Is There an Optimal Time to Distract Dual Growing Rods?

Study Design: Retrospective multicenter observational cohort study.

Objectives: To determine whether there is a significant difference in final spinal height achieved, instrumented height, or Cobb angle related to the mean time interval between distractions of dual growing rods.

Summary Of Background Data: Patients were prospectively enrolled in "The Treatment of Progressive Early Onset Spinal Deformities: A Multi-Center Study." Additional data were collected via a retrospective review of medical records.

Methods: Using data from a multicenter database, the authors identified 46 patients (23 boys and 23 girls) with early-onset scoliosis who were treated with dual growing rods and who had surgical treatment spanning more than 4 years. The patients were divided into 2 groups: those who had less than 9 months (16 patients) and those who had 9 months or more (30 patients) between distractions. Standard univariate statistics were calculated. The researchers performed 2-tailed t tests. Significance was set at p = .05.

Results: The differences in primary Cobb angle, T1-S1 height, and instrumented segment length at the last distraction or final arthrodesis, compared with the post-index procedure values, were not significantly different (p = .52, .58, and .60, respectively) between groups with the available data. The normalized instrumented height gains, in millimeters per year, were not significantly different (p = .22).

Conclusions: Patients with longer times between growing-rod distractions (9 or more months) had no significant differences in primary Cobb angle, T1-S1 length, or instrumented length gain compared with patients with shorter times (less than 9 months) between distractions.