[Accuracy of free-hand thoracic pedicle screw placement in severe idiopathic scoliosis via CT scan].

OBJECTIVE

To analyze the accuracy of free-hand thoracic pedicle screw placement in severe idiopathic scoliosis via CT scan.

METHODS

Twenty patients with complete CT data were chosen out of 58 patients of severe idiopathic scoliosis from June 1996 to December 2006. The Cobb angle of the main thoracic curve was from 82 degree to 142 degree (96.3 degree +/- 14.3 degree). The kyphotic angle in the main curve was 66.2 degree +/- 12.4 degree. The placement of thoracic pedicle screw was completed free-handedly, and the accuracy of screws placement was evaluated with CT thin-slice scan postoperatively.

RESULTS

Altogether 174 thoracic pedicle screws were inserted, 157 (90.2%) of which were fully contained within the cortical boundaries of the pedicle.The other 17 screws (9.8%) were misplaced in 9 patients: 11 screws (6.8%) were lateral, 9 of which had a breach <or= 2 mm, and the other 2 were between 2 and 4 mm; 6 screws (3.5%) were medial, 3 screws had a breach <or= 2 mm, and the other 3 were between 2 and 4 mm. Of the total 94 thoracic pedicle screws inserted on the convex side,6 were misplaced,with the accuracy rate of 96.3%. Eighty screws were inserted on the concave side, 11 of which screws were misplaced, with the accuracy rate of 86.3%. There was no statistical difference between the convex and concave side as to the accuracy rate of screw implantation (P > 0.05). There was no neural complication in all patients.

CONCLUSION

It is fairly accurate place thoracic pedicle screw in severe idiopathic scoliosis free-handedly, with some misplacements.