Evaluation of the Diagnostic and Therapeutic Value of Tissue Ultrafiltration in Patients at Risk of Acute Compartment Syndrome (ACS)

INCLUSION CRITERIA The target population for this study include adults ages 18-60 with high-energy injuries of the upper leg considered at risk for ACS at time of admission by virtue of their mechanism of injury, fracture pattern, clinical signs, or need to undergo fracture fixation surgery (internal or external fixation) within 48 hours of admission. Recruitment of participants will happen during hospital admission for treatment of injury. Eligible patients must meet all of the following criteria and be enrolled during one of two possible times: within 14 hours of injury, or prior to undergoing surgical intervention (internal or external fixation on the injured limb) within 48 hours of admission. Eligible patients will be: 1. Between the ages of 18 and 60 years 2. Have sustained a high-energy upper leg injury such as open or closed proximal tibial shaft fracture with displacement, comminution, or segmental pattern; proximal fibula fracture; bicondylar tibial plateau fracture; Schatzker IV medial knee fracture-dislocation; proximal leg injury due to shotgun, rifle, or other projectile, or severe crushing injury. 3. Patient can be enrolled in the study and study procedures initiated within 14 hours of injury,\* or be enrolled prior to undergoing urgent surgical intervention on the injured limb (defined as internal or external fixation) within 48 hours of admission. 4. Patient (or authorized legal representative) willing to sign informed consent. * If a patient has an eligible injury and is going to surgery within 2 hours (except for fasciotomy - which is an exclusion criteria), the patient can be enrolled and the study procedures initiated at the end of surgery. If an eligible patient is enrolled and there is no surgery anticipated within 2 hours, initiate study procedures immediately. EXCLUSION CRITERIA An individual who meets any of the following criteria will be excluded from participation in this study: 1. Patients not willing to participate 2. Patients with non-traumatic cases of acute compartment syndrome (e.g. severe exertion, snakebite, high-pressure injection injury) 3. Patients diagnosed with ACS or impending ACS such that immediate fasciotomy is recommended 4. Soft tissue wounds, including lacerations or abrasions, that are in a location that will interfere with safe insertion of indwelling pressure or TUF catheters (anterior - anterolateral aspect of the leg) 5. Patients not likely to follow-up (are homeless, incarcerated, live out-of-state). 6. Patients with known peripheral vascular disease 7. Non-ambulatory due to an associated complete spinal cord injury; Non-ambulatory before the injury due to a pre-existing condition. 8. Very low clinical concern for ACS at time of admission.