The functional status of the paraspinal muscles among patients with degenerative lumbar kyphosis before and after surgery

Abstract

Objective To study any changes in the surface electromyography of the paraspinal muscles before and after surgery in patients with degenerative lumbar kyphosis. Methods Thirty patients with lumbar degenerative kyphosis (LDK) were enrolled and underwent pedicle subtraction osteotomy. Surface electromyograms were recorded before the operation and 3 months afterward to observe the myoelectric activity of the paraspinal muscles. The electromyograms were also compared with those of healthy counterparts. Results The preoperative average EMG (AEMG) values in the LDK group in static standing were significantly higher than those of the control group. After the operation the values had decreased significantly, but were still significantly higher than in the control group. The preoperative AEMG values of the LDK group from the L1-2 segment during torso stretching were significantly lower than those of the control group. They increased significantly after the operation and were no longer significantly different from the control groups′ readings. The pre- and post-operative AEMG values from the L4-5 segment were not significantly different and remained significantly lower than in the control group. During lifting and holding the mean power frequency slopes of the LDK group were significantly lower than those of the controls both before and after the operation, though the postoperative slopes were significantly higher than the preoperative ones. Conclusion Patients with lumbar degenerative kyphosis have obvious paraspinal muscle weakness and severe fatigue. Early pedicle subtraction osteotomy can significantly improve the functional status of the paravertebral muscles in the short term. Key words: Lumbar degenerative kyphosis; Kyphosis; Surface electromyography; Neuromuscular function; Paraspinal muscles