Implant-associated spine infections are complicated by biofilms, as hardware often cannot be removed after placement. A biofilm is a structured community of microorganisms (e.g., bacteria) embedded in a self-produced matrix that preferentially adheres to surfaces such as implanted hardware (Figure 1A). Bacteria in biofilms can tolerate >1000x antibiotic concentrations than planktonic bacteria (Figure 1B).

  Current issues with treating these biofilm-associated infections in the spine include:

 1. Toxicity from increasing systemic antibiotic doses

2. Limited drug delivery to infection sites due to compromised vasculature2

3. Failure to achieve a sustained, high antibiotic concentration

  To address this clinically unmet need, we have been developing a refillable intrawound drug delivery system (Figure 2), referred to herein as a pouch. The device comprises a temporarily implanted (<30 days) antimicrobial-filled reservoir with a permeable rate-controlling membrane. The implanted reservoir communicates externally with a refilling port. Passive diffusion of antibiotics through the rate-controlling membrane and daily refilling maintain high target concentrations of antibiotics in the site tissues. We hypothesized that tobramycin, locally delivered via the pouch, would eliminate biofilms to a greater degree in a sheep model of spinal fusion rod-related infection than systemic antibiotics alone.