**9. Conclusion**

Our study provided further insight into the mechanism of aseptic loosening of hip arthroplasty. The most interesting aspect of this study is the evidence of elevated production of ROS, which are known to cause tissue fibrosis and may help explain the initiation of aseptic loosening. We feel that the thick pseudocapsule around loose prostheses is not an adaptive but a reactive tissue as a result of decreased degradation and increased formation of collagen matrix and proliferation of fibroblasts due to high oxidative stress. Furthermore, we demonstrated that elevated oxidative stress is associated with aseptic loosening of hip arthroplasty, suggesting that oxidative stress might induce periprosthetic osteolysis and subsequent loosening. Research in this line may help introducing new strategies for therapeutic prevention and/or treatment of osteolysis and subsequent aseptic loosening of total hip arthroplasty.
