J Korean Neurosurg Soc.  2013 May;53(5):305-308. 10.3340/jkns.2013.53.5.305.

Non-Traumatic Myositis Ossificans in the Lumbosacral Paravertebral Muscle

• Jung D
• Cho KT
• Roh JH

• KMID: 1426201
• DOI: http://doi.org/10.3340/jkns.2013.53.5.305

Abstract

Myositis ossificans (MO) is a benign condition of non-neoplastic heterotopic bone formation in the muscle or soft tissue. Trauma plays a role in the development of MO, thus, non-traumatic MO is very rare. Although MO may occur anywhere in the body, it is rarely seen in the lumbosacral paravertebral muscle (PVM). Herein, we report a case of non-traumatic MO in the lumbosacral PVM. A 42-year-old man with no history of trauma was referred to our hospital for pain in the low back, left buttock, and left thigh. On physical examination, a slightly tender, hard, and fixed mass was palpated in the left lumbosacral PVM. Computed tomography showed a calcified mass within the left lumbosacral PVM. Magnetic resonance imaging (MRI) showed heterogeneous high signal intensity in T1- and T2-weighted image, and no enhancement of the mass was found in the postcontrast T1-weighted MRI. The lack of typical imaging features required an open biopsy, and MO was confirmed. MO should be considered in the differential diagnosis when the imaging findings show a mass involving PVM. When it is difficult to distinguish MO from soft tissue or bone malignancy by radiology, it is necessary to perform a biopsy to confirm the diagnosis.

Keyword

Myositis ossificans; Lumbosacral spine; Paravertebral muscle

MeSH Terms

Biopsy
Buttocks
Diagnosis, Differential
Magnetic Resonance Imaging
Muscles
Myositis
Myositis Ossificans
Osteogenesis
Physical Examination
Thigh

Figure

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  Fig. 1 Lateral X-ray and T2-weighted sagittal magnetic resonance imaging of the lumbosacral spine. A : Lateral lumbosacral spine X-ray shows calcific density near the spinous process of L5 and S1 (white arrows). B : T2-weighted sagittal magnetic resonance imaging shows heterogeneous high signal intensity at the paravetebral muscle from L5 to S2.

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  Fig. 2 Axial magnetic resonance imaging and computed tomography of the lumbosacral spine. A and B : T2- (A) and T1-weighted axial magnetic (B) resonance imaging shows a heterogeneous high signal intensity mass in the left paravetebral muscle. Neither edema nor low signal intensity in the surrounding tissue are found. C : T1-weghted postcontrast magnetic resonance imaging shows no enhancement of the mass. D : Computed tomography reveals an inhomogenously calcified mass, and the periphery of the mass is more calcified. The mass is in continuity with the left-side lamina, facet joint of the L5, and the sacrum.

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  Fig. 3 Histopathologic study. Pathologic specimen shows osteocartilagenous tissue in the fibrous tissue and no malignant cell is found. A transition from immature woven bone (black arrows) to mature lamellar bone (white arrows) is present and normal osteocytes (arrow heads) are seen (Hematoxylin & Eosin stain, ×400).

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