title: Measurement of forces generated during distraction of growing-rods in early onset scoliosis.
abstract: OBJECTIVE
  To measure the forces applied during distraction of growing-rods in early onset scoliosis (EOS), aimed at developing a motorized elongation device.
  
  
  METHODS
  A consecutive series of measurements were carried out to analyze the forces applied by the surgeon during distraction of single growing-rods in 10 patients affected by EOS (mean age 8.3 years; range 6 to 10 years) undergoing the first distraction 6 months following implantation of the rods. For each measurement, output from the transducer of a dedicated pair of distraction calipers was recorded at zero load status and at every 1 mm of distraction, up to a maximum of 12 mm for each of the two connected rods.
  
  
  RESULTS
  Twenty measurements were obtained showing a linear increase of the load with increasing distraction, with a mean peak force of 485 N at 12 mm distraction and a single reading over 500 N. We did not observe bone fractures or ligament disruptions during or after rod elongations. There was one case of superficial wound infection in the cohort.
  
  
  CONCLUSIONS
  The safe peak force carrying capacity of a motorized device for distraction of growing-rods is 500N.
authors.affiliation: Marco Teli, Consultant Orthopaedic Surgeon, Orthopaedic Spine Unit, Policlinico San Marco, Corso Europa 7, 24040 Osio Sotto, Bergamo, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Teli
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Grava
authors.forename: Victor
authors.initials: V
authors.lastname: Solomon
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Andreoletti
authors.forename: Emanuele
authors.initials: E
authors.lastname: Grismondi
authors.forename: Jay
authors.initials: J
authors.lastname: Meswania