SELL and Sepsis: This study examines the changes in cell surface markers of neutrophil and monocyte activation, namely, L-selectin (CD62L), CD64, CD11b, CD18, and CXCR1 in the perioperative period to definitive orthopaedic surgery, to predict poor outcomes of postoperative sepsis and MOF at a clinically meaningful time point for decision making about planned urgent surgery.