Osteomyelitis: Keys To Diagnosis And Treatment

Gina A. Hild, DPM, and Allan M. Boike, DPM, FACFAS

Can new technological advances facilitate a more accurate diagnosis of osteomyelitis and more successful treatment? These authors consider this question and offer insights from the literature on lab tests, imaging modalities and effective treatments with an eye toward prevention.

Diabetes prevalence is at an all time high and current estimates show that 200 million individuals have the disease worldwide. This number is expected to grow to over 300 million over the next 10 years.1 Even though patients with diabetes are not the only patient population plagued by osteomyelitis, they are certainly at the top of the list when we consider those most at risk for this complication.

   New and emerging developments are happening in the areas of laboratory testing, radiographic imaging and antibiotic bead preparations. The single most important development in the treatment of osteomyelitis, however, may be a new focus toward early diagnosis and prevention, particularly in those at risk for diabetic neuropathy.

   Patients acquire acute osteomyelitis through a number of different mechanisms. Hematogenous methods of bacterial seeding are present in a bimodal distribution that occurs in both the very young and elderly populations. A small defect in the bone with a simultaneous or prior remote infection can result in seeding of the highly vascular and tortuous metaphyseal areas of bone. This means of acquiring osteomyelitis is rare in adult populations and most commonly happens in children.2

   Direct or contiguous extension involves the penetration of bone by means of a sharp object or surgical implant. Bacterial implantation in this instance can occur at any age and in any potential patient. Additionally, vascular insufficiency can lead to osteomyelitis and most often occurs among diabetic populations. Most commonly, patients acquire osteomyelitis through the contiguous spread of bacteria from a neighboring ulceration or cellulitis. Osteomyelitis in the absence of these entities is extremely rare. Areas that are most prone to ulceration and subsequent bone infection include the digits, metatarsal heads, calcaneus and malleolus.

   Traditionally, clinicians have utilized a probe-to-bone test in the clinical evaluation of osteomyelitis. Two studies have evaluated the reliability of the probe-to-bone test in evaluating the true incidence of bone infection. Lavery and colleagues determined that the probe-to-bone test was both sensitive (0.87) and specific (0.91).3 This study also found that the probe-to-bone test had a relatively low positive predictive value (0.57) and a high negative predictive value (0.98), indicating that a negative test could reliably exclude the diagnosis. Grayson confirmed the reliability of the probe-to-bone test in his earlier study.4

What You Should Know About Lab Tests

One can usually reject osteomyelitis as a differential diagnosis if an open ulceration is not present or a traumatic inoculation did not occur.5 Clinicians should pursue initial laboratory studies, including complete blood count, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), for any patient in whom there is suspected infection. If the results of these tests are unremarkable, bone or soft tissue infection are much less likely.6,7

   White blood cell counts and oral temperature may not be reliable indicators of the presence of osteomyelitis or soft tissue infection in the patient with diabetes. One study found white blood cell count to be elevated in approximately half of those with positive bone cultures.8 Fever was also present in only 20 percent of the same population. The study found ESR to be a valuable tool in the initial evaluation of the patient with diabetes as it was elevated in 96 percent of these patients.8

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