Complications and curve progression in EOS patients with extended distraction surgery intervals in growing rod surgery: a retrospective cohort study in China.

Study design: Retrospective case-control study.

Purpose: This study aimed to explore the relationship between the rod-lengthening interval and the incidence of postoperative complications as well as the outcomes in patients with early-onset scoliosis (EOS) undergoing growing rod surgery.

Overview of literature: EOS is characterized by a spinal deformity that manifests before the age of 10 years. The growing rod technique allows for spinal curvature correction while preserving spinal growth through periodic lengthening surgeries typically performed every 6 months. However, we found that due to challenges, many patients undergo a 1-year or even longer interval between lengthening surgeries.

Methods: We conducted a retrospective analysis of 59 patients with EOS who underwent growing rod surgery at our institution between August 2012 and June 2022. We collected radiographic parameters to compare the differences in outcomes and complications between patients who underwent lengthening surgeries at intervals of 12 months versus those with intervals of >12 months.

Results: In this study, we found 29 complications in 59 patients. The complication rate was significantly lower in the group with lengthening intervals of 12 months compared with the group with intervals longer than 12 months (35.3% vs. 68%, p <0.05). In addition, patients in the group with intervals of 12 months showed less progression of the main curve, a lower maximum kyphosis angle, and greater increases in height in the fixed segments (d=7.53±3.69 cm, p <0.05). In contrast, patients with lengthening intervals longer than 12 months were more likely to experience sagittal plane imbalance (p <0.05).

Conclusions: Lengthening intervals of greater than 12 months have a higher rate of complications and increase the risk of curve progression and spinal imbalance. Increasing the interval time just to minimize the number of surgeries before the final fusion is unwise.