Mechanically induced disruption of the healthy bovine intervertebral disc.
METHODS
An intact bovine caudal disc model was used to investigate how combinations of biomechanical parameters influence the severity of disruption during compressive loading.


OBJECTIVE
To quantify the combined influence of flex-ion, hydration level, and compressive loading rate on nuclear disruption.


BACKGROUND
The risk of disc pro-lapse is known to increase when the disc is loaded flexed. However, there are few experimental data available quantifying the extent to which loading parameters might interact to produce disruption in the healthy disc.


METHODS
Reproducible states of full and partial hydration were established for 96 isolated caudal discs. These discs were then subjected to compression under combined conditions of high or low hydration, zero or full flexion, and moderate or low loading rate. The extent of disc disruption was assessed macroscopically using a damage weighting procedure.


RESULTS
Maximum disruption of the intact, healthy disc occurred under combined conditions of full hydration and flexion. Loading rate, whether at 0.004 MPa/sec or 4 MPa/sec, had little influence when applied without flexion, but there was an increased risk of disruption when the moderate rate was combined with full flexion.


CONCLUSIONS
The investigation demonstrates that significant levels of disruption can be induced by mechanical loading in intact discs free of degenerative change. Our findings support the hypothesis that mechanical injury to a healthy disc might initiate a process of degeneration.
Simunic
David I
DI
Department of Mechanical Engineering, University of Auckland, Auckland, New Zealand.
Robertson
Peter A
PA
Broom
Neil D
ND
D000818:Animals; D001696:Biomechanical Phenomena; D002417:Cattle; D066298:In Vitro Techniques; D007403:Intervertebral Disc / Q000737:chemistry / Q000502:physiology / Q000503:physiopathology*; D007405:Intervertebral Disc Displacement / Q000503:physiopathology*; D008954:Models, Biological; D016059:Range of Motion, Articular; D013131:Spine / Q000502:physiology; D013314:Stress, Mechanical; D013623:Tail; D014867:Water / Q000032:analysis
D014867:Water