Vascularization and morphological changes of the endplate after axial compression and distraction of the intervertebral disc.
METHODS
An in vivo study of the rabbit's endplate and intervertebral disc (IVD).


OBJECTIVE
To assess the histologic features and vascularization of the endplate after axial compression and distraction, along with the degeneration and regeneration status of IVD.


BACKGROUND
Current studies mainly focus on the changes in the IVD in response to degeneration and regeneration. However, the basic science regarding degenerative changes of the vertebral endplate and its actions on the IVD is lacking. The endplate is responsible for nutrient flow to the IVD through diffusion. It has been postulated that changes in the endplate may be responsible for the degeneration of the IVD.


METHODS
Twenty New Zealand white rabbits were equally divided into 4 groups as follows; group A, 28 days of compression only; group B, 28 days of disc compression followed by 28 days of unloading; group C, 28 days of disc compression followed by 28 days of distraction; and group D, sham operated animals with apparatus placement only. At the end of the study, all the animals in the 4 groups were killed and the lumbar segments harvested for analysis of their disc height, vascularity, and histologic examination.


RESULTS
Compression decreased the disc height and the rabbits showed signs of disc degeneration. Ossified endplates with decreased cells and extracellular matrix, and decreased vascular channel volume were observed. Cellular and morphologic regeneration were observed on unloading and distraction of the compressed discs, although the cartilaginous endplates were partially ossified. The volume of vascular channels increased significantly after distraction. Fluorescent vascular tracer showed the presence of active blood flow in the vascular channels near the cartilaginous endplates.


CONCLUSIONS
Compression resulted in degeneration of the cartilaginous endplate and decrease in the osseous endplate vascular channel volume, both of which led to the degeneration of the IVD. Unloading and distraction allowed the regeneration of the extracellular matrix in both the endplate and the recovery of vascular channels.
Department of Orthopaedic Surgery, Yong Loo Lin School of Medicine, National University of Singapore, Singapore. doshht@nus.edu.sg
Hwan Tak
HT
Hee
Yon Jin
YJ
Chuah
Bryan Hsi Ming
BH
Tan
Tony
T
Setiobudi
Hee Kit
HK
Wong
D000818:Animals; D001368:Axis, Cervical Vertebra / Q000098:blood supply* / Q000473:pathology / Q000601:surgery; D007403:Intervertebral Disc / Q000098:blood supply* / Q000473:pathology / Q000601:surgery; D007405:Intervertebral Disc Displacement / Q000209:etiology / Q000473:pathology* / Q000601:surgery; D019857:Osteogenesis, Distraction / Q000379:methods*; D011817:Rabbits; D013117:Spinal Cord Compression / Q000150:complications / Q000473:pathology* / Q000601:surgery