The Bone & Joint JournalOnline First Trauma Hong Xu, Jin-Wei Xie, Li Liu, Duan Wang, Ze-Yu Huang, Zong-Ke Zhou Abstract Aims Monocyte-lymphocyte ratio (MLR) or neutrophil-lymphocyte ratio (NLR) are useful for diagnosing periprosthetic joint infection (PJI), but their diagnostic values are unclear for screening fixation-related infection (FRI) in patients for whom conversion total hip arthroplasty (THA) is planned after failed internal fixation for femoral neck fracture.