AJCC October 2000
Biomechanical and Neurophysiological Responses of Chiropractic Adjustments: Ongoing Original Research
By Christopher J. Colloca, D.C.
Applying
the scientific method to chiropractic procedures allows for exciting
venue of collaboration between clinicians and researchers to validate
chiropractic care. Over the past 3 years, Tony Keller, Ph.D., associate
professor and interim chair at the Department of Mechanical Engineering
at the University of Vermont has come to work with me in my private
practice in Phoenix, Arizona to investigate biomechanical and
neurophysiologic responses of chiropractic adjustments. Supported by the
National Institute of Chiropractic Research and the Foundation for the
Advancement of Chiropractic Education this collaboration in both in
Arizona and Vermont together with projects conducted in Europe has
resulted in 8 scientific conference presentations and over 10
manuscripts in the past 3 years paving the way for a new understanding
of the mechanisms of chiropractic adjustments. I am pleased to share
with you the exciting work that we have been doing and our current and
future projects.
Biomechanical
Research
Previous biomechanical work in human experiments published by Dr.
Keller and his graduate student in 1994 involved the placement of
Steinmann pins into the lumbar spinous processes of human subjects
bridged by an intervertebral motion device to measure spinal motions
(Nathan and Keller, 1994). Thrusts to the spine were delivered with an
Activator® Adjusting Instrument (AAI) equipped with an impedance head
(load cell and accelerometer). Significant rotations and translations
were observed in response to AAI thrusts providing the first
quantitative evidence for chiropractic adjustments moving bones in
humans. Interestingly, in this research it was learned that degenerative
functional spinal units (FSUs) moved less than normal FSUs, which also
correlated to impedance measurements of increased spinal stiffness in
degenerative joints. Of course, this prompted the notion of someday
being able to non-invasively quantify dynamic spinal stiffness in a
clinical setting as a biomechanical outcome measure.
More recently, this research has led to the development of a new
5-degree-of-freedom model to predict intervertebral motion based upon
forces imparted to the spine and the applied vector (line of drive)
which we presented at the 2000 meeting of the European Society of
Biomechanics (ESB) in Dublin, Ireland in August (Figures 1 & 2)
(Keller and Colloca, 2000a). As you might imagine, significant spinal
coupling occurs in adjacent vertebrae to the segmental contact point
producing quantifiable accompanying motions above and below. These
results are in contrast to traditional chiropractic teachings of
contacting one specific bone with the pisiform and moving it from point
A to B irrespective of the adjacent segments. Applying data obtained
from assessing dynamic spinal stiffness in patients with lumbar spinal
disorders from my office, we also looked at stiffness across different
frequencies to determine how low back function and spine stiffness are
related. Because the spine is a viscoelastic structure, it exhibits both
time-dependent and frequency-dependent properties. We found that spinal
stiffness was different across different frequencies and reported this
in our platform presentation at ESB 2000 in Dublin (Colloca et al.,
2000a).
As discussed, understanding the spine’s response to input
forces during an adjustment enables assessment of spinal stiffness. The
first step was to validate the procedure. Using a steel beam with a
known flexural stiffness (similar to the human spine) Dr. Keller
conducted tests and determined that we could accurately predict the
mechanical behavior of the structure with a stiffness device (Keller et
al., 1999). Next, normal subjects (students from the University of
Vermont) were assessed to begin to understand dynamic spinal stiffness
profiles (Keller et al., 2000).
In 1998, we then began testing patients with low back and leg
pain in my office with a clinical research protocol consisting of
physical exam, lumbar spine radiographs, and outcome assessments as we
sought to determine differences in dynamic stiffness amongst patients
with lumbar spinal disorders. To understand the physiological
significance of the spine’s stiffness we attached surface electrodes
over the paraspinal muscles to record their reflex reactions to the
perturbations. We found that patients with worsening symptom frequency
were stiffer and had higher reflex thresholds, thus correlating spinal
dysfunction clinically using this new biomechanical outcome measure. We
presented this research at the 1999 meeting of the International Society
of the Lumbar Spine (ISSLS) (Colloca et al., 1999) and the manuscript
that followed is currently in review.
