PEEK biomaterials in trauma, orthopedic, and spinal implants

Abstract

Since the 1980s, polyaryletherketones (PAEKs) have been increasingly employed as biomaterials for trauma, orthopedic, and spinal implants. We have synthesized the extensive polymer science literature as it relates to structure, mechanical properties, and chemical resistance of PAEK biomaterials. With this foundation, one can more readily appreciate why this family of polymers will be inherently strong, inert, and biocompatible. Due to its relative inertness, PEEK biomaterials are an attractive platform upon which to develop novel bioactive materials, and some steps have already been taken in that direction, with the blending of HA and TCP into sintered PEEK. However, to date, blended HA-PEEK composites have involved a trade-off in mechanical properties in exchange for their increased bioactivity. PEEK has had the greatest clinical impact in the field of spine implant design, and PEEK is now broadly accepted as a radiolucent alternative to metallic biomaterials in the spine community. For mature fields, such as total joint replacements and fracture fixation implants, radiolucency is an attractive but not necessarily critical material feature.

Figures

Figure 1

Chemical formula of poly(aryl-ether-ether-ketone), commonly abbreviated as PEEK, and poly(aryl-ether-ketone-ether-ketone-ketone), commonly abbreviated as PEKEKK. Image provided courtesy of Exponent, Inc.

Figure 2

(A) Chain conformation of PEEK; (B) Orthorhombic crystal unit cell for PEEK. Image provided courtesy of Exponent, Inc.

Figure 3

Effect of strain rate on the stress-strain curves at 23°C in (A) uniaxial tension and (B) compression of 450G PEEK (Victrex, Manchester UK), as reported by Rae et al. [84]. Reproduced with permission from Elsevier.

Figure 3

Effect of strain rate on the stress-strain curves at 23°C in (A) uniaxial tension and (B) compression of 450G PEEK (Victrex, Manchester UK), as reported by Rae et al. [84]. Reproduced with permission from Elsevier.

Figure 4

Effect of temperature on the 450G PEEK stress-strain curves in (A) uniaxial tension (rate = 1.7 × 10−4 s−1) and (B) compression (rate = 1 × 10−3 s−1) as reported by Rae et al. [84]. Reproduced with permission from Elsevier.

Figure 4

Effect of temperature on the 450G PEEK stress-strain curves in (A) uniaxial tension (rate = 1.7 × 10−4 s−1) and (B) compression (rate = 1 × 10−3 s−1) as reported by Rae et al. [84]. Reproduced with permission from Elsevier.

Figure 5

Scanning electron micrograph of the fracture surface of a PEEK-10% HA composite. Note complete debonding of the HA particles from the PEEK matrix. Reproduced from [90] with permission from Elsevier.

Figure 6

Example of bioactive surface engineering in PEEK implants: Developmental stage, three-dimensional porous PEEK material, image courtesy of Invibio.

Figure 7

(A) CF-PEEK Brantigan spine fusion cage, image provided courtesy of Invibio; (B) Lateral radiograph of a Brantigan cage with a solid fusion, image provided courtesy of Depuy Spine. Note that the Brantigan cage has tantalum microspheres for visualization on radiographs.

Figure 7

(A) CF-PEEK Brantigan spine fusion cage, image provided courtesy of Invibio; (B) Lateral radiograph of a Brantigan cage with a solid fusion, image provided courtesy of Depuy Spine. Note that the Brantigan cage has tantalum microspheres for visualization on radiographs.

Figure 8

Posterior dynamic stabilization of the spine using PEEK rods, image provided courtesy of Medtronic Sofamor Danek.

Figure 9

(A) Wear performance of PEEK composites and historical, gamma-air sterilized UHMWPE in a cylinder-on-flat (knee-like) wear simulator; (B) Wear performance of PEEK composites and historical, gamma-air sterilized UHMWPE materials in a hip simulator. Image provided courtesy of Exponent, Inc., adapted from [17].

Figure 9

(A) Wear performance of PEEK composites and historical, gamma-air sterilized UHMWPE in a cylinder-on-flat (knee-like) wear simulator; (B) Wear performance of PEEK composites and historical, gamma-air sterilized UHMWPE materials in a hip simulator. Image provided courtesy of Exponent, Inc., adapted from [17].