The effect of serial growing rod lengthening on the sagittal profile and pelvic parameters in early-onset scoliosis

STUDY DESIGN.: Retrospective case series. OBJECTIVE.: To report the effect of repeated growing rod (GR) lengthenings on the sagittal and pelvic profile in patients with early-onset scoliosis. SUMMARY OF BACKGROUND DATA.: Posterior distraction-based GRs have gained popularity as a technique for the surgical management of early-onset scoliosis. However, there are no published studies on the effect of serial GR lengthenings on sagittal balance, thoracic kyphosis (TK), lumbar lordosis (LL), and pelvic parameters. METHODS.: We retrospectively reviewed data from a multicenter early-onset scoliosis database. Forty-three patients who were able to walk with minimum 2-year follow-up who underwent single- or dual-GR surgery were included for review. Mean number of lengthenings was 6.4 (range, 3-16). Mean preoperative age was 5.6 years (standard deviation, 2.4 yr), and mean follow-up was 3.5 years. Maximum TK, LL, and sagittal balance were assessed preoperatively, after index surgery, and at the latest follow-up. RESULTS.: There was a significant decrease both in TK and LL after index surgery, which then increased during the lengthening period. There was a significant increase in both proximal junctional kyphosis and distal junctional angle. Pelvic parameters (pelvic tilt, pelvic incidence, sacral slope) were unchanged during the treatment period. Significant improvement was observed in sagittal balance. There was a correlation between the change in TK and change in LL. CONCLUSION.: TK decreased after index surgery and increased between the index surgery and the latest follow-up, which was accompanied by an increase in LL. All-screw proximal constructs had mean 9° more proximal junctional kyphosis than all-hook proximal constructs. An increase in proximal junctional kyphosis and distal junctional angle was found during the treatment period. Although there was an independent effect of number of lengthenings on TK, there was no significant detrimental effect on other sagittal spinopelvic parameters. GRs had a positive effect on sagittal vertical axis, which returned patients to a more neutral alignment through the course of treatment.Level of Evidence: 4.