Biomaterials are expected to perform flawlessly in the extremely aggressive environment of the human body. In fact, there is high demand for materials that mimic living tissue on account of mechanical, chemical, biological and functional performance. Polymer biomaterials offer great variation in properties. PU, PE, POM and implantable-grade PEEK are materials commonly used in the development of in vivo devices.
New advanced polymeric biomaterials such as PEEK are changing the face of the implantable medical device industry. Introduced in 1999, PEEK has already been used for orthopaedic and dental implants, cleared by FDA and CE�marked. Indeed, PEEK presents many advantages: it is biocompatible and its mechanical properties are very close to bone�s values. PEEK has received acceptance as a highly reliable implantable biomaterial with great confidence from the medical community. From an engineering viewpoint, its properties, including superior strength and toughness as well as extensive biocompatibility, make it one of the most versatile biomaterials available and ideal for the manufacturing of in vivo medical device applications. Traditionally, metals or ceramics are chosen for hard tissue applications and polymeric materials are selected for soft tissue applications. One of the major problems in orthopedic surgery is the mismatch of stiffness between the bone and the metallic or ceramic implants. The moduli of metals and ceramics are fixed at inherently high levels, whereas the modulus of implantable-grade PEEK can be adapted, limiting such complications as stress shielding. Stress shielding can lead to increased bone porosity through resorption, which sometimes results in fractures of the supporting bone or the loosening of the implant. The high strength of implantable-grade PEEK can be further enhanced by adding particles or fibers to increase its physical and mechanical performance for applications requiring very high strength. For example, it may be modified with the addition of short carbon fibers to increase the stiffness (from approximately 4 to 18 GPa) and strength (from 100 to 230 MPa) of the base polymer. Substantially higher strength and stiffness levels can be achieved with longer fibers at higher mass ratios. In contrast, when carbon fiber-reinforced ultra-high molecular weight polyethylene (UHMWPE) was employed clinically in both acetabular and tibial components, it failed especially when used as a tibial component. UHMWPE failures have been attributed to poor bonding strength between the carbon fiber and the UHMWPE matrix and to the poor creep resistance of the UHMWPE matrix, which promotes de-bonding of the carbon fibers under loads. These concerns are not as applicable to polymers such as implantable-grade PEEK due to its outstanding creep performance, which allows it to sustain comparatively large stresses over long periods of time without significant time-induced extension and with good fiber/matrix interfacial bond strength.
Implantable-grade PEEK polymer offers exceptional imaging versatility by being inherently radiolucent�in other words, transparent to X-rays�as well as non-magnetic and non-conducting. However, it also can be easily modified to be radiopaque. Radiographic qualities include the elimination of imaging artifacts and scatter generated from metallic implants, which prevent a complete inspection of tissue and bone growth when using conventional imaging techniques such as X-rays, MRI technology, and computer tomography.
In vivo medical devices may be sterilized in several ways including gamma radiation, ethylene oxide gas, and steam. Many polymers cannot be sterilized by all these methods because of changes that occur within the polymer, which often lead to embrittlement or hydrolytic decomposition. In contrast, implantable-grade PEEK polymer can be repeatedly sterilized using any of these methods without adversely affecting its mechanical properties or biocompatibility.

Because of the versatility of PEEK, implantable-grade PEEK polymer devices are being investigated and developed in nearly every application area for long-term implants. Device manufactures have used the material in the development of spinal-fusion cages, finger joints, hip and femoral bone replacements, bone screws and pins, components for implanted cardiac pumps, and dental posts and caps. Implantable-grade PEEK polymer presents an ideal solution for the long-term implantable medical device industry because of its superior combination of strength, toughness, extensive biocompatibility, ideal imaging properties, optimal modulus, excellent chemical resistance and the ability to be repeatedly sterilized without the degradation of its mechanical properties.