title: The aging disc: using an ovine model to examine age-related differences in the biomechanical properties of the intralamellar matrix of single lamellae.
abstract: To determine the effect of age on the biomechanical properties of the intralamellar matrix of single annulus fibrosus (AF) lamellae.
  
  
  
  One intervertebral disc (IVD) was excised from five young (<12 months), five middle-aged (2-4 years) and five older (5-7 years) ovine lumbar spines. From each IVD, a maximum of four single AF lamellae samples were harvested: two from the anterior region and two from the posterior region. Tissues were mounted in a tensile testing apparatus such that tension was applied perpendicular to the orientation of the collagen fibers to isolate the intralamellar matrix. Variables of interest from the stress-strain relationship were: end of toe-region strain and corresponding stress, initial failure stress and strain, and elastic stiffness.
  
  
  
  When compared to the middle-aged and old samples, the intralamellar matrix of young AF samples displayed significantly higher stress values at the end of the end of toe-region (p = 0.008) and at initial failure (p = 0.002). Further, the young samples were stiffer than both middle-aged and old samples (p = 0.04).
  
  
  
  This study was the first to show that the intralamellar matrix of single AF lamellae is weaker and more compliant in middle-aged and old ovine IVDs compared to young IVDs. These findings are likely a result of the remarkable age-related changes that occur that ultimately weaken the IVD as a whole.
authors.affiliation: Department of Kinesiology and Physical Education, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON, N2L 3C5, Canada.
authors.forename: Danielle M
authors.initials: DM
authors.lastname: Stewart
authors.affiliation: Department of Biology, Wilfrid Laurier University, Waterloo, ON, Canada.
authors.forename: Lauren A
authors.initials: LA
authors.lastname: Monaco
authors.affiliation: Department of Kinesiology and Physical Education, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON, N2L 3C5, Canada. dgregory@wlu.ca.|Department of Health Sciences, Wilfrid Laurier University, Waterloo, ON, Canada. dgregory@wlu.ca.
authors.forename: Diane E
authors.initials: DE
authors.lastname: Gregory
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D000070616:Annulus Fibrosus / Q000502:physiology*; D001696:Biomechanical Phenomena / Q000502:physiology; D008159:Lumbar Vertebrae / Q000502:physiology*; D012756:Sheep; D013314:Stress, Mechanical; D013718:Tensile Strength / Q000502:physiology
keywords: Aging; Annulus fibrosus; Intralamellar matrix; Material testing; Mechanical properties