title: In situ rigidity of a new sliding rod for management of the growing spine in Duchenne muscular dystrophy.
abstract: METHODS
  This biomechanical, in vitro laboratory study determined the static stiffness of a new telescoping rod and the axial motion of this implant during various loading conditions.
  
  
  OBJECTIVE
  To compare the stability of the new telescoping rod with the classic Luque instrumentation, and to determine whether the sliding rod elongates or contracts during spine motion.
  
  
  BACKGROUND
  A new telescoping rod was developed to stabilize the spine in children with Duchenne muscular dystrophy and to provide capacity for spinal growth.
  
  
  METHODS
  The stability of 11 instrumented calf spines was determined in flexion, extension, lateral bending, and torsion to determine the stiffnesses of the spines instrumented with these two implants. The telescoping motion in the left and right rod was measured in the new rod system.
  
  
  RESULTS
  In flexion, the spines with the telescoping rods were stiffer than those with the Luque implant. However, no significant differences in the stiffness coefficients were found for extension, lateral bending, or torsion. The restoring force of the telescoping system was greater than that of the Luque system in all directions. All modes of loading produced an accommodating change of length in the construct.
  
  
  CONCLUSIONS
  The dynamic telescoping system provides stiffness comparable with that of established systems while allowing elongation during growth of the young patient.
authors.affiliation: Department Unfallchirurgische Forschung und Biomechanik, University of Ulm, Germany.
authors.forename: H J
authors.initials: HJ
authors.lastname: Wilke
authors.forename: P
authors.initials: P
authors.lastname: Kluger
authors.forename: T
authors.initials: T
authors.lastname: Naumann
authors.forename: T
authors.initials: T
authors.lastname: Kron
authors.forename: L E
authors.initials: LE
authors.lastname: Claes
authors.forename: W
authors.initials: W
authors.lastname: Puhl
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001858:Bone Nails; D002417:Cattle; D004867:Equipment Design; D005069:Evaluation Studies as Topic; D009136:Muscular Dystrophies / Q000503:physiopathology* / Q000601:surgery*; D013131:Spine / Q000254:growth & development*