The strength profile of the thoracolumbar endplate reflects the sagittal contours of the spine.
METHODS
human cadaveric biomechanical study of indentation tests on the thoracolumbar vertebral endplates.


OBJECTIVE
to map the strength profile of the thoracolumbar endplates using indentation testing, and to document any changes in this profile with vertebral level.


BACKGROUND
the strength profile of the lumbosacral endplate was described previously. Based on these data, we hypothesized that the periphery of the endplate would be stronger than the center and that the strength profile would vary with the sagittal contour and level of the spine.


METHODS
indentation testing was performed on the T9, T12, and L2 endplates of fresh-frozen human cadaver spines, using a materials testing machine. A 3-mm hemispherical indenter was lowered at 0.2 mm/s to a depth of 3 mm to produce local endplate failure. A minimum of 25 indentations were performed in a rectangular grid (rows: lateral, left to right; columns: A-P, anterior to posterior). Three-way analysis of variance was used to address changing strength profile patterns.


RESULTS
there were highly significant variations of indentation strength across the endplates in both the lateral and anterior to posterior directions. Each row of indentations was significantly stronger than the rows anterior to it (P < 0.04), except for the most anterior row. The most lateral columns were stronger than the central columns (P < 0.05). The ratio of the mean strength of the posterior row compared to that of the anterior row was significantly different across levels (P = 0.026).


CONCLUSIONS
the periphery of the thoracolumbar endplate was stronger than the center. The difference in posterior to anterior ndplate strength ratio between vertebral levels suggests a relative strength increase in the anterior aspect of the endplate with rostral ascent into the thoracic spine.
Bailey
Christopher S
CS
Department of Orthopaedics, University of British Columbia, Vancouver, Canada.
Sjovold
Simon G
SG
Dvorak
Marcel F
MF
Fisher
Charles G
CG
Oxland
Thomas R
TR
D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D013131:Spine / Q000502:physiology*; D013314:Stress, Mechanical; D013718:Tensile Strength / Q000502:physiology*; D013904:Thoracic Vertebrae / Q000502:physiology*