Objective: When percutaneous bone biopsy is done by radiologists, local anesthetics such as lidocaine are routinely used. Although percutaneous bone biopsy of neoplasms is well accepted, it has been suggested that this procedure not be used to diagnose osteomyelitis because of a reported bactericidal effect of lidocaine and related drugs on certain organisms. The purposes of this study were to determine if lidocaine is bactericidal in vitro and to determine if it has an effect on the culture of bacteria in specimens obtained by percutaneous bone biopsy in vivo.
Subjects and methods: The minimal inhibitory concentration and minimal bactericidal concentration of 1% lidocaine hydrochloride (10 mg/ml preserved with methylparaben) were determined in vitro for seven bacteria known to be frequent causes of osteomyelitis by using conventional clinical microbiologic methods. Percutaneous core bone biopsy for suspected osteomyelitis was done in 28 patients: 21 with and seven without the use of lidocaine. Sites sampled included vertebrae (14); calcanei, pubis, and ischia (two each); and intervertebral disks (eight). Six of the 21 patients who had percutaneous biopsy with lidocaine also had an open surgical biopsy without lidocaine. The results of cultures of the specimens were compared. Histologic evaluation and radiographic follow-up were used to identify false-negative results.
Results: The minimal inhibitory and the minimal bactericidal concentrations, respectively, of lidocaine (in milligrams per milliliter) were as follows: Klebsiella pneumoniae, 5.0 and > 5.0; group B streptococci, 2.5 and 5.0; Staphylococcus aureus, > 5.0; and > 5.0; methicillin-resistant S. aureus, > 5.0 and > 5.0; Escherichia coli, 2.5 and > 5.0; Pseudomonas aeruginosa, 5.0 and 5.0; Salmonella species, 5.0 and > 5.0. We found no difference in bacterial growth and the number of false-negative results between patients who had biopsies with and those who had biopsies without lidocaine. Fifty percent of patients who had growth on cultures of specimens from percutaneous biopsies done with lidocaine had no growth on cultures of specimens from surgical biopsies done without lidocaine. This likely occurred because the surgical specimens were not obtained under cross-sectional imaging guidance.
Conclusion: Up to a 50% mixture of lidocaine has no significant effect in vitro on the bacterial growth of the seven organisms that cause osteomyelitis most frequently, and no inhibitory effect on bacterial growth was seen in biopsies done with lidocaine in vivo. The inhibitory effect of lidocaine therefore occurs at a greater concentration than is used clinically. We conclude that lidocaine used for biopsy does not interfere with the diagnosis of osteomyelitis.