CLINICAL RESULTS OF CROSS-LINKED POLYETHYLENE SOCKETS

Introduction: The excellent character of cross-linked polyethylene on wear has been reported from basic researches. However, few clinical results were seen about irradiated polyethylene sockets. This presentation reports a long-term clinical result of irradiated polyethylene sockets. Material and method: Two 100M-rad gamma irradiated polyethylene sockets were retrieved, each 25 and 27 years after implantation. Socket joint surface were scanned by 3-D scanner and analyzed. On the other hand, ten patients had total hip replacements with 6.5M-rad irradiated polyethylene sockets. Anterior-posterior and lateral radiograph were taken and the movement of the head to the socket was analyzed by 3-D wear measurement software GAWDI. The results were compared to conventional polyethylene sockets of matched patients. Results: Wear of the 100M-rad sockets were 0.23mm/ 25yrs and 0.46mm/27yrs respectively. The direction of wear was observed over the whole surface. Wear of the conventional polyethylene socket retrieved 15yrs after implantation were 2.54mm/15yes and 1.76mm/12yrs. The wear were toward weight bearing directions. The average movement of heads in 6.5M-rad irradiated polyethylene sockets was 0.22mm one year post operation and its direction was toward backside of patients’ body. The average movement of conventional polyethylene sockets was 0.24mm one year post operation and its direction was just the same as irradiated polyethylene sockets. Discussion: The difference of long term results between 100M-rad irradiated polyethylene and conventional one was obvious. A definite wear path way was observed on conventional polyethylene sockets. However, it was ambiguous on 100M-rad irradiated polyethylene because it was small or it did not exist. No remarkable difference was observed in short term after operation between 6.5M-rad irradiated and conventional sockets. The present analysis suggests that a high dose irradiated polyethylene socket may benefit a good long-term clinical result.