From the enormous amount of data that has been collected in
patients from over 1600 adjustments, we performed several other clinical
research projects. These include assessing the muscular contributions to
spine stiffness (Figure 3), and investigating the relationship between
radiological parameters such as disc height and dynamic spine stiffness.
Both of these projects were presented at the 2000 meeting of the
International Conference on Spinal Manipulation (ICSM) in Bloomington,
MN this past September (Colloca et al., 2000b; Colloca et al., 2000c)
Neurophysiological
Research
Numerous studies have demonstrated the neurophysiologic
influences of dynamic spinal stiffness noting the muscular contributions
to spine stability (Stubbs et al., 1998; Solomonow et al., 1998;
Solomonow et al., 1999). Characterizing neuromuscular and biomechanical
aspects of the spine simultaneously allows us to understand how the
spine’s stiffness parameters are contributing to the spine’s
function (dysfunction) (Figure 4).
Inasmuch, we have assessed the overall reflex responses to
instrument delivered adjustments stratified according to patient
symptomatic and functional measures. In this manner, simultaneously, we
have recorded dynamic spinal stiffness and neuromuscular responses
during adjustments. We presented this at the 2000 meeting of the ISSLS
in Adelaide, Australia (Colloca et al., 2000d) and the manuscript has
been accepted for publication in the prestigious journal, Spine. After
characterizing the reflex responses to adjustments, we then sought to
determine if a functional change in patient status occurred from
adjustments. We conducted a controlled clinical trial 40 patients with
LBP comparing their trunk muscle strength pre-post adjustment and again
presented this at ISSLS 2000 (Keller and Colloca, 2000b). Because the
manuscript is currently in press, I cannot elaborate further on the
results here, but the paper will appear in the JMPT in the November/
December 2000 issue.
Lastly, for over 100 years chiropractors have claimed that they
affect the nervous system with their adjustments. But where is the data?
Embarking on a historic journey to Belgium, together with a research
team comprised of orthopaedic surgeons, Dr. Keller, Dr. Arlan Fuhr, and
I investigated direct nerve root responses of AAI adjustments with
varying segmental contact points and lines of drive intraoperatively. We
found that action potential magnitude was dependent upon the segmental
contact point and line of drive. This paper appears in the September
issue of JMPT (Colloca et al., 2000e). With another study design, we now
have collected data to quantify vertebral motions by means of
accelerometers attached to Steinmann pins implanted into the spinous
processes, together with simultaneous neurophysiological nerve root
responses, and neuromuscular needle EMG reflex responses to chiropractic
adjustments in humans.
In a time where it has been stated in our own JMPT, “The
assumption that chiropractic tests can locate and define a manipulative
lesion is purely hypothetical. (Hestoek and Leboeuf-Yde, 2000),” we
feel that it is time that our profession comes to terms with what is
necessary to quantify the “lesion” that we treat (subluxation), and
document its reduction through reliable and valid chiropractic
interventions. This is the goal of the current research that we are
conducting. Although a lot of professional changes have occurred
recently, the research that are working on continues to move forward
full steam ahead and our team continues to grow. In October, 2000, we
will collect data in my office to investigate the postural and loading
effects of dynamic spinal stiffness. We feel that an understanding of
the basic biomechanical and physiological mechanisms of chiropractic
adjustment will not only serve to better care for patients but to
validate and advance our great profession.
Figure
1
Figure 2 
Figure
3
References
Colloca,C.J., Keller,T.S., Seltzer,D.E., Fuhr,A.W. (2000a).
Mechanical impedance of the human lower thoracic and lumbar spine
exposed to in vivo posterior-anterior manipulative thrusts. Proceedings
of 12th Conference of the European Society of Biomechanics. Dublin,
Ireland.
Colloca,C.J., Keller,T.S., Peterson,T.K., Seltzer,D.E., Fuhr,A.W.
