Semi-quantitative assessment methods for backside polyethylene damage in modular total knee replacements

Two semi-quantitative grading methods (referred to as the Hood/Wasielewski-method and the Modified-method) were described and then applied to 52 retrieved tibial polyethylene inserts from modular total knee replacements. Their ability to assess backside surface damage was compared. The damage score correlation with the implantation period greater than 24 months was better using the Modified-method (R=0.524, p=0.006) than using the Hood/Wasielewski-method (R=0.328, p=0.102). Also, the Modified-method gave significantly higher damage scores for males with gamma-in-air irradiated polyethylene inserts whereas the Hood/Wasielewski-method did not. Thus, the damage score obtained using the Modified-method seemed to provide a better representation of clinical surface damage and possibly PE wear.