Correction of main thoracic adolescent idiopathic scoliosis using pedicle screw instrumentation: does higher implant density improve correction?

ABSTRACT

STUDY DESIGN: Single institution, retrospective cohort study of 49 consecutive patients with Lenke I adolescent idiopathic scoliosis, all operated by a single surgeon using identical surgical technique and type of instrumentation. OBJECTIVE: To evaluate the early coronal and sagittal correction of main thoracic adolescent idiopathic scoliosis using all-pedicle screw instrumentation and to determine whether implant density influences correction. SUMMARY OF BACKGROUND DATA There is an increasing trend in the use of pedicle screws in scoliosis correction surgery, particularly in using segmental all-pedicle screw constructs. No previous studies have investigated whether higher pedicle screw implant density improves correction of scoliosis in vivo. METHODS: Forty-nine consecutive patients with Lenke I main thoracic adolescent idiopathic scoliosis underwent single stage posterior correction and instrumented spinal fusion with pedicle screw fixation between 2006 and 2008. Pre- and postoperative radiographs were analyzed. Mean patient age at the time of operation was 14.4 years (range 11-19.7 years). RESULTS: The preoperative main thoracic curve of 60.0 degrees +/- 13.4 degrees was corrected to 17.4 degrees +/- 6.9 degrees (69.9% correction) on the postoperative radiographs. The preoperative thoracic kyphosis of 20.0 degrees +/- 10.2 degrees decreased to 11.6 degrees +/- 4.9 degrees after surgery. There was a significant correlation between decrease in sagittal kyphosis and magnitude of coronal Cobb angle correction (P = 0.002). There was no correlation between implant density and magnitude of coronal or sagittal curve correction, with and without curve flexibility taken into consideration. CONCLUSION: Pedicle screw constructs provided excellent coronal correction of thoracic idiopathic scoliosis, however, this was at the expense of sagittal contour. Bilateral segmental pedicle screw fixation did not improve curve correction compared with unilateral or alternate segmental fixation.