Objective—To investigate the biomechanical behavior
of the lumbosacral disk under compressive load in
dogs, using pressure profilometry, and to investigate
the relationship between pressure profile features
and background and disease variables.
Sample Population—23 lumbosacral disks and adjacent
vertebrae harvested from medium and large
Procedure—A 1.3-mm unidirectional needle-mounted
pressure transducer was inserted into the disk in a
ventral-to-dorsal manner while the disk was loaded in
compression by a materials testing machine.
Withdrawal of the transducer resulted in a pressure
profile for cranial and lateral stress. Pressure profiles
were analyzed, and relationships to age and gross evidence
of degeneration were investigated.
Results—There was a moderate positive correlation
between age and degree of nuclear degeneration
(rs = 0.420, P = 0.046), but no relationship between
age and mean nuclear pressure was detected. Mean
nuclear pressure correlated negatively with severity of
degenerative changes in the nucleus pulposus.
Receiver operator characteristic curves to evaluate
mean nuclear pressure as a diagnostic test for nuclear
degeneration revealed a sensitivity and specificity of
82 and 83%, respectively. In addition, age was moderately
correlated with the magnitude of stress peaks
(rs = –0.571, P = 0.004). Stress peaks were not related
to the severity of nuclear degeneration.
Conclusions and Clinical Relevance—Determination
of the mean nuclear pressure by disk profilometry
provides information on the severity of lumbosacral
disk degeneration with a high degree of sensitivity
and specificity. The magnitude of single stress
peaks within the dorsal annulus fibrosus is correlated
with age and may not necessarily reflect advancing
degeneration. (Am J Vet Res 2001;62:1734–1739)