En bloc vertebral column derotation provides spinal derotation but no additional effect on thoracic rib hump correction as compared with no derotation in adolescents undergoing surgery for idiopathic scoliosis with total pedicle screw instrumentation

Abstract

Study design: A comparative review of 2 cohorts with prospective data collection.

Objective: To compare clinical and radiographical parameters in patients with adolescent idiopathic scoliosis undergoing surgery, using total pedicle screw instrumentation with and without en bloc vertebral column derotation (DVR).

Summary of background data: All pedicle screw instrumentations with or without DVR are an effective surgical method for adolescent idiopathic scoliosis correction. However, there are limited data comparing pedicle screw instrumentation alone with pedicle screws with DVR on clinical and radiographical outcomes.

Methods: We followed 72 consecutive children and adolescents (14 males, mean age at surgery: 14.7 [range, 9.0-18.0] years; 6 juveniles, 66 adolescents) operated for a structural thoracic idiopathic scoliosis (Lenke 1-4, or 6) using all pedicle screw construct in a prospective manner for a minimum of 2 years. Of them, 24 had pedicle screw instrumentation with apical monoaxial screws without derotation (N-DVR) and 48 with en bloc DVR.

Results: Preoperatively, the mean (SD) main thoracic curve was 56° ± 9° and 57° ± 11° and was corrected to 16° ± 6° in both groups at 2-year follow-up (not significant). Thoracic rib hump averaged 12.3° ± 3.6° versus 14.2° ± 5.0° (P = 0.075) preoperatively and 7.2° ± 3.8° versus 8.3° ± 3.7° at 2-year follow-up in the N-DVR and in the DVR both groups, respectively (P = 0.30). Correction of spinal rotation in the main thoracic curve as assessed by the Upsani score was significantly better in the DVR group than in the N-DVR group at 6 months (P = 0.038) and 2-year follow-up (P = 0.039). Thoracic kyphosis reduced from a mean of 23° ± 18° to 20° ± 9° in the N-DVR group but remained unchanged in the DVR group (P = 0.11 between groups at 2-year follow-up).

Conclusion: En bloc DVR has a significant effect on radiographical spinal column derotation and may help prevent flattening of thoracic kyphosis, but this derotation is not reflected by better thoracic rib hump correction at 2-year follow-up.

Level of evidence: 2.