Age / Sex : 16 / M

C.C.: right foot drop 

PHx: Injury during football game on Oct. 4th, 2006
        Development of right foot drop on the morning of Oct. 5th  

acute compartment SD

Discussion

Findings:
 - Marked swelling of tibialis anterior, extensor digitorum longus, extensor hallucis longus muscles with heterogeneous signal intensities on T1- and T2-weighted images suggesting hemorrhage and edema
- Surrounding soft tissue edema and hemorrhages
- Fluid collections in the fascial planes.

Diagnosis: Acute anterior compartment syndrome

Discussion:
- Compartment syndrome occurs when the pressure inside a closed fascial compartment increases to the point where it compromises the blood supply to the structures. Impairment of myoneural function and necrosis of soft tissues are followed.
- There are four anatomic compartments in the leg: the anterior, posterior, deep posterior (medial), and anterolateral. The anterior compartment muscles include the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus, and the peroneus tertius. The anterior compartment neurovascular bundle consists of deep peroneal nerve and the anterior tibial artery.
- Acute compartment syndrome is related to fracture or severe trauma and is associated with resting intracompartmental pressure greater than 30 mmHg. Patients often present with pain that is disproportionate to the injury. There is palpable swelling (possibly with tense skin), pallor, paralysis, and paresthesias. The distal pedal pulses are usually intact.
- MR techniques using axial STIR or FS PD FSE sequences are sensitive to early changes of muscle compartment edema, which is seen as an infiltrative or feather-like pattern of hyperintensity. Bulging and hyperintensity may also be seen in the adjacent fascia. Other MR findings: Loss of normal muscle striations, Subacute hemorrhage, Foci of hemosiderin deposition, Enlargement and peripheral convex bowing of affected muscle group, Calcification (in chronic compartment syndrome), fat and muscle atrophy (in chronic compartment syndrome), Chronic fibrous replacement, calcific myonecrosis (liquefied necrotic muscle and with a calcific shell), T1 images may be normal in exertional compartment syndrome., Diffuse hyperintensity within the cross-sectional anatomic boundaries of affected muscle and proximal/ distal extension on FS D FSE images, Fluid, hemorrhage, and edema between muscles in the fascial planes, Edema, rhabdomyolysis, and fascial convexity, Subcutaneous tissue edema, Intermediate to increased muscle signal on FS PD FSE or STIR images in exertional compartment syndrome, Muscle herniation.
- Untreated, compartment syndrome leads to nerve and muscle ischemia, and after 12 hours there is usually permanent injury, including muscle necrosis and Volkmann’s contracture (fibrous contracture and neurologic damage). Surgical decompression is required, and fasciotomy procedures include fibulectomy, perifibular fasciotomy, or double-incision fasciotomy. Reperfusion injury is a potential complication.

References:
1. Stoller DW and Ferkel RD. The ankle and foot. In: Stoller DW. Magentic resonance imaging in orthopaedics and sports medicine, 3rd ed. Philadelphia: Lippincott Williams & Wilkins 2007:996-1000