3D-Printed PEEK Stent Revolutionizes Nutcracker Syndrome Treatment

In the medical industry, metal 3D printing technology has been widely used for hard tissue repair and replacement. Metal materials such as stainless steel and titanium alloys are traditional raw materials for hard tissue implants. With the promotion of 3D printing within medical applications, PEEK material has gradually emerged among many medical 3D printing raw materials, and for good reasons. PEEK has excellent biocompatibility and is relatively easy to process and shape compared with traditional titanium used for implants. PEEK is also more X-ray transmissive and has advantages similar to bone elasticity. Because of these outstanding characteristics, PEEK has become the most important thermoplastic substitute for titanium implants, and is now used in production.

Nutcracker syndrome, also known as left renal vein entrapment syndrome, is characterized by impeded outflow from the left renal vein into the inferior vena cava due to an abnormally narrow angle between the abdominal aorta and the superior mesenteric artery or between the abdominal aorta and the spine, resembling a nut between the jaws of a nutcracker. This phenomenon results in the formation of venous reflux, renal hilar varices, and an increase in left renal vein pressure, which mainly cause hematuria, proteinuria, and left flank/abdominal pain, as well as pelvic congestion in females and left-sided varicocele in males. Although uncommon, this diagnosis is important due to the risk of associated morbidities, including chronic kidney disease due to long-term left renal vein hypertension and left renal vein thrombosis.

Surgical treatment is the most effective way to relieve the compression of the left renal vein and alleviate symptoms. In 2018, the Department of Urology at Tangdu Hospital in China conducted the world’s first operation using 3D printing technology to manufacture human implants using bio-compatible PEEK material, creating another precedent for the treatment of nutcracker syndrome. PEEK printing requires very high environmental and nozzle temperatures, so 3D printing equipment must maintain a constant temperature environment and be able to print at these high temperatures. Tangdu Hospital found in the INTAMSYS FUNMAT HT 3D printer the perfect solution to meet the needs of medical printing with PEEK and to explore more opportunities with this material. The main benefits of the FUNMAT HT are its chamber temperature, which can reach up to 90°C, and the extrusion nozzle, which can reach 450°C, preventing warping of PEEK printed parts.

In the past, the implants for this operation were mostly titanium alloys. With the deepening of 3D printing applications, PEEK has received more and more attention. As a thermoplastic engineering plastic, PEEK enjoys excellent mechanical properties and shows good performance. Its biocompatibility, chemical resistance, easy processing, and repeatable sterilization have turned it into a substitute for titanium alloys.

According to Professor Cao Tiesheng, head of the 3D Printing Research Center of a Medical University in China, “PEEK implants have many advantages compared to the previously used titanium alloy implants. First of all, PEEK material will not affect the later medical examination of patients, such as CT, B-ultrasound, magnetic resonance medical exams, etc. At the same time, it will not cause trouble for the patient to board the plane and to go through the security check. Moreover, PEEK and its composite materials have good wear resistance, which can effectively avoid inflammation and osteolysis around the implant caused by wear particles. Therefore, the application of PEEK in orthopedic implants is considered to be one of the best candidate materials to replace traditional titanium alloy implants.”