subject lead? Both Drs. Lavery and Lipsky would like to see further research on the efficacy of the probe to bone test. Dr. Lipsky supports the development of inexpensive commercial kits for the probe to bone and bone biopsy tests.

    “I think the work in this area further confirms that osteomyelitis is indeed a clinical conundrum but it is not as difficult or as acute a problem as many make it out to be,” says Dr. Armstrong. “With osteomyelitis, unlike with necrotizing infections or acute abscesses, the clinician has a bit of time to consider the problem and take palliative or definitive action as the situation requires.”

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