The forearm is divided into 3 compartments: the volar compartment (separated into deep and superficial), the dorsal compartment (also divided into deep and superficial), and the lateral compartment (often called the mobile wad). Compartment syndrome will most often affect the volar compartment.
Classic history and presentation: Patients will typically present after a high-energy trauma with increasing pain and tight compartments on physical examination. Diagnosis can be made with physical examination alone. The most sensitive finding in FCS is out-of-proportion pain with passive stretching of the fingers and thumb. The hand is typically held in an "intrinsic minus position" in which the metacarpophalangeal (MCP) joints of the digits are hyperextended, the interphalangeal (IP) joints are flexed, the thumb is held in adduction, and the wrist is flexed.
If there is a high suspicion for FCS, consultation with a hand surgeon / orthopedic surgeon should not be delayed.
ICP can be used if the examination is equivocal or if the patient is obtunded / intubated and unable to participate in an examination. A compartment pressure of ≥ 30 mm Hg or within 30 mm Hg of the diastolic blood pressure (called ΔP) is diagnostic. Pressures must be checked before anesthesia, as this can falsely lower the diastolic blood pressure.
AFCS has several causes, ranging from prolonged compression from patients being found down to high-energy trauma. Proper assessment of the patient includes removal of any tight dressings / casts / splints.
Causes of FCS include fracture, penetrating trauma, infection, arterial injury, crush injury, constrictive dressings, bleeding disorders, reperfusion, injection injury, casting, spider bites, in utero compression, suction injury, burns, snake bites, extravasation of infusion, injection of illicit drugs, regional anesthesia, and prolonged compression.
Prevalence: While the forearm is the most common site of compartment syndrome in the upper extremity, it has a relatively low prevalence. It can affect any age or sex.
The most common clinical scenarios are:
- High-energy trauma
- Fractures –
- Increased pressure within a fibro-osseous space leads to decreased tissue perfusion from swelling, causing decreased venous outflow. The imbalance between arteriole patency and venule collapse causes inflow to exceed outflow in the compartment, causing the increased pressure.
- When the pressure increases to greater than the capillary pressure, there is decreased microcirculation to the muscles and nerves, leading to cell death. Muscle necrosis can occur at ΔP greater than 20 mm Hg within 4 hours.