Endplates changes related to age and vertebral segment.

Endplate separations are defined as the presence of a space between the hyaline cartilage and the cortical bone of the adjacent vertebral body. This study evaluates endplate separations from the vertebral body and intervertebral discs and verifies if endplate separation is related to age and the spinal level. Groups were formed based on age (20-40 and 41-85 years old) and the vertebral segment (T7-T8 and L4-L5 segments). Histological analysis included assessment of the length of the vertebral endplates, the number and dimensions of the separations, and orientation of the collagen fibers, in the mid-sagittal slice. Two indexes were created: the separation index (number of separations/vertebral length) and separation extension index (sum of all separations/vertebral length). The results of the study demonstrated a direct relationship between the density of separations in the endplate and two variables: age and spinal level.

EVALUATION OF TERMINAL VERTEBRAL PLATE ON CERVICAL SPINE AT DIFFERENT AGE GROUPS AND ITS CORRELATION WITH INTERVERTEBRAL DISC THICKNESS.

UNLABELLED: To evaluate, by means of histomorphometry, terminal vertebral plate thickness, intervertebral disc thickness and its correlation on different age groups, seeking to identify its correlation. METHODS: C4-C5 and C5-C6 cervical segments removed from human cadavers of both genders were assessed and divided into five groups of 10-year age intervals, from 21 years old. TVP and intervertebral disc thickness evaluation was made by means of histomorphometry of histological slides stained with hematoxylin and eosyn. Lower C4 TVP, upper C5 TVP, and upper C6 TVP de were compared between each other and to the interposed intervertebral disc thickness between relevant TVP. RESULTS: The thickness of terminal vertebral plates adjacent to the same ID did not show statistic differences. However, the comparison of upper and lower vertebral plates thickness on the same cervical vertebra (C5), showed statistical difference on all age groups studied. We found a statistical correlation coefficient above 80% between terminal vertebral plate and adjacent intervertebral disc, with a proportional thickness reduction of both structures on the different cervical levels studied, and also on the different age groups assessed. CONCLUSION: Terminal vertebral plate shows a morphologic correlation with the intervertebral disc next to it, and does not show correlation with the terminal vertebral plate on the same vertebra.

BIOMECHANICAL EVALUATION OF THE INFLUENCE OF CERVICAL SCREWS TAPPING AND DESIGN.

OBJECTIVE: To assess if the screw design (self-drilling/self-tapping) and the pilot hole tapping could affect the insertion torque and screw pullout strength of the screw used in anterior fixation of the cervical spine. METHODS: Forty self-tapping screws and 20 self-drilling screws were inserted into 10 models of artificial bone and 10 cervical vertebrae of sheep. The studied parameters were the insertion torque and pullout strength. The following groups were created: Group I-self-tapping screw insertion after pilot hole drilling and tapping; Group II-self-tapping screw insertion after pilot hole drilling without tapping; Group III-self-drilling screw insertion without drilling and tapping. In Groups I and II, the pilot hole had 14.0 mm in depth and was made with a 3mmn drill, while tapping was made with a 4mm tap. The insertion torque was measured and the pullout test was performed. The comparison between groups was made considering the mean insertion torque and the maximum mean pullout strength with the variance analysis (ANOVA; p≤ 0.05). RESULTS: Previous drilling and tapping of pilot hole significantly decreased the insertion torque and the pullout strength. CONCLUSION: The insertion torque and pullout strength of self-drilling screws were significantly higher when compared to self-tapping screws inserted after pilot hole tapping.