Avoiding Unnecessary Contamination of Implant-Bone Interface: A Multi-center study

Presented at SMISS Annual Forum 2018
By Anand Agarwal MD
With Michael Weiss DO, Reginald Davis MD,

Disclosures: Anand Agarwal MD D; Spinal Balance Inc & Osteonovus Inc. F; Paradigm Spine & joimax. Michael Weiss DO None, Reginald Davis MD None,


SSI is known to occur at the rate of 12.7% following spinal fusion. Recently there has been a considerable interest in the handling and delivery of surgical devices, with contemporary practices such as plastic surgery, general surgery etc. using a shielding methodology as a standard of care. In the field of spine surgery, pedicle screws are the key implants used and is synonymous with the term spinal fusion. Thus, there lies merit in evaluating the intraoperative bioburden carried by such implants and if a shielding method using a guard, similar to keller funnels and wound protectors, could produce a better aseptic alternative to the current standard of care.


Assess to what degree contamination of pedicle screws occur in standard intraoperative practice and if use of an impermeable guard could mitigate or reduce such an occurrence.


Two groups of sterile prepackaged pedicle screws, one with an intraoperative guard (group 1) and the other without such a guard (group 2), each consisting of 15 samples distributed over three-time points (spinal fusion surgeries) and two surgical centers, were loaded onto the insertion device by the scrub tech and left on the sterile table. Approximately 20 minutes later, the lead surgeon who had just finished preparing the surgical site, touches the pedicle screw. Then instead of implantation it was transferred to a sterile container using fresh clean gloves for bacterial and gene analysis. Unguarded screw refers to the standard practice of unwrapping the screw from its package whereas guarded screw implies that even after unwrapping from the package, the screw carriers an impermeable barrier along its the entire length, which is only removed seconds prior to insertion (i.e. the impermeable barrier guards the screw from being exposed to the air, physical surface like the table or other instruments, scrub tech's bloody/soiled gloves, surgeon's bloody/soiled gloved etc.).


The standard unguarded pedicle screws presented bioburden in the range of 105-107 (CFUs per implant/screw) with bacterial genus mostly consisting of Staphylococcus and Micrococcus, the two most common genera found in SSI reports. The common species among them were Staphylococcus epidermis, Staphylococcus aureus, Micrococcus luteus, and Staphylococcus pettenkoferi, whereas the guarded pedicle screws showed no bioburden.


Shielding the pedicle screws intraoperatively using a guard provides a superior level of asepsis than currently practiced. All unshielded pedicles screws were carrying bioburden of virulent bacterial species, which provides an opportunity for development of post-operative infections.