Imaging-guided bone biopsy for osteomyelitis: Are there factors associated with positive or negative cultures?

OBJECTIVE. The objective of our study was to identify the clinical and technical factors associated with positive or negative culture results in histologically positive cases of osteomyelitis obtained from imaging-guided bone biopsies. MATERIALS AND METHODS. A retrospective review was performed of 800 consecutive patients undergoing imaging-guided core bone biopsies at two institutions. Seventy-five biopsies were performed for suspected osteomyelitis and 41 patients had histologically proven osteomyelitis. A chart review was performed to determine whether the following factors affected the culture result: histologic type of osteomyelitis, antibiotic therapy before biopsy, fever ( temperature = 38.0 degrees C), elevated WBC count (>= 10 x 10(3) mu L), elevated erythrocyte sedimentation rate ( ESR) (>= 10 mm/h), elevated C-reactive protein value ( CRP) (>= 6 mg/L), the size of the biopsy needle, and the amount of purulent fluid obtained at biopsy. RESULTS. Of the 41 cases of osteomyelitis, 14 ( 34%) had positive cultures. Eighteen ( 44%) of 41 cases were chronic osteomyelitis. Seventeen ( 41%) of 41 patients received antibiotics before biopsy, seven ( 17%) were febrile, five ( 12%) had an elevated WBC count, 16 ( 39%) had an elevated ESR, and six ( 15%) had an elevated CRP value. The biopsy needle size ranged from 11- to 18-gauge. These factors did not have any significant association with positive or negative culture results. Purulent fluid was aspirated in 10 ( 24%) of the 41 cases. In six ( 15%) of the cases, >= 2 mL of purulent fluid was aspirated and five ( 83%) of the six cases were associated with positive culture ( p = 0.02). CONCLUSION. The rate of positive culture results in histologically proven cases of osteomyelitis obtained from imaging-guided bone biopsies is low. Aspirating >= 2 mL of purulent fluid is associated with a significantly higher rate of positive cultures.