A review of the manufacturing process and infection rate of 3D-printed models and guides sterilized by hydrogen peroxide plasma and utilized intra-operatively

Abstract

3D printing in the context of medical application can allow for visualization of patient-specific anatomy to facilitate surgical planning and execution. Intra-operative usage of models and guides allows for real time feedback but ensuring sterility is essential to prevent infection. The additive manufacturing process restricts options for sterilisation owing to temperature sensitivity of thermoplastics utilised for fabrication. Here, we review one of the largest single cohorts of 3D models and guides constructed from Acrylonitrile butadiene styrene (ABS) and utilized intra-operatively, following terminal sterilization with hydrogen peroxide plasma. We describe our work flow from initial software rendering to printing, sterilization, and on-table application with the objective of demonstrating that our process is safe and can be implemented elsewhere. Overall, 7% (8/114 patients) of patients developed a surgical site infection, which was not elevated in comparison to related studies utilizing traditional surgical methods. Prolonged operation time with an associated increase in surgical complexity was identified to be a risk factor for infection. Low temperature plasma-based sterilization depends upon sufficient permeation and contact with surfaces which are a particular challenge when our 3D-printouts contain diffusion-restricted luminal spaces as well as hollows. Application of printouts as guides for power tools may further expose these regions to sterile bodily tissues and result in generation of debris. With each printout being a bespoke medical device, it is important that the multidisciplinary team involved in production and application understand potential pitfalls to ensuring sterility as to minimize infection risk.

Does Low-Temperature Sterilization Affect the Geometrical Properties of 3D Printed Models and Surgical Guides from a Reconstruction of CT Images using the Mimics Innovation Suite?

“…FDM 3D printing is likely to produce devices with some degree of sterility, given the high temperatures used during the manufacturing process (18). However, handling in non-sterile conditions contaminate the devices and lead to an intraoperative infection (7). Therefore, the sterility of those models and guides is critical during surgery but without sacri cing the accuracy of the devices.…”

“…The sterilization methods adequate for different 3D-printing materials have been tested in terms of infection rate, mechanical performance, and dimensional stability, or, on the contrary, geometrical deformation (7,9,15,(19)(20)(21). Low-temperature hydrogen peroxide gas plasma has been an optimal sterilization procedure for printouts produced by FDP in ABS.…”

“…The authors stated the infection rate was comparable to that reported by others using traditional surgical techniques and sterilization processes (7). On the other hand, Popescu et al, in two different publications (7)(8)(9), have demonstrated that low-temperature gas plasma sterilization does not in uence the tensile and exural strength of ABS specimens (9) nor the dimensions of the geometrical features remained stable (8). However, it has been indicated that for more multifaceted structures, mostly containing large surfaces of low depth, sterilization with VH2O2 could signi cantly impact the accuracy (22).…”

“…Fused deposition modeling (FDM) is the most common 3D printing method, primarily because of the simple processing and cost-e ciency. One of the most frequently used manufacturing materials in FDM 3D printers is acrylonitrile-butadiene-styrene (ABS) (2,3,(6)(7)(8). ABS is a cost-effective polymer that is easy to manage; it has good resistance, strength, and stiffness (1,(3)(4)(5)9).…”

“…When intrasurgical manipulation is needed, the models and guides printed in ABS must be sterilized before entering the operating room (7)(8)(9)(10). The ABS devices can be sterilized by low-temperature hydrogen peroxide gas plasma (vaporized hydrogen peroxide, VH2O2), a method appropriate for sensitive instruments as the temperature cycles does not exceed 50 °C (7-10).…”