Acute Compartment Syndrome

The classic features such as pain, pallor, paresthesias, paralysis, and pulselessness are all late findings of acute compartment syndrome and are associated with irreversible damage. However, pain out of proportion to injury and pain with passive stretch of muscles are early symptoms that require further attention and monitoring.⁸

The earliest objective finding on physical examination is compartment firmness.⁸ Unfortunately, the sensitivity of physical examination by orthopedic physicians is low (22%-26%) on cadaver models with elevated compartment pressures.¹⁸ Peripheral nerve tissue is very sensitive to ischemia and will stop functioning after 75 minutes.⁹ A review of clinical findings in acute compartment syndrome showed that the positive predictive values of these individual symptoms are low, but there is a high likelihood of compartment syndrome when at least three clinical findings are present simultaneously.¹⁹ In patients who are at high risk for developing acute compartment syndrome, but who may not be able to describe or who do not show clear symptoms (eg, patients who are obtunded, intubated, or very young/old), compartment pressure measurement can be a valuable aid in the diagnosis.

Compartment Pressure Measurement

There are several readily available methods to directly measure the compartment pressure. It is imperative to measure the compartment pressure closest to the fracture location (within 5 cm) because the pressure dissipates as distance increases from the fracture site.²⁰

Solid-State Transducer Intracompartmental Catheter. The Stryker Intra-Compartmental Pressure Monitor System (Stryker Surgical) is a commonly used solid-state transducer intracompartmental catheter (STIC) that allows measurement of compartment pressure.

The STIC system consists of a side-port needle, syringe of saline flush, and a digital read-out manometer. It has been validated against commonly used alternatives and found to be accurate^21,22 with a confidence interval between ± 5 to 6.23. This device uses a side port needle to allow for testing multiple compartments with the same needle as it is less likely to be occluded by tissue when compared to a standard needle.

The following technique should be employed to properly measure compartment pressure using the Stryker STIC device²³:

1. Place the side port needle on the tapered end of the diaphragm chamber.
2. Connect the prefilled syringe of normal saline to the diaphragm chamber.
3. Place the diaphragm chamber in the pressure monitor with the black side down and push until it is seated in the device.
4. Close the cover until it snaps.
5. Place the needle up and fill the system with normal saline from the syringe until there are no air bubbles in the system.
6. Turn the pressure monitor on.
7. Select an intended angle and press the “Zero” button and wait until it reads “00.”
8. Under sterile technique and appropriately anesthetized skin, insert the device into the compartment. Once in the compartment, slowly inject a small amount of saline into the compartment and record the provided number.

For details on needle-placement techniques, including depths, see Figures 1 to 4 for lower extremity compartments and Figures 5 to 7 for upper extremity compartments.²⁴

Arterial Line Transducer System. An arterial pressure monitoring system can be adapted to measure compartment pressures. This technique has been validated against commercially available products.1,7,8

The following technique should be followed to properly measure compartment pressure using an arterial monitoring system^25,26:

1. Connect 1 L of normal saline to the pressure-monitoring tubing.
2. Place the normal saline into a pressure bag.
3. Flush the line and all stopcocks in the pressure monitoring tubing.
4. Inflate the pressure bag to 300 mm Hg.
5. “Zero” the system that is level with the compartment you are testing.
6. Connect an 18-gauge spinal needle to the arterial line tubing.
7. Flush fluid through the needle.
8. Under sterile technique and appropriately anesthetized skin, insert the needle into the compartment approximately 2 to 3 cm deep.
9. To confirm the needle is in the correct location, squeeze the compartment to note a transient rise on the monitor.

Laboratory Evaluation

Although the diagnosis of compartment syndrome is made by clinical findings and direct pressure measurement, laboratory tests can support the diagnosis.

Serum creatinine phosphokinase (CPK) is elevated with muscle necrosis. Both CPK and myoglobin proteins are glomerulotoxic, and acute kidney injury is a common complication of acute compartment syndrome. A CPK of greater than 1,000 IU/L has a sensitivity of 0.91 for acute compartment syndrome, but a specificity of only 0.52.2

In a multivariate model for predicting acute compartment syndrome, CPK greater than 4,000 IU/L, chloride greater than 104 mEq/L, and a blood urea nitrogen less than 10 mmol/L were found to be predictive of compartment syndrome during a patient’s hospital admission. No patient had compartment syndrome when all three variables were negative, and all patients with all three positive variables had acute compartment syndrome.²² This model was conducted on admitted patients during their inpatient hospital stay; therefore its application in the ED may not be valid, and the model has yet to be validated prospectively.