Traditional hard tissue implanted metal materials such as stainless steel, titanium and its alloys are widely used in the field of hard tissue repair and replacement due to their high mechanical strength, good biocompatibility and fatigue resistance. However, the elastic modulus of these traditional metal implant materials is much higher than that of bone tissue, and it is difficult to form a reasonable gradient strength . After suffering from special external forces, patients will damage the surrounding normal organs , which ultimately leads to implant failure, which is called " stress Shielding effect.
It's been 10 years since the first patient to implant a 3D printed titanium alloy hip
Furthermore, metal implants may release harmful metal ions, resulting in formation of osteolysis or allergen; and the metal implant with a conventional nuclear magnetic resonance imaging, computed tomography incompatibility, is not conducive to bone growth and Healing is monitored.
Nevertheless, metal implants also have their unique advantages
The chemical structural characteristics of thermoplastic special engineering plastic PEEK give it excellent mechanical properties, good biocompatibility, chemical resistance, easy processing and repeatable disinfection. Since the 1980s, it has received increasing attention from materials science researchers and bone science researchers, and it is possible to replace metal materials in the field of hard tissue repair and replacement. With the deepening of 3D printing applications, PEEK has gained more attention .
PEEK skull and intervertebral implants
Advantages of PEEK instead of metal implants
Compared with metal implants, PEEK has two outstanding advantages .
First, the elastic modulus of PEEK is close to the elastic modulus of cortical bone, especially the elastic modulus of carbon fiber reinforced PEEK is more closely matched with the elastic modulus of cortical bone. This close or matched elastic modulus weakens or eliminates the stress shielding effect to a certain extent, which is beneficial to the bone integration between the implant and the bone tissue and ensures the long-term stability of the PEEK implant .
PEEK semi-rigid rod
Second, PEEK can transmit X-rays, CT or MRI scans without artifacts , so it is easier to monitor bone growth and healing process. In addition, PEEK has the characteristics of good biocompatibility, wear resistance, fatigue resistance, corrosion resistance, and easy processing, and PEEK is lighter than metal materials. The above advantages make PEEK widely used in the fields of trauma, spine and joints.
PEEK used for dental implants is lighter, more comfortable than titanium, and has no metallic taste, has obtained FDA certification
Compared with stainless steel, titanium alloy and ultra-high molecular weight polyethylene implants, 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 polyetheretherketone in orthopedic implants is considered to be one of the candidate materials to replace traditional implants.
The First Affiliated Hospital of Kunming Medical University replaced the clavicle with 3D printed PEEK material prosthesis
In April 2017, the domestic Tangdu Hospital completed the first international PEEK rib implant surgery. In January 2018, the hospital completed the first domestic PEEK implant case for the treatment of the Nutcracker Syndrome; in August of the same year, the first Kunming Medical University The affiliated hospital used the 3D printed PEEK material prosthesis for the first time to replace the clavicle. To date, there have been dozens of clinical cases of 3D printed PEEK prostheses . However, this does not mean that PEEK is no problem.
Disadvantages of PEEK for orthopedic implants
PEEK has a lower surface energy due to its relatively hydrophobic surface, which limits cell adhesion . The biological inertia of PEEK makes the bone integration between the PEEK implant and the host bone tissue poor, and clinically often encounter many complications , such as implant displacement, cage or pseudo-joint, which is Both in vitro and clinical applications have led to unsatisfactory results.
The ideal PEEK surface should enable cell adhesion, proliferation, and osteoblast differentiation, promote mineralization on the surface of the PEEK implant, and produce a large amount of bone fusion.
In order to construct an ideal PEEK surface, the researchers prepared a series of PEEK and its composite materials through bioactive ceramic filling, fiber reinforcement, PEEK porosity and other methods, the ultimate purpose of which is to make the implant of the material have both the ability to maintain blood vessels The functions of freshmen and nutrient transfer have sufficient mechanical strength and wear resistance, but maintaining the balance of various indicators is still the difficulty of current research .
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In September last year, the microporous hydrophilic PEEK material developed by the medical polymer company DiFusion was named one of the top ten spine materials in 2018 by plastic surgeons. The material is recognized because it supports the growth of orthopedic implants while retaining the mechanical properties and imaging capabilities of traditional PEEK. The material can be used for injection molding, 3D printing or mechanical processing. It is currently being expanded and put into commercial use in 2019.
It is undeniable that PEEK has excellent application prospects, but also has outstanding problems, and material breakthrough will be the key to its safe application .
In fact, no product can be perfect . Even though the metal implant materials have so many deficiencies, the first patient implanted with a 3D printed titanium alloy hip joint has been walking healthy for more than 10 years. This article aims to obtain more knowledge for professionals, and for ordinary patients who do not need to pay too much attention to the advantages and disadvantages of materials, the doctor will make the best decision.
This article reference
"Study on Bioactive Modification of Polyether Ether Ketone Implanted on Hard Tissue"
"Application of polyetheretherketone in bone transplantation"