Mechanisms of anular failure resulting from excessive intradiscal pressure: a microstructural-micromechanical investigation.
METHODS
Microstructural/micromechanical investigation of pathways of anular wall disruption.


OBJECTIVE
To investigate the fundamental mechanisms by which both intralamellar and interlamellar relationships are disrupted by nuclear pressurization.


BACKGROUND
Understanding how anular failure might occur following increased nuclear pressurization requires an experimental approach that avoids artifactual injury to the anulus but reveals structural disruption resulting directly from the pressurization event.


METHODS
Bovine motion segments were subjected to internal pressurization using a novel "through vertebra" gel injection method. Intralamellar and interlamellar sections were deliberately chosen so as to expose systematic patterns of structural disruption resulting from the pressurization event. This microdisruption was investigated using a novel method that combined microtensile manipulation and simultaneous differential contrast imaging of the fully hydrated unstained sections.


RESULTS
The inner anulus was most severely disrupted, the middle regions developed a series of regular clefts along axes of weakness within the in-plane arrays, with only mild array disruption occurring in the outer regions.


CONCLUSIONS
A mechanism is proposed whereby an anular failure pathway, driven by hydrostatic nuclear pressure, could track through the complex anular structures via a set of disruptive events causing weakening of both the in-plane and interlamellar junction interconnections.
Pezowicz
Celina A
CA
Faculty of Mechanical Engineering, Wroclaw University of Technology, Wroclaw, Poland.
Schechtman
Helio
H
Robertson
Peter A
PA
Broom
Neil D
ND
D000818:Animals; D001696:Biomechanical Phenomena / Q000379:methods; D002417:Cattle; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000502:physiology* / Q000648:ultrastructure*; D008846:Micromanipulation / Q000379:methods*; D011312:Pressure; D011859:Radiography; D013314:Stress, Mechanical