Journal article
Advanced Testing Protocols Simulate Failures and Validate Antioxidant Polyethylene in Ankle Implants
Journal of orthopaedic research, v 44(1), e26103
Jan 2026
PMID: 40384049
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
Total ankle replacement (TAR) has become an effective treatment for end-stage ankle osteoarthritis. Multiple factors, including patient characteristics, surgical technique, alignment, and bearing surfaces, influence TAR survivorship. Polyethylene (PE) fatigue is a key consideration in improving outcomes. This study establishes a novel, clinically relevant testing protocol incorporating varus-valgus rotation to simulate polyethylene fatigue failures observed in mobile-bearing total ankle replacements. Using this robust methodology, we evaluated the impact of oxidation and antioxidant stabilization on ultrahigh-molecular-weight polyethylene (UHMWPE) performance in a mobile bearing implant application. A six-degree-of-freedom simulator was used to iteratively adjust loading parameters (1500-3000 N, -4° to +8° flexion-extension, ±5° axial rotation, and ±3° or ±8° varus-valgus rotation at 37 ± 3°C in 20 g/L bovine serum) until clinically observed midline fractures were replicated. Oxidation levels were measured by Fourier-transform infrared spectroscopy per ASTM F2102. This validated loading protocol was then applied to conventional (25 kGy GUR 1020) and vitamin E-stabilized (75 kGy GUR 1020-E) UHMWPE inserts and tested to visible fracture or a 3-million-cycle runout. Post-test fractographic analysis identified crack initiation sites. Conventional aged UHMWPE demonstrated fatigue failure under varus-valgus rotation (OI = 2.59 ± 1.11) but no failure without rotation. Vitamin E-stabilized UHMWPE showed no fatigue failure after 3 million cycles, even under varus-valgus rotation (OI = 0.23 ± 0.02). Fractography revealed fractures originating at the trough and propagating with cyclic loading. Oxidation significantly reduces polyethylene fatigue life, and varus-valgus rotation exacerbates this effect in mobile bearing TAR implants. Antioxidant-stabilized UHMWPE showed promising resistance to fatigue and oxidation. These findings support the role of antioxidant stabilization in improving TAR performance, and the protocols developed here provide a framework for assessing the safety of alternative materials.
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Details
- Title
- Advanced Testing Protocols Simulate Failures and Validate Antioxidant Polyethylene in Ankle Implants
- Creators
- Ryan Siskey - Drexel University, School of Biomedical Engineering, Science, and Health SystemsPatrick Hall - Exponent (United States)Ruth Heckler - Clovis Oncology (United States)David Safranski - Foot and Ankle Division, Enovis, Atlanta, Georgia, USAJames Johnson - Clovis Oncology (United States)Ariel Palanca - Palomar Health
- Publication Details
- Journal of orthopaedic research, v 44(1), e26103
- Grant note
- This study was internally funded by Enovis.
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- School of Biomedical Engineering, Science, and Health Systems
- Web of Science ID
- WOS:001489801500001
- Scopus ID
- 2-s2.0-105005451263
- Other Identifier
- 991022170452504721
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- Collaboration types
- Industry collaboration
- Domestic collaboration
- Web of Science research areas
- Orthopedics