Orthopedic implant infection:: Prognostic factors and influence of long-term antibiotic treatment on evolution.: Prospective study, 1992-1999

INTRODUCTION. Orthopedic implant infections are significant because of their morbidity, a tendency to serious relapses and an elevated health cost. OBJECTIVES. To study prognostic factors and the influence of long-term antibiotic treatment on the evolution of orthopedic implant infections. METHODS. This prospective study was performed in 110 patients with orthopedic implant infections. Clinical, analytical, and microbiological studies, as well as gammagraphy with Tc, Ga and labeled leukocytes, were performed in all patients. Controls were carried out at 7, 15 and 30 days after starting treatment, every 3 months thereafter until the end of treatment, and every 6 months thereafter up to one year after stopping treatment. Initial antibiotic treatment was prescribed according to the epidemiological characteristic of the type of infection and was modified according to the microorganism isolated. Duration of treatment was established by patient and implant characteristics, severity of infection and evolution of the process, and it was adjusted to criteria of cure, failure and relapse. RESULTS. Among the 110 cases, 63 were women and 37 men, with a mean age of 59.6 years (range 18-79 years). Implants included 72 joint prostheses (42 knee, 29 hip and 1 shoulder) and 38 bone implants. Microbiological documentation was obtained in 60%; among these, 60.6% were gram-positive cocci, with a predominance of staphylococci, 33.3% were gram-negative bacilli and 6.1% were anaerobic microorganims. Prognostic factors significantly associated with failure or relapse included previous joint surgery, previous hospital stay longer than 15 days, diabetes, microbiological isolation and treatment with cefuroxim plus rifampicin. Mean treatment duration was 9.8 months (range 2-17 months). Antibiotic treatment consisted of the following: 61 cases received fluorquinolones or cotrimoxazole plus rifampicin, 29 received cefuroxime-axetil plus rifampicin and the remaining 20 received monotherapy. Among 110 cases, 91 cured (83%). Treatment failures or relapses were observed in 19 (17%) patients; 26.7% of the latter were related to the implants. Tolerance to long-term antibiotic treatment was good. CONCLUSION. Long-term antibiotic treatment lasting a mean of 9.8 months had a positive influence on the evolution of orthopedic implant infections.