Impact of dry heat sterilization on the mechanical and functional performance of 3D printed medical devices for image-guided intervention

Abstract

Polymer additive manufacturing (AM) is a powerful method for medical device prototyping, producing low-cost medical devices for resource limited settings and patient-specific customization. Plastic medical devices created with AM must undergo sterilization prior to in vivo experiments or use with patients. While prior studies have verified the feasibility and safety of sterilization of such devices, the impact on mechanical performance has not been studied. Temperatures during autoclave sterilization, a commonly used and widely available method, can match or exceed the melt temperature of Nylon-12 used for selective laser sintering. Here we tested the impact of single or multiple cycles of autoclave sterilization on the mechanical and functional performance of plastic components used with interventional radiology related medical devices (catheter hub, ablation probe handle, and implantable port). We found that up to 2 cycles of sterilization did not tangibly impact the manufacturability, function or surface finish of these devices. However, we found that more than one cycle of sterilization can compromise the mechanical strength of the devices, with geometric-linked variations in the level of change in stiffness (ranging from 12 - 23 %). In conclusion, autoclave sterilization is safe for single use AM medical devices, where repetition of the sterilization for device reuse can compromise mechanical performance.

Keywords: 3D printing; Additive Manufacturing; Interventional Radiology; Medical Devices; Rapid Prototyping.

Fig. 1.. Sample 3D printed parts of medical devices using SLS printer.

A, D.) Body of a implantable port. B, E.) Hub of a endovascular catheter. C, F.) Handle of an ablation probe.

Fig. 2.

Experimental workflow.

Fig. 3.. Critical dimensions measured using CMM (A, C, D) and CAD visualization of CMM fixture set-up (B, E, F).

Dotted line on devices depicts location of measurement. A-B.) Ablation Handle. C, E.) Catheter Hub. D, F.) Port device.

Fig. 4.. CAD representation of fixture setups for 3-point bending and compression mechanical tests using the universal test machine.

The red parts are the device stands and machine parts, and the gray parts are the medical devices. A.) Ablation handle. B.) Catheter hub. C.) Port Device.

Fig. 5.. Dimension measurements from CMM.

For all graphs, the circle datapoints represent control, square points represent the first sterilization trial, and trial points represent the second sterilization trial. A.) Ablation handle. B.) Catheter Hub. C-F.) dimensional measurements for the port device for the following dimensions labeled in Fig. 3. C.) Cone 2 circularity. D.) Cone 2 circularity. E.) cylindricity. F.) Plane flatness.

Fig. 6.. Stereomicroscopy inspection of critical surfaces.

Pre- and post-second sterilization surface finishes were compared for each medical device. A.) Ablation handle. B.) Catheter hub. C.) Port device.

Fig. 7.. Elastic region of force versus displacement graphs for 3-point bending and compression mechanical tests.

A, D.) Ablation handle. B, E.) Port Device. C, F.) Catheter hub.