Diagnostic value of sinus-tract cultures in chronic osteomyelitis.

Sinus-tract cultures were compared with cultures of operative specimens from 40 patients with chronic osteomyelitis. Thirty-five patients (87.5%) had a single pathogen isolated from their operative specimens. Only 44% of the sinus-tract cultures contained the operative pathogen. Isolation of Staphyloccus aureus from sinus tracts correlated with the presence of S aureus in the operative specimen. However, less than half of the sinus-tract cultures obtained from patients with S aureus osteomyelitis contained this organism. Isolation of bacteria other than S aureus from sinus tracts had a low likelihood of predicting the pathogen isolated from bone. A presumptive diagnosis of S aureus osteomyelitis is justified if S aureus is isolated from an associated sinus tract. A bacteriologic diagnosis of chronic osteomyelitis based on isolation of common pathogens other than S aureus from sinus tracts must be verified by an appropriate operative culture.