Efficacy of periprosthetic erythromycin delivery for wear debris-induced inflammation and osteolysis

We have reported that oral erythromycin (EM) inhibits periprosthetic tissue inflammation in a group of patients with aseptic loosening. The purpose of this study was to assess the efficacy of local, periprosthetic EM delivery in a rat model. Uncoated Ti pins were press-fit into the right tibia of fourteen Sprague-Dawley rats following an intramedullar injection of UHMWPE (ultra high molecular weight polyethylene) particles. Revision surgeries were performed 2 months after the primary surgery. EM was applied to the Peri-Apatite (TM) (PA) layer of the titanium (Ti) pins. The previously implanted Ti pins were withdrawn and replaced with Ti pins coated either with (n = 7) or without (n = 7) EM. The rats were killed 1 month after revision surgery. The EM efficacy was evaluated by (MicroCT) mu CT and histology. mu CT analysis showed that bone volume percentage (BV/TV) was significantly higher in the EM-treated group compared to the untreated group (p < 0.05). Histological analysis showed that EM treatment inhibits UHMWPE particle-induced periprosthetic tissue inflammation compared to the untreated group. This study demonstrated that periprosthetic EM delivery reduced periprosthetic inflammation and improved the quality of surrounding bone.