BACKGROUND:Percutaneous vertebroplasty is a minimal y invasive treatment for spinal metastasis tumor, but the mechanism of the injected polymethylmethacrylate (PMMA) bone cement in the treatment of tumor is not ful y understood. OBJECTIVE:To explore the cytotoxicity of PMMA bone cement and its monomers on tumor cel s. METHODS:PMMA extracts in the wire drawing and curing periods and different mass concentrations of monomer dilutions were co-cultured with human lung cancer cel s spc-A1. The cel morphology was observed using inverted microscope, the absorbance (A) values were detected by cel counting kit-8 assay, the relative growth rate was calculated, and the toxicity of PMAA bone cement and its monomers was evaluated at 1 and 3 days of culture, respectively. RESULTS AND CONCLUSION:At 1 day of culture, the absorbance values in the 1 and 10 g/L groups were significantly lower than that in the negative control group (P<0.01). The absorbance values in the 1 g/L, 10 g/L, 100 mg/L and wire drawing extract groups were significantly lower than those in the negative control group at 3 days of culture (P<0.05). The relative growth rate in the 1 and 10 g/L groups was 26%-29%, and the level of toxicity was grade 4 after 1-day culture;at 3 days, the relative growth rate was decreased to 12%-16%, and the level of toxicity was grades 4-5. After 3-day culture, the level of toxicity reached to grade 2 in the 100 mg/L and wire drawing extract groups. These results indicate that PMMA bone cement in wiredrawing period and its monomers exert toxic effects on tumor cels.

Objective:There are limited data describing the clinical characteristics and prognosis of culture negative pyogenic spondylitis.The aim of this study was to investigate the treatment,prognosis and clinical characteristics of culture negative pyogenic spondylitis.Methods: A retrospective study reviewed 74 patients who were diagnosed with spondylitis in Peking University First Hospital from January 2010 to December 2015.A total of 27 patients suffered from pyogenic spondylitis.According to the pa-thogenic culture results,the patients were divided into two groups: culture negative group and culture positive group.The clinical characteristics and treatment outcomes between the two groups were compared.Results: The elder were more vulnerable to pyogenic spondylitis,and of the 27 patients,12 patients were female and 15 male.All patients had no history of administration of antibiotics prior to obtaining culture samples.A causative germ was identified in 14/27 patients (51.9％) with Staphylococcus aureus being the most common pathogen.There was no significant difference between the two groups in the patient's age,gender,visual analogue score (VAS),predisposing factor,clinical symptom,sign and spinal segment (P>0.05).Erythrocyte sedimentation rate (ESR) (P=0.056) and C-reactive protein (CRP) (P=0.040) of culture negative group were lower in contrast to culture positive group.The incidence of vertebral abscess in culture negative group was higher than in culture positive group (P=0.046).After treatment,ESR dropped almost equally in both groups,and CRP dropped faster in the culture positive group (P=0.192).At last,there was no significant difference between the two groups in hospital stay,pain relief,open debridement operation rate,and recurrence rate of infection.Conclusion: ESR and CRP of the culture negative patient were lower than those of the culture positive patient,and the incidence rate of paravertebral abscess was higher than that of the culture positive patient.After administration of antibiotics,there was no significant difference between the two groups in duration of antibiotics,open debridement operation rate and recurrence rate of infection.So,culture negative may not necessarily be a negative prognostic factor for pyogenic spondylitis.However,we should watch out for the drug resistant bacteria or double infection,due to the long term use of wide-spectrum antibiotic in culture negative patients.