Prophylactic cephazolin to prevent discitis in an ovine model.

Area of Science:

• Spinal Surgery
• Infectious Disease
• Pharmacology

Background:

• Standard prophylactic cephazolin doses in spinal surgery may not achieve adequate intervertebral disc levels.
• Cephazolin's poor diffusion into discs, due to its negative charge, raises concerns about its prophylactic efficacy.
• Understanding antibiotic concentration in disc tissue is crucial for optimizing surgical infection prevention.

Purpose of the Study:

• To evaluate the efficacy of a 4-hour, multi-dose cephazolin regimen in preventing iatrogenic discitis in an ovine model.
• To determine cephazolin concentrations in nucleus and anulus tissues following intravenous administration.
• To compare prophylactic efficacy between juvenile (lamb) and adult sheep.

Main Methods:

• An ovine model was used, with 18 animals (9 lambs, 9 sheep) receiving intravenous cephazolin over 4 hours.
• Control animals (1 lamb, 1 sheep) did not receive antibiotics.
• Bacterial inoculation of incised and non-incised lumbar discs was performed, followed by radiographic, pathological, and biochemical analysis after 12 weeks.

Main Results:

• All control animals developed discitis.
• Cephazolin prophylaxis was highly effective in adult sheep, with no discitis observed when given 30 minutes pre-inoculation.
• Discitis occurred in 1/9 sheep and 4/9 lambs receiving cephazolin; concentrations were higher in the anulus than nucleus.

Conclusions:

• A 4-hour prophylactic cephazolin regimen effectively prevented discitis in most sheep, but was less successful in lambs.
• The timing of antibiotic administration is critical for preventing iatrogenic disc infections.
• Further research is needed to understand the increased susceptibility in lambs despite enhanced vascularity.