Purpose: Intravasation of intramedullary contents and immune activation under the stimulus of cytokines and other inflammatory mediators released during canal preparation are presumed to be significant factors in the evolution of acute lung injury following stabilization of femoral shaft fractures with intramedullary nailing.

We aimed to quantify the development of acute endo-thelial permeability changes (within 4hours from canal instrumentation) with the reamed (RFN) and unreamed (UFN) nailing technique and assess the effect of coexisting lung contusion.

Materials and methods: A standardized sheep model (n=8 animals/group) was used. In the control groups, a thoracotomy without lung injury was performed prior to canal instrumentation. In the study groups a lung contusion of the right middle and lower lobe was induced. Osteosynthesis of the femur was carried out by the reamed (group RFN; standard Synthes reamer, old version) and unreamed technique (group UFN). Bronchoalveolar lavage was performed in order to assess the extent of lung parenchymal damage (permeability). The amount of protein leakage (determination of protein (Lowry assay) and urea (biochemical test) in BALF and serum) at different time points was analysed. Polymorphonuclear leukocyte activation was quantified by chemi-luminescence. IL-8 and coagulatory disturbances (Protein C) were also measured. All animals were sacrificed four hours following canal instrumentation and histological analysis was performed.

Results: In the control groups both the reamed and the unreamed nailing techniques were associated with a significant increase in pulmonary permeability compared to baseline values, p< 0.05. The experimental lung contusion induced prior to canal instrumentation caused also a significant increase in pulmonary permeability compared to baseline values. However, the subsequent canal instrumentation amplified further, significantly so, the degree of pulmonary permeability only in the reamed group (RFN).Both the activation of leukocytes and IL-8 release were also significantly raised following lung contusion and reamed femoral nailing compared to the UFN group with lung contusion (data not shown). Histological analysis illustrated the presence of fat globules in the pulmonary vasculature.

Conclusion: In a standardised sheep model without chest injury, instrumentation of the femoral canal with the reamed and the unreamed nailing techniques induced a rise in pulmonary permeability changes. In the presence of lung contusion, reamed intramedullary femoral nailing provoked a further increase in pulmonary permeability damage, IL-8 release and leukocyte activation. The findings of this study support the view that reaming of the femoral canal can act as an additional stimulus for adverse outcome in the presence of co-existing chest trauma.