The Relationship Between Shelf Life and In Vivo Wear for Polyethylene Acetabular Liners

Although laboratory studies have correlated shelf life for gamma-irradiated-in-air polyethylene with material degradation, it is unknown whether this clinically affects wear. Therefore, we examined the relationship between shelf life and clinical wear for 152 gamma-irradiated-in-air acetabular liners. True wear rates were calculated from computer-assisted head penetration analyses of serial radiographs. Follow-up averaged 6.6 years. Shelf life averaged 11.8 months with 96% of liners having shelf lives of less than 3 years. Data analysis revealed no correlation between shelf life and true wear rates (r2 = 0.002; P = .60). This study provides useful information for surgeons concerned about shelf life as a potential cause of high wear in previously implanted components. For conventional liners in inventory less than 3 years, we found no evidence of increased wear in vivo.