Preventing Spinal Implant Contamination in Spine Surgery

Highlight from the North American Spine Society 32nd Annual Meeting

Bacteria are tougher to kill when they attach to the surface of a spinal implant, even before they form a biofilm, explained Jordan Katz, PhD, at the NASS 2017 symposium, What Lurks Beneath? Understanding the Link Between the Presence of Occult Pathogens and Failed Surgery—What is the Prevalence and What Should We Do? Perioperative and early post-operative contamination are the main sources of infection, with contaminating bacteria still coming from gloves and airflow, Dr. Katz told the audience.

The biofilm life cycle begins with an initially reversible attachment—ie, bacteria landing on the implant surface, said Dr. Katz, who is Executive Director of Research and Development at Orthobond Corporation. Once these bacteria start producing polysaccharides, they become more difficult to eradicate. Next, maturation starts and the bacteria start building up biofilm around themselves, making them “thousands of times less susceptible to antibiotics and no longer visible to the immune system.” Finally, “some bacteria will actually queue up enzymes that free them out of the biofilm, so they can go back to the planktonic phase and find new sites to attach to and propagate the biofilm,” Dr. Katz told the audience.
Biofilm containing bacteria, 3D illustrationThe biofilm life cycle begins with an initially reversible attachment—that being bacteria landing on the spinal implant surface. Photo research demonstrates that the bacteria go into a different physiological state (ie, a phenotypic switch) once they attach to a surface making them more resistant to antibiotics than if the same strains were in suspension, Dr. Katz explained.1

“These are not antibiotic-resistant bacteria; they are just tougher to kill,” Dr. Katz said. The decreased antibiotic susceptibility is not related to biofilm formation, but rather to the physiological status of the individual cells as a result of the adherence process.2

Is Preventing Device-Related Infection a Life-Long Battle?

Dr. Katz questioned whether physicians need to keep spinal instrumentation free of bacteria for the entire life of the implant. Current theories suggest that initial attachment of bacteria to spine implants and devices may occur perioperatively, post-operatively, or through hematogenous (late) contamination.

However, animal research suggests that hematogenous contamination may not occur in animals or humans, but rather may be caused by delayed appearance of perioperatively introduced bacteria.3,4

“I think this is important because if we have an infection show up two years later, it is oftentimes called in the clinical literature hematogenous; we say this may have been caused by a dental procedure” Dr. Katz said. “But there is often no proof that bacteria were introduced through the bloodstream, just the fact that [an infection] is showing up years later.”

Sources of Intraoperative Contamination

Surgical glove perforations commonly occur (31% of cases in one study) and are linked to a 2-fold risk for infection.5,6 Studies involving joint replacement surgery show that the glove contamination rate increases from at least 15% at draping to 38% after reduction.7,8

Airflow is another source of contamination. In a recent study that study tracked the sedimentation of bacteria in 80 orthopaedic procedures, researchers found the rate of sedimentation varied from as low as between 48 colony forming units (CFU)/m2h when large laminar air flow systems were used to 1870 CFU/m2h when smaller or less sufficient airflow systems were used. In cases where no laminar air flow was used, the rate was >2000 CFU/m2h.9

Research shows that it takes approximately 1,000 bacteria contaminating a device to achieve close to a 100% device-related infection rate, Dr. Katz said. Given that implant placement surgery poses an infection rate of about 1% with an inoculum of approximately 25 bacteria, with a clear linear relationship between the number of bacteria and the infection rate, reducing the level of contamination is a useful endeavor, he noted.

Thus, “You don’t have to eradicate every last bacterium during surgery,” Dr. Katz said. “Everything you are doing—gloving procedures, gowning, good operating room protocol, and considering antimicrobial technologies—will slide the risk down the scale,” he added.

“Do everything in your practice possible to reduce bacteria … even if all bacteria can’t be eliminated,” Dr. Katz concluded.

Other presentations related to this symposium:

Dr. Katz is a paid employee of Orthobond Corporation and owns stock in the company.

Updated on: 09/03/19
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