Postoperative Disc Wedging in Adolescent Idiopathic Thoracolumbar/Lumbar Scoliosis: a Comparison of Anterior and Posterior Approaches

OBJECTIVE: To evaluate the different influences of anterior and posterior correction and fusion approaches upon disc wedging in adolescent idiopathic thoracolumbar/lumbar scoliosis. METHODS: The retrospective study was conducted with the medical records and radiographs of adolescent idiopathic thoracolumbar/lumbar scoliosis patients that underwent anterior (group A) or posterior (group B) correction and fusion surgery from December 1998 to May 2008. The correction of the main curve and changes of the disc wedging were analyzed. RESULTS: Fifty-three patients were included, 26 in group A and 27 in group B. The mean coronal Cobb angles of the main curve in group A and group B were significantly corrected after surgery (P < 0.05), with an average correction rate of 75.2% and 88.2%, respectively. Upon final follow-up, the coronal Cobb angles of the two groups were 18.90 +/- 11.1 degrees and 7.70 +/- 5.6 degrees, respectively, with an average correction loss of 6.8 degrees +/- 6.5 degrees and 2.7 degrees +/- 3.3 degrees, respectively. The coronal Cobb angle after operation and at final follow-up, and the correction rate were significantly better in group B than those in group A (P < 0.05), while the coronal Cobb angle loss in group A was greater than that in group B (P < 0.05). The disc wedging before operation, after operation, and at final follow-up were 3.2 degrees +/- 3.0 degrees, 5.7 degrees +/- 3.0 degrees, and 8.6 degrees +/- 4.4 degrees in group A, and 2.4 degrees +/- 3.2 degrees, 3.3 degrees +/- 3.4 degrees, and 3.7 degrees +/- 3.6 degrees in group B, respectively. Postoperative disc wedging was significantly larger compared with preoperative measurements in group A (P < 0.05), but not in group B (P > 0.05). The difference between disc wedging at final follow-up and that after surgery was significant in group A (P < 0.05), but not in group B (P > 0.05). Between the two groups, group A had larger disc angles after operation and at final follow-up (P < 0.05), and a greater loss of disc angle (P < 0.05). CONCLUSION: For adolescent idiopathic thoracolumbar/lumbar scoliosis, posterior approach using all pedicle screws might produce a better result in terms of disc wedging compared with anterior approach.