Infrarenal Aortic Aneurysm
This article is based on a case provided by a Vascular Center two weeks prior to a planned intervention. A 75-year-old patient was diagnosed with an Infrarenal Aortic Aneurysm. It's the most common type of abdominal aortic aneurysm, accounting for about 60% of all cases. An infrarenal aortic aneurysm is a bulge or dilation in the abdominal aorta that occurs below the kidneys. Aneurysms are caused by a weakening of the aortic wall, which can be due to a loss of smooth muscle cells or inflammatory processes. Risk factors include smoking, age, being male, family history, and other aneurysms.
To stabilize the Aorta and prevent a life-threatening rupture, the surgical team planned to perform an intervention called Endovascular Aneurysm Repair (EVAR). This is a minimally invasive procedure that uses only small incisions in the groin to access the vascular system. It uses a catheter to place a stent graft inside the aneurysm. The stent graft acts as a new pipe to reline the aneurysm and prevent it from rupturing.
What made the case challenging for the physicians was a specific pathology of the right Common Iliac Artery. This had a special shape that could influence the guidance of the catheter and the placement of the distal end of the stent graft.
In this case, the model provided by HumanX had to be able to fulfill the following purposes:
- represent the pathological situation in great detail
- allow the surgeon to practice the procedure
- help explain the situation and the procedure to the patient
- keep the case for later training with younger physicians and residents
We decided to design a two-part vascular model. The Aortic Aneurysm was intended to be made of transparent acrylic material to enable a clear view in the vessel. The bony structures should serve as anatomical landmarks as well as a secure stand for the acrylic model.
In an endovascular procedure, the inner lumen of the vascular structure is used to guide the catheter to the aneurysm. Therefore, the model must represent a hollow vessel. We used a technology called Digital Light Processing or DLP to 3D print the vascular model. DLP 3D printing is a resin 3D printing technique that uses a projected light source to cure liquid resin into solid plastic objects. These printers can produce highly detailed parts with smooth surfaces and exceptional accuracy. The final model has a high level of transparency, which would not have been possible with an FDM 3D printer.
To print the bony part of the model we used common FDM technology. This part of the model represents rigid bone structures and there were no special mechanical or medical requirements to the material. The material we have chosen is PLA, but it’s also possible to use ABS or PETG. The total print time for this part was 8 and a half hours.
Assembling the model of the aortic aneurysm is very simple. The transparent model of the vessel is placed on the bony structures. The shape determines the correct placement in relation to the spine and pelvis. To avoid unintended displacement during use, the vessel model can be secured to the base with a rubber band.
Besides the common use as a dry model, it also can be submerged in a container filled with water. This enables some additional advantages. First, the level of transparency is being highly improved. Second, the fluid works as a lubricant for the guidewire and catheter, especially when using tools with a hydrophilic coating. Finally, when using warm water with a temperature equivalent to the human body, the use of self-expanding stent grafts will be enabled. Due to these benefits, we recommend the wet-use of vascular models.
The total time required to create the model was around 14 hours. After the model was delivered to the hospital, the medical team was able to test and train the desired procedure. Together with the manufacturer of the stent graft, they were able to validate the result of the procedure and the changes in blood flow in the aorta after insertion of the stent graft. Finally, they found a solution for the unique pathology of the right common iliac artery. This reduced the risk of rupture of the vessel during the procedure and shortened the time in the operating room by 25%.