Predicting Acute Compartment Syndrome (PACS)

Specific Aim 1: Prospectively enroll and follow for 6 months a sample of 200 patients.
Patients will receive continuous tissue perfusion monitoring using NIRS in all 4 leg
compartments and intramuscular pressure (IMP) via indwelling catheters placed in the anterior
and deep posterior compartments. These measures will be blinded and not provided in real time
to treating physicians. All clinical care, including diagnosis of ACS, will be according to
current standard-of-care practiced at each institution.

Specific Aim 2: Convene expert panels of 5 orthopaedic surgeons experienced in the diagnosis
and treatment of ACS to retrospectively assess the likelihood that each patient had ACS. This
retrospective assessment will be based on a 'patient profile' summarizing data collected as
part of this study.

Specific Aim 3: Determine the extent to which clinicians agree in retrospective assessments
of the likelihood of ACS.

Hypothesis: On the basis of known clinical and functional outcome at 6 months and monitoring
information, clinicians will agree on the likelihood of ACS in < 90% of cases.

Specific Aim 4: Model the panel's assessment of the likelihood of ACS as a function of data
available to the clinician within the first 48 hours of injury using a training set of the
data. This model can then be used to compute a point estimate of the risk of ACS (and
associated 95% confidence interval) for any given patient.

Specific Aim 5: Assess, for patients in a test/validation data set, the performance of the
model in predicting the panel's assessment of the likelihood of ACS.

Hypothesis: In < 95% of the cases, the panel's assessment of the likelihood of ACS will fall
within the 95% interval of uncertainty predicted by the model.

Inclusion Criteria:

1. Patient between the ages of 18 and 60

2. Weight of > 88 lb/40 kg

3. Patient presents with one of the following injuries:

- Closed tibial shaft fracture with displacement, comminution, or segmental pattern

- Closed bicondylar tibial plateau fracture or medial tibial plateau-knee
dislocation

- Open tibial shaft fracture (Gustilo Type I, II or IIIA)

- Open bicondylar tibial plateau fracture or medial tibial plateau-knee dislocation
(Gustilo Type I, II or IIIA)

- Severe soft tissue crush injury to lower leg

- Gun shot injury to leg

- Proximal fibula fracture

4. Injury resulted from a high-energy mechanism (e.g. pedestrian struck; fall > 10 ft;
MVA/MCA at speed > 30 mph; injury due to shotgun, rifle, or projectile)

5. The injury occurs no more than 12 hours prior to initiation of monitoring

6. If bilateral leg injuries are present, only the limb that is most severely injured in
the judgment of the investigator will be studied

7. At least one extremity must be uninjured to serve as a control for muscle oximetry

8. Patients may have other injuries except as noted below under exclusion criteria

9. Patient may have impending compartment syndrome at time of evaluation; however, the
surgeon must be able to initiate monitoring and take at least one set of muscle
pressures and obtain one set of tissue oxygenation measurements prior to performing
fasciotomy

Exclusion Criteria:

1. Soft tissue wounds that will interfere with monitoring (i.e. the insertion of
indwelling pressure catheters and/or application of NIRS pads to the anterior and deep
posterior compartments of the leg)

2. Patients with known peripheral vascular disease

3. Informed consent from the patient or from a legally authorized representative (LAR) is
not obtained early enough to begin monitoring within 12 hours post-injury

4. Non-ambulatory due to an associated complete spinal cord injury

5. Non-ambulatory before the injury due to a pre-existing condition

6. Patient speaks neither English nor Spanish

7. Severe problems with maintaining follow-up (e.g. patients who are homeless at the time
of injury or those how are intellectually challenged without adequate family support).

8. Prior extensive traumatic injury requiring surgery to either lower extremity.