title: Is There an Optimal Time to Distract Dual Growing Rods?
abstract: METHODS
  Retrospective multicenter observational cohort study.
  
  
  OBJECTIVE
  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.
  
  
  BACKGROUND
  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.
authors.affiliation: OrthoCarolina, 1915 Randolph Road, Charlotte, NC 28207, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Paloski
authors.affiliation: Department of Orthopaedic Surgery, The Johns Hopkins Hospital, Baltimore, 601 N Caroline Street, Baltimore, MD 21287, USA. Electronic address: ehenze1@jhmi.edu.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Sponseller
authors.affiliation: Department of Orthopaedic Surgery, University of California-San Diego, 200 West Arbor Drive, San Diego, CA 92103, USA; San Diego Center for Spinal Disorders, 4130 La Jolla Village Drive, La Jolla, CA 92037, USA.
authors.forename: Behrooz A
authors.initials: BA
authors.lastname: Akbarnia
authors.affiliation: Division of Pediatric Orthopaedic Surgery, Rainbow Babies and Children's Hospital, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106, USA.
authors.forename: George H
authors.initials: GH
authors.lastname: Thompson
authors.affiliation: Children's Orthopedic Center, 4650 Sunset Boulevard, Los Angeles, CA 90027, USA.
authors.forename: David L
authors.initials: DL
authors.lastname: Skaggs
authors.affiliation: San Diego Center for Spinal Disorders, 4130 La Jolla Village Drive, La Jolla, CA 92037, USA.
authors.forename: Jeff B
authors.initials: JB
authors.lastname: Pawelek
authors.affiliation: OrthoCarolina Research Institute, 2001 Vail Avenue, Suite 300, Charlotte, NC 28207, USA.
authors.forename: Phuong T
authors.initials: PT
authors.lastname: Nguyen
authors.affiliation: OrthoCarolina Research Institute, 2001 Vail Avenue, Suite 300, Charlotte, NC 28207, USA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Odum
keywords: Distractions; Early-onset scoliosis; Growing rods; Lengthenings; Scoliosis