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Identifier

000407773

Title

Η μηχανική ανεπάρκεια του μεσοσπονδύλιου δίσκου μετά από κάταγμα της τελικής πλάκας ως παράγοντας κινδύνου για παρακείμενα σπονδυλικά κατάγματα

Alternative Title

Altered disc pressure profile after an osteoporotic vertebral fracture is a risk factor for adjacent vertebral body fracture

Author

Τζερμιαδιανός, Μιχαήλ Ν.

Thesis advisor

Κοντάκης, Γεώργιος

Reviewer

Δαμηλάκης, Ιωάννης
Αλπαντάκη, Καλλιόπη
Παπαϊωάννου, Αλεξάνδρα
Ζώρας, Οδυσσέας
Σπανάκη, Κλειώ
Τσέτης, Δημήτριος

Abstract

Residual kyphotic deformity of the vertebral body after an osteoporotic fracture has been associated with the increased risk of subsequent, especially adjacent vertebral fractures. However, the role of endplate deformity has not been evaluated. This study tested the hypothesis that the altered pressure profile of the intervertebral disc after an osteoporotic vertebral fracture, even in the absence of kyphotic deformity, will alter load transmission to the adjacent vertebra and increase the risk for adjacent vertebral fracture. Eight human lower thoracic or thoracolumbar specimens, each consisting of five vertebrae were used. To selectively fracture one of the endplates of the middle VB of each specimen a void was created under the target endplate and the specimen was flexed and compressed until failure. The fractured vertebra was subjected to spinal extension under 150 N preload that restored the anterior wall height and vertebral kyphosis, while the fractured endplate remained significantly depressed. The VB was filled with cement to stabilize the fracture, after complete evacuation of its trabecular content to ensure similar cement distribution under both the endplates. Specimens were tested in flexion extension under 400 N preload while pressure in the discs and strain at the anterior wall of the adjacent vertebrae were recorded. Disc pressure in the intact specimens increased during flexion by 26 ± 14%. After cementation, disc pressure increased during flexion by 15 ± 11% in the discs with un-fractured endplates, while decreased by 19 ± 26.7% in the discs with the fractured endplates. During flexion, the compressive strain at the anterior wall of the vertebra next to the fractured endplate increased by 94 ± 23% compared to intact status (p<0.05), while it did not significantly change at the vertebra next to the unfractured endplate (18.2 ± 7.1%, p> 0.05). Subsequent flexion with compression to failure resulted in adjacent fracture close to the fractured endplate in six specimens and in a non-adjacent fracture in one specimen, while one specimen had no subsequent fractures. In healthy discs with intact endplates the nucleus pressure increases during flexion avoiding load concentration on the anterior portion of the vertebral bodies. The increased available space for nucleus after an osteoporotic endplate-depressed fracture impairs its load bearing abilities and forces the anterior annulus to bear more weight in flexion, resulting in excessive loading on the anterior portion of the adjacent vertebra that predisposes to fracture even after correction of kyphosis. These data suggest that correction of endplate deformity may play a role in reducing the risk of adjacent level fractures.

Language

English

Subject

Kyphoplasty

Vertebroplasty

Κυφοπλαστική

Σπονδυλοπλαστική

Issue date

2017-03-29

Collection

School/Department--School of Medicine--Department of Medicine--Doctoral theses

Type of Work--Doctoral theses