Current Concepts In Treating Diabetic Foot Osteomyelitis

Author(s): 
William B. Hoffman, BS, Khurram H. Khan, DPM, FAPWCA, and Mark Kosinski, DPM, FIDSA

   Culture results were available for 102 of 117 episodes of osteomyelitis. Of these cultures, the researchers obtained 74 from a deep swab of exudate overlying bone, five from bone, and 23 from both exudate and bone. In the 23 episodes in which both culture types were available, 17 (81 percent) identified the same organisms in both samples. Of the 102 cultures, 80 came back positive with aerobic gram positive cocci being the most common isolates (60 percent). This was followed by aerobic gram negative bacillus (33 percent) and anaerobes (7 percent). Overall, Staphylococcus aureus was the most common organism isolated as it showed up on 36 of the 80 cultures that came back positive.3

   Of the 117 episodes of osteomyelitis in the study, 93 were treated with oral antibiotics with amoxicillin/clavulanic acid being the most commonly used single drug. Of the 93 treated in this manner, 81 (87 percent) were found to be in remission or improving at 50 weeks after the initiation of treatment. Of the 93 episodes, only 29 (31 percent) received an initial short course of intravenous antibiotic treatment for associated acute skin and soft tissue infections. In short, of the 93 episodes treated with oral agents, 75 (80.5 percent) went into remission (78 percent) without bone debridement after a mean duration of oral therapy of 40 weeks.3

   Based on the findings of this study, it appears that oral antibiotic treatment may be a viable option when surgical facilities and intravenous antibiotic therapy are not readily available.5

Why Bone Biopsy Cultures Are Preferred

   A 2008 retrospective study by Senneville and colleagues looked to identify criteria predictive of remission in non-surgical treatment of osteomyelitis of the diabetic foot.4

   One of the variables they assessed was the efficiency of antibiotic treatment based on cultures obtained from bone biopsies in comparison to those cultures obtained from soft tissue swabs. Even though bone biopsy has been declared the gold standard for determining appropriate antibiotic therapy, only one of the recent major studies by Senneville and colleagues evaluated the effectiveness of non-surgical treatment of osteomyelitis of the diabetic foot using bone cultures to determine the appropriate antibiotics.4,11,12

   Senneville and colleagues evaluated 50 patients at nine different treatment centers who were treated with conservative therapies. Of the nine centers, only four routinely used bone biopsies while the other five routinely used soft tissue swabs. Researchers obtained soft tissue swabs by running a sterile compress over the ulcer after a brief cleansing with sterile saline. They obtained bone biopsies in the operating room under fluoroscopic guidance, using an 11 gauge needle they inserted through a 5 to 10 mm skin incision at least 20 mm from the periphery of the ulcer.4

   Antibiotic treatment was based on culture reports and the route of administration was either orally for the entire duration of treatment or a short course of intravenous antibiotics followed by a longer course of oral antibiotics. Other treatments included general wound care such as the use of alginates, hydrocolloids or hydrogels along with offloading of the affected area. They did not use topical antimicrobials.4

   The researchers defined remission as the absence of any sign of infection at the initial site or any contiguous site they evaluated at least one year after the end of antibiotic treatment. Out of the 50 patients with forefoot osteomyelitis, remission without surgical debridement occurred in 32 (64 percent) patients with a mean duration of therapy of 11.5 weeks. The most commonly used antibiotics were fluoroquinolones, clindamycin and rifampin.4

   Of all the variables analyzed, only bone culture-based antibiotic therapy was proven to be a predictive factor of remission based on univariate and multivariate analysis. Remission rates with bone culture directed therapy was 56.3 percent versus 22.2 percent without bone cultures.4

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