Non-Traumatic Myositis Ossificans in the Lumbosacral Paravertebral Muscle
A 42-year-old man presented with a 4-month history of low back pain and pain in the left posterolateral part of the buttock and thigh. The patient appeared healthy and had no history of previous trauma or musculoskeletal disease. On physical examination, a slightly tender, hard, and fixed mass was palpated in the left PVM at the L5 level. Complete blood cell count, erythrocyte sedimentation rate, and blood chemistry values including serum calcium, phosphate, C-reactive protein, and alkaline phosphatase were all within normal limits.\nLateral lumbosacral spine X-ray showed calcific density near the spinous process of L5 and S1 (). T2-weighted sagittal magnetic resonance imaging (MRI) showed heterogeneous high signal intensity at the PVM from L5 to S2 (). Axial MRI showed a heterogeneous high signal intensity mass in T1- and T2-weighted image in the left PVM, and no enhancement of the mass was found in the Gadolinium-enhanced T1-weighted MRI (). Findings on computed tomography revealed an inhomogenously calcified mass, and the mass was in continuity with or eroding the left-sided lamina, facet joint of the L5, and the sacrum ().\nThe lack of typical imaging features required an open biopsy, which showed no evidence of malignancy and confirmed MO (). The patient was followed up for 6 months after the biopsy and the patient's pain had been reduced gradually. However, a follow-up image could not be obtained, because of the patient's refusal due to financial difficulties.