Development of an Additively Manufactured Template for Physician-Modified Endografts

Background: Fenestrated or branched prostheses are used to treat complex aortic aneurysms. In urgent cases, fenestrations are manually cut by the surgeon into a straight endoprothesis. The technique is called Physician modified Endograft (PMEG). In this process, the distances in the sectional image data are measured and manually transferred to the three-dimensional surface of the prosthesis. This may result in deviations from the previously measured distances of the individual branches. With the aim of improving the precision of the fenestration, an additively manufacturable, patient-specific template was to be developed. This template should simplify, standardize and accelerate the modification of the endoprosthesis while taking material biocompatibility into account.

Methods: Based on the preoperative CT data set, the patient-specific centerline was segmented, which serves as the basis for the template production. A two-part design template with a locking ring at each end of one template half, to prevent vertical and horizontal translation, was chosen. The templates were additively manufactured with a transparent material. By means of cytotoxicity tests with human endothelial cells and bacterial tests with S. aureus, the material was tested for biocompatibility and the possibility of sterilization. As a control, the templates were compared and validated with the current manufacturing method for PMEG in terms of outlet position precision and constant spacing between the vessel outlets.

Results: The segmentation, design and additive manufacturing process could be realized within a few hours. The two-part design of the templates allowed easy attachment and removal of the template without damaging the vascular prosthesis. The choice of the centerline as the template base created a smooth inner surface, allowing a rotation of the prosthesis within the template. The cytotoxicity tests confirmed the biocompatibility of the material. The bacterial tests showed that the material could be reliably sterilized. Based on a retrospective patient collective, 25 templates for the modification of prostheses could be developed, printed and sterilized. The manufacturability was guaranteed for all but 3 data sets. Excessive layer thickness, extreme curvatures and extreme angles of the renal arteries were defined as exclusion criteria. The in-vitro evaluation showed a high accuracy of the template fenestrations, comparable to the previous standard method.

Conclusion: The developed method allows the creation of a sterilized, precise and patient-specific template for use in the operating theatre within one day.

Publication History

Article published online:
13 February 2024