Few studies have examined the outcome of prolonged intravenous antimicrobial therapy in the treatment of osteomyelitis, partly because this disease is in transition.As the U.S. population has aged, the prevalence of diabetes and peripheral vascular disease has increased. These diseases predispose patients to develop osteomyelitis and are complicating factors in its treatment. The number of infections after joint replacements or complex surgical interventions also has increased, and newer surgical interventions and antibiotics, including outpatient parenteral therapy, are being used. The current regimen for the treatment of osteomyelitis is four weeks of high-dosage intravenous therapy. Tice and associates studied the effects of diabetes, peripheral vascular disease, age, and antimicrobial therapy on clinical outcomes in patients with osteomyelitis treated in the outpatient setting.
The study design was a retrospective chart review of patients treated for osteomyelitis in an infectious disease clinic. The review included patients diagnosed with osteomyelitis who were seen from January 1982 through April 1998. Inclusion criteria included identification of one clear pathogen by initial culture results, treatment with at least 14 continuous days of antimicrobial therapy, treatment with no more than two antimicrobial agents, and follow-up for at least six months. Standard antimicrobial therapy in patients with normal renal function included 2 g of a penicillinase-resistant penicillin such as oxacillin, nafcillin, or methicillin every six hours; 2 g of cefazolin every eight hours; 2 g of ceftriaxone every 24 hours; or 1 g of vancomycin every 12 to 24 hours. Patients were identified as cured or having a recurrence, which was defined as an infection in the same site after the original infection apparently had been eliminated. The recurrences were further divided into relapse if the infection was with the original pathogen, or reinfection if the organism was different.
A total of 454 patients met the inclusion criteria and were included in the study. Of these patients, 31 percent had recurrences, and 6 percent had amputations. More than three fourths of the recurrences occurred in the first six months, and 95 percent occurred in the first 12 months after the initial infection. Peripheral vascular disease and diabetes were associated with the risk of recurrence; age was not. Patients with Staphylococcus aureus infection who took ceftriaxone and cefazolin had a risk for recurrence similar to that of patients taking the penicillinase-resistant penicillins. Compared with patients taking penicillinase-resistant penicillins, patients who took vancomycin had a relative risk of recurrence of 2.5.
The authors conclude that diabetes and peripheral vascular disease are risk factors for developing recurrent osteomyelitis. Most recurrences occur within the first year after treatment. Recurrence rates for S. aureus osteomyelitis were higher in patients who originally took vancomycin. This point may be related to findings from a study suggesting that vancomycin may be less effective against methicillin-susceptible strains of staphylococci.