Needle penetration test - qualifying examination of 3D printable silicones for vascular models in surgical practice

Abstract

Background During cardiogenic shock blood circulation is minimal in the human body and does not suffice to survive. The extracorporeal life support system (ECLS) acts as a miniature heart-lung-machine that can be temporarily implanted over major vessels e.g. at the groin of the patient to bridge cardiogenic shock. To perform this procedure in an emergency, a proper training model is desirable. Therefore, a 3-dimensional-printable (3D) material must be found that mimics large vessel needle penetration properties. A suitable test bench for material comparison is desirable. Methods A test setup was built, which simulated the clinically relevant wall tension in specimens. The principle was derived from an existing standardized needle penetration test. After design, the setup was fabricated by means of 3D printing and mounted onto an universal testing machine. For testing the setup, a 3D printable polymer with low Shore A hardness and porcine aorta were used. The evaluation was made by comparing the curves of the penetration force to the standardized test considering the expected differences. Results 3D printing proved to be suitable for manufacturing the test setup, which finally was able to mimic wall tension as if under blood pressure and penetration angle. The force displacement diagrams showed the expected curves and allowed a conclusion to the mechanical properties of the materials. Although the materials forces deviated between the porcine aorta and the Agilus30 polymer, the graphs showed similar but still characteristic curves. Conclusions The test bench provided the expected results and was able to show the differences between the two materials. To improve the setup, limitations has been discussed and changes can be implemented without complications.

Needle Penetration Simulation: Influence of Penetration Angle and Sample Stress on the Mechanical Behaviors of Polymers Applying a Cast Silicone and a 3D-Printed Resin

“…Some parts were adopted from a previous study [7], e.g., the needle holder, which clamps a specific cannula type (see Appendix B) in place with a constant orientation of its angled opening. The cannula was clamped at its shaft with a polylactide cuboid and a M6 screw countered with a nut embedded in the holder; this resulted in a constant alignment with the test direction.…”

“…The principle of this attachment was adopted from the preliminary setup [7]. Instead of a square plateau, a circular one was designed (Figure 1a).…”

“…Then, the force and the resulting masses were calculated from the wall stress and the cross-section area of the sample dimensions. The calculations and results were taken from the preliminary work [7]. Table 1.…”

“…Table 1. Masses of the weights for the attachment at 90 • with prestress in gram, which were already calculated in our prior study [7]. The masses 1-8 are mentioned clockwise starting with the one on the opposite of the cannula's opening.…”

“…To evaluate the suitability of materials for vessel puncture models, a setup was created in preliminary work [7]. The needle penetration test reported in this case enabled to examine nonbiological materials for their puncture properties and to compare them with biological samples.…”