Endplate indentation of the fourth lumbar vertebra - biomed 2010.

This study presents the results of indentation tests on the superior vertebral endplate of the 4th lumbar vertebra (L4) of eleven male cadaveric subjects (65 +/- 7 years). Three locations on the superior endplate surface were loaded with a 7.9 mm spherical indentor at either a low (1 mm/s) or high (1000 mm/s) rate. Anterior midline and posterior right and left indentation locations were chosen to prevent local deformations and fractures from influencing the results of subsequent and preceding tests. Peak forces were higher in the dynamic tests (498 +/- 261 N) than in the quasi-static tests (451 +/- 256 N) on the posterior side, although the difference was not significant (p = 0.139). However, the peak forces in the anterior tests (304 +/-166 N) were significantly lower (p =0.0157) than in the posterior tests with the same loading rate. The variation in failure forces in the current study correlates with the variation in thickness of endplate cortical bone (between specimens and between anterior and posterior locations on the same specimen) as measured from small field of view computed tomography scans.