(2000b). Correlation of L5 Dynamic Posteroanterior Spinal Stiffness to
Plain Film Radiographic Images of Lumbosacral Disc Height. Proceedings
of the 2000 International Conference on Spinal Manipulation.
Bloomington, MN.
Colloca,C.J., Keller,T.S., Seltzer,D.E., Fuhr,A.W. (2000c).
Muscular and soft-tissue contributions of dynamic posteroanterior spinal
stiffness. Proceedings of the 2000 International Conference on Spinal
Manipulation. Bloomington, MN.
Colloca,C.J., Keller,T.S., Seltzer,D.E., Fuhr,A.W. (2000d).
Electromyographic responses to mechanical force, manually-assisted
spinal manipulative therapy. Proceedings of the 27th conference of the
International Society for the Study of the Lumbar Spine, Adelaide,
Australia.
Colloca,C.J., Keller,T.S., Gunzburg,R., Van de Putte,K., Fuhr,A.W.
(2000e). Neurophysiological response to intraoperative lumbosacral
spinal manipulation. J Manipulative Physiol Ther., 23,(7), in press.
Colloca,C.J., Keller,T.S., Fuhr,A.W. (1999). Muscular and
mechanical behavior of the lumbar spine in response to dynamic
posteroanterior forces. Proceedings of the 26th conference of the
International Society for the Study of the Lumbar Spine, Kona, Hawaii.
Hestoek,L. & Leboeuf-Yde,C. (2000). Are chiropractic tests
for the lumbo-pelvic spine reliable and valid? A systematic critical
literature review. J Manipulative Physiol Ther, 23,(4), 258-75.
Keller,T.S., Colloca,C.J. (2000a). Dynamic response of the human
lumbar spine: a 5 degree-of-freedom lumped parameter time and frequency
domain model. Proceedings of 12th Conference of the European Society of
Biomechanics. Dublin, Ireland.
Keller,T.S., Colloca,C.J. (2000b). Mechanical force spinal
manipulation increases trunk muscle strength assessed by
electromyography: A comparative controlled clinical trial. Proceedings
of 2000 Conference of the International Society for the Study of the
Lumbar Spine, Adelaide, Australia.
Keller,T.S., Colloca,C.J., Fuhr,A.W. (1999). Validation of the
force and frequency characteristics of the activator adjusting
instrument: effectiveness as a mechanical impedance measurement tool.
J.Manipulative.Physiol Ther., 22,(2), 75-86.
Keller,T.S., Colloca,C.J., Fuhr,A.W. (2000). In Vivo Transient
Vibration Analysis of the Normal Human Thoracolumbar Spine. J
Manipulative.Physiol Ther., in press.
Nathan,M. & Keller,T.S. (1994). Measurement and analysis of
the in vivo posteroanterior impulse response of the human thoracolumbar
spine: a feasibility study. J.Manipulative.Physiol Ther., 17,(7),
431-41.
Solomonow,M., Zhou,B.H., Baratta,R.V., Lu,Y., Harris,M. (1999).
Biomechanics of increased exposure to lumbar injury caused by cyclic
loading: Part 1. Loss of reflexive muscular stabilization. Spine,
24,(23), 2426-34.
Solomonow,M., Zhou,B.H., Harris,M., Lu,Y., Baratta,R.V. (1998).
The ligamento-muscular stabilizing system of the spine. Spine, 23,(23),
2552-62.
Stubbs,M., Harris,M., Solomonow,M., Zhou,B., Lu,Y., Baratta,R.V.
(1998). Ligamento-muscular protective reflex in the lumbar spine of the
feline. J.Electromyogr.Kinesiol., 8,(4), 197-204.
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CONTENTS
Biomechanical & Neuro responses to Adjustment
Communicating From the Inside Out
Normal Values in Anatomy, Physiology, Disease and Chiropractic
Ambulatory Translational Traction
Percutaneous Radiofrequency Neurotomy...