Journal of Applied Biomechanics, 2006; 22:234-239. © 2006 Human Kinetics, Inc.
Measurement of In Vivo Lumbar Intervertebral Disc
Pressure During Spinal Manipulation: A Feasibility Study
Anthony J. Lisi,1,2 Conor W. O’Neill,3 Derek P. Lindsey,4
Robert Cooperstein,1 Elaine Cooperstein,5 and James F. Zucherman6
Palmer Center for Chiropractic Research; 2VA Connecticut Healthcare System;
California Spine Diagnostics; 4Palo Alto, CA; 5University of California, San Francisco;
6
St. Mary’s Spine Center, San Francisco
1
3
This paper presents the first reported measurements of lumbar intervertebral disc pressure
in vivo during spinal manipulation. A pressure
transducer was inserted into the nucleus pulposus of one normal-appearing lumbar disc in an
asymptomatic adult volunteer. Pressures were
recorded during several body positions and
maneuvers, then during spinal manipulation, and
lastly during a repetition of the pre­intervention
body positions. Baseline pressures in the prone
and side-lying positions measured 110 kPa and
150 kPa, respectively. During the manipulation,
pressure rose to a peak of 890 kPa over 250 ms.
Immediately following, pressures in the prone
and side-lying positions measured 150 kPa and
165 kPa, respectively. These data do not support
the hypotheses that manipulation can reduce a
herniation by decreasing intradiscal pressure, or
cause a herniation by raising pressure to failure
levels. Further work may lead to a better understanding of this treatment method.
Key Words: spine, manometry, human
High-velocity, low-amplitude spinal manipulation (HVLASM) is commonly used in the treatment
of low back disorders (Coulter et al., 2002; Wolsko,
Eisenberg, Davis, Kessler, & Phillips, 2003). There
Palmer Center for Chiropractic Research, Davenport, IA; 2VA
Connecticut Healthcare System; 3California Spine Diagnostics;
4
Palo Alto, CA; 5University of California San Francisco; 6St.
Mary’s Spine Center.
1
234
is some evidence that spinal manipulation is effective in the treatment of low back pain (Assendelft,
Morton, Yu, Suttorp, & Shekelle, 2004; Bronfort,
Haas, Evans, & Bouter, 2004).
Data on the biomechanical effects of HVLASM
have been emerging. Previous investigators have
used pressure mats to measure the external loads
applied at the contact interface between clinicians
and subjects (Herzog, Conway, Kawchuk, Zhang,
& Hasler, 1993; Herzog, Kats, & Symons, 2001),
inverse dynamics with data obtained from tablemounted force plates and surface electromyography
to estimate the loads passing through the lumbar
spine (Triano & Schulz, 1997), and magnetic resonance imaging (MRI) to measure gapping of the
lumbar zygapophysial joints before and after lumbar
HVLASM (Cramer et al., 2002).
However, the biomechanical effects of HVLASM
on the lumbar intervertebral disc are largely un­known; thus, the use of HVLASM in patients with
lumbar disc pathology has been controversial. A
recent systematic review found inconclusive evidence on safety and effectiveness (Lisi, Holmes, &
Ammendolia, 2005). Historically, it has been postulated that the loads applied during lumbar HVLASM
can reduce a herniated disc (Cyriax, 1953). Based
on case reports of adverse effects after lumbar
manipulation, others have suggested that such
manipulation delivers pathological loads to the disc
(Malmivaara & Pohjola, 1982). Preliminary results
from cadaveric work suggest that intra­discal pressure may rise or fall during manipulation (Maigne &
Disc Pressure During Manipulation 235
Guillon, 2000). Exploring the effects of HVLASM
on the lumbar intervertebral disc in vivo may help
clarify the indications and contra­indications of this
intervention in patients with low back pain.
Measurement of lumbar intradiscal pressure
emerged as an accepted method for assessing in vivo
loading of the lumbar disc in the 1960s and 1970s
(Nachemson, 1981; Nachemson & Morris, 1964).
Recently, consistent pressure measurements have
been obtained from both healthy and degenerated
lumbar discs (Sato et al., 1999; Wilke et al., 1999).
The purpose of this study was to determine the
feasibility of measuring in vivo pressures in normal
lumbar discs before, during, and after HVLASM.
Materials and Methods
9. Previous experience of receiving lumbar spinal
manipulation resulting in an audible cavitation,
or “popping,” without adverse effects.
