197. Subtherapeutic perioperative levels of cefuroxime inside cannulated pedicle screw commonly used in spine surgery: results from an experimental microdialysis study

Abstract

BACKGROUND CONTEXT Despite minimal invasive spine techniques, postoperative implant associated vertebral osteomyelitis remains a risk of great morbidity for the patient. Perioperative antibiotic prophylaxis is important for prevention of postoperative infection and local tissue concentrations can be measured with microdialysis. We hypothesized that cefuroxime concentrations in relation to a cannulated pedicle screws may be insufficient for prevention of postoperative infection. PURPOSE The aim was to compare perioperative cefuroxime concentrations inside a cannulated pedicle screw to the adjacent noninstrumented lumbar vertebral pedicle. STUDY DESIGN/SETTING In vivo experimental pharmacokinetics study of cefuroxime concentrations in an acute preclinical porcine model. PATIENT SAMPLE Not applicable. OUTCOME MEASURES The primary end-point was the time above cefuroxime clinical breakpoint minimal inhibitory concentration for Staphylococcus aureus of 4 µg/mL (T>MIC4) METHODS Microdialysis probes were placed in a cannulated pedicle screw and the adjacent non-instrumented lumbar vertebral pedicle (L1) in 8 female pigs through a surgical posterior open lumbar approach. Following a single-dose intravenous cefuroxime administration (1.5 g), microdialysates and plasma were dynamically sampled over 8 hours. RESULTS Mean T>MIC4 (range) was 123 min (112-175) in plasma, 101 min (68-144) in the non-instrumented vertebral pedicle and 0 min (0-0) inside the cannulated pedicle screw. CONCLUSIONS A single-dose intravenous cefuroxime administration (1.5 g) seems insufficient for antibiotic prophylaxis inside a cannulated pedicle screw placed in the lumbar spine. Sufficient concentrations were achieved in the adjacent non-instrumented vertebral pedicle for up to 1.5-2 hours. Therefore, alternative dosing regimens should be considered in minimal invasive spine surgery longer than 1.5 hours and additional prophylactic strategies against infection may be applied in high-risk patients. FDA DEVICE/DRUG STATUS Cefuroxime (Approved for this indication) Despite minimal invasive spine techniques, postoperative implant associated vertebral osteomyelitis remains a risk of great morbidity for the patient. Perioperative antibiotic prophylaxis is important for prevention of postoperative infection and local tissue concentrations can be measured with microdialysis. We hypothesized that cefuroxime concentrations in relation to a cannulated pedicle screws may be insufficient for prevention of postoperative infection. The aim was to compare perioperative cefuroxime concentrations inside a cannulated pedicle screw to the adjacent noninstrumented lumbar vertebral pedicle. In vivo experimental pharmacokinetics study of cefuroxime concentrations in an acute preclinical porcine model. Not applicable. The primary end-point was the time above cefuroxime clinical breakpoint minimal inhibitory concentration for Staphylococcus aureus of 4 µg/mL (T>MIC4) Microdialysis probes were placed in a cannulated pedicle screw and the adjacent non-instrumented lumbar vertebral pedicle (L1) in 8 female pigs through a surgical posterior open lumbar approach. Following a single-dose intravenous cefuroxime administration (1.5 g), microdialysates and plasma were dynamically sampled over 8 hours. Mean T>MIC4 (range) was 123 min (112-175) in plasma, 101 min (68-144) in the non-instrumented vertebral pedicle and 0 min (0-0) inside the cannulated pedicle screw. A single-dose intravenous cefuroxime administration (1.5 g) seems insufficient for antibiotic prophylaxis inside a cannulated pedicle screw placed in the lumbar spine. Sufficient concentrations were achieved in the adjacent non-instrumented vertebral pedicle for up to 1.5-2 hours. Therefore, alternative dosing regimens should be considered in minimal invasive spine surgery longer than 1.5 hours and additional prophylactic strategies against infection may be applied in high-risk patients.