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27.09.2016 | Symposium: Advances in PEEK Technology | Ausgabe 11/2016 Open Access

Clinical Orthopaedics and Related Research® 11/2016

Are PEEK-on-Ceramic Bearings an Option for Total Disc Arthroplasty? An In Vitro Tribology Study

Zeitschrift:
Clinical Orthopaedics and Related Research® > Ausgabe 11/2016
Autoren:
MS Ryan Siskey, MS Lauren Ciccarelli, MS Melissa K. C. Lui, PhD Steven M. Kurtz
Wichtige Hinweise
The research presented in this article was funded by Simplify Medical (Sunnyvale, CA, USA; SMK, Principal Investigator). One of the authors (MKCL) is an employee of Simplify Medical. One of the authors (SMK) is an employee and shareholder of Exponent, Inc (Philadelphia, PA, USA), a scientific and engineering consulting firm. Exponent has been paid fees by companies and suppliers for this author’s consulting services on behalf of such companies and suppliers. One of the authors (SMK) has received institutional support from Smith & Nephew (London, UK); Stryker (Kalamazoo, MI, USA); Zimmer Biomet (Warsaw, IN, USA); DePuy Synthes (Warsaw, IN, USA); Medtronic (Dublin, Ireland); Invibio (Lancashire, UK); Stelkast (McMurray, PA, USA); Formae (Paoli, PA, USA); Kyocera Medical (Osaka, Japan); Wright Medical Technology (Memphis, TN, USA); Ceramtec (Laurens, SC, USA); DJO (Vista, CA, USA); Celanese (Irving, TX, USA); Aesculap (Center Valley, PA, USA); SpinalMotion (Mountain View, CA, USA); Active Implants (Memphis, TN, USA); and Ferring Pharmaceuticals (Parsippany, NJ, USA).
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research ® editors and board members are on file with the publication and can be viewed on request.
Clinical Orthopaedics and Related Research ® neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA-approval status, of any drug or device prior to clinical use.
This work was performed at Exponent, Inc, Philadelphia, PA, USA.
A comment to this article is available at http://​dx.​doi.​org/​10.​1007/​s11999-016-5096-5.

Abstract

Background

Most contemporary total disc replacements (TDRs) use conventional orthopaedic bearing couples such as ultrahigh-molecular-weight polyethylene (polyethylene) and cobalt-chromium (CoCr). Cervical total disc replacements incorporating polyetheretherketone (PEEK) bearings (specifically PEEK-on-PEEK bearings) have been previously investigated, but little is known about PEEK-on-ceramic bearings for TDR.

Questions/purposes

(1) What is the tribologic behavior of a PEEK-on-ceramic bearing for cervical TDR under idealized, clean wear test conditions? (2) How does the PEEK-on-ceramic design perform under impingement conditions? (3) How is the PEEK-on-ceramic bearing affected by abrasive wear? (4) Is the particle morphology from PEEK-on-ceramic bearings for TDRs affected by adverse wear scenarios?

Methods

PEEK-on-ceramic cervical TDR bearings were subjected to a 10 million cycle ideal wear test based on ASTM F2423 and ISO 181912-1 using a six-station spine wear simulator (MTS, Eden Prairie, MN, USA) with 5 g/L bovine serum concentration at 23° ± 2° C (ambient temperature). Validated 1 million cycle impingement and 5 million cycle abrasive tests were conducted on the PEEK-on-ceramic bearings based, in part, on retrieval analysis of a comparable bearing design as well as finite element analyses. The ceramic-on-PEEK couple was characterized for damage modes, mass and volume loss, and penetration and the lubricant was subjected to particle analysis. The resulting mass wear rate, volumetric wear rate, based on material density, and particle analysis were compared with clinically available cervical disc bearing couples.

Results

The three modes of wear (idealized, impingement, and abrasive) resulted in mean mass wear rates of 0.9 ± 0.2 mg/MC, 1.9 ± 0.5 mg/MC, and 2.8 ± 0.6 mg/MC, respectively. The mass wear rates were converted to volumetric wear rates using density and found to be 0.7 ± 0.1 mm3/MC, 1.5 ± 0.4 mm3/MC, and 2.1 ± 0.5 mm3/MC, respectively. During each test, the PEEK endplates were the primary sources of wear and demonstrated an abrasive wear mechanism. Under idealized and impingement conditions, the ceramic core also demonstrated slight polishing of the articulating surface but the change in mass was unmeasurable. During abrasive testing, the titanium transfer on the core was shown to polish over 5 MC of testing. In all cases and consistent with previous studies of other PEEK bearing couples, the particle size was primarily < 2 µm and morphology was smooth and spheroidal.

Conclusions

Overall, the idealized PEEK-on-ceramic wear rate (0.7 ± 0.1 mm3/MC) appears comparable to the published wear rates for other polymer-on-hard bearing couples (0.3–6.7 mm3/MC) and within the range of 0.2 to 1.9 mm3/MC reported for PEEK-on-PEEK cervical disc designs. The particles, based on size and morphology, also suggest the wear mechanism is comparable between the PEEK-on-ceramic couple and other polymer-on-ceramic orthopaedic couples.

Clinical Relevance

The PEEK-on-ceramic bearing considered in this study is a novel bearing couple for use in total disc arthroplasty devices and will require clinical evaluation to fully assess the bearing couple and total disc design. However, the wear rates under idealized and adverse conditions, and particle size and morphology, suggest that PEEK-on-ceramic bearings may be a reasonable alternative to polyethylene-on-CoCr and metal-on-metal bearings currently used in cervical TDRs.

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