Study Identifies Risk Factors For Osteomyelitis In The Diabetic Foot
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.”
How Effective Is NPWT For Children?
By Lauren Grant, Editorial Assistant
Should physicians consider the use of negative pressure wound therapy (NPWT) for lower extremity wounds in pediatric patients? A new study abstract, which will be presented at the upcoming Symposium on Advanced Wound Care (SAWC), investigates the potential of NPWT in a pediatric population.
The study, conducted over three years, assessed the use of NPWT with reticulated open cell foam (ROCF) in 97 patients with 101 foot wounds. The median age of the patients was 16 and the majority of wounds involved non-dehisced surgical wounds, soft tissue and orthopedic trauma. Researchers found that the use of NPWT/ROCF healed 90 percent of wounds with a median length of treatment of 30 days, according to the abstract.
Allen Gabriel, MD, the lead author of the abstract, hopes his study will incline more physicians to use VAC therapy on pediatric wounds. He feels that not using this therapy for appropriately indicated pediatric wounds is “practicing below the standard of care.”
When asked if patient activity level affected healing time, Dr. Gabriel is skeptical.
“I do not believe the activity level affected healing rates as the patients that are treated with the VAC therapy can be mobile since this device acts as a splint on the wound,” says Dr. Gabriel, who is affiliated with the Department of Plastic Surgery at Loma Linda University in Loma Linda, Calif. He says this is another benefit of using VAC therapy in managing complicated wounds in the pediatric population.
Dr. Gabriel also saw no correlation between patient age and slower healing rates for pressure ulcers.
The SAWC will be held from April 26 to 29 at the Gaylord Texan Hotel and Convention Center in Dallas. For more information, visit www.sawc.net.
Abstracts Study Potential Of Hyperspectral Imaging
By Brian McCurdy, Senior Editor
Can hyperspectral imaging be a valuable tool in preserving limbs and preventing amputation? Two abstracts, which will be presented at the aforementioned SAWC, examine the potential of the technology.
For the first abstract, researchers assessed five patients with diabetes and limb-threatening neuroischemic foot lesions. Each patient either had no revascularization options or had already gone revascularization, and had necrotic wounds that necessitated partial foot amputation, according to the abstract. Authors noted that OxyVu (HyperMed) correctly predicted the probability of successful healing in contrast with standard measures of perfusion — such as ankle-brachial index (ABI), toe pressures and TcPO2 — which predicted failure. The abstract notes that OxyVu was critical in determining the appropriate level of amputation based on microcirculatory assessment.
The second abstract focused on 20 patients with foot lesions that required partial amputation at the foot or ankle level. Absent benchmark data for the new technology, researchers found that hemoglobin values above 50 (arbitrary units) at the planned amputation site accurately predicted healing. However, the abstract authors note that inflammation or infection made assessment more difficult due to the sensitivity of the technology.
Abstract lead author Robert Frykberg, DPM, says that by measuring oxyhemoglobin levels, OxyVu gives him the ability to determine the likelihood of a patient’s healing at several levels as he plans partial foot amputations. Other advantages are the technology’s enduring visual media and he says he can review the results at any time.
Dr. Frykberg notes he can also select areas within the image to review the levels of oxyhemoglobin/deoxyhemoglobin, which he says is particularly important when revisional surgery is necessary and in determining why an area may not have healed following a procedure.
There are several disadvantages. As the technology is new, there is a lack of benchmark data available and OxyVu is relatively expensive, according to Dr. Frykberg, the Chief of Podiatry at the Carl T. Hayden Veterans Affairs Medical Center in Phoenix.
What Is The Future Of Hyperspectral Imaging?
Dr. Frykberg notes several other potential applications of hyperspectral imaging. He says one may be able to use the technology at the initial exam to predict the wound healing of potential ulcers. This can lead to earlier vascular intervention, according to Dr. Frykberg.
He adds that the technology may also have potential with preoperative assessment of the vascular status of patients with borderline peripheral vascular disease who may need reconstructive surgery.
