Calcific myonecrosis has been reported as a late sequela of compartment syndrome, injury to the common peroneal nerve, and injury to the lower extremity without documented compartment syndrome or neurological injury1-8,13-19. This rare condition has been reported to occur ten to sixty-four years after the initial injury and typically presents as an enlarging mass in the anterior compartment of the leg. The characteristic radiographic appearance is that of a large fusiform soft-tissue mass in the anterior compartment, with peripheral plaque-like calcifications and usually with a well defined border. The calcifications may extend along fascial planes13. Erosion of bone had been reported in only four patients8,13. The benign radiographic appearance usually allows the lesion to be differentiated from an enlarging malignant mass in the soft tissues7. A sterile abscess usually is found at the time of operative treatment, but there is a high prevalence of chronic draining sinuses and secondary infection3,7,8,18.
We report the case of a patient who was seen because of a painless, enlarging mass in the anterior and lateral compartments of the leg thirty years after he had been hit by an automobile. At the time of the initial injury, he had sustained damage to the knee, a partial sciatic-nerve palsy, and a probable compartment syndrome of the leg. The case of our patient differs substantially from previously reported cases of calcific myonecrosis in that there was extensive erosion of bone, giving the lesion the appearance of an invasive neoplasm.
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
†Department of Orthopaedics, University of California, Davis, Medical Center, 2230 Stockton Boulevard, Sacramento, California 95817.
A forty-nine-year-old man was referred for evaluation of a slowly enlarging mass in the right leg. Thirty years previously, he had been struck by an automobile while walking. He stated that he had sustained an injury to the ligaments of the right knee as well as a partial loss of motor and sensory function in both divisions of the sciatic nerve, with associated weakness of dorsiflexion of the ankle. Soon after the injury, he had reapir of the ligaments of the right knee. The medical records from the time of the injury and the operation were not available, and the patient could not recall which ligaments had been repaired. Fifteen years after the injury, he noticed a mass in the anterolateral aspect of the leg; the mass slowly increased in size. The medical history was otherwise unremarkable, and the patient did not have diabetes.
Physical examination revealed massive enlargement of the right leg: the circumference of the calf was thirty-seven centimeters compared with twenty-four centimeters on the contralateral side. The mass predominantly involved the anterior and lateral compartments of the leg and had the consistency of a tense, fluid-filled cyst. The range of motion of the knee was 0 to 100 degrees of flexion. The ankle had a 5-degree equinus contracture and 5 degrees of plantar flexion from this position. There was no motion of the subtalar joint. There was clawing of all of the toes. Motor strength was grade 0 (of 5) for dorsiflexion of the ankle, grade 3 for plantar flexion of the ankle, grade 0 for dorsiflexion of the toes, grade 0 for eversion of the hindfoot, and grade 0 for inversion of the hindfoot. Sensation was not present in the dorsum of the first web space and was subjectively diminished on the dorsal, plantar, medial, and lateral aspects of the foot. The contractures in the limb were consistent with the residua of a deep posterior compartment syndrome9,10.
Imaging Studies
Radiographs of the right leg that had been made when the patient was forty-two years old (seven years before he was seen by us) showed a large mass. The middle third of the fibula was sclerotic, and the tibia appeared uninvolved (Fig. 1-A). Plain radiographs of the right leg that were made when the patient was seen by us showed a large fusiform soft-tissue mass with extensive plaque-like and amorphous calcifications. The middle portion of the fibula was eroded, and there was a small area of cortical erosion involving the lateral aspect of the tibia (Fig. 1-B). The pathological process appeared to have progressed markedly since the time of the previous radiographs. Magnetic resonance imaging demonstrated a non-homogenous mass that had eroded and, in some areas, completely destroyed portions of the fibula (Fig. 2).
Operative Findings
The skin, subcutaneous tissue, and deep fascia appeared normal at the time of the operation. All of the tissues in the anterior and lateral compartments of the leg were completely necrotic, and bone spicules resembling rice bodies permeated the tissue, giving it a gritty texture. The was erosion of the anterior and lateral borders of the entire diaphysis of the fibula as well as scalloping of the posterior and medial borders, which were widely expanded into a thin shell over a distance of twelve centimeters. There was minimum erosion of the tibial cortex. No neurovascular bundles were present in either compartment. The blood loss was approximately 1600 milliliters, and two units of packed red blood cells were transfused during the operation. Frozen sections of multiple samples of tissue were evaluated in order to rule out malignant disease. Analysis of all of the specimens revealed necrotic debris, blood, fibrin, and multifocal areas of calcification. Specimens were sent for aerobic, anaerobic, fungal, and mycobacterial culture; all cultures were negative. The wound was closed over a suction drain, and a bulky compressive dressing was applied to the leg. Postoperatively, while still in the hospital, the patient was managed empirically with intravenous administration of antibiotics, including cefazolin (one gram every eight hours for three days) and gentamicin (400 milligrams every twenty-four hours for two days). The wound healed without drainage or infection. At the fourteen-month follow-up evaluation, the patient had no additional problems and no evidence of recurrence.
Pathological Findings
The pathological evaluation revealed that the major resection specimen consisted of necrotic tissue, skeletal muscle, and scant fragments of bone; the specimen was twelve by five by five centimeters. Histological evaluation demonstrated mostly necrotic soft tissue and bone admixed with blood and fibrin. Extensive calcification was noted. The wall of the cyst was densely fibrotic. The histological diagnosis was necrotic tissue.