Is There an Optimal Time to Distract Dual Growing Rods?

Retrospective multicenter observational cohort study.

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.

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.

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.

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).

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.