Prostaglandin E2 Synthesis by the Tissue Surrounding Ultrahigh Molecular Weight Polyethylene in Different Physical Forms

Publisher Website
Google Scholar
Abstract
Twenty mature, New Zealand white, female rabbits were divided into three groups. Using sterile technique, a 6-mm drill hole was made in the proximal tibia bilaterally. The marrow was scooped out underneath the hole. In Group 1, the left tibia received a bulk pellet of ultrahigh-molecular-weight polyethylene (UHMWP). The right tibia received UHMWP particles averaging 67 μm. In Groups 2 and 3 the right tibia received UHMWP particles averaging 16 μm. The left tibia functioned as a drilled, but nonimplanted, control. The animals in Groups 1 and 2 received regular water ad libitum. The animals in Group 3 drank water in which naproxen sodium was dissolved (1.375 mg/mL). The animals were killed at 16 weeks postoperatively. An equal volume of medullary canal contents was harvested sterily from the right and left tibia in each animal and maintained in tissue culture. The cumulative collection of tissue culture supernatants over a 3-day period was assayed for prostaglandin E2 (PGE2) by radioimmunoassay. Specimens from Group 1 produced on average 54.45 ± 12.77 ng PGE2 on the right side, and 65.85 ± 22.32 ng PGE2 on the left side [not significant (NS)]. The polyethylene (PE) particles were relatively large and could not undergo phagocytosis; these particles did not stimulate increased PGE2 production in comparison with bulk implants. Specimens from Group 2 produced 72.15 ± 13.60 ng PGE2 on the right side and 67.53 ± 16.59 ng PGE2 on the left side (NS). Specimens from Group 3 produced 28.40 ± 4.54 ng PGE2 on the right side and 33.30 ± 7.69 ng PGE2 on the left side (NS). Naproxen sodium significantly reduced PGE2 production on both the right and left sides in Group 3 compared with Group 2 (P < 0.05). UHMWP particles and PGE2 production have been implicated in the periprosthetic bone lysis associated with aseptic loosening in humans.