Current Concepts In Treating Osteomyelitis

By Nicholas Bevilacqua, DPM

It has been estimated that a person with diabetes has a 25 percent lifetime risk of developing a foot ulceration.1 Diabetic foot ulcers commonly become infected, can involve bones and joints and may progress to amputation. Osteomyelitis frequently complicates ulcerations in people with diabetes and may be present in up to 20 percent of mild to moderate and 50 to 60 percent of severely infected wounds.2 Diagnosing osteomyelitis in people with diabetes who present with a foot ulcer is challenging and becomes a clinical conundrum. Misdiagnosis may lead to unnecessary treatment, specifically prolonged antibiotic therapy and surgery. Accordingly, let us take a closer look at osteomyelitis in the diabetic foot, the importance of early detection, the benefits and limitations of the available diagnostic tests, and the current evidence of both surgical and non-surgical treatment. Osteomyelitis is an inflammatory process caused by an infecting microorganism.3,4 This infectious process is accompanied by bone destruction and, in most cases, clinical signs of inflammation.4,5 Waldvogel classified osteomyelitis based on etiology and developed three categories: hematogenous, contiguous and osteomyelitis associated with vascular insufficiency.6 Hematogenous osteomyelitis mostly occurs among children and elderly patients, and the infected bone is caused by bacteria seeded in the blood. Most often, this form of osteomyelitis involves the metaphysis of long bones. Local (chills, fever and malaise) and systemic (pain and local swelling) signs are typical.4 In contiguous osteomyelitis, the bone becomes infected from an external contaminated source (penetrating trauma, open fracture, bone surgery or joint replacement). This can occur at any age and can affect any bone. In regard to osteomyelitis associated with vascular insufficiency, physicians will most often see this among patients with diabetic neuropathy.6 Foot ulcers serve as portals for infection and bacteria to gain access to the bone by contiguous spread. If a diabetic foot ulcer fails to heal after at least six weeks of appropriate care and offloading, one should suspect osteomyelitis.7 In almost all cases of osteomyelitis in the diabetic foot, the infection starts in the soft tissue and spreads to bone. A Primer On The Microbiology Of Osteomyelitis There have been many classification schemes devised for osteomyelitis and researchers utilized traditional staging with the Waldvogel classification system. However, the Waldvogel classification is an etiologic system and does not convey a specific treatment regimen. Buckholz described seven different types of bone infection based on pathophysiology.8 Researchers have developed other classifications to emphasize different clinical aspects of osteomyelitis.9 Cierny and Mader developed a descriptive classification for surgeons treating patients with chronic osteomyelitis. The Cierny-Mader classification is based on the anatomy of bone infection and the physiology of the host. Anatomic characteristics of the bone infection are divided into four stages: stage I, medullar; stage II, superficial; stage III, localized; and stage IV, diffuse osteomyelitis. Likewise, the physiology of the host is subdivided into different categories. An A-host has a normal systemic defense. A B-host has systemic and local compromise. A C-host is a non-surgical candidate as surgical treatment may be worse than the disease. The Cierny-Mader classification permits the development of a comprehensive treatment guideline for each stage.9 This detailed classification system applies best to long bones and is not very useful for the small bones of foot.4,10 As far as microbiology goes, eradicating infection in bone is difficult. Among the many pathogenic microorganisms, Staphylococcus aureus is the most commonly involved.

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