Management of Acute Osteomyelitis: A Ten-Year Experience

Osteomyelitis is an infection of the bone; proper management requires prolonged antibiotic treatment. Controversy exists as to when a patient should transition from intravenous to oral antibiotics. However, due to the high bioavailability of some oral antibiotics, optimal time to transition from high to low bioavailability antibiotics is a more valid consideration. Additionally, there are questions surrounding the efficacy of certain antibiotics, specifically trimethoprim-sulfamethoxazole (TMP-SMX), in treating osteomyelitis. After obtaining Institutional Review Board approval from both universities, a retrospective chart review was conducted, utilizing an author-created severity scale, on all patients seen by Pediatric Infectious Diseases at the Universities of Michigan and Toledo with an acute osteomyelitis diagnosis from 2002-2012. There were 133 patients, 106 treated successfully. Success was defined in this study specifically as treatment of <14 weeks without recurrence within 30 days of stopping antibiotics or permanent site disability. Seventeen patients were treated with TMP-SMX at comparable cure rates. Patients with pre-existing bone defects (noted in radiological reports), initial erythrocyte sedimentation rate (ESR)≥70, hematogenous osteomyelitis with soft tissue extension, and skull osteomyelitis were associated with increased failure rate. Switch to low bioavailability antibiotics occurred, on average, at 3.5 weeks; however, switching before then was not associated with decreased cure rate. As prevalence of methicillin-resistant Staphylococcus aureus (MRSA), especially clindamycin-resistant MRSA, increases, TMP-SMX appears to be an acceptable antibiotic. There does not appear to be a minimum length of high bioavailability treatment required for cure. Prior bone defect, extensive infection, ESR≥70, or skull osteomyelitis may be indications for more aggressive management. Introduction Osteomyelitis is an infection of the bone and/or bone marrow. In children it is typically found in one of the long bones and management requires prolonged antibiotic courses with or without surgical debridement.1-6 While there is some literature suggesting that 3 weeks of antibiotic treatment is sufficient for most acute osteomyelitis cases, pediatric patients at the Universities of Michigan and Toledo are typically treated for 4-6 weeks.2 The pathogenesis of osteomyelitis is either via hematogenous seeding, which is more common in pediatric patients, or an extension from a contiguous infection.1-3,5 The most common pathogen in osteomyelitis is Staphylococcus aureus, although a variety of organisms can cause this disease.1-5,7,8 There are 3 classifications of osteomyelitis: acute duration of infection prior to treatment is less than 2 weeks, subacute duration of infection prior to treatment is 2 weeks to approximately 3 months, or chronic duration of infection prior to treatment is greater than 3 months.2,4,5 An acute or subacute infection can progress to chronic osteomyelitis due to treatment failure as well. For the purposes of this study, we are investigating acute infections. While osteomyelitis is not a new or exceedingly rare condition, there is no consensus as to the best medical management of this disease.4,9 Controversy exists with regards to intravenous (IV) versus oral (PO) medication, more specifically as to the ideal length of each treatment and when (or if) the transition from IV to PO medication should occur.4,7,8,10,11 Transitioning from IV to PO has many advantages including: reduction in economic burden for the patient because PO antibiotics are less expensive than IV as well as shorter inpatient hospital stays because a medical professional is not required to administer antibiotics.12 Additionally, prolonged use of a central venous catheter or a PICC line is noted in the literature to be associated with increased risk of additional infections.13 However, due to the high bioavailability, defined as Fraction of a dose of drug that is absorbed from its site of administration and reaches, in an unchanged form, the systemic circulation, of some of the oral antibiotics used to treat osteomyelitis, the optimal time to transition from high (IV±high bioavailable PO) to low bioavailability antibiotics is a more valid consideration.12,14,15 This concept has not been extensively studied in the literature, instead focusing on the transition from IV to PO; therefore, this study aims to begin the conversation about the role of bioavailability in pediatric acute osteomyelitis treatment. With the emergence of clindamycin resistant methicillin-resistant S. aureus (MRSA), the efficacy of trimethoprim-sulfamethoxazole (TMP-SMX), which has high bioavailability as a PO antibiotic, has begun to be considered to be a viable treatment option for pediatric acute osteomyelitis and needs to be studied further.14,15 The objectives of this study were to identify in pediatric patients with acute osteomyelitis: criteria that indicate an increased likelihood of treatment failure, the optimal time to transition from high to low bioavailability, and the efficacy of TMP-SMX for the treatment of acute osteomyelitis in pediatric patients. Materials and Methods After Institutional Review Board (IRB) approval was obtained at both institutions, a retrospective chart review was conducted on all patients seen by the Pediatric Infectious Disease Divisions at the Universities of Michigan and Toledo with a diagnosis of acute osteomyelitis from 2002 to 2012. Diagnosis of acute osteomyelitis during this time period was the only criteria for entry in the study; age was not explicitly a rule out criteria, but no patient above the age of 21 was included because both divisions examined were pediatric divisions. The acute osteomyelitis patients were identified via query of electronic medical records via ICD-9 codes. Patients were not explicitly diagnosed in this study, but rather they were identified by the ICD-9 code search and were included unless there was clear evidence of an incorrect classification upon chart review; for example, if explicitly stated that there was a period of >2 Infectious Disease Reports 2016; volume 8:6350 Correspondence: Deepa Mukundan, Divisions of Pediatric Infectious Diseases, University of Toledo, 2222 Cherry Street, #2300, Toledo, OH