Research Article: 3D printed PLA Army-Navy retractors when used as linear retractors yield clinically acceptable tolerances

Date Published: November 21, 2019

Publisher: Springer International Publishing

Author(s): Joshua V. Chen, Alexis B. C. Dang, Carlin S. Lee, Alan B. C. Dang.


Modern low-cost 3D printing technologies offer the promise of access to surgical tools in resource scarce areas, however optimal designs for manufacturing have not yet been established. We explore how the optimization of 3D printing parameters when manufacturing polylactic acid filament based Army-Navy retractors vastly increases the strength of retractors, and investigate sources of variability in retractor strength, material cost, printing time, and parameter limitations.

Standard retractors were printed from various polylactic acid filament spools intra-manufacturer and inter-manufacturer to measure variability in retractor strength. Printing parameters were systematically varied to determine optimum printing parameters. These parameters include retractor width, thickness, infill percentage, infill geometry, perimeter number, and a reinforced joint design. Estimated retractor mass from computer models allows us to estimate material cost.

We found statistically significant differences in retractor strength between spools of the same manufacturer and between manufacturers. We determined the true strength optimized retractor to have 30% infill, 3 perimeters, 0.25 in. thickness, 0.75 in. width, and has “Triangle” infill geometry and reinforced joints, failing at more than 15X the threshold for clinically excessive retraction and costs $1.25 USD.

The optimization of 3D printed Army-Navy retractors greatly improve the efficacy of this instrument and expedite the adoption of 3D printing technology in many diverse fields in medicine not necessarily limited to resource poor settings.

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Current literature explores the role of 3D printing in changing the surgical landscape through the new ability to create more resource efficient in-house surgical instruments, along with anatomical models of patients that assist in training and preoperative planning, prosthetics, personalized surgical equipment better suited for patient morphologies, and 3D printed implants [1–14]. Notably, these vast strides in 3D printing technologies are also allowing healthcare providers to create robust, low-cost medical and surgical equipment in resource scarce areas, such as in developing nations and in aerospace medicine where weight and space limitations exist [15–17]. 3D printing allows for rapid prototyping and manufacturing that expedites the improvement of medical equipment, examples of which are the development of better splints, syringes, and surgical suction tips [18–20]. Furthermore, it is shown that the high heat used during the 3D printing process sterilizes the final print [21]. Specifically, 3D printed polylactic acid (PLA) Army-Navy retractors offer a cheaper, lighter-weight, and more space-efficient alternative to traditional stainless steel Army-Navy retractors without compromising surgical retraction capabilities [22]. Army-Navy retractors are commonly used in a myriad of procedures involving retraction of shallow incisions and are listed at an online retail price of approximately $24 USD per retractor. Though literature exists in quantifying the mechanical strength of 3D printed Army-Navy retractors, none have sought to optimize printing settings and retractor designs, which could lead to additional discussion about improving the efficacy of 3D printed surgical instruments and allow healthcare providers in resource scarce areas to adopt this technology.

This study demonstrates how even pre-optimized 3D printed PLA Army-Navy retractors have comparable surgical retraction capabilities to stainless steel retractors, but can be created in-house at a fraction of the cost and adopted in resource poor settings. These retractors fail at a force that greatly exceeds what is required for clinically excessive retraction, 35 N. The optimization of 3D printed Army-Navy retractors greatly improve the efficacy of this instrument and expedite the adoption of 3D technology in many diverse fields in medicine not necessarily limited to resource-poor settings. With the optimization of the 3D printed PLA Army-Navy retractor, a staple surgical instrument, researchers can pave the way towards and gain trust for an array of 3D printed medical supplies, allowing populations around the globe to receive higher quality health care and treatment.




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