Ohuchi et al. (11) and Ott et al. (12) described the first cannulabased irrigation system for the treatment of septic wounds and osteomyelitis. Currently, closed irrigation systems are used to successfully treat infections of sternotomy, craniotomy, and long-bone osteomyelitis.

The general principles of closed drain systems include constant instillation of antibiotic solution and removal of
necrotic debris from the site of infection. The position of drains is variable. With deep infections, the inflow drain is placed in the subfascial plane and the outflow drain is placed suprafascially. The fascial layer is loosely approximated to allow flow of irrigation and debris away from the infected site. Alternatively, one can place both the inflow and outflow drains subfascially with tight closure of the fascial layer. Both techniques have been associated with effective resolution of spine infections. Vender et al. (13) conducted a retrospective review of 36 patients who developed infection after spinal instrumentation surgery and were treated with inflow and outflow drains and intravenously administered antibiotics. At the 2-year follow-up, each infection had completely resolved and no patient required removal of instrumentation. One patient developed a recurrent infection that subsequently resolved once bilateral drains were replaced. Levi et al. (14) successfully treated 17 patients with postoperative infection after posterior spinal instrumentation with a combination of surgical débridement, intravenously administered antibiotics, and insertion of an antibiotic irrigation system for a mean duration of 5 days. At the 8-month follow-up, no patient had clinical or radiographic evidence of wound infection. Controversy exists regarding the prophylactic use of drains to prevent spine infections. In theory, drains reduce the risk of infection and incision breakdown by decompressing wound hematomas. Payne et al. (15) prospectively randomized 200 patients undergoing single-level unilateral laminectomy without instrumentation to the use of drains and noted no difference in infection rates or hematoma development. Brown and Brookfield (16) prospectively randomized 83 patients undergoing instrumented lumbar surgery to the prophylactic use of closedsuction drain and observed no significant difference in rates of infection, hematoma, or neurologic deficit.

Polymethylmethacrylate (PMMA) bone cement impregnated with antibiotic agents constitutes an effective vehicle of local delivery of antibiotics to treat both bone and soft tissue infection. It provides therapeutic levels of antibiotics to areas of hypoxic devitalized tissue that intravenously administered antibiotics cannot reach. The development of antibiotic beads began in 1970, with Buchholz and Engelbrecht (17) showing a high concentration of antibiotics in the local tissue after antibiotic agents were mixed with acrylic bone cement.

Antibiotic-impregnated cement beads can be made intraoperatively by the surgeon or can be purchased commercially. Although most common antibiotics can be mixed with cement, the aminoglycosides (tobramycin and gentamicin) and vancomycin have the highest elution rates and drug availability in vitro. The type of cement also affects elution rates. In vitro studies (18,19) have shown superior antibiotic elution rates with Palacos bone cement (Zimmer, Inc., Minneapolis, MN). Penner et al. (18) compared elution rates of vancomycin and tobramycin in Palacos R (Zimmer) and CMW (DePuy, Inc., Raynham, MA) acrylic cements. At the end of 9 weeks, the group observed that Palacos released 24% more tobramycin and 36% more vancomycin (p < 0.05). In another study, Kuechle et al. (19) noted superior elution rates for vancomycin, daptomycin, and amikacin in Palacos compared with Simplex (Stryker, Inc., Cambridge, MA), Zimmer dough type, and Zimmer LVC.