Early definitive fracture fixation (EDFF) does not alter circulatory neutrophil activation status in physiologically restored polytrauma: a 72-h porcine observation study

Abstract Dysregulation of the cellular innate immune system, particularly involving leukocytes and mainly neutrophils, underlies post-traumatic inflammatory complications. Early definitive fracture fixation (EDFF) triggers immune activation and may exacerbate inflammatory complications, especially in polytraumatized patients. Although, stable polytrauma patients may benefit from EDFF, a staged treatment strategy using temporary external fixation is most often applied. To justify this staged surgery, we hypothesized that EDFF is associated with increased presence and activation of neutrophils in experimental cardiopulmonary restored polytrauma. 12 adult pigs were subjected to a standardized polytrauma (ISS = 27), including a unilateral femoral fracture. Regarding surgical treatment strategy, animals were randomized to either EDFF consisted of intramedullary nailing or a Damage Control Orthopedics (DCO) group, which included external fixation. Animals were observed for 72 h following injury induction. Blood samples were collected at predefined time points. Routine laboratory analysis was performed and neutrophil numbers and activation status (Mac-1/CD11b and L-selectin/CD62L) were determined by flow cytometry. All animals survived the 72-h observation period. No significant differences were encountered in hemodynamics, ventilation and metabolic status between groups. The neutrophil-to-lymphocyte-ratios (NLR) increased after the intervention (pooled: baseline: 0.89 ± 0.08 vs. 4.5 h: 2.99 ± 0.11, P < 0.001). Thereafter NLRs gradually returned to baseline levels. Similar kinetics were seen in both study groups. Neutrophil CD11b-expression slightly increased 6.5 h after trauma and thereafter normalized in the pooled analysis of all animals. CD62L-expression dropped after trauma and thereafter started to rise significantly ( P < 0.05) in both groups. Peak levels were measured after 72 h. No differences in neutrophil CD11b/CD62L-expression level changes were seen between groups. In conclusion, this porcine polytrauma study shows that damage control orthopedics is not associated with altered systemic neutrophil presence or activation in physiologically restored polytrauma compared to EDFF. In line with the concepts from Safe Definitive Surgery, this implies avoidance of instant definitive fracture fixation may be redundant in specific patients with restored physiology.