Are breech rates for pedicle screws higher in the upper thoracic spine?

Study Design: A case-control study. Objectives: To evaluate pedicle screw placement in pediatric patients with various etiologies of scoliosis, and to identify predictors of misplacement. Summary of Background Data: Accuracy of placement of pedicle screws has not been well documented for posterior spinal instrumentation and fusion performed in the non-idiopathic population. Methods: A total of 54 patients (29 idiopathic, 16 neuromuscular, and 9 congenital/syndromic scoliosis), ages 5-19 years, were included. Computed tomography scans were obtained on patients postoperatively to assess screw position. Three pediatric orthopedic surgeons evaluated screw placement, and risk factors for misplacement were examined. Results: Of 1,042 pedicle screws, 8.3% were misplaced. Among all etiologies, screws placed at T1 (28.6%) and T2 (18.2%) had higher misplacement rates. T2 screws and curve correction greater than 75% had higher misplacement rates in congenital/syndromic patients; screws at T3, screws at upper end of construct, and proximal screws had significantly higher misplacement rates in neuromuscular patients; and no variables predicted misplacement in idiopathics. Screws placed at the most proximal end of the screw/rod construct also had a higher misplacement rate (14.1%) compared with all remaining levels (7.8%). Nonidiopathic patients had higher anterior misplacement compared with idiopathic. No screws were removed or revised, and no screw-related complications were observed. Conclusions: Pedicle screw instrumentation in the thoracolumbar spine was safe for pediatric patients. We found that pedicle screws placed at top levels are at higher risk for misplacement among all pediatric scoliosis patients. Nonidiopathic patients are at higher risk for anterior screw misplacement, and the predictive effect of vertebral level is more profound in nonidiopathic patients. Because of these findings, we routinely use fluoroscopic guidance for the placement of T1 and T2 screws, and screws at the proximal end of construct.