Paraspinal muscle activities of patients with scoliosis after spine fusion - An electromyographic study

Study Design. This prospective study compared the electromyographic activities of paraspinal muscles between normal subjects and patients with scoliosis before and after spine fusion. Objective. To investigate the functional changes of paraspinal muscles before and after spine fusion using surface electromyography. Summary of Background Data. Idiopathic scoliosis is a common spine deformity. Surgical correction followed by spine fusion is the basic method of treatment, but the functional changes in paraspinal muscles after spine fusion still are unknown. Methods. For this study, 15 healthy subjects and 19 patients with idiopathic scoliosis were recruited. All 19 patients received posterior spine fusion from T2 to T5 to T12. The surface electromyography for normal subjects and for patients before and after spine fusion was recorded bilaterally along the thoracic and lumbar paraspinal muscles for different postures. Root mean square and median frequency values of electromyographic activities were used to compare results between normal subjects and patients with scoliosis before and after spine fusion. Results. Electromyographic activities showed significant differences between normal control subjects and patients with pre- or postoperative scoliosis. After spine fusion, electromyography showed lower root mean square activity in the thoracic region and higher root mean square activity in the lumbar region. Patients with preoperative scoliosis showed lower median frequency in the thoracic region and higher median frequency in the lumbar region than normal subjects and patients with postoperative scoliosis. The group with preoperative scoliosis showed the least symmetrical paraspinal muscle activity, followed by the postoperative and normal groups. Conclusions. Patients with scoliosis present unbalanced electromyographic activity in the paravertebral muscles, which is diminished by spine fusion, but does not return to the values found in normal subjects. The paraspinal muscles in the thoracic region showed lower activity after spine fusion, probably because of atrophy. Higher muscular activity was found in the lumbar region, which may lead to muscle hypertrophy.