How can I place my fenestrations?

The modification of an endograft by the surgeon is arguably one of the most complex techniques in endovascular aortic repair. This typically involves a fragile patient in a high-risk scenario that requires urgent treatment, making it impossible to wait for the standard manufacturing timelines offered by the industry.

The physician must independently plan the modification (without the support of a core lab), adapt the endograft to fit the patient’s anatomy, and finally implant it. There are several critical moments in this process where any error could have severe consequences. One of these is accurately marking the location of the fenestrations on the endograft. Complexity increases when fenestrations must avoid alignment with the metal structure of the endograft to ensure proper bridging stent placement and expansion. It may happen that in the initial plan, one of the fenestrations aligns with a strut of the endograft, which requires moving all fenestrations collectively to achieve the optimal placement.

In this blog, we’ll analyze different strategies, with their pros and cons, for positioning fenestrations:

Traditional Method: Ruler Measurement

This was the initial method and requires no complex equipment. It involves longitudinal measurements from the fabric origin to the center of each target vessel. Axial measurements from the 0º line to the center of the target vessel are more challenging.

Advantages: no special requirements in terms of material-logistics

Disadvantages: if one fenestration aligns with a strut, all fenestrations need to be repositioned individually, which can be time-consuming. Complex to define axial possition with accurancy.

"American" Method: 3D Printed Aortic Mold

Since Drs. Starnes and Leotta (Seattle, US) described this technique in 2015 , its use has grown significantly, with many published series and cases. The process involves segmenting the patient's anatomy based on CT scan findings to create a volume of the visceral aorta. A virtual aortic mask is created, with holes corresponding to the ostia of the target vessels. This mask is then 3D printed (options include FDM or resin printers, and materials such as PLA or biocompatible resin, opaque or transparent).

Using the sterilized mold, the endograft is deployed inside it and adjusted axially until no fenestration aligns with a strut. The fenestrations are then marked and cut after removing the mold.

Advantages: Millimeter-level precision it provides through 3D printing. Less risk of physician error in the plannification (position of the fenestration lies on volumen rendering from the CT scan).

Disadvantages: it requires 3D printing logistics and mold preparation time (12–48 hours).

"Hungarian" Method: Laser-Printed Template

This year, the team at Semmelweis Aortic Centre in Budapest, led by Dr. Csaba Csobay-Novák, published a new measurement approach.

It involves a laser-printed template on a plastic film with fenestration positions based on longitudinal increments of 5 mm and axial increments of 1 hour (Fig. A).

Once printed, the template is sterilized at a low temperature. Placed around the deployed endograft, it helps identify ideal fenestration locations, which are marked with a surgical pencil (fig. B).

Advantages: avoids the need for complex 3D printing logistics, allowing fenestrations to be moved as a block.

Disadvantages: slightly less precision than 3D printing, with increments of 5 mm in length and hourly angles.

"Spanish" Method: Patented Fenestration Transporter

At our center, we initially used Dr. Starnes’ technique with good results, given our access to one of Europe’s best medical printing units. However, we sought an option suitable for centers without 3D printing resources and that would be readily available. In collaboration with the Medical Imaging and 3D Design Unit at Gregorio Marañón Hospital, we designed and patented this fenestration transporter. So far, six urgent cases have shown promising outcomes, with publication pending.

The transporter is a multiperforated translucent resin cylinder, printed to the desired diameter based on the endograft, with a length sufficient to include all fenestrations.

Holes are spaced 3 mm apart longitudinally and 15º axially, with a diameter that fits a 21G needle.

Here’s how it’s used: The 0º line is defined on the tube, and the physician measures longitudinally from the edge and axially from the zero line to locate each fenestration center. Then, a 6–8 mm diameter circle is drawn around the center based on the desired fenestration size.

Once the fenestrations are drawn, the endograft is deployed within, and the Transporter is adjusted to the optimal position. A 21G needle is passed through the holes to mark the fabric where each fenestration center will be.

The precision is 3 mm longitudinally and 15º rotationally, but if needed, marking with consecutive holes can refine it to a 1.5 mm longitudinal and 7.5º axial precision.

Advantages: Potential for off-the-shelf availability (CE marking required; currently tailored to specific anatomy to meet regulations). Rapid availability. High precision.

Disadvantages: Not as precise as 3D printing for fenestration placement, as the fenestration location depends on the physician’s measurements. Until off-the-shelf use is achieved, there may be delays in adjustment and printing for individual patients.

Well, we’ve summarized the current options for positioning fenestrations in a physician-modified endograft. If you know of any other methods, please contact us at (info@physicianmodifiedendograft.com) so we can include them on our website.