Emerging ideas: can erythromycin reduce the risk of aseptic loosening?

BACKGROUND: Persistent inflammatory reaction to wear debris causes periprosthetic osteolysis and loosening. Some authors have advocated pharmaceutical approaches to reduce the inflammatory reaction. Erythromycin has antiinflammatory effects independent of its antimicrobial properties. Although oral erythromycin reportedly inhibits periprosthetic tissue inflammation in patients with aseptic loosening, long-term systematic erythromycin treatment is not recommended owing to its side effects. Therefore, it would be advantageous to restrict erythromycin delivery to the inflammatory periprosthetic tissue without causing side effects. QUESTIONS/HYPOTHESES: Erythromycin eluted from hydroxyapatite-coated titanium (Ti) pins inhibits periprosthetic tissue inflammation and osteolysis. METHOD OF STUDY: We propose restricting erythromycin delivery to the inflammatory periprosthetic site. A previously described rat model of ultrahigh molecular weight polyethylene (UHMWPE) particle-induced periprosthetic tissue inflammation and osteolysis will be used to test the effect of local delivery of erythromycin via Peri-Apatite(TM)-coated Ti implants. The outcome measures will include bone ingrowth (μCT), implant stability (pullout test), and histologic analysis of periprosthetic tissues. SIGNIFICANCE: Pharmacologic intervention aimed at slowing, preventing, or reversing the aseptic loosening process would represent an advance in the management of joint replacement. Erythromycin may be appropriate for prophylactically treating patients who have repeated revision surgery and/or show early signs of progressive osteolysis after arthroplasty.