Overview

Ultra high molecular weight polyethylene (UHMWPE) components are aged in an oxygen bomb (pressure vessel) per ASTM F2003. The vessel is designed to provide accurate temperature and pressure control, with accuracies of ±1°C and ±7 kPa, respectively. After conditioning of the specimens, which includes up to 28 days of constant temperature (23°C), specimens are aged at a constant elevated temperature of 70°C and at an equilibrium pressure of 503 kPa of pure oxygen for two weeks (14 days). The goal of the procedure is to simulate effects of real life oxidation on the polymer components, and is typically performed in advance of additional testing, simulating a worse-case scenario. The procedure can be applied to conventional polymers, as well as advanced UHMWPE components, e.g. Vitamin E stabilized UHMWPE.

Applications and Benefits

A dedicated oxygen bomb vessel has been developed and calibrated to provide accurate aging of UHMWPE components prior to subsequent mechanical testing. As the oxidation may affect the mechanical performance of implants and devices, the accelerated aging condition represents a worse case environment for evaluation.

Typical applications include aging of acetabular liners in advance of total hip joint wear testing (ISO 14242) and impingement testing (ASTM F2582), and aging of tibial inserts in advance of total knee joint wear testing (ISO 14243). The testing is typically performed to support FDA and regulatory submissions, as well as R&D programs on new polymer materials.

Related Tests

• Wear of Total Hip Joint Prostheses – ISO 14242-1; ISO 14242-2; ISO 14242-3
• Wear of Total Knee Joint Prostheses – ISO 14243-1; ISO 14243-2; ISO 14243-3
• Impingement of Acetabular Prostheses – ASTM F2582
• Wear of Total Intervertebral Spinal Disc Prostheses – ISO 18192-1; ISO 18192-2
• Static and Fatigue Testing of Orthopaedic Implants.