3D printing technology (3DP), also known as Additive Manufacturing (AM), is a technology that extracts data to reconstruct a computer three-dimensional model and piles up printed objects layer by layer. By providing an effective combination mode, objects can be printed in any material and in any form. This unique technical advantage enables 3D printing materials to accurately simulate the structure of autogenous bone, which can be used for precision and personalized treatment in orthopedics, bringing orthopedics into a new era of individualized customization.
Currently, the 3D-printed orthopedic implant materials that have been put into clinical application mainly include organic polyether ether ketone (PEEK) and metallic titanium alloy. Titanium alloy has a long history of application, high specific strength, good biocompatibility, corrosion resistance, and is widely used at present.
3D printed titanium alloys can be precisely regulated to quickly build macro and micro implants that are close to natural bone tissue. 3D printing is divided into three processes: first, collect 3D image data, build digital 3D models, etc.; Secondly, the titanium alloy powder and cytokines are made into "bio-ink", and finally, the structure and performance of the bioprinted body were improved by applying the bioprinted 3D printer according to the orthopedic related parameters, and finally the orthopedic implant meeting the requirements was produced. At present, it is often used in clinical hip prosthesis, knee prosthesis, artificial vertebra and so on.
Properties of titanium alloys
The main component of titanium alloy is Ti6Al4V, which is widely used in orthopedics because of its good properties. Bone is mainly composed of cortical bone in the outer layer and cancellous bone in the inner layer, and the elastic modulus is about 0.5 GPa and 10 ~ 20GPa, respectively. The elastic modulus of dense titanium alloy is about 110GPa, and the elastic modulus of titanium alloy material after 3D printing is lower than that of ordinary titanium alloy, which is closer to the physiological structure of bone. Titanium alloy has good biocompatibility, is conducive to bone growth and bone integration, and is suitable for the preparation of orthopedic implants. Titanium alloy not only has rigidity, but also has outstanding flexibility, and has good fatigue resistance, which is suitable for joint support and can replace other metal materials. Titanium alloy is insoluble in strong acids and alkali, still has a high specific strength at 500 ° C, and is non-toxic to the human body, has good chemical stability, and is suitable for implantation in the human body. Titanium alloy has good corrosion resistance, fatigue resistance and stability, compared with other metal materials, its elastic modulus is closer to bone, suitable for orthopedics.
Clinical application of 3D printed titanium alloy in orthopedics
3D printed titanium alloy has been widely used in orthopedic clinical, such as spine surgery, trauma surgery, joint surgery, bone tumor surgery and so on. 3D printed titanium alloys are mainly used to make artificial prostheses, internal fixations, interbody fusion devices, guide plates, artificial bone trabeculae and so on.
Summary and prospect
3D printing technology has the great advantages of personalized and precise customization. Combined with the excellent characteristics of titanium alloy, the implant is customized according to the original bone structure of the patient, and the implant is made consistent with its own bone shape and similar microstructure. The advantage of shape matching can be used to restore biomechanics to the maximum extent, shorten the process of soft tissue re-adaptation, and better realize bone growth. Faster bone healing.
At present, the clinical application of 3D printing technology also has its limitations: (1) Accurate and personalized 3D printing relies too much on imaging data, which requires high accuracy of image data. In some special cases where the acquisition of imaging data is limited, the implementation of 3D printing materials will be affected. (2) To collect image data and make 3D titanium alloy printing requires 3D printers, supporting CT, MRI equipment, titanium alloy materials, modeling and software systems, and the material cost is high, which is difficult for some patients to afford; The input and use of equipment requires the cooperation of doctors and engineers, and the coordination and participation of multiple disciplines; At present, limited by technology, the production cycle is long, and it is difficult to apply in emergency surgery. (3) In the manufacture of orthopedic implants, the optimal mechanics, degradability, pore size and void size of 3D printed titanium alloys still need to be further studied. (4) The short-term effect of 3D printing titanium alloy is satisfactory, but due to the short application time, there is still a lack of long-term follow-up results and treatment of complications. In summary, although there are still many problems to be solved in 3D printing titanium alloy technology, this technology has unique advantages, consistent with the concept of precision medicine currently advocated, and has great research value in the field of orthopedics. It is believed that with the continuous in-depth development of technology, 3D printing titanium alloy can overcome its current shortcomings and produce a qualitative leap.
