This patient has developed a muscular compartment syndrome.
This condition happens after revascularization of an acutely ischemic limb in a patient who has an ischemic or traumatic injury to a muscle group that causes acute muscular edema.
Compartment syndrome is a painful condition caused by increased intracompartmental pressure, compromising perfusion and resulting in muscle and nerve damage within that compartment, resulting in edema of the muscle. Because many muscles are encased in an inelastic, fascial compartment, edema increases the volume, and ultimately the pressure, within the compartment. As the pressure builds up, muscle perfusion decreases, resulting in further ischemic injury, which worsens the edema. As the compartment pressure approaches 20-40 mm Hg, irreversible ischemic injury of muscles and nerves may occur, with motor or sensory loss or loss of the distal arterial pulses.
In this case, a fasciotomy was performed to open the compartment of the forearm.
Typically, the muscle bulges out at the point of excision, relieving the pressure and improving perfusion. Once the acute episode is resolved, the fasciotomy is closed with a split-thickness graft.