Less Invasive Method IDs Bone Infection in Diabetic Foot

Marlene Busko

March 26, 2013

In a small study of diabetic patients presenting with a foot ulcer and no signs of soft-tissue infection, bone infection was safely and accurately diagnosed in a 2-step method that included less invasive bedside bone puncture rather than a bone biopsy.

First, patients underwent single-photon-emission computed tomography and X-ray computed tomography (SPECT/CT) using a gallium (67Ga) tracer. Then, patients with positive scans had bone punctures.

The method successfully identified osteomyelitis with a specificity of 88% and a sensitivity of 94% and cut down on unneeded use of antibiotics.

"Coupling of  67Ga SPECT/CT imaging and bedside percutaneous bone puncture appears to be accurate and safe for diagnosing diabetic foot osteomyelitis in patients without signs of soft-tissue infection, obviating the need for antibiotic treatment in 55% of suspected cases," the authors, led by Elisabeth Aslangul, MD, from the Université Paris Descartes, Paris, France, write.

The study was published online March 20 in the Diabetes Care.

About 25% of patients with diabetes mellitus have foot ulcers, and about 50% of these present with infected ulcers that may involve the bone, increasing the risk for lower-limb amputation. In most clinical practices, osteomyelitis is diagnosed from clinical presentation and an imaging scan, since bone biopsy, which would allow appropriate tailoring of antibiotics, is often perceived as complex and risky.

In the current study, the researchers enrolled 55 consecutive patients with diabetes aged 18 years and older presenting at a clinic for diabetic foot conditions at a single center in France between 2007 and 2009. The patients underwent 67Ga SPECT/CT scans. The 13 patients with negative scans did not receive antibiotics.

A total of 42 patients had scans showing a marked uptake of gallium, consistent with a diagnosis of osteomyelitis. The patients were mostly men (93%), and they had a mean age of 63 and had had diabetes for about 20 years. They underwent bedside bone-marrow aspirations at a puncture site determined by gallium accumulation on the 67Ga SPECT/CT scan.

The bone-marrow samples were cultured in 2 media. A total of 24 patients had positive blood cultures — almost all gram-positive staphylococci — and received targeted antibiotic therapy based on these findings.

Two patients were excluded from subsequent analysis, because they had received recent antibiotics.

The patients were followed for at least 1 year. At follow-up, of the remaining 53 patients, 3 had died, 3 had undergone amputation, and 47 met the primary study end point of having no clinical evidence of foot infection at follow-up.

None of the patients with negative 67Ga SPECT/CT scans had any evidence of bone infection at follow-up. Use of this technique made it possible to avoid bone puncture in 13 of 55 cases (24%).

Accurate, Safe, Easier, Less Costly Screening

This screening method also provides cost advantages. "67Ga SPECT/CT has a similar cost to magnetic resonance imaging [MRI] and is widely available in France, both in public and private hospitals," the authors write. "The bone-puncture procedure can be carried out at the patient’s bedside, by a clinician, without the need for an orthopedic surgeon or radiologist and imaging equipment. It is also less expensive than surgically or radiologically guided procedures."

The authors have disclosed no relevant financial relationships.

Diabetes Care. Published ahead of print March 20, 2013. Abstract