Reprocessing of Pedicle Screws and Exposure in Sterile-Field Leads to Infection in Spinal Surgery

Written by Kristin Della Volpe; Reviewed by Aakash Agarwal, PhDNeel Anand, MD and Jeffrey C. Wang, MD

Bacterial infections following spinal fusion occur at a rate of approximately 12.7%.1 These infections most commonly involve Staphylococcus epidermidis and Staphylococcus aureus, and are linked to reprocessing (rewashing and resterilizing) pedicle screws and exposure inside “sterile-field” in spinal surgery.2-4 Reprocessed screws have been found to harbor corrosion, biofilm, endotoxins, fatty tissue, and soap residue mixed with fat, whereas exposed pedicle screws in “sterile-field” become contaminated.3-5

New research suggests that avoiding reprocessing altogether and shielding pedicle screws intraoperatively with an impermeable guard can prevent or reduce the degree of contamination and resulting surgical site infections (SSIs).4 SpineUniverse spoke with coauthors of this study—Aakash Agarwal, PhDNeel Anand, MD, and Jeffrey C. Wang, MD—to determine the magnitude of the issue, and how to prevent surgical site contamination linked to pedicle screws in spine surgery.

Research highlights that even though the operating room is a “sterile” environment, there are several factors that can allow bacteria to be seeded into implants. Photo Source: 123RF.com.

What are the sources of contamination found on pedicle screws in spine fusion surgery, and what is the scope of this issue?

Dr. Agarwal: Current literature has shown that all pedicle screws become contaminated, to various degrees, if the following takes place:2-5

  1. Reprocessing (before and after surgery): repeated washing of bulk quantity of screws with soil devices leftover from surgery.
  2. Handling (during surgery): touching the screw to load it onto an insertion device, and general exposure (eg, air and surface) until implantation.

The only way to avoid variability (various degrees of contamination) is to avoid these two modes of contamination via providing the implant in an individual sterile pack (single-use and ready for implantation), and each implant should have a functional guard around it to protect from direct exposure during handling.2,4,5

The latest randomized clinical trial demonstrated 12.7% infection rate in spine surgery.1 The authors concluded that “…SSI occurs at the higher end of the range cited in the literature (2-13%), which is largely based on retrospective data not subjected to the inclusivity of SSI as defined by the CDC. Staphylococcus aureus continues to be the most common causative organism and continued vigilance and searching for preventive measures need to be a high priority.”1

In addition to clinical presentation of SSI, there have been several studies performed on occult forms of SSI. According to literature data, these occult SSI were present in at least 10% to 30% of patients with chronic pain and were detected only during revision spine surgery.6-9

Is the magnitude of the problem tied to the growth of the device (eg, pedicle screw) industry?

Dr. Agarwal: The situation is ubiquitous; however, with the growth of instrumented orthopaedic surgery (including spine surgery), the effect is much more pronounced. Thus, a contamination rate of approximately 12% today means a lot more in absolute numbers than it did a decade ago.

Dr. Anand: Our research highlights what spine surgeons have speculated, but nobody has paid enough attention to: there is a lot of contamination found on pedicle screws used in spine surgery.2-5 The data is fully solid, sobering, and scary. I hope it will open the eyes of surgeons around the world that we can do better. While there is a tremendous scope of contamination, there also is a tremendous scope for improvement. A radical change is needed.

Dr. Wang: The scope of this issue is huge. Our research indicates that even though we are in the operating room, in a “sterile” environment, there are contaminants that can allow bacteria to be seeded onto the implants, making the risk of infection higher.

Are most spine surgeons aware of this contamination risk? For example, is an academic surgeon more likely to be informed?

Dr. Agarwal: Most are aware of first mode of contamination (reprocessing)—ie, sometimes their instruments and implants have residual particulates left from previous surgeries. However, many aren’t aware of second mode of contamination (handling/exposure).

Dr. Anand: Most orthopaedic and spine surgeons would agree that our current process of having trays of implants sitting open for hours before we use them in the operating room is problematic. In addition, these trays move from hospital to hospital, and from patient to patient. Yes, pedicle screws get cleaned and sterilized, but there is a lot of movement that occurs, and it really takes attention to detail when cleaning them out. It is really easy to increase bioburden through movement of these trays.

Dr. Wang: I believe that most surgeons understand that contamination, at some level, can occur in the operating room. Many are very aware that as the case goes on, the room air, movement in the room, and handling of the implants can lead to some bacteria being able to reach the implants. However, no one knows the scope of the problem. Our study and others are making us aware of the magnitude of the problem.

Does contamination risk differ among surgery centers?

Dr. Agarwal: Difference in contamination risk depends on several other factors, such as the type of air flow in the OR, attire requirements (for example, is shoe gown mandatory?), patient traffic, methods of sanitization and schedules of such, newer versus older facility, extent of oversight, training and improvement protocols being employed in the center. Therefore, it is hard to devise a controlled study to identify differences in these base metrics.

I would like to mention that SSI alone isn’t the correct metrics for comparison, for example differences in patient demographics (eg, older age, immunocompromised, unhealthy lifestyle) between two centers with same level of contamination will have different SSI rates, even if we follow the same surgical protocol.

Would you like to comment on protective measures taken by plastic/ general surgery and cross-over to spine surgery? What can be learned from other surgical specialties?

Dr. Agarwal: Studies have demonstrated a contemporary (ie, in other surgical fields) use of a physical shield between the sources of contaminants and the implants (or any other vector being transmitted to the surgical site).2 They represent methods employed to avoid the second mode of contamination, which in our multicenter trial, and in other analogous trials such as by Rehman et al, has shown significant differences in level of contamination and SSI rates respectively.5,10

What are the clinical implications of your study in Global Spine Journal on using guarded pedicle screws as a means of intraoperative implant prophylaxis?

