Topical Antibiotic Treatment for Spine Surgical Site Infection

Surgical site infection (SSI) after spine surgery is a devastating complication. Spine SSIs occur in as many as 40,000 people each year, causing considerable disability and resulting in re-operative costs of over $100,000. Even with the use of standard perioperative infection prevention techniques, SSIs occur as often as 3-5% depending on the surveillance technique and time-window used, with widespread variability between practice sites and surgeons. A mainstay of SSI prevention is the timely administration of antibiotics, but one of the limits of intravenous antibiotic prophylaxis is that bone tissue concentrations of antibiotics are lower than blood levels. As a result, there has been increasing interest in the use of in-wound antibiotics (IWA), placed directly on the spine at the completion of surgery. IWAs have been supported by several observational studies with a recent systematic review suggesting an 84% decrease in SSI. However, most of these studies failed to address important confounding in the ways IWA were used and had variable follow-up. The only IWA randomized controlled trial (RCT), albeit underpowered failed to identify a protective effect, leading to uncertainty about the role of IWA. Because of the relative infrequency of SSI, variable windows of follow-up and high rates of confounding in prior studies of IWA a large scale trial of IWA with an appropriate follow-up period is needed to evaluate its effectiveness in spine surgery. Such a trial would be more feasible if randomization occurred at the level of hospital "cluster" (cRCT), to account for existing variation in practices regarding IWA use, variable rates of SSI, and use of other SSI prevention techniques.

Several pilot and feasibility questions need to be addressed before a cRCT of IWA can be proposed. SSI can appear as long as a year after spine surgery and short follow-up time in prior studies may have undercounted events and may have failed to recognize SSIs that may have been potentially delayed in detection because of the IWA. For example, the rationale for surgeon use of IWA, antibiotic type, or dose is unclear, as is whether surgeons use IWA in a similar fashion across patients and sites and if this represents confounding for which researchers must account. It is also unclear if surgeon use of IWAs is related to knowledge about existing data, beliefs and attitudes that may be barriers or enablers to a trial that promotes greater use of IWAs. To address these issues and direct an eventual cRCT, the investigators will perform surveys of spine surgeons assessing knowledge, behaviors and attitudes about IWA.