Accuracy of thoracic pedicle screws in patients with and without coronal plane spinal deformities

Abstract

Study design: This retrospective observational study evaluated 399 transpedicular thoracic screws using postoperative computed tomography (CT).

Objectives: To examine the in vivo accuracy of transpedicular thoracic screws in patients with and without coronal plane spinal deformities.

Summary of background data: There are no comparative studies regarding the safety and accuracy of thoracic pedicle screws in patients with and without coronal plane spinal deformities.

Methods: Curve magnitude and segmental vertebral rotation were determined from preoperative radiographs. Postoperative CT was used to assess the placement accuracy of titanium thoracic pedicle screws.

Results: Forty-seven patients underwent instrumented posterior spinal fusion using 399 titanium thoracic pedicle screws. Fully contained screw accuracy in patients with coronal plane spinal deformities was less than in patients without coronal plane spinal deformities at T9-T12 (59% vs. 73%, P = 0.04) and overall (42% vs. 62%, P = 0.001). There was no difference between the overall percentages of acceptably positioned screws (< or = 2 mm of medial or < or = 6 mm of lateral pedicle perforation) in patients with coronal plane spinal deformities (98%) versus patients without coronal plane spinal deformities (99%) (P = 0.69). Penetration of the anterior vertebral cortex was more frequent in patients with coronal plane spinal deformities than in those without coronal plane spinal deformities (8.0% vs. 1.0%, P = 0.008). There was no correlation between the accuracy of screw placement and the degree of segmental rotation, screw proximity to the curve apex, or screw position relative to the curve concavity or convexity (P > 0.12). There were no neurologic or vascular complications.

Conclusions: The overall percentage of acceptably positioned screws was 98% in patients with coronal plane spinal deformities and 99% in patients without coronal plane spinal deformities. In patients with coronal plane spinal deformities, penetration of the pedicle wall and the anterior vertebral cortex was increased at T9-T12 and overall.