Compartment syndrome is a self-perpetuating cascade of events. It begins with the tissue edema that normally occurs after injury (eg, because of soft-tissue swelling or a hematoma). If edema develops within a closed fascial compartment, typically in the anterior or posterior compartments of the leg, there is little room for tissue expansion, so interstitial (compartment) pressure increases. As compartment pressure exceeds the normal capillary pressure of about 8 mm Hg, cellular perfusion slows and may ultimately stop. (NOTE: Because 8 mm Hg is much lower than arterial pressure, cellular perfusion can stop long before pulses disappear.) Resultant tissue ischemia further worsens edema in a vicious circle.
As ischemia progresses, muscles necrose, sometimes leading to rhabdomyolysis, infections, and hyperkalemia; these complications can cause loss of limb and, if untreated, death. Hypotension or arterial insufficiency can compromise tissue perfusion with even mildly elevated compartment pressures, causing or worsening compartment syndrome. Contractures may develop after necrotic tissue heals.
Compartment syndrome is mainly a disorder of the extremities and is most common in the lower leg and the forearm. However, compartment syndrome can also occur in other locations (eg, upper arm, abdomen, buttock).
Common causes of compartment syndrome include
Rare causes include snakebites, burns, severe exertion, drug overdose (of heroin or cocaine), casts, tight bandages, and other rigid circumferential devices that limit swelling and thus increase compartment pressure. Prolonged pressure on a muscle during coma may cause rhabdomyolysis.
The earliest symptom of compartment syndrome is
It is typically out of proportion to the severity of the apparent injury and is exacerbated by passive stretching of the muscles within the compartment (eg, for the anterior leg compartment, by passive ankle plantar flexion and toe flexion, which stretches the anterior compartment muscles). Pain, one of the 5 Ps of tissue ischemia, is followed by the other 4: paresthesias, paralysis, pallor, and pulselessness. Compartments may feel tense when palpated.
Diagnosis of compartment syndrome must be made and treatment started before pallor or pulselessness develops, indicating necrosis. Clinical evaluation is difficult for several reasons:
Thus, in patients with at-risk injuries, clinicians must have a low threshold for measuring compartment pressure (normal ≤ 8 mm Hg), usually with a commercially available pressure monitor. Compartment syndrome is confirmed if compartmental pressure is more than about 30 mm Hg or within about 30 mm Hg of diastolic blood pressure (BP).
(See also the American Academy of Orthopaedic Surgeons' clinical practice guideline for the management of acute compartment syndrome.)
Initial treatment of compartment syndrome is removal of any constricting structure (eg, cast, splint) around the limb, correction of hypotension, analgesia, and supplemental oxygen as needed.
Usually, unless compartment pressure decreases rapidly and symptoms abate, urgent fasciotomy is required. Fasciotomy should be done through large skin incisions to open all fascial compartments in the limb and thus relieve the pressure. All muscle should be carefully inspected for viability, and any nonviable tissue should be debrided.
Amputation is indicated if necrosis is extensive.
Once the process triggering compartment syndrome begins, compartment syndrome tends to increase in severity.
Consider compartment syndrome if pain appears to be out of proportion to the severity of injury and is increased by passive stretching of muscles within the compartment or if the compartment is tense.
Measure compartment pressure to confirm the diagnosis; a finding of more than about 30 mm Hg or within about 30 mm Hg of diastolic BP confirms it.
Unless the disorder resolves rapidly after initial treatment, fasciotomy must be done as soon as possible.
American Academy of Orthopaedic Surgeons' clinical practice guideline for the management of acute compartment syndrome