Amorphous and crystalline polyetheretherketone: Mechanical properties and tissue reactions during a 3‐year follow‐up

Abstract

The study was aimed to test the mechanical strength, structural stability, and tissue reactions of optically amorphous and crystalline polyetheretherketone (PEEK) plates during a 3-year follow-up in vivo and in vitro. The injection-moulded PEEK plates were implanted to the dorsal subcutis of 12 sheep, which were sacrificed at 6-156 weeks. Thereafter, the plates were subjected to tensile tests, and levels of crystallinity were assessed by differential scanning calorimetry (DSC). Histological evaluation was carried out using the paraffin technique. In vitro properties were examined with the tensile test and DSC at 0-156 weeks. Tissue reactions were mild and fairly similar for the amorphous and crystalline plates at corresponding points in time. The mechanical characteristics of the plates remained stable over the entire follow-up. The tensile yield load and elongation at the yield load of the crystalline plates were roughly double ( approximately 500 vs. 270 N and 2.4 vs. 1.4 mm, respectively) in comparison to the amorphous plates. The elongation at break load of the crystalline plates was smaller than that of the amorphous ones (6 vs. 10). The level of crystallinity in both the optically amorphous ( approximately 15%) and crystalline (32-34%) plates remained invariable during the follow-up. The in vitro and in vivo data coincided remarkably well. In conclusion, both optically amorphous and crystalline PEEK plates are suitable for the fixation of fractures and osteotomies.

Do Surface Porosity and Pore Size Influence Mechanical Properties and Cellular Response to PEEK?

“…Interest in improving PEEK's osseointegration has accelerated in recent years after numerous reports have described its inability in smooth form to facilitate bone apposition [9,23,25,34,51]. Reasons why this interest persists (as opposed to abandoning PEEK altogether) are often attributed to the other qualities of PEEK that make it favorable in orthopaedic and spinal applications, mainly its radiolucency, MRI compatibility, high strength, and fatigue resistance.…”

“…However, attributable in part to PEEK's relatively inert and hydrophobic surface, recent evidence has demonstrated that smooth PEEK can exhibit poor osseointegration [9,25] and fibrous capsule formation around the implant [23,34]. Lack of bone-implant contact can induce micromotion and inflammation that leads to fibrous layer thickening, osteolysis, and implant loosening [2,13,29,37,48].…”

Biomechanical evaluation and surface characterization of a nano-modified surface on PEEK implants: a study in the rabbit tibia

“…In addition to its excellent mechanical properties, PEEK is chemically inert and resistant to sterilization. [1][2][3][4][5][6][7][8] These features may be of great advantage for a biomaterial. PEEK has been used in orthopedic applications for decades and in the late 1990s, became widely used as a substitute for metal implants in spinal surgery.…”

A novel bioactive PEEK/HA composite with controlled 3D interconnected HA network

“…Conrad et al [26] demonstrated that this increased mould temperature may also increase the compressive modulus, yield strength and strain of the traditional PEEK/HA composites. Working temperatures greater than 380℃ have been shown to reduce crystallinity, which is known to be beneficial for ductility and toughness [27,28] , with no adverse effect on biocompatibility in vivo [27] . Given the positive effects described on both shear viscosity and mechanical properties of the resulting PEEK samples, a mould temperature of 400℃ was selected for this study.…”