Biomechanical Characteristics of Chiropractic Adjustments
Christopher J. Colloca, D.C.
"There
is a preoccupation with outcome and efficiency studies in chiropractic
research. Although it is interesting to know that patients receiving
chiropractic manipulations fare better than those receiving
physiotherapy, or that chiropractic treatments are more cost-effective
than back surgery, these facts describe (from a scientific point of
view) irrelevant findings. For chiropractic research, a single study
that could describe precisely the mechanics, physiology, and
neuromuscular responses of a treatment, and that had quantified the
healing effect of these responses, would be more use to chiropractic as
a profession than any clinical outcome study."
-
Walter Herzog, Ph.D., 2000. The Mechanical, Neuromuscular, and
Physiologic Effects Produced by Spinal Manipulation. In: Herzog W.
Clinical Biomechanics of Spinal Manipulation. Philadelphia: Churchill
Livingstone, 2000:206.
Growing
consideration has been given in the past 20 years to the biomechanical
characteristics of chiropractic adjustments. Most of the interest in
this field stems from the necessity of quantifying the forces produced
during spinal manipulation to assure the safety of chiropractic
adjustments and protect doctors of chiropractic from frivolous
malpractice claims of alleged injury.
Bone Movement During Spinal Manipulation in Humans
Tony
S. Keller, Ph.D., from the Department of Mechanical Engineering,
University of Vermont, conducted pioneering research in the field of in
vivo analysis of motions produced during spinal manipulation in human
subjects with a group from the University of Göthenburg, Sweden in the
early 1990's.
Using an intervertebral motion device (IMD) connected to implanted Steinmann pins in the L3-L4 or L4-L5 spinous processes, intervertebral motions were quantified using a strain gauge (Kaigle et al., 1992).
Dr. Keller and his graduate student published data (Nathan and Keller, 1994)obtained from three subjects: one normal, one patient diagnosed with L4-5 degenerative disk disease, and one patient diagnosed with L5 retrospondylolisthesis to examine differences in spinal motions in response to spinal manipulation among the groups.
Spinal thrusts were delivered to each of the spinous processes (T11-L3) using an Activator Adjusting Instrument equipped with an impedance head and intervertebral displacements were quantified using the IMD.
Using an intervertebral motion device (IMD) connected to implanted Steinmann pins in the L3-L4 or L4-L5 spinous processes, intervertebral motions were quantified using a strain gauge (Kaigle et al., 1992).
Dr. Keller and his graduate student published data (Nathan and Keller, 1994)obtained from three subjects: one normal, one patient diagnosed with L4-5 degenerative disk disease, and one patient diagnosed with L5 retrospondylolisthesis to examine differences in spinal motions in response to spinal manipulation among the groups.
Spinal thrusts were delivered to each of the spinous processes (T11-L3) using an Activator Adjusting Instrument equipped with an impedance head and intervertebral displacements were quantified using the IMD.
With
this design, posteroanterior dynamic spinal stiffness measurements were
obtained from impedance analysis so that correlation could be made to
intervertebral motions.
The most spinal motion occurred during the spinal manipulative thrusts in the normal subject.
Thrusts applied to the L2 spinous process in the normal subject (72 +/- 9 N) produced a 1.62 +/- 1.06 mm peak-to-peak intervertebral axial displacement, 0.48 +/- 0.1 mm PA shear displacement, and 0.89 +/- 0.49 degrees FE rotation at the L3-4 spinal segment.
Thoracolumbar PA stiffness values tended to be higher for the patient with a severely degenerated disk (85-362 KN/m), whereas the patient with retrospondylolisthesis had a lower PA stiffness (32-96 KN/m).
Such in vivo kinematic measurements of the normal and pathologic human lumbar spine indicated that low force, PA impulses produce measurable segmental motions and reinforced the notion that mechanical processes play an important role in spinal manipulation and mobilization.
The most spinal motion occurred during the spinal manipulative thrusts in the normal subject.
Thrusts applied to the L2 spinous process in the normal subject (72 +/- 9 N) produced a 1.62 +/- 1.06 mm peak-to-peak intervertebral axial displacement, 0.48 +/- 0.1 mm PA shear displacement, and 0.89 +/- 0.49 degrees FE rotation at the L3-4 spinal segment.
Thoracolumbar PA stiffness values tended to be higher for the patient with a severely degenerated disk (85-362 KN/m), whereas the patient with retrospondylolisthesis had a lower PA stiffness (32-96 KN/m).
Such in vivo kinematic measurements of the normal and pathologic human lumbar spine indicated that low force, PA impulses produce measurable segmental motions and reinforced the notion that mechanical processes play an important role in spinal manipulation and mobilization.
More recently, Dr. Keller and I designed a new study to quantify spinal motions during spinal manipulation.
Specifically, we aimed to examine different segmental contact points, vectors (lines of drive), and excursions that occur during spinal manipulation using a modified chiropractic adjusting Instrument.
In 1999, and 2002 we traveled to Antwerpen, Belgium to collect data from surgical patients with the assistance of orthpaedic spine surgeon, Robert Gunzburg, M.D., Ph.D.
Prior to our departure, Dr. Keller tested a new 6-degree-of-freedom accelerometer system that we could mount to implanted bone pins into the spinous processes to be able to more accurately quantify spinal motions during spinal manipulation.
We then designed the study to account for the variables important to chiropractic clinicians.
Specifically, we aimed to examine different segmental contact points, vectors (lines of drive), and excursions that occur during spinal manipulation using a modified chiropractic adjusting Instrument.
In 1999, and 2002 we traveled to Antwerpen, Belgium to collect data from surgical patients with the assistance of orthpaedic spine surgeon, Robert Gunzburg, M.D., Ph.D.
