title: Smaller Interval Distractions May Reduce Chances of Growth Rod Breakage Without Impeding Desired Spinal Growth: A Finite Element Study.
abstract: BACKGROUND
  Growth rods allow regular distraction of the spine to compensate for growth. Traditionally such distractions are performed every 6 months via open surgery. However with the advent of minimally invasive techniques like magnetically controlled growing rods, the distractions can be performed non-surgically. This also implies that the interval of distraction could be changed or customized based on individual patient's need.
  
  
  OBJECTIVE
  In this study we have hypothesized that the distraction at shorter intervals reduces the stresses on the rods which in turn reduces the chance of rod failure.
  
  
  OBJECTIVE
  A finite element model of a juvenile spine was instrumented with growth rods and distractions were applied at different frequencies (2 months, 3 months, 6 months, and 12 months) for a period of two years to study the effects of frequency of distraction on maximum von Mises stresses on the rods for different loading conditions were studied.
  
  
  RESULTS
  The stresses on the rods were highest for 12-month distraction (2 distractions in 2 years) and lowest for 2-months distraction (12 distractions in 2 years).
  
  
  CONCLUSIONS
  It was found that the shorter intervals of distraction led to reduction of stresses on the rod for same spinal height gain in two years.
authors.affiliation: Department of Bioengineering and Orthopaedics Surgery, Engineering Center for Orthopaedic Research Excellence (ECORE), Colleges of Engineering and Medicine, University of Toledo, Toledo, OH 43606, USA. Electronic address: Vijay.Goel@utoledo.edu.
authors.forename: Aakash
authors.initials: A
authors.lastname: Agarwal
authors.affiliation: Department of Bioengineering and Orthopaedics Surgery, Engineering Center for Orthopaedic Research Excellence (ECORE), Colleges of Engineering and Medicine, University of Toledo, Toledo, OH 43606, USA.
authors.forename: Anand K
authors.initials: AK
authors.lastname: Agarwal
authors.affiliation: Department of Orthopaedics, All India Institute of Medical Sciences (AIIMS), Ansari Nagar East, Gautam Nagar, New Delhi, DL 110029, India.
authors.forename: Arvind
authors.initials: A
authors.lastname: Jayaswal
authors.affiliation: Department of Bioengineering and Orthopaedics Surgery, Engineering Center for Orthopaedic Research Excellence (ECORE), Colleges of Engineering and Medicine, University of Toledo, Toledo, OH 43606, USA.
authors.forename: Vijay
authors.initials: V
authors.lastname: Goel
keywords: Distraction frequency; Finite element study; Interval of distraction; Juvenile scoliosis; Magnetic growth rods