The Impact of Intramedullary Nailing of Tibia Fractures on the Innate Immune System.

INTRODUCTION: Inflammation after trauma is thought to be aggravated by intramedullary nailing (IMN) and predisposes to acute respiratory distress syndrome. Polymorphonuclear granulocytes (PMNs) are the main effector cells in this process. However, in patients with a femur fracture, the injury severity was the decisive factor for the PMN phenotype. A tibia fracture is often caused by a more moderate injury and might allow for a window to assess the innate immune response caused by IMN.

METHODS: A consecutive series of patients with a tibia fracture were included. The innate immune response was measured before and after IMN by plasma interleukin 6, PMN Mac1, and active FcγRII (FcγRII*) expression both before and after fMLF (N-formylmethionyl-leucyl-phenylalanine) stimulation. Furthermore, HLA-DR on monocytes was analyzed.

RESULTS: Twenty-five consecutive patients were included. Polymorphonuclear granulocyte fMLF-induced Mac1 and FcγRII* were decreased. In concordance, HLA-DR expression on monocytes was decreased in patients compared with control subjects. Intramedullary nailing was associated with a further decrease of HLA-DR-positive monocytes, whereas no changes in PMN phenotype or plasma interleukin 6 levels were observed.

CONCLUSION: Intramedullary nailing of a tibial fracture did not affect the PMN phenotype. The impact from injury determined the PMN phenotype. In contrast, the monocyte phenotype changed after the additional insult by IMN in patients with an isolated tibial fracture.