The
polyurethane elastomer (PU)
Corethane 80A (Corvita) is being considered as the acetabular bearing material in a novel total replacement hip joint. The biostability of
Corethane 80A was investigated in vitro (this work) and in vivo (reported separately) in a fully functioning ovine
total hip arthroplasty (THA) model, with the PU as the bearing layer in a prototype compliant layer acetabular cup. The in vitro studies assessed the resistance of
Corethane 80A to the main degradation mechanisms observed in
PUs: hydrolysis, environmental stress cracking (ESC),
metal ion oxidation (MIO) and calcification. The performance of the
polycarbonate PU
Corethane 80A was assessed alongside three other commercially available biomedical
PUs: polyether
PUs Pellethane 2363-80A (DOW Chemical) and PHMO-PU (CSIRO, not supplied as a commercial material) as well as
polycarbonate PU
ChronoFlex AL-80A (CardioTech). Chemical and structural variables that affect the properties of the materials were analysed with particular attention to the nature of the material's hard and soft segments. PU degradation was probed using a range of analytical tools and physical-testing methods, including mechanical testing, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and environmental scanning microscopy (ESEM).
Corethane 80A displayed the best overall resistance to hydrolysis, ESC, MIO and calcification, followed by ChronoFlex 80A and PHMO-PU.
Pellethane 80A was the least stable. This study provides compelling evidence for the biostability and effectiveness of
Corethane 80A and points to its suitability for use as a compliant bearing layer in hip
arthroplasty, and possibly also other joints.