Alternative bearing materials for intervertebral disc arthroplasty

Area of Science:

• Biomaterials Science
• Orthopedic Engineering
• Tribology

Background:

• Cervical total disc arthroplasty (TCTA) commonly uses metal-on-polyethylene articulations.
• There is a need for alternative bearing materials with improved biotribological properties and radiolucency.
• Polymer-on-polymer designs are being explored to enhance TCTA performance.

Purpose of the Study:

• To evaluate alternative polymer-on-polymer articulations for TCTA.
• To compare the wear performance of PEEK, CFR-PEEK, and PEK against a standard UHMWPE/CoCr29Mo6 coupling.
• To assess the potential of these materials for next-generation cervical disc replacements.

Main Methods:

• In vitro wear simulation of cervical artificial discs according to ISO 18192-1:2008 (E).
• Testing of activ C discs with UHMWPE/CoCr29Mo6, PEEK, CFR-PEEK, and PEK materials for 10 million cycles.
• Gravimetric and geometric wear assessment, surface characterization, and particle analysis.

Main Results:

• The clinical reference (UHMWPE/CoCr29Mo6) had a wear rate of 1.0±0.1 mg/million cycles.
• PEEK showed a wear rate of 1.4±0.4 mg/million cycles, with signs of pitting and delamination.
• PEK exhibited a wear rate of 0.8±0.1 mg/million cycles, with no substantial benefit over the reference.
• CFR-PEEK demonstrated significantly lower wear at 0.02±0.02 mg/million cycles, a reduction of nearly two orders of magnitude.

Conclusions:

• Carbon fibre reinforced PEEK (CFR-PEEK) exhibits superior wear resistance compared to conventional polyethylene-on-metal and other polymer-on-polymer articulations.
• CFR-PEEK demonstrates excellent biotribological properties, making it a strong candidate for TCTA.
• Polymer-on-polymer articulations using CFR-PEEK hold high potential for next-generation cervical disc replacements.