Selective Posterior Thoracic Fusions for Adolescent Idiopathic Scoliosis: Comparison of Hooks versus **Pedicle Screws

Summary: Although spontaneous lumbar curve correction often occurs following a selective thoracic spinal fusion, there are few reports that focus on selective posterior thoracic spinal fusion in the presence of a lumbar C modifier curve. In this study we found that selective thoracic fusion of main thoraciccompensatory lumbar C modifier AIS curves with pedicle screws allowed for better thoracic correction and less postoperative coronal decompensation than seen with hooks.

Purpose: Although spontaneous lumbar curve correction often occurs following a selective thoracic spinal fusion, there are few reports that focus on selective posterior thoracic spinal fusion in the presence of a lumbar C modifier curve. The purpose of this study was to compare the results of selective posterior thoracic fusion using hooks versus pedicle screws in patients with major thoracic-compensatory lumbar C modifier adolescent idiopathic scoliosis (AIS) curves.

Methods: Sixty-six consecutive patients with major thoracic-compensatory lumbar C modifier AIS curves underwent selective posterior thoracic fusion to T12, L1, or L2 at a single institution (1987-2001). Hooks were used for instrumentation in 32 patients and pedicle screws were used in 34 patients. Patients were evaluated at a minimum 2-year follow-up. To test for differences between groups analysis of covariance (ANCOVA) was used.

Results: There was no statistical difference between the preoperative thoracic and lumbar Cobb values for the hook group versus the pedicle screw group. The amount thoracic Cobb correction obtained surgically and the amount of spontaneous lumbar Cobb correction was significantly greater in the pedicle screw group (p <0 .001). The incidence of postoperative coronal decompensation, with a greater than 20 mm shift to the left C7 plumbline, was higher in hook group (13 patients) as compared pedicle screw 4 patients (p<0.005). There were no complications or re-operations either group.

Conclusion: Previous reports have shown postoperative coronal decompensation is correlated with overcorrection of the thoracic curve. However, we did not see this in our pedicle screw group even though correction of the thoracic Cobb exceeded that as obtained with hooks.

Significance: Selective thoracic fusion of main thoracic-compensatory lumbar C modifier AIS curves with pedicle screws allowed for better thoracic correction and less postoperative coronal decompensation than seen with hooks.

FDA Diclosure Cleared: No ** Thoracic Pedicle Screws