Background: The treatment of idiopathic scoliosis has shifted to pedicle screw fixation. This study was conducted to assess the intermediate-term effectiveness of posterior correction with low-density all-pedicle-screw constructs.

Objective: To review the intermediate-term outcome of low-density posterior-only pedicle screw constructs for a 5-year minimum follow-up.

Material and Method: The retrospective review included 30 patients who underwent posterior correction with low-density all-pedicle-screw constructs during 2004-2008. The radiographic measurements at pre-operation, immediate post-operation, 2-years post-operation, and 5-years post-operation were evaluated.

Results: Four males and 26 females were included in this study. The mean follow-up was 6.1 years (range: 5.0-9.0). The average age at operation was 14.2±2.2 years. The preoperative Cobb angle of the major curve was 55.3±12.8°, which was significantly corrected to 15.6±7.8° immediately post-operation, and significantly increased to 17.2±8.2° and to 18.5±8.7° at 2-years post-operation and 5-years post-operation, respectively. The major curve correction loss rate was 25.2%. In the normal thoracic kyphosis group (range: 10º-40°), the preoperative thoracic kyphosis angle was 28.0±12.3°, which was non-significantly decreased to 24.1±9.1°, 25.8±8.1°, and 25.8±8.5° at immediately post-operation, at 2-years post-operation, and 5-years post-operation, respectively. Preoperative lumbar lordosis non-significantly decreased from 42.7±13.0° to 39.5±10.1°, 40.5±9.1° and 41.2±9.4° at immediately post-operation, 2-years post-operation and 5-years post-operation, respectively. Screw density was 0.9 screw per level or 51%.

Conclusion: This study reviewed the 5-year post-operative outcome of posterior correction with low-density all-pedicle-screw constructs. The Cobb angle in coronal alignment correction was improved, but was significantly lost at 2- and 5-years post-operation. Thoracic kyphosis andlumbar lordosis were improved but did not significantly change at 2- and 5-years post-operation.

Keywords: Adolescent Idiopathic scoliosis, pedicle screws, posterior spinal fusion all-pedicle-screw constructs, low screw density (Spinal Fusion)