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Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_3 | Pages 26 - 26
1 Feb 2017
INFLUENCE OF OXIDE VERSUS NON-OXIDE FEMORAL HEADS ON THE OXIDATION OF POLYETHYLENE ACETABULAR LINERS
Bal B Puppulin L McEntire B Pezzotti G
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Introduction

The longevity of highly cross-linked polyethylene (XLPE) bearings is primarily determined by its resistance to long-term oxidative degradation. Addition of vitamin E to XLPE is designed to extend in vivo life, although it has unintended consequences of inducing higher frictional torque and increased wear when articulating against metallic femoral heads.1–3 Conversely, lower friction was observed when oxide ceramic heads were utilized.3 Previous studies suggest that oxide ceramics may contribute to XLPE oxidation, whereas a non-oxide ceramic, silicon nitride (Si3N4), might limit XLPE's degradation.4 To corroborate this observation, an accelerated hydrothermal ageing experiment was conducted using static hydrothermal contact between XLPE and commercially-available ceramic femoral heads.

Materials and Methods

Two sets of four types of ceramic femoral heads, consisting of three oxides (Al2O3 BIOLOX®forte, and ZTA BIOLOX®delta, CeramTec, GmbH, Plochingen, Germany; and m-ZrO2 OXINIUMTM, Smith & Nephew, Memphis, TN, USA) and one non-oxide (MC2®Si3N4, Amedica Corp., Salt Lake City, UT, USA) were cut into hemispherical sections. Six highly crosslinked polyethylene liners (X3TM Stryker Orthopedics, Inc., Mahwah, New Jersey, USA) were also sectioned, gamma irradiated (32 kGy), and mechanically clamped (25 kN) to the convex surfaces of the ceramic heads (Figure 1(a)). All surfaces were dipped in water and placed into an autoclave at 121°C under adiabatic conditions for 24 hr. The test was repeated three times using two couples for each material along with XLPE-on-XLPE controls. Each XLPE sample was characterized before and after ageing using Raman spectroscopy for variations in their crystalline phase and oxidation indices using the intensities of unpolarized vibrational bands at 1296, 1305, and 1418 cm−1. Significance (p<0.05) was determined using Student's t-test with a sample size of n=18.

Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_9 | Pages 130 - 130
1 May 2016
THE EFFECT OF CERAMIC FEMORAL HEAD MATERIAL COMPOSITION ON POLYETHYLENE STRUCTURE AND OXIDATION IN TOTAL HIP BEARINGS
Pezzotti G Puppulin L Boffelli M McEntire B Rahaman M Yamamoto K Bal B
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Introduction

In total hip arthroplasty (THA), polyethylene (PE) liner oxidation leads to material degradation and increased wear, with many strategies targeting its delay or prevention. However, the effect of femoral head material composition on PE degradation for ceramic-PE articulation is yet unknown. Therefore, using two different ceramic materials, we compared PE surface alterations occurring during a series of standard ceramic-PE articulation tests.

Materials and Method

Ceramic-PE THA bearings were tested in a simulator, using ASTM F2003-02, ASTM F1714-96 (2013) and ISO 14242:1–3 standards. Acetabular liners (Apex-Link PolyTM, OMNI Life Science, East Taunton, MA, USA) were articulated against Ø28 mm Si3N4 femoral heads (Amedica Corp., Salt Lake City, UT, USA). For comparison, ArCom® PE liners (Biomet Inc. Warsaw, IN, USA) were also tested against Ø28 mm zirconia-toughened alumina (ZTA) femoral heads (BIOLOX®delta, CeramTec GmbH, Plochingen, Germany), under the same conditions. After 5 million cycles of wear, all specimens were examined using nano-spectroscopy tools. Evaluations were performed on six couples per group, plus 3 untested control couples; n= 6 (+3). Spectrographic examinations generated 8 maps of 400 points each randomly selected on the wear zones of each liner, with each map area being 20 µm2 at an in-plane spatial resolution of 1 µm.

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