The most frequent pathogenic organism in arthroplasty infections is Staphylococcus. The immune response impairment is a frequent finding in elderly people. Objective: to investigate the response of some cytokines and the effect of age in an experimental model of osteomyelitis.

Materials and methods. 40 adult male Wistar rats received a stainless steel needle, intramedullarily in the left tibia. Young rats (3 months old) and Old rats (22 months old) were alloted in: Group A: Sterile implant. Group B: Sterile implant + slime producing S. aureus. 9 weeks after surgery, rats were sacrified. Determinations: Cytokines (IL-1b, IL-2, L-4, IL-6, IL-10 and IL-12)(ELISA) in blood (previous to surgery and to sacrifice) and in tibia extract (after sacrifice); the number of bacteria in tibia and implant. The Wilcoxon, Mann-Whitney U test were used (p≤ 0.05 significant).

Results. Infection was detected in all the operated tibias in old rats receiving S.aureus, and in 7/10 of young rats. IL-2 levels increased in blood in the S.aureus group after surgery in old and young rats. Pre and postoperative IL-2 levels in blood were higher in old rats in both groups than in the corresponding groups of young rats. There was a decrease with age in blood of IL-4 (previous and after surgery), and a decrease of IL-1. S.aureus groups increased IL-1 levels in the operated tibia independently of age; increased IL-2 and IL-10 levels in young rats in the operated tibia; increased IL-4, IL-6 and IL-12 in old rats in blood, decreased IL-4 and increased IL-2 and IL-10 in blood in young rats

Conclusions. Significant differences in tibia infection were found with age. Old rats presented differences with young rats in cytokine response in an experimental model of osteomyelitis, showing an immune response impairment associated with old age.