Abdominal aortic aneurysm (AAA) is a common clinical condition that poses a considerable threat to patients’ lives (1,2). As recently as 2001, over two-thirds of AAA repairs were performed using open repair (3). However, over the last two decades, catheter based minimally invasive interventions, such as, endovascular aortic aneurysm repair (EVAR), have rapidly become a mainstay of treatment for AAA requiring operative intervention (4,5,6).
Endovascular aneurysm repair (EVAR) demands a high-level of technical-competency, particularly if the patient presents with a Juxtarenal Abdominal Aortic Aneurysm (JAAA). This anatomical complexity is characterised by a short proximal neck – less than 10 mm of normal aorta between the renal artery takeoff and aneurysm sac – making it impossible to secure a series of modular synthetic tubes with metal mesh supports to the vessel proximal and distal to the aneurysm sac to create a new “pipe,” as is done in the standard EVAR procedure, preventing further growth and subsequent aneurysm rupture.
A more technically challenging fenestrated endovascular aortic repair (FEVAR) procedure is required. A graft with small cut outs for the renal arteries and the superior mesenteric artery (SMA) allow graft-vessel apposition at the proximal aneurysm neck, a type of placement not possible with standard EVAR grafts. As the takeoff angle and offset height of the renal arteries and SMA vary from patient to patient, the grafts are custom-designed and manufactured for each case based on diagnostic CT angiogram imaging (CTA). Small stents are placed from the graft through the fenestrations into each visceral artery to keep it open.
So what role does 3D printing play? FEVAR cases are challenging because both CT scans and CT three-dimensional reconstruction are difficult to interpret and may not present the precise anatomical geometry of the aorta. This makes achieving the exact fit and positioning of the graft to allow cannulation of the aortic branches, critical to the success of the procedure, difficult to achieve (7).
“On average, CT scans with 1000-2000 images can be made per vascular-related patient case, which the surgeons use to analyse and diagnose the illness. This can be ambiguous and time-consuming when the issue is complex,” says Dr. Dorweiler. “With 3D printed models, we can quickly understand the individual patient anatomy and best determine the type of treatment required to successfully treat it.”
This was illustrated in a recent case Dr. Dorweiler and his team undertook in a 53-year-old woman who had already been turned down by several other hospitals in Germany and beyond – because of the complexity of her anatomy and the potential operating risk. Due to an aortic malformation close to the heart, the patient was suffering from a bulging blood vessel on her neck. Recognizing the need for urgent medical attention, Dr. Dorweiler and his team reviewed CT scans; however, the results did not provide the level of clarity required to make an accurate diagnosis.
“Looking through the CT scans, it was impossible to clearly visualise the anatomy,” says Dr. Dorweiler. “So we decided to 3D print a model, and it was then for the first time that it became clear what the origin and magnitude of the problem was.”
Dr. Dorweiler and the surgical team was not only able to use the model to visualise the problem, but to explain the findings to the patient – facilitating informed consent for the planned 3-step operation.
“We even took it into each of the three surgeries as a point of reference during the operation, which was crucial to the successful outcome,” comments Dorweiler.
Why was the model helpful in surgery? Fenestrated stent grafts have a complex deployment process including: 1) critical image guided placement and deployment to ensure the fenestrations open to three major branching arteries of the abdominal aorta, 2) concurrent control of multiple catheter systems from up to three arterial access points, 3) coordinating overlap of five or six modular stent grafts to achieve a leak-proof system and avoid the possibility of endoleak, a major complication requiring further surgical intervention. To date, treatment of complex aortic aneurysms with the endovascular method has been a difficult procedure, with surgeons relying on intraoperative images on a 2D monitor to implant a small stent through the arteries to be placed at the affected area of the aorta.
In this case, Dorweiler and his team faced the deployment challenge in a very complex aortic arch aneurysm. Requiring an intricate implant, the team undertook a pre-operative simulation of the surgery using a stent prototype and 3D printed patient-specific aortic arch model. This process has since been repeated across several cases with surgeons able to practice surgery on the model repeatedly, ensuring the correct design and fit of the stent implant the first time – significantly reducing time and cost in the operating room.
“As pointed out in current published studies, there are savings in operating time of 5-45 minutes when using 3D printed models prior to surgery,” said Dorweiler. “Research is still ongoing, but if you take an average surgery time of 2-4 hours, you are looking at time savings of up to 40 percent. When you are dealing with complex vascular cases every day, these time-savings can be the difference between life and death.”
The University Hospital Mainz has an extensive training facility, in which its library of 3D printed patient-specific models plays an integral role. “We use the Stratasys Eden260VS 3D Printer in our BiomaTicS research platform to produce models of aortic anatomies from real-life cases, so that we can use them to teach future vascular surgeons how to successfully perform complex endovascular surgeries,” said Dorweiler. “With the ability to 3D print patient-specific aortic models in clear transparent material, the trainees can practice endovascular procedures and learn difficult wire-skills using the accurate replicas of blood vessels. For healthcare, it is crucial that we continue to leverage the capabilities of 3D printing for medical training, education and research for future breakthrough-implementation.”
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