Abstract: Objective: To determine the antibiotic concentration in disc space under different micro-circumstances and to provide theoretic basis for clinical antibiotic treatment of pyogenic discitis.Methods: The pyogenic discitis model was established by injecting Staphylococcus aureus into the intervertebral space of the dog.Cefazolin was injected into the inferior vena cava,and 30 minutes later,the infected disc(B) was obtained and the infected disc debrided.One week later,cefazolin 40 mg/kg was injected and the tissues of infected disc space was harvested after debridement(D) and normal nucleus(E).The cefazolin concentrations of B,D,and E were tested by High-pressure Liquid Chromatography method.Results: The cefazolin concentrations of the normal nucleus,infected disc and the tissues of the infected disc space after debridement were(4.62±1.74) μg/mg,(7.00±2.48) μg/mg,and(14.11±2.10) μg/mg,respectively.Significant difference in cefazolin concentration existed between the tissues of infected disc space after debridement and the normal nucleus,as well as between the tissues of infected disc space after debridement and the infected disc(P<0.01).Conclusions: The concentration of cefazolin in the tissues of infected disc space rises significantly after debridement.