title: The effect of loading rate and degeneration on neutral region motion in human cadaveric lumbar motion segments.
abstract: BACKGROUND
  The quasistatic neutral zone is a surrogate for neutral region stiffness of spinal motion segments. No similar measure of dynamic stiffness has been validated. Because parameters related to stiffness are likely to be affected by loading rate and disc degeneration, we examined the effect of those factors on motion parameters derived from continuous motion data.
  
  
  METHODS
  Fifteen human lumbar motion segments were tested with continuous flexion-extension pure moments at 0.5, 3.0 and 6.0 degrees /s. Range of motion, width of the hysteresis loop, transitional zone width, and slopes of the upper and lower arms of the hysteresis loop within the transitional zone were measured. Discs were then graded for degeneration.
  
  
  RESULTS
  As the loading rate increased from 0.5 degrees /s to 6.0 degrees /s there were significant increases in range of motion, hysteresis area, hysteresis loop width, and the upper and lower transitional zone slopes. At the same time transitional zone width decreased significantly. Degeneration had a significant effect on all parameters except hysteresis loop width. The transition zone slopes appeared to best discriminate between normal and degenerative discs.
  
  
  CONCLUSIONS
  Loading rate had a significant effect on all parameters. As degeneration increased consistent effects were observed indicating decreasing stiffness from grade 1 to grade 3 then slightly increased stiffness in grade 4 specimens. The slopes of the transitional zone have potential to be a useful measure of neutral region stiffness during dynamic motion testing.
authors: Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN 55905, USA. rgay@mayo.edu
authors: Ralph E
authors: RE
authors: Gay
authors: Brice
authors: B
authors: Ilharreborde
authors: Kristin
authors: K
authors: Zhao
authors: Emir
authors: E
authors: Boumediene
authors: Kai-Nan
authors: KN
authors: An
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000502:physiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular