title: Effects of shear force on intervertebral disc: an in vivo rabbit study.
abstract: OBJECTIVE
  A new in vivo rabbit model was developed to investigate the effects of shear force on intervertebral disc (IVD).
  
  
  METHODS
  Japanese white rabbits (n = 38) were used for this study. The L4/5 discs in Group A (n = 10) were subjected to a constant shear force (50 N) using a custom-made external loading device for 1 month; in Group B (n = 10) for 2 months; whereas in Group C (n = 10), loading device was attached to the spine but the discs remained unloaded. Group D (n = 8) was a non-operated intact control group. After loading, the loading devices were taken out and the animals were given X-ray and MRI examination. After X-ray and MRI examination, the animals were euthanized for histological analysis.
  
  
  RESULTS
  After 1 and 2 months of loading, radiographic findings showed significant disc height narrowing in L4/5 discs of the animals in loading groups, and slight lumbar spondylolisthesis in some animals of Group B. MRI showed a significant decrease in nucleus pulposus (NP) area and signal intensity from T2-weighted images. Histologically, loss of normal NP cells and disorganization of the architecture of the annulus occurred, and proteoglycan stain decreased.
  
  
  CONCLUSIONS
  The results of this study suggest that disc degeneration can be induced by hyper-physiological shear loading in the rabbit IVD. Long-term shear loading may result in structural disc failure inducing lumbar spondylolisthesis and progressive disc degeneration, which, however, has to be proven by further studies.
authors.affiliation: Department of Spinal Surgery, Shanghai East Hospital, Tongji University, School of Medicine, 150# Jimo RD, Pudong New Area, Shanghai, 200120, China.
authors.forename: Dong-Dong
authors.initials: DD
authors.lastname: Xia
authors.forename: Sheng-Lei
authors.initials: SL
authors.lastname: Lin
authors.forename: Xiang-Yang
authors.initials: XY
authors.lastname: Wang
authors.forename: Yong-Li
authors.initials: YL
authors.lastname: Wang
authors.forename: Hong-Ming
authors.initials: HM
authors.lastname: Xu
authors.forename: Feng
authors.initials: F
authors.lastname: Zhou
authors.forename: Jun
authors.initials: J
authors.lastname: Tan
mesh_terms: D000818:Animals; D005260:Female; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000473:pathology*; D055959:Intervertebral Disc Degeneration / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D007405:Intervertebral Disc Displacement / Q000473:pathology; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D011817:Rabbits; D011859:Radiography; D011897:Random Allocation; D013168:Spondylolisthesis / Q000000981:diagnostic imaging / Q000209:etiology; D013314:Stress, Mechanical; D016474:Weight-Bearing