ObjectiveTo compare the effectiveness and radiological changes between KMC interspinous dynamic reconstruction and Coflex for degenerative lumbar spinal disorders and evaluate the clinical outcome of the KMC interspinous dynamic internal fixation for degenerative lumbar spinal disorders. MethodsA randomized controlled double-blind trial was conducted. Thirty-three patients with degenerative lumbar spinal disorders were divided into 2 groups between May 2011 and July 2012, 19 patients received Coflex treatment (group A), and 14 patients received KMC (group B). Single Coflex or KMC fixation was used. There was no significant difference in age, gender, disease duration, affected segment, and disease diagnosis between 2 groups (P>0.05). The Oswestry disability index (ODI) score and visual analogue scale (VAS) score were used to evaluate the effectiveness. The anterior disc height, middle disc height, posterior disc height, and foramen intervertebral height and width of operated segment were measured and compared between at preoperation and last follow-up on the X-ray films. Range of motion (ROM) of operated segment and adjacent segment was measured. ResultsThere was no significant difference in operation time, intraoperative blood loss, postoperative recovery time, and hospitalization time between 2 groups (P>0.05). The patients were followed up 12-24 months (mean, 16.2 months) in group A and 12-26 months (mean, 17.9 months) in group B. No shift, loosening, or breaking of internal fixation occurred. The ODI score and VAS score were significantly decreased at last follow-up when compared with preoperative scores (P<0.05); there was no significant difference in the ODI score and VAS score at preoperation and last follow-up, and in improvement rate at last follow-up between 2 groups (P>0.05). The middle disc height and posterior disc height, and foramen intervertebral height and width were significantly increased when compared with preoperative ones (P<0.05), while there was no significant difference in anterior disc height (P>0.05). At last follow-up, ROM of the operated segments was significantly improved when compared with preoperative one in 2 groups (P<0.05), but no significant difference was found at the upper adjacent level (P>0.05). There was no significant difference in ROM of the operated segment and upper adjacent segment between 2 groups at preoperation and last follow-up (P>0.05). ConclusionThe early effectiveness is satisfactory to treat degeneration lumbar spinal disorders with KMC interspinous dynamic internal fixation.