Accuracy of thoracic pedicle screw placement using freehand technique and triggered EMG in adolescent idiopathic scoliosis: Is it different between concave and convex side?

Purpose: To evaluate and compare the accuracy of the placement of thoracic pedicle screws between concave and convex side curve using freehand technique and triggered electromyogram (EMG). Methods: Three-hundred sixty eight thoracic pedicle screws were included for the evaluation of accuracy from postoperative computed tomography (CT) scans in 24 patients with adolescent idiopathic scoliosis with a mean follow-up of 27 months (range 24-58 months). All screws had stimulation thresholds greater than 6 mA. We divided the screws into two groups: (1) group A: concave side curve-254 screws (2) group B: convex side curve-114 screws. Results: The mean age at surgery was 12.8 years (range 11-17 years). The preoperative Cobb angle was 57.5 degrees (range 50-75 degrees). There were 41 total breaches (medial = 21, lateral = 20, p = 0.66) with an overall incidence of 11.1%. The overall breach rate did not attain statistically significant difference (group A = 11.8%, group B = 9.6%, p = 0.59). The rate of medial breaches was also similar for both concave and convex side (group A = 6.1%, group B = 5.9%, p > 0.05). No postoperative neurological or vascular complications were noted in both groups. Conclusion: Thoracic pedicle screw placement using both freehand technique and triggered EMG for adolescent idiopathic scoliosis surgery is safe and reliable. The overall accuracy rate is 88.9% with similar breaches on the concave and convex side on postoperative CT scans.