SPINE Volume 35, Number 15, pp 1437–1444
©2010, Lippincott Williams & Wilkins
Free Axial Vibrations At 0 to 200 Hz Positively Affect
Extracellular Matrix Messenger Ribonucleic Acid
Expression in Bovine Nucleus Pulposi
Geoffrey T. Desmoulin, MSc,* Carol R. Reno, MSc,† and Christopher J. Hunter, PhD†‡
Study Design. Bovine caudal intervertebral discs (IVDs)
were exposed to free axial vibration for 10 to 60 minutes at 0
to 0.5g and 0 to 200 Hz. Expression of messenger ribonucleic
acid for aggrecan, collagen type I, collagen type II, biglycan,
decorin, and versican were assayed, as was apoptosis.
Objective. To determine the vibration conditions
which are most effective in altering intervertebral disc IVD
gene expression.
Summary of Background Data. Various studies have
suggested widely varying effects of vibration in the IVD,
ranging from harmful (increased risk of degeneration) to
beneficial (increased analgesia) to neutral (no effect).
Methods. Vibration was applied using a custom de-
signed voice coil system, which generated controlled mo-
tion in the axial direction. Gene expression in the nucleus
pulposus was assessed using RT-PCR and the SYBR green
chemistry; apoptosis was assessed using TUNEL staining.
Results. Expression of messenger ribonucleic acids for
biglycan, collagen type I, collagen type II, decorin, and
versican were significantly affected by vibration duration,
frequency, and amplitude. Aggrecan was unaffected. Of
the 3 factors, amplitude had the largest and widest effect.
Conclusion. Expression of extracellular matrix genes
was significantly upregulated at high amplitudes (0.4 g) in
as little as 10 minutes. This may indicate a potential therapeutic
stimulus; periodic application of controlled vibration could
positively influence matrix maintenance. Further studies on
the protein level and long-term effects are warranted.
Key Words: intervertebral disc, gene expression, vi-
bration, biomechanics, mechanical stimulation of tis-
sues. Spine 2010;35:1437–1444
Chronic low back pain is a significant health problem
in modern society. Low back pain is often associated
with degeneration of the intervertebral discs (IVDs).
1
Numerous epidemiological studies have suggested var-
ious causes for disc-related back pain, including genet-
ics,
2
smoking,
3
and loading history.
4
Of particular in-
terest is the fact that an increased risk of disc-related
back pain is associated with exposure to whole-body
vibrations in the frequency range 2 to 11 Hz (ISO
2613).
5–7
The IVDs provide mobility and a degree of shock ab-
sorbance to the spinal column. They also transmit forces
between the adjacent vertebrae and prevent direct con-
tact between the bones. It has been shown that the me-
chanical properties of the IVDs play an important role in
their functionality.
1
Disc degeneration is often character-
ized by reduced disc height and stiffness, resulting in
pressure on the radiating nerves. The dominant surgical
treatment at present is spinal fusion, wherein 2 or more
adjacent vertebral bodies are physically locked together
using bone graft or instrumentation. Although this pro-
cedure often successfully restores disc height and allows
for the return of a pain-free lifestyle, degeneration of
adjacent motion segments (adjacent segment disease) is a
common long-term complication. Although initially
thought to be a rare event, adjacent segment disease is
becoming more of a concern. One current theory states
that by fusing dynamics of the joint, they are altered in a
way that affects the healthy discs next to the fused seg-
ment, likely by altering loading and kinematics on these
adjacent discs.
8 –10
The relationship between vibrations and low back
pain has been studied since the 1950s. The main goal
of those early studies was to mitigate low back pain
often experienced by workers sitting and driving for
long periods of time. However, the results of subse-
quent epidemiological studies have been somewhat
mixed. When healthy (asymptomatic) individuals
were compared with operators of heavy earth-moving
machinery in an age-matched cohort, no differences
were found with respect to water content, disc height,
viscoelastic behavior, strength of the vertebrae as in-
dicated by water content (magnetic resonance imag-
ing) or bone density (QCT).
11
Similarly, when clinical
and MRI assessment was performed on asymptomatic
tractor driving farmers and a matched cohort, no differ-
ence was found in the degeneration of the spine.
12
In con-
trast, professional drivers have an increased risk of being
hospitalized because of spinal disorders, with bus- and
long-haul truck drivers having more frequent spinal disor-
From the *Optima Health Solutions International Corporation (KKT
International), Vancouver, British Columbia, Canada; †McCaig
Institute for Bone and Joint Health; and ‡Centre for Bioengineering
Research and Education, University of Calgary, and Department of
Mechanical and Manufacturing Engineering, Schulich School of
Engineering, University of Calgary, Calgary, Alberta, Canada.
Acknowledgment date: June 12, 2009. First revision date: July 7, 2009.
Acceptance date: August 31, 2009.
The manuscript submitted does not contain information about medical
device(s)/drug(s).
Corporate/Industry funds were received in support of this work. No
benefits in any form have been or will be received from a commercial
party related directly or indirectly to the subject of this manuscript.
Supported by a research contract from Optima Health Solutions Inter-
national Corporation.
C.J.H. is an Alberta Heritage Foundation for Medical Research
Scholar. G.T.D. is an employee of Optima Health Solutions Interna-
tional Corp. and is sponsored in part by the National Research Council
of Canada’s Industrial Research Assistance Program.
Address correspondence and reprint requests to Christopher J. Hunter,
Department of Mechanical and Manufacturing Engineering, Univer-
sity of Calgary, 2500 University Drive NW, Calgary, Alberta T2N
1N4, Canada; E-mail: chunter@ucalgary.ca
1437