Prior to our departure, Dr. Keller tested a new 6-degree-of-freedom accelerometer system that we could mount to implanted bone pins into the spinous processes to be able to more accurately quantify spinal motions during spinal manipulation.
We then designed the study to account for the variables important to chiropractic clinicians.
 Flouroscopic image of special bone pins implanted into adjacent spinous processes of a functional spinal unit and accelerometers mounted in place externally. |
In this research, we were
able to collect data on 9 surgical patients. Bone pins were placed into
the spinous processes of the levels tested using Flouroscopic guidance.
With the hardware in place, we then tested the fixation and the impedance of the pin by plucking it and measuring its inherent mechanical properties as a baseline.
With the hardware in place, we then tested the fixation and the impedance of the pin by plucking it and measuring its inherent mechanical properties as a baseline.
Next, we began our protocol
delivering spinal manipulative thrusts with varying segmental contact
points, vectors, and force settings (including sham settings).
Data was simultaneously recorded on a laptop computer.
We are currently analyzing the data and preparing the abstracts and manuscripts derived from this work.
You can look forward to several conference presentations and publications in the future from this unique line of study.
Data was simultaneously recorded on a laptop computer.
We are currently analyzing the data and preparing the abstracts and manuscripts derived from this work.
You can look forward to several conference presentations and publications in the future from this unique line of study.
 Bone pin being plucked to test its fixation and mechanical properties to establish baseline measurements. Needle electromyographic leads are also visualized. |
 Dr. Chris Colloca delivers a thrust to the spinous process of L5 as intervertebral motions are quantified at the L3-L4 functional spinal unit. |
 Typical force-time profile of an Activator Adjusting Instrument thrust, and corresponding posteroanterior motion response of the adjacent lumbar vertebrae observed as acceleration profiles. |
New Spinal Model
Using
original data from our work in human subjects, and the published
reports of forces and speeds of other spinal manipulative or
mobilization techniques by that of others, Dr. Keller has developed a
new spinal model that predicts spinal motions resulting from spinal
manipulation with different lines of drive.
We presented this work at the 2000 meeting of the European Society of Biomechanics in August, 2000 in Dublin, Ireland, and at the World Federation of Chiropractic Congress in May, 2001 in Paris. The manuscript from this work appears in the journal, Clinical Biomechanics (2002).
We presented this work at the 2000 meeting of the European Society of Biomechanics in August, 2000 in Dublin, Ireland, and at the World Federation of Chiropractic Congress in May, 2001 in Paris. The manuscript from this work appears in the journal, Clinical Biomechanics (2002).
Because
numerous spinal manipulation/adjustment and mobilization techniques
exist, it is necessary to quantify and model the spines response to the
clinician's applied force from a biomechanical standpoint so that we
may begin to understand which techniques may be beneficial in different
circumstances.
Model results have been compared to force measurements reported during Diversified spinal thrusts, mechanical force-manually assisted spinal thrusts, and quasi-static and oscillatory mobilization procedures that have been reported.
This model has recently been enhanced to include two additional displacement degrees of freedom, (axial displacement and rotation {flexion-extension}) and thorax and pelvis regions have been added.
Model results have been compared to force measurements reported during Diversified spinal thrusts, mechanical force-manually assisted spinal thrusts, and quasi-static and oscillatory mobilization procedures that have been reported.
This model has recently been enhanced to include two additional displacement degrees of freedom, (axial displacement and rotation {flexion-extension}) and thorax and pelvis regions have been added.
 (L-R )- Chris Colloca, D.C., Tony Keller, Ph.D. and Michelle Anderson, D.C. collected data on 30 patients in 2 days on a new biomechanical assessment project. |
As a result, it is
now possible to characterize the segmental and intersegmental, sagittal
plane motion response of the lumbar spine.
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.
We also believe this work will assist in an understanding of the inherent safety of chiropractic adjustments.
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.
We also believe this work will assist in an understanding of the inherent safety of chiropractic adjustments.
View animations of spine motion response to an mechanical force, manually-assisted adjustment with an Anterior Line of Drive, Anterior-Superior Line of Drive, or an Anterior-Inferior Line of Drive.
We
are more excited now than ever at the possibilities that await us in
the understanding of just how chiropractic adjustments work from a
biomechanical standpoint. We believe that such an understanding will
assist in making chiropractic a continued leader in conservative health
care.
References
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Pope,M.H., Fleming,B.C., Hansson,T., 1992. A method for the intravital
measurement of interspinous kinematics. J Biomech, 25,(4), 451-456.
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), 431-441.
For
References and Abstracts of Original Research on Biomechanical
Characteristics of Chiropractic Adjustments {Link to Publications}
Related Research on Biomechanical Characteristics of Chiropractic Adjustments
Cohen,E.,
Triano,J.J., McGregor,M., Papakyriakou,M., 1995. Biomechanical
performance of spinal manipulation therapy by newly trained vs.
practicing providers: does experience transfer to unfamiliar
procedures? J Manipulative Physiol Ther, 18,(6), 347-352.
Colloca,C.J.,
Keller,T.S., Seltzer,D.E., Fuhr,A.W., 2000. Mechanical impedance of the
human lower thoracic and lumbar spine exposed to in vivo
posterior-anterior manipulative thrusts. Proceedings of the 12th
Conference of the European Society of Biomechanics, August 10-14, 2000,
Dublin.
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 25th Annual Meeting of
the The International Society for the Study of the Lumbar Spine, Kona,
Hawaii. Toronto: ISSLS; 1999: p.136A..
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AW. Movements of vertebrae during manipulative thrusts to unembalmed
human cadavers (Letter). J Manipulative Physiol Ther 1998; 21(2):128-9.
(RE: Gal J, Herzog W, Kawchuk G, Conway PJ, Zhang YT. J Manipulative
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