Myolysis of the erector spinae muscles as the cause of scoliosis in osteoid osteoma of the spine.

Abstract

A case of an osteoid osteoma at the lower thoracic spine with scoliosis is reported. To suggest that myolysis of the erector spinae muscles reflected by signal abnormalities on magnetic resonance images causes back pain, protective muscle contraction, and scoliosis. Osteoid osteomas of the spine are frequently accompanied by scoliosis. The proposed mechanism of the scoliosis has been explained as a postural adaptation of the spine through predominant muscle spasm on the concave side. The history of the patient and radiologic, magnetic resonance imaging, and histologic findings of the peritumoral area were reviewed. Magnetic resonance images showed signal abnormalities on muscles surrounding the tumor, and use of gadopentetate dimeglumine resulted in an enhancement. The microscopic examination of the erector spinae muscles that demonstrated high intensities on T2-weighted images showed derangement or destruction of the muscle fibers and replacement of the muscle fibers with fat tissue and infiltrating inflammatory cells. These findings were interpreted as those of myolysis. The suggested mechanism of the induction of scoliosis by the present osteoid osteoma is that the unaffected iliocostalis and quadratus lumborum muscles on the tumor side predominantly contracted over those on the opposite side to decrease the tension of the erector spinae muscles involved in myolysis, thereby producing a functional scoliosis.