Experimental Study For Surgical Treatment Of Pyogenic Spinal Infections With Instrumentation

Objective:To evaluate the effectiveness and the safety of the one-stage debridement, autogenous bone grafting and anterior instrumentation in the management of pyogenic spinal infections.Material and Methods:Totally24dogs were adopted in the study. We used a bioluminescent strain of Staphylococcus aureus Xen29to develop a canine model of acute pyogenic spondylodiscitis. The animals were subjected for X-radiography, CT and MRI examinations。We evaluated the Spinal segment and range of infection through dynamic radiological observation. We evaluate the radiological result upon which proper surgical protocols were lay out. All the animals were managed with one-stage debridement, autogenous bone grafting and anterior titanium plate instrumentation. Infected tissues was taken during the surgery for bacterial cultivation in order to confirm the infection。 Antibiotics containd Cefazolin and Gentamicin were administrated daily since perioperative period to four weeks after surgery. The situation of operative incisions were observed and recorded。The implants and adjacent vertebra (bone of approximately1cm beneath the implant) were removed surgically at various postoperative time points (4,8,12,24 weeks). The excised tissues and retrieved implants were transported in sterile bottles and analyzed by the routine procedure. Polymerase chain reaction (PCR) were used to detect the presence of bacteria in the biopsy specimen by amplifying the highly conservative gene sequence of16S ribosomal RNA. Bioluminescence imaging technique was also used.Results:One animal was died within1day after surgery and one animal was died within4days after surgery by unknown causes. Other animals were no particular discovery. Three animals model-developing were failed because of the negative result of bacterial cultivation during the surgery. Staphylococcus aureus was positive in other animals’ bacterial cultivation during the surgery. The surgical wound healed uneventfully. No sinus formation or pus or other signs of infection was observed during experiment. Gross observation of the specimen showed that titanium plates were surrounded by tissues and no Signs of infection was observed on titanium plates surrounding. There was no signs of infection recurrence according to the MRI examination. The infection rate was41.7%(10724) according to traditional bacterial cultivation procedure; The infection rate was75%(18/24) according to using PCR to detect the presence of bacteria at the molecular level. The result showed that the sensibility of PCR technique which was used to detect the presence of bacteria by amplifying the highly conservative gene sequence of16S ribosomal RNA was higher than the sensibility of the traditional bacterial cultivation procedure. The difference was significant (P<0.05). The detection of specific Nuc gene of Staphylococcus aureus according to PCR showed the existence of Staphylococcus aureus. The positive rate was4.2%(1/24). However, Staphylococcus aureus Xen29with genetic marker was not detected according to Bioluminescence imaging technique. All of the results showed that bacteria adhering to prosthesis in vivo was universal phenomenon relatively. The bacteria identified from prosthesis which was taken during the surgery and the bacteria by which the spine was infected before the surgery was not homologous.Conclusion:The one-stage debridement, autogenous bone grafting and anterior titanium plate instrumentation in the management of pyogenic spinal infections was safe and effective. Using of internal fixation did not lead to recurrence or persistence of infection.