Can Pedicle Screw Guards Reduce Surgical Site Infections?

Surgical hardware contamination is always a risk in spine surgery, but Aakash Agarwal, PhD believes he has a solution. Learn more.

Peer Reviewed

What if there was a simple way for orthopedic surgeons to significantly reduce the risk of surgical site infections from spinal fusion surgery? There is, according to Aakash Agarwal, PhD.

Pedicle screw guardsUnguarded screws had a vastly increased bioburden growth compared to guarded screws

Dr. Agarwal’s company, Spinal Balance Inc. of Swanton, Ohio, has developed a pedicle screw with a preinstalled intraoperative guard that it claims reduces these risks. What’s more, they say they do it without disrupting existing operating room workflows or adding significant costs.

Hardware contamination has long been one of the most pressing safety concerns in orthopedic surgery, with an infection rate that approaches 13%.1

The problem is that, despite preventive measures like the widespread use of vancomycin powder at the surgical site, there is no way to sterilize the screw-bone interface once implantation occurs. “Any contamination of pedicle screw before implantation is permanent and has the potential to cause deep-bone infection or hardware loosening due to encapsulation of biofilm between the bone and the screw,” says Dr. Agarwal, Spinal Balance’s director of research and clinical affairs.

Comparing Guarded and Unguarded Screws Head to Head

Dr. Agarwal was the lead author on a prospective multicenter trial published recently in Clinical Spine Surgery that examined intraoperative bacterial contamination.2 The authors compared the bioburden of both guarded and unguarded pedicle screws that were prepped for use in actual surgeries but then not implanted. They found that the unguarded pedicle screws had bioburden growth ranging from 105 to 107 colony-forming units (CFUs) per screw. Guarded pedicle screws showed no bioburden.

To conduct the study, Agarwal et al. provided two groups of sterile prepackaged pedicle screws to five independent hospitals. Half the screws had guards and half did not. Each study group consisted of 28 screws that were used in 28 spinal fusion surgeries, the first three of which used two screws each to test methodology (31 screws total). Multiple surgeons and surgical technicians participated in the trial, and no workflow changes were requested.

During surgery, surgical technicians held and loaded screws from each group, then left them on the sterile working table. Approximately 20 minutes later, the lead surgeon had finished preparing the surgical site. He or she then handled the instrument holding the pedicle screws and checked their alignment and fit against the insertion device.

Instead of implanting them, both the guarded and unguarded screws were transferred to separate sterile containers using fresh sterile gloves for bacterial analysis. The technician discarded all screw guards before the transfer.

Agarwal et al. concluded that using guards to shield the pedicle screw intraoperatively until it is implanted into the patient significantly decreases bacterial count and growth. “We found that the use of a screw guard resulted in zero contamination, which may not eliminate surgical site infections completely but should be an important precautionary measure,” he says.

Dr. Agarwal also emphasizes that the study results highlight the need to prevent bacterial exposure in any instrument that is inserted into the pedicle hole, such as awls, bone probes, and taps. “We demonstrated that the current use of unguarded pedicle screws acts as a vehicle for transmitting contaminants deep inside the bone,” he says.

What’s Next for Pedicle Screw Guards?

Asked when screw guards might be commonly accepted by U.S. surgeons, Dr. Agarwal notes that surgeons may be cautious about adopting any product that could interrupt their established workflow. “That’s why we structured our trial so that multiple surgeon and techs participated,” he says. “It was also important to the trial that surgeons and techs did not vary their routine.”

Dr. Agarwal sees another obstacle to wider screw guard adoption: the continued reliance of many U.S. hospitals on boxes of surgical screws for the surgeon’s on-the-spot selection before unused screws are resterilized. “At the very least, we think all screws should come in presterile individual packages,” he says. “The U.S. is behind in still allowing screws to be reprocessed. Scotland banned the practice in 2008 and many other hospitals in places such as Europe and Japan no longer allow that.”

In  2018, Dr. Agarwal had filed an official citizen petition with the U.S. Food and Drug Administration (FDA) calling for a ban on the reprocessing of pedicle screws. Specifically, he requested “the Commissioner of Food and Drugs to cease clearing 510(k)s and approving PMAs [pre-market approvals] for reprocessing of pedicle screws and other implantable orthopedic devices and cease clearing 510(k)s for re-usable implantable orthopedic device[s].”

The FDA promptly accepted the petition for review as docket number FDA-2018-P-4143, although the agency has yet to reach a determination.

In the meantime, Dr. Agarwal remains optimistic that widespread acceptance of pedicle screw guards to prevent surgical site infections is just a matter of time. “Avoiding bacterial contamination is at the core of surgical philosophy, so it baffles me why someone wouldn’t use something that prevents infection,” he says. “There was a time when surgeons didn’t even wear gloves. In future, will be a time when not using a screw guard would seem equally unthinkable.

Spinal Balance’s pedicle screw system is currently available in the U.S. and Japan.

Updated on: 09/04/20
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Reprocessing of Pedicle Screws and Exposure in Sterile-Field Leads to Infection in Spinal Surgery
Aakash Agarwal, PhD
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