Compartment Syndrome and Fasciotomy

Teaching notes

Acute compartment syndrome (ACS) is a surgical emergency in which rising pressure within a closed fascial space impairs perfusion of the contained muscles and nerves. Irreversible muscle loss begins within hours of ischemia onset, making prompt recognition and complete fasciotomy decisive.

Compartmental anatomy

The leg has four compartments: anterior, lateral, superficial posterior, and deep posterior. Each is a distinct fascial envelope with its own muscle groups, nerves, and vessels. The deep posterior compartment contains tibialis posterior, flexor digitorum longus, flexor hallucis longus, and the posterior tibial nerve and vessels; it must be opened deliberately during fasciotomy because it is not reached by a lateral skin incision alone.

The thigh has anterior, posterior, and adductor compartments. The forearm has volar (superficial and deep layers), mobile wad, and dorsal compartments. The foot has interosseous spaces, medial, central, and adductor hallucis compartments, with the calcaneal compartment at hindfoot level.

• Anterior leg: tibialis anterior, EDL, EHL, deep peroneal nerve, anterior tibial vessels.
• Superficial posterior leg: gastrocnemius, soleus, plantaris, sural nerve.
• Deep posterior leg: tibialis posterior, FDL, FHL, posterior tibial nerve and vessels.

Clinical diagnosis

Pain out of proportion to the injury and pain with passive stretch of compartment muscles are the earliest clinical findings. Paresthesia, weakness, swelling, and loss of pulse are progressively later. Paralysis and absent pulse are late signs that carry a poor prognosis; they must never be awaited as a threshold for intervention.

In young children the classical signs are unreliable. The three A's — anxiety, agitation, and an increased analgesic requirement — are the clinical alerts. Normal resting compartment pressure is higher in children (13.3 to 16.6 mm Hg) than in adults (5.2 to 9.7 mm Hg), so the adult absolute-pressure threshold does not transfer directly to a child.

• One positive sign: probability of confirmed ACS is less than 26%.
• Three or more findings: probability exceeds 90%, but paralysis is already present.

Pressure measurement and the delta P criterion

Delta P equals diastolic blood pressure minus compartment pressure. The Rockwood threshold for adults is a delta P at or below 30 mm Hg. A single measurement is insufficient in most patients; the pressure trend and the duration of low delta P matter. The Edinburgh protocol calls for immediate fasciotomy when delta P remains at or below 30 mm Hg for more than two hours with a rising compartment pressure.

When the clinical picture is unambiguous, Campbell states that pressure measurement is not required and the surgeon should open the compartment without delay. When the patient is not alert and examination is unreliable, serial pressure monitoring becomes essential.

• Muscle dysfunctional after 2 to 4 hours of ischemia; irreversible loss after 4 to 12 hours.
• Nerve injury: abnormal after 30 minutes; irreversible after 12 to 24 hours.

Leg fasciotomy technique

The standard two-incision technique releases all four leg compartments. A lateral incision approximately 2 cm anterior to the fibula, over the septum between the anterior and lateral compartments, gives direct access to both fasciae. A medial incision approximately 1 to 2 cm posterior to the medial tibial border allows release of both posterior compartments; the surgeon must retract the superficial compartment posteriorly and elevate it off the tibia to enter the deep compartment.

The superficial peroneal nerve exits the fascia approximately 10 cm above the lateral malleolus and must be identified during the lateral incision. In the medial incision field, the saphenous vein and nerve require identification and protection, as do the posterior tibial vessels and nerve.

Fasciotomy in other regions and wound care

For the thigh, a single lateral incision releases anterior and posterior compartments; a separate medial incision is added when the adductor compartment requires decompression. For the forearm, a volar incision from the lacertus fibrosus to the carpal tunnel, with the deep interval opened between flexor carpi ulnaris and flexor digitorum superficialis, is performed first; if dorsal pressure remains elevated, a straight dorsal incision follows. For the foot, two dorsal incisions over the second and fourth metatarsals decompress the interosseous spaces; a medial incision addresses the calcaneal compartment in hindfoot injuries.

Fasciotomy wounds must never be closed primarily; compartment pressure may remain elevated. A second-look at approximately 48 hours allows closure only when all muscle groups are confirmed viable.