Influence of location, fluid flow direction, and tissue maturity on the macroscopic permeability of vertebral end plates.
METHODS
We implemented a pilot study in a growing animal model. The macroscopic permeability of the vertebral endplates was measured. The influence of location, tissue maturity, and fluid flow direction was quantified.


OBJECTIVE
We hypothesized that the macroscopic permeability of vertebral endplate may decrease with maturity of the vertebral segment.


BACKGROUND
The alternation of loading induced by the diurnal cycle generates convective flux into the vertebral segment with the dominant flow path through the vertebral endplates. The alteration of mass transport at the disc-vertebrae interface may interrupt the mechanobiologic balance, and have an effect such as degenerative changes or scoliosis.


METHODS
A previously validated method for measuring permeability, based on the relaxation pressure caused by a transient-flow rate was used. Three specimens were extracted from each L1 to L5 endplate. Seventy-one specimens were frozen, and 64 were stored fresh in a standard culture media. A microscopic analysis completed the biomechanical analysis.


RESULTS
At 2, 4, and 6 months, the mean permeability (10(-14) m/N x s, flow-in/flow-out) of the central zone was respectively: 1.23/1.66, 1.03/1.29, and 0.792/1.00. Laterally, it was 1.03/1.19, 1.094/1.001, and 0.765/0.863. For all groups, cartilage endplate and growth plate were both thinner in the center of the plate. Weak differences of the vascular network were detected, except for a small increase of vascular density in the central zone.


CONCLUSIONS
The results from this animal study showed that the central zone of the vertebral endplate was more permeable than the periphery and the flow-out permeability was up to 35% greater than the flow-in permeability. Increase of permeability with decrease of cartilage thickness was noticed within the same age group. We also found a statistically significant decrease of the macroscopic permeability correlated with the tissue maturity.
Accadbled
Franck
F
Biomechanics Laboratory EA3697, Toulouse University Hospital, Toulouse, France. faccadbled@wanadoo.fr
Laffosse
Jean-Michel
JM
Ambard
Dominique
D
Gomez-Brouchet
Anne
A
de Gauzy
Jérôme Sales
JS
Swider
Pascal
P
D000818:Animals; D000831:Animals, Newborn; D008159:Lumbar Vertebrae / Q000098:blood supply* / Q000254:growth & development* / Q000648:ultrastructure; D023421:Models, Animal; D009045:Motor Endplate / Q000098:blood supply* / Q000254:growth & development* / Q000648:ultrastructure; D010539:Permeability; D010865:Pilot Projects; D012756:Sheep