3D Printing Techniques – Bone Printing

Bone reconstruction is a difficult procedure that can yield several complications. Scientist have recently discovered a way to reconstruct bones that is specific to each individual patient. Through 3D bone printing, medical professionals can make implants and prosthetics specifically designed to fit each patients’ unique needs with less complications.

According to Patient-Specific Surgical Implants Made of 3D Printed PEEK: Materials, Technology, and Scope of Surgical Application “The technologies, such as additive manufacturing (AM) also known as rapid prototyping (RP) or three-dimensional printing are robustly growing and have positively influenced the biomedical sector over the last decade. (Honigmann, 2018)” In the last few years, the FDA has increased their approval rate of 3D printing, which allows healthcare providers to obtain the necessary tools needed to perform these procedures. In a 3D printed model, the model is built entirely, layer by layer, using a digitally controlled operating tool, which allows it to be built for a specific individual. The FDA has recently approved two specific 3D printers, the digital light processing printer (DLP) and the Polyjet printer, to assure patient-specific quality assurance.

According to Characterization of 3D Printing Techniques: Towards Patient Specific Quality Assurance Spine-Shaped Phantom for Stereotactic Body Radiation Therapy, it is important to note the differences in the two printers when determining which one to use for a specific procedure. “The DLP printing technology uses a more conventional light source, such as an arc lamp with a liquid crystal display panel or a deformable mirror device which is applied to the entire surface of the vat of photopolymer resin in a single pass (Kim 2017) The DLP printing technique also produces highly accurate parts with excellent resolution (Kim 2017) The main advantages of this technique are that DLP technique can harden a whole layer in a fraction of the time and it takes to a laser to trace around and fill in each item on the print bed (Kim 2017) With use of this production method, DLP can provide higher printing speeds at a relatively low cost (Kim 2017)”

“The Polyjet 3D printer is similar to an ink jet printer; however, this technique applies resins instead of ink (Kim 2017) The resin is laid down on a print bed layer by layer and then it is hardened using UV light (Kim 2017) Some Polyjet machines can make a combination of hybrid materials because of their multiple print heads (Kim 2017) Printing materials used for Polyjet technique are very diverse, ranging from hard plastics to soft rubber (Kim 2017)”

A picture from the article Characterization of 3D Printing Techniques: Toward Patient Specific Quality Assurance Spine-shaped Phantom for Stereotactic Body Radiation Therapy, compares the difference between the DLP printer and PolyJet printers with printed vertebrae and spinal columns.

In typical procedures, implants have been made from metals such as gold, titanium alloy, cobalt chromium, etc. These metals have been used as hip and knee prosthesis, cranial prosthesis, dental implants and even temporary implants such as pins, screws and rods. While there is nothing wrong with using these materials in the human body and they have strength and friction resistance, normal human bone tissues maintain a higher strength and elastic modulus. Using metals in the body can also cause streaking on CT scans and many metals are MRI incompatible. A long-term use of metals in the body can cause hypersensitivity and osteolysis, which is the break down of normal bone. According to Patient Specific Surgical Implants Made of 3D Printed PEEK: Material, Technology, and Scope of Surgical Application, “Due to an array of limitations observed with metallic and ceramic biomaterials, more recently the use of polymers as a viable alternative is being explored (Honigmann 2018) A large number of polymers, such as ultrahigh molecular weight polyethylene (UHMWPE), polymethyl methacrylate (PMMA), polylactide (PLA), polyglycolide (PGA), and polyhydroxybutyrate (PHB), are also widely used in various biomedical applications(Honigmann 2018) However, only a limited number of polymers have been used for bone replacement purposes because they tend to be too flexible, and too weak for orthopedic and load-bearing implants applications (Honigmann 2018)”