Reduction of postoperative spinal implant infection using gentamicin microspheres.
METHODS
Three noncontiguous spinal implant sites in 1 rabbit were challenged with Staphylococcus aureus and local antibiotic prophylaxis was given with gentamicin in controlled-release microspheres (poly(lactic-coglycolic-acid) [PLGA]). Postoperative biomaterial-centered infection on and around the titanium rods was assessed using standard bacterial quantification essays.


OBJECTIVE
To assess surgical site and biomaterial-centered infection reduction with controlled release gentamicin from microspheres against S. aureus.


BACKGROUND
A postoperative biomaterial-centered infection can be devastating after successful thoracolumbar spinal surgery and puts a high burden on patients, families, surgeons, and hospitals, endangering both our healthcare budget and our ability to perform challenging cases in patients with increasing numbers of comorbidities. Systemic antibiotics often do not reach "dead-space" hematomas where bacteria harbor after surgery, whereas local, controlled release gentamicin prophylaxis through PLGA microspheres showed favorable pharmacokinetics data to achieve local bactericidal concentrations for up to 7 days after surgery.


METHODS
A well published rabbit spinal implant model with systemic cephalosporin prophylaxis was challenged to create a baseline infection of approximately 70% in control sites. We then challenged 3 noncontiguous titanium rods inside the laminectomy defect with 10e6 colony forming units S. aureus and randomly treated 2 sites with gentamicin PLGA microspheres and 1 site with PLGA carrier only (control). Standard quantification techniques were used to assess biomaterial centered and soft tissue bacterial growth after 7 days.


RESULTS
After establishing reliable infection rates in control sites, the therapeutic arm of the study was started. Surgical site infections were found in 75% of control sites, whereas gentamicin microspheres reduced the incidence down to 38% in the same rabbits. Biomaterial-centered infection was reduced from 58% to 23% only in all sites challenged with 10e6 S. aureus.


CONCLUSIONS
Postoperative, biomaterial-centered infection was reduced at least 50% with intraoperative gentamicin microspheres in the face of systemic cephalosporin prophylaxis and high dose S. aureus in a laminectomy defect in rabbits. The data are statistically and clinically significant, and further animal testing is planned to confirm these results.
Stall
Alec C
AC
University of Maryland, Shock Trauma Center, Baltimore, MD 21212, USA.
Becker
Ed
E
Ludwig
Steven C
SC
Gelb
Daniel
D
Poelstra
Kornelis A
KA
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001672:Biocompatible Materials; D001858:Bone Nails; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D005260:Female; D005839:Gentamicins / Q000494:pharmacology*; D006406:Hematoma; D019344:Lactic Acid; D007796:Laminectomy; D008863:Microspheres; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D016459:Prosthesis-Related Infections / Q000188:drug therapy / Q000517:prevention & control*; D011817:Rabbits; D013123:Spinal Fusion; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000517:prevention & control*; D013530:Surgical Wound Infection / Q000188:drug therapy / Q000517:prevention & control*; D014025:Titanium
D000900:Anti-Bacterial Agents; D001672:Biocompatible Materials; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D005839:Gentamicins; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D014025:Titanium