Calcific myonecrosis. A late sequela to compartment syndrome of the leg.

The clinicopathologic features of calcific myonecrosis are presented from results of an examination of 3 cases of this rare syndrome and review of the literature. Calcific myonecrosis is a painful, expansile, calcified mass that develops in muscle several decades after lower extremity trauma that typically has been associated with vascular injury. Plain radiographs show a well-defined and heavily calcified mass replacing the leg musculature. The calcifications are present in a thin, linear pattern and are organized around the periphery of the lesion. Smooth erosion of the adjacent bone may be present, whereas magnetic resonance imaging shows a heterogeneous signal with enhancement limited to the periphery of the mass. Pathologic features consist of a centrally cystic mass arising in muscle filled with friable, tan to dark red, soft debris. The cyst walls are firm and fibrous and contain many needle-like, elongated, calcified shards of necrotic tissue composed of hypocellular fibrous tissue with focal aggregates of hemosiderin-laden macrophages. The cyst contents are composed of necrotic skeletal muscle and acellular amorphous debris containing many cholesterol crystals, fibrin, and recent hemorrhage, including focal aggregates of organizing thrombus. The pathologic findings suggest that calcific myonecrosis might expand with time by virtue of recurrent intralesional hemorrhage into a chronic calcified mass that eventually becomes symptomatic. Surgical intervention is associated with a high rate of complication, particularly in cases in which intralesional procedures have been done.