Implant contamination during spine surgery

Abstract

Background context: Postoperative spine infections have been reported to occur in 1% to 15% of patients and subsequently lead to significant morbidity and cost, with an elevated risk for instrumented cases. Every effort should be made to minimize the risk of intraoperative wound contamination. Consequently, certain practices are followed in the operating room to prevent contamination, many of which are not evidence based. Conversely, certain objects believed to be sterile are frequently overlooked as potential sources of contamination.

Purpose: To assess to what degree contamination of spinal implants occurs during spine surgery and evaluate whether coverage of implants alters the rate of contamination.

Study design: Prospective study.

Study sample: This study included 105 consecutive noninfection surgical cases performed by a single spine surgeon that required the use of instrumentation.

Outcome measure: Spinal implant contamination.

Methods: Cases were randomized to have all implant trays either remain uncovered (n=54) or covered (n=51) with sterile surgical towels on opening until implants were required for the case. After the last implant was placed, a sterile culture swab was used to obtain a sample from all open implants that had been present at the start of the case. The paper outer wraps of the implant trays were sampled in each case as a positive control, and an additional 105 swabs were capped immediately after they were opened to obtain negative controls. Swab samples were assessed for bacterial growth on 5% sheep blood Columbia agar plates. Of note, only departmental funding was used and no applicable financial relationships exist with any author.

Results: No growth was observed on any of the 105 negative controls, whereas 99.1% of positive controls demonstrated obvious contamination. Cultures from implant samples demonstrated a 9.5% overall rate of contamination with 2.0% (n=1) of covered implants versus 16.7% (n=9) of uncovered implants demonstrating contamination. Length of time implant trays were open before sample collection; implant type (plate, rods, vs. polyetheretherketone), number of scrubbed personnel, and number of implants used were all not found to be significantly associated with implant contamination (p>.05). However, coverage of implants was found to significantly reduce the implant contamination rate (p=.016).

Conclusions: The contamination of sterile implants during spine surgery was found to occur. However, this contamination was independent of the amount of time the implant trays remained open. Coverage of implants significantly reduces this contamination. Therefore, no matter the expected duration of a case, implant coverage is a simple modifiable way to reduce the risk of intraoperative wound contamination and potentially reduce postoperative infections.