Objective: To study the therapeutic mechanism of an innovative instrumentation - Plate-Rod System for Scoliosis (PRSS) and its effectiveness for the surgical management of early onset scoliosis (EOS) and adolescent scoliosis (AIS). Method: A new device - PRSS was developed in our department. Between June 2000 and July 2008, 23 patients with progressive EOS, and from October 1998 to August 2003, a total of 66 AIS patients, who underwent one-stage PRSS procedure without bony fusion and had been followed up for more than two years, were evaluated prospectively. The mean age at the time of surgery was 7.98 years in the EOS group, and was 12.15 years in the AIS group. Experimental studies including X-ray analysis, photo-elastic test and type X collagen were used to test the therapeutic mechanism. Results: The subjects were followed up for more than 2 years. The mean scoliosis improved from 80.7deg to 30.5deg after surgery with a corrective rate of 62.2. The length of the growth of the instrumented spine was on average 13.3 mm in EOS group. In AIS group, the mean precentage of correction was 68.86. There were no severe complications in our studies. When PRSS was in place, compressive stress was found to exert on the convex side, while tensile stress on the concave side of the curvature, which was reflected by the changes in the color band in the photo-elastic test and the changes in the width of the disc spaces, and more type X collagen was expressed on the convex side than the concave side. This suggests that compressive stress leads to increase in earlier cartilage degeneration of end plate on the convex side, which is correlated with the decreased growth of the end plate of this side, resulting in maximum spinal realignment. Conclusion: The PRSS which dispenses with spinal fusion and allows extension along with the children's growth, is able to provide and maintain desirable correction of scoliosis in the later growing years due to its modulating efficiency in normalizing the spinal growth. This new device is an effective instrumentation for correcting scoliosis, especially for EOS.
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