Gene Expression in Lower Extremity Acute Traumatic Compartment Syndrome

Acute compartment syndrome is associated with infection, contractures, fracture non-union, and chronic pain syndromes. The most common cause of acute compartment syndrome is fracture. Individuals with compartment syndrome associated with a lower extremity fracture have demonstrated worse patient reported outcome scores compared to individuals who suffer lower extremity fractures alone.

The pathophysiology of compartment syndrome has been traditionally described as loss of tissue perfusion and subsequent cellular anoxia related to supra-physiologic pressure within a closed myofascial space. Both animal and clinical studies have suggested that compartment syndrome develops when the intra-compartmental pressure approaches systemic diastolic blood pressure. However, other studies have demonstrated that high absolute compartment pressures and/or narrowed delta pressures have poor sensitivity for predicting compartment syndrome, suggesting that the pathophysiology of compartment syndrome is likely more complex than the currently accepted understanding of the disease process.

Animal models suggest that fracture promotes inflammation and exacerbates microvascular dysfunction, which may act synergistically with elevated intra-compartmental pressures to create clinical compartment syndrome. It is known that fracture causes microvascular damage and inflammation in surrounding muscle tissue. Several models have demonstrated that the microvascular environment in compartment syndrome is characterized by tenuous, intermittent blood supply to the musculature, which displays asymmetric microvascular dysfunction in response to elevated compartment pressures. Similarly, recent animal research has demonstrated that elevated intra-compartmental pressure is associated with a pro-inflammatory state, which directly contributes to skeletal muscle injury and may exacerbate microvascular injury.

It is unknown whether individual genomic and/or transcriptomic variability is clinically relevant with respect to response to fracture or the development of compartment syndrome. However, there is evidence from the vascular surgery literature in both animal and human models that individual variability in gene expression meaningfully affects skeletal muscle response to acute ischemia. The investigators hypothesize that there may be an individual pre-disposition to developing clinical compartment syndrome in the setting of at-risk fractures which manifests itself in the cellular response to inflammation and low grade ischemia. The overarching goal of this study is to characterize cellular level dysfunction in human compartment syndrome and to determine whether there are unique gene expression profiles associated with the development of clinical compartment syndrome. Specific aim 1 of this study is to compare genetic and transcriptomic differences individuals with high-risk tibia fractures who do not develop compartment syndrome and individuals with high-risk tibia fractures who do develop clinical compartment syndrome. Specific aim 2 of this study is to to compare genetic differences between acute compartment syndrome patients and chronic exertional compartment syndrome patients.