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Level IV-Retrospective case series.

Management of spondylodiscitis is a challenging clinical problem requiring medical and surgical treatment strategies. The purpose of this study was to establish a rat model of spondylodiscitis that utilizes bioluminescent Staphylococcus aureus, thus permitting in-vivo surveillance of infection intensity. Inocula of the bioluminescent S. aureus strain XEN36 were created in concentrations of 102 CFU/0.1 mL, 104 CFU/0.1 mL, and 106 CFU/0.1 mL. Three groups of rats were injected with the bacteria in the most proximal intervertebral tail segment. The third most proximal tail segment was injected with saline as a control. Bioluminescence was measured at baseline, 3 days, and weekly for a total of 6 weeks. Detected bioluminescence for each group peaked at day three and returned to baseline at 21 days. The average intensity was highest for the experimental group injected with the most concentrated bacterial solution (106 CFU/0.1 mL). Radiographic analysis revealed loss of intervertebral disc space and evidence of osseous bridging. Saline injected spaces exhibited no decrease in intervertebral spacing as compared to distal sites. Histologic analysis revealed neutrophilic infiltrates, destruction of the annulus fibrosus and nucleus pulposus, destruction of vertebral endplates, and osseous bridging. Saline injected discs exhibited preserved annulus fibrosus and nucleus pulposus on histology. This study demonstrates that injection of bioluminescent S. aureus into the intervertebral disc of a rat tail is a viable animal model for spondylodiscitis research. This model allows for real-time, in-vivo quantification of infection intensity, which may decrease the number of animals required for infection studies of the intervertebral disc.

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Percutaneous pedicle screw fixation has evolved as a useful tool in the management of spinal trauma. As a minimally invasive approach, it provides the stability of open instrumentation while limiting blood loss, avoiding excessive muscle/soft-tissue insult, and improving postoperative pain and mobilization. Muscle-dilating techniques also preserve greater paraspinal muscle volume and strength compared with open midline approaches. In patients with spinal trauma, the use of percutaneous instrumentation and indirect reduction can theoretically preserve the fracture hematoma and its osteogenic inflammatory factors. The evolution of spinal instrumentation and the refinement of indirect reduction techniques has improved the capacity for correction of traumatic deformity. Although perioperative and short-term results have been well described, few long-term outcomes data exist.

Only the screw nearest the gap had significant effect on torsional and failure stiffness but not axial stiffness. Construct mechanics depended on the type of screw placed in this position. This screw nearest the fracture dictates working length stiffness when the working length itself is constant and in turn determines overall construct stiffness in osteoporotic bone.

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