Three-dimensional (3D) printing refers to several manufacturing technologies that generate a physical model from digital information. Every year, 3D printing (also called additive manufacturing or additive layer manufacturing) offers more applications in the healthcare field, helping to save and improve lives in ways never imagined up to now.
Medical 3D Printing
3D printing in medicine can be used to manufacture custom medical implants for many different applications, including spine, dental, and oral and maxillofacial surgery. Using silicon nitride (Si3N4) for these implants can give them antibacterial and osteogenic (promoting bone growth) properties.
SINTX has invested new resources into the development of 3D printed, composite silicon nitride polyetheretherketone (SN-PEEK) spinal implants, and recently received U.S. government funding. The National Institute of Health (NIH) awarded SINTX $308,301 in a Phase 1 grant to fund research addressing antibacterial and ossesointegrative properties of silicon nitride, representing the first NIH grant that SINTX has received to date.
The government-funded research will be a collaboration between SINTX and Drexel University, Thomas Jefferson University, and the University of Pennsylvania School of Veterinary Medicine over the next 9-11 months. SINTX hopes to demonstrate static compression, shear, and torsion strength of 3D printed SN-PEEK cages that exceed the loading requirements guidelines established by the American Society for Testing and Materials (ASTM).
The study will include:
- Develop three 3D cervical cage designs – solid, partially porous, and overall porous.
- Utilize Kumovis R1 to produce test cages having four concentrations of Si3N4 (0, 5, 10, and 15 vol.%; n=5 cages per design x 3 designs x 4 Si3N4 concentrations = 60 cages).
- Verify static mechanical properties to be in accordance with ASTM F2077.
- Utilized micro-CT and SEM to qualitatively evaluate surface topography, total % porosity, average pore size, and pore interconnectivity.
- Once a successful static design is established, conduct additional fatigue testing in preparation for the Phase II in vivo studies.
SINTX is very excited about the opportunities that 3D printing presents for biomedical implants and the increased outcomes it may present for surgeons.
Opportunities for 3D Printed Silicon Nitride
With over 40,000 human spine implantations over 10 years and a very low percentage of reported adverse events, FleX SN-MC2 has an excellent safety record. It is biocompatible, bioactive, and has shown bacterial resistance and superb bone affinity.
As a dental implant material, FleX SN-MC2 has been thoroughly tested to ISO 10993-01 standards and shown to be highly biocompatible. Silicon nitride ceramic is metal-free, like all ceramics, and free of corrosion, galvanism, and electronic disturbances, offering the latest technology in dental implants.
When used in implants for CMF applications, silicon nitride has the potential to accelerate bone healing, eliminate metal toxicity, and enhance radiographic imaging. Because it’s antipathogenic, silicon nitride can also decrease infection rates and ease the health care burden associated with failed implants.
A midline exposure was made to the L4-L5 level and confirmed radiographically. A standard spinal decompression was performed and the facet cyst was resected en bloc. The L4-L5 transforaminal space was then decompressed allowing access to the intervertebral disc space. A traditional posterior lumbar discectomy and disc preparation was performed.
The intervertebral space was trialed to a 12 mm implant – Valeo® TL (Amedica Corporation, Salt Lake City UT, USA). The intervertebral space and silicon nitride implant were then filled with a combination of local autograft bone, morselized allograft bone and bone-morphogenetic
protein (rh-BMP2).* After placement of the intervertebral device, posterior pedicle screw instrumentation was positioned at L4 and L5 with connecting rods being applied and tightened. Standard wound closure over a suction drain was performed.
The patient reported complete relief of leg pain within 24 hours and was discharged from an uneventful hospitalization 3 days after surgery (Figures 4, 5).