Different intramedullary nailing strategies display homogeneous circulatory neutrophil kinetics in a porcine model of polytrauma

Abstract text (incl. references and figure legends)

Introduction:

Increased incidences of inflammatory complications have been described after intramedullary nailing (IMN) in polytrauma. It is believed that neutrophils dysregulation has a key role in the development of post-traumatic inflammatory complications. The impact of fracture fixation strategy on neutrophil homeostasis is unclear. We hypothesized that reamed femoral nailing (RFN) is associated with a more profound systemic neutrophil response than alternative treatment options (unreamed femoral nailing, UFN and Reamed-Irrigation and Aspiration (RIA)-nailing in cardiopulmonary polytrauma.

Methods:

A standardized porcine polytrauma model (thoraco-abdominal trauma plus hypovolemic shock and a femur fracture) was used. Cardiopulmonary compensated animals were thereafter treated by different protocols of IMN. Three intervention groups (N=18) and a sham group (N=6) were composed: Gr. UFN, Gr. RFN and Gr. RIA. Circulatory immune cells were isolated at baseline, prior to surgery and after 6hrs. Cell-surface receptor kinetics of Mac-1/CD11b and FcyRIII/CD16 were determined by flowcytometry.

Results:

All 24 animals survived the observation period. As anticipated, an instant upregulation of Mac-1-expression on blood neutrophils was seen after trauma. (62,3% rise (P=0.01) vs. 29.3% rise (P=0.2) in the sham-group). The circulatory neutrophils fraction, however, increased first after IMNg (43.2% to 71.0% (P<0.01)). Neutrophil CD16-expression dropped gradually over time in all intervention groups (38,3% P<0.01). No statistically significant differences between intervention groups were seen.

Conclusion:

This standardized large-animal study shows that trauma-induced alterations in activation status of blood neutrophils precede later changes in circulatory neutrophil numbers. Furthermore, in cardiopulmonary trauma, applied IMN-nailing technique does not affect circulatory neutrophil numbers or cell surface expression profiles.

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