3D printing is a powerful technology that continues to improve medical practice. Its impact on the treatment of challenging abdominal aortic aneurysms (AAA) continues to evolve as the technology advances.
Rupture of the abdominal aortic aneurysm is the 15th leading cause of death in the United States and the 10th leading cause of death for men over the age of 55. Resulting from an enlargement of the abdominal aorta, AAA can be treated through minimally invasive procedure called EndoVascular Aortic Repair stent grafting (EVAR). Although EVAR is an effective procedure, approximately 15% of AAA cases are not eligible for the procedure due to anatomical complexity. These 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 making exact fit and positioning of the graft, critical to the success of the procedure, difficult to achieve.
To overcome these challenges, patient-specific 3D printed models have been utilized in a number of centers to enable greater direct visibility of the aneurysm and to understand the spatial relations between the aorta, its branches and visceral arteries. The models have successfully been used to make and refine patient-specific grafts, to identify patient-specific challenges, and to practice and refine the surgical approach in a risk-free environment.
This use of 3D models may result in avoiding peri-procedural complications and extra time spent on device learning during the actual procedure. Shorter procedures result in reducing radiation exposure to the patient and staff, decreasing anesthesia and contrast agent exposure to the patient, and reducing procedure time by avoiding “on the fly treatment changes.” Four recent publications on the use of 3D printed patient-specific models in AAA highlight the benefits.
Stent insertion diagram.
A recent study from the Department of Vascular and Endovascular Surgery, Wilhelminenspital Hospital found that thirteen of 60 (21.7%) custom-made stent grafts were modified on the basis of testing in a 3D model. The authors conclude, “Prototype testing in 3D aortic models is a valuable tool to test the fit of a custom-made endograft before implantation. This may help avoid potentially debilitating adverse events associated with misaligned fenestrations and unconnected aortic branches.”
The Jacobs Institute reports that clinical simulation using patient-specific 3D models in JAAA cases is more effective at planning for peri-procedural challenges and complications than standard pre-surgical planning using CTA diagnostic imaging alone. In this study, a patient-specific model was printed on the Stratasys Eden 260 printer using FullCure 930 TangoPlus, a flexible photopolymer with material tensile strength mimicking AAA lumen wall tissue. Fluoroscopic guided simulation of the patient-specific procedure was performed by interventionists using custom-made endografts and all accessory devices.
The study found that seven out of ten (70%) procedural steps of the original planned procedure based on CTA imaging were changed after simulation on the 3D printed model. Possible complications were identified such as: 1) the need for fenestrated graft realignment during deployment, 2) challenging positioning of a renal stent, 3) identification of the need for a longer renal stent post-deployment, and 4) the necessity to confirm distal body graft ostium access via balloon inflation prior to iliac limb graft advancement. The authors conclude, “These impactful lessons require a surplus of time in a risk-free environment, which are not feasible in a patient procedure.”
The Department of Surgery, São Paulo University Medical School, Brazil finds training with patient -specific 3D models prior to EVAR improved residents’ surgical performance and increased their self-confidence. Fluoroscopy time, total procedure time, and the amount of contrast used during surgery were significantly reduced when compared with procedures performed by vascular residents trained only according to the routine practice of the institution. The study concludes that 3D models offer a cost-effective solution over virtual or other commercially available simulators.
With advancements in 3D printing technology, the clinical applications continue to evolve. The Department of Engineering San Sabastian, Spain reports applying multi-material 3D printing technology to enhance the realism of the model using the Objet260 Connex 2 printer based on the PolyJet technology and digital materials FLX9940 and FLX9960 (Stratasys Ltd., Minneapolis, MN, USA) The model produced demonstrated the same mechanical properties as human AAA tissue making it a valuable asset for surgical planning and education.