Dr. Agarwal: The single center study,4 as well as our multicenter study,5 showed that all unguarded screws resulted in bacterial contamination inside the “sterile field” during live surgeries, whereas guarded screws had no such contamination. The key constituents that define the pathogenesis of SSI are the virulence, host-site immunity, and dosage. We demonstrated the preventative method effective on reducing the dosage (of bacteria).

The guards used on the single-use pedicle screw are commercially available.

Dr. Wang: Our study basically shows that surgeons should try not to touch the implants. Perhaps in the future, there will be “guards” or mechanisms that allow for the handling and manipulation of the implants, without touching the implants.

Should these single-use screws with guards be the standard of care for spine surgery?

Dr. Agarwal: Absolutely. It would positively affect the lives of millions undergoing spine surgery.  

Dr. Anand: I hope that guarded pedicle screws will become the standard of care in spine surgery, and that all manufacturers will start putting guards on their screws. It makes logical sense as long as the cost is not prohibitive. Within the means of economics, there is no reason why we should not have a sterile implant opened up at the time of placement. The only argument against guarded screws would be that the screws are sterile in the factory and are auto cleaned and sterilized. However, our data clearly shows that the pedicle screws are not clean, and there is bacterial contamination.2-5

What barriers to increased use of these guards exist in the United States?

Dr. Agarwal: Although patient safety cannot be equated with cost, the addition of guard, along with outer sterile tube might increase the manufacturing cost of a pedicle screw from $50-100 to $60-120. However, the selling price of this same medical device is between $600-$2,000. Furthermore, hospitals save substantially by not having to reprocess them. Reduction in SSI rates will also bring substantial economic savings.11

In summary, this approach will be economically beneficial to our healthcare. The total cost of the current approach is $4.7 billion annually in the US, and the total costs of the new proposed approach (avoiding two modes of contamination via guard and outer sterile tube) will be $1.4 billion—in other words a net saving of $3.3 billion, just in spine surgery.11

This calculation does not consider the additional cost of insurance and liability associated with reprocessed and unguarded implants (in light of these evidences), neither does it consider current back up inventory (for reprocessing error) just sitting in the hospital. It also does not consider the loss of income and trauma to at least 100,000 people suffering infections per year, just in spine surgery.

What steps does your surgical team take before and during surgery to prevent SSIs during spine surgery, particularly with regard to pedicle screws?

Dr. Wang: We do everything possible, according to best practices. We take preoperative precautions, and do all of the standard things to minimize the risk of infection. During the surgery, we use diluted-betadine washes and intra-wound antibiotics. However, when it comes to implants, we take extra precautions. We keep them sterilely covered until we need them. We use the “no-touch” technique where we are careful not to touch the implants if possible, or to minimize anyone touching them. We change our gloves prior to the implantation of the screws. Even with all of these precautions, infections can happen.

What are the main take-away messages for spine surgeons/ surgical teams on this topic?

Dr. Agarwal: They key messages are:

  1. Both preoperative/postoperative reprocessing and intraoperative handling of the implants contaminate them.
  2. The average infection rate is high in spine/orthopaedic surgery, and there is a rise in antibiotic resistant bacteria. Furthermore, recent evidences have shown presence of occult forms of infection post-spine surgery which later presents as late onset SSI, and/or hardware loosening.
  3. Currently, only an intraoperatively guarded, and individually packaged implants avoids the two current modes of contamination (of implants).

Dr. Wang: The top strategies to prevent SSI in spine surgery are:

  1. Instituting preoperative measures according to best practices, and optimizing the patient prior to surgery.
  2. Use of intra-wound antibiotics and washes at the end of the case prior to closing.
  3. Minimal or no-touching of the implants.

You noted that patients are not very knowledgeable about infection/ contamination causation. Do you expect this to change?

Dr. Agarwal: I am sure no patient that undergoes spine surgery is aware of the exact level (likelihood) of risks involved, let alone the exact process of implant contamination. I am sure, as we make transition into avoiding these two modes of implant contamination, the patient will become aware of it, and perhaps they will help advocate for such transition.

Dr. Agarwal reports royalties from Paradigm Spine and joimax; consultancy/employment from Spinal Balance Inc.; is an editorial board member for the journals Clinical Spine Surgery and Spine; is an advisory board member for the Center for Disruptive Musculoskeletal Innovation (CDMI).

Dr. Anand reports royalties from Medtronic, Globus Medical, and Elsevier; is a consultant for Medtronic, Spinal Balance Inc., Spinal Simplicity, TheraCell; is on the scientific advisory board for TheraCell, Spinal Balance Inc., Globus Medical; has stock/stock options in TheraCell, Paradigm Spine, Globus Medical, AF Cell, Bonovo Orthopedics, Inc.

Dr. Wang reports the following relationships:
Royalties: Biomet, SeaSpine, Amedica, Synthes
Investments/Options: Bone Biologics, PearlDiver, Electrocore, Surgitech
Board of Directors: Past-President Cervical Spine Research Society, Past-President Society for Brain Mapping and Therapeutics, President North American Spine Society, AO Foundation Board
Fellowship Funding: AO Foundation
Editorial Boards: Spine, JAAOS, The Spine Journal, Clinical Spine Surgery, Global Spine JournalView SourcesUpdated on: 06/12/19


Drue is Managing Partner for The De Angelis Group.

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