Criteria 2 and 3 above were included to ensure that
subjects were fully informed of what they would
undergo during the procedure.
Informed consent describing the risk of spinal
injection procedures and spinal manipulation procedures was obtained from two volunteers: a 41-yearold female, 56, 130 lbs; and a 42-year-old male,
511, 180 lbs. In both subjects, the L3–4 disc was
identified to be without abnormalities on MRI by a
radiologist not affiliated with this study.
Pressure Sensor
5. No history of chronic pain in any region.
The pressure measurement probe consisted of
a flexible catheter with a specially constructed
piezo-resistive pressure transducer mounted on
the sidewall of a 2.5-mm long, 1.45-mm diameter
metal tip (Unisensor AG, Attikon, Switzerland). The
transducer had a reported linear pressure range of
0–5 mPa, linearity of ±1.0 mmHg, and thermal drift
of 0.1 per mm Hg/°C. The sensor was tested in a
custom air pressure chamber pre- and postinsertion
and was found to be accurate to within ±0.02 mPa
at a pressure of 1 mPa.
The transducer signal was amplified (Mammen­
dorfer Institut für Physik und Medizin, GmbH,
Hattenhoffen, Germany), read by an analog-todigital card (DAQCard 1200, National Instruments,
Austin, TX), and collected on a laptop computer
(Micron Transport VLX) using Labview software
(National Instruments, Austin TX). Static pressure
measurements were acquired at a rate of 22 Hz and
averaged over a minimum of 5 s. Manipulation data
were acquired at a sampling rate of 1,000 Hz and
smoothed with a moving average over 10 samples.
6. No signs of disc degeneration or other significant pathology at the target disc on MRI.
Measurement Procedure
Study Participants
This study was approved for two human subjects by
the institutional review board of the Palmer Center
for Chiropractic Research, Davenport, IA. Inclusion
criteria were developed to maximize the chances of
finding a normal disc and to minimize the likelihood
of adverse effects. These criteria were as follows.
1. 25–45 years old.
2. Licensed chiropractor with experience receiving
and delivering lumbar side-posture HVLASM.
3. Previous experience observing percutaneous
spinal procedures, such as intradiscal pressure
measurement, discography, or spinal injection
procedures.
4. No significant past or present low back pain
(Score of 0/10 on Numeric Rating Scale;
William­son & Hoggart, 2005).
7. No abnormal psychometric testing on the Zung
Self-Rating Depression Scale (Zung, 1965) or
Modified Somatic Perception Questionnaire
(Main, 1983).
8. No bleeding diathesis, no use of aspirin or
non­steroidal antiinflammatory drugs within
past 7 days, no anticoagulant medications, no
diabetes mellitus, and/or no active infection
requiring treatment with antibiotics.
Placement of the transducer was performed by an
anesthesiologist with extensive experience with
lumbar discography and percutaneous intradiscal
procedures. Cefazolin 2 g was administered intravenously 20 min before the procedure. The back
was sterilely prepped and draped, and strict sterile
technique was maintained throughout the procedure.
Prior to needle placement, the skin, subcutaneous,
and deep muscular tissues along the trajectory of
236 Lisi, O’Neill, Lindsey, Cooperstein, Cooperstein, and Zucherman
the needle were infiltrated with 1% lidocaine. A
14-gauge needle with a plastic catheter was placed
into the center of the disc using fluoroscopic guidance and a standard extrapedicular approach. The
needle was removed, leaving the plastic catheter in
the disc, and the pressure probe was inserted through
the catheter. The catheter was then withdrawn while
the tip of the probe was monitored under fluoroscopic guidance, ensuring that it remained in the
nucleus beyond the end of the catheter. The probe
was inserted in this manner into the L3–4 disc of
each of the two subjects. In the first subject (EC),
owing to operator error the probe came out of the
disc as the plastic catheter was withdrawn and was
not replaced because of concerns about multiple
disc punctures. The probe was placed successfully
in the second subject (AJL). After the probe was in
place, measurements were recorded in the prone
and side-lying positions. Pressure was then measured with the subject in a prethrust manipulative
position described below. Measurements were then
taken during the administration of a high-velocity,
low-amplitude thrust also described below. After
the thrust, the measurements were repeated in the
side-lying and prone positions. Fluoroscopic imaging confirmed that the probe remained within the
nucleus throughout this process (Figure 1).
Manipulation Procedure
Spinal manipulation was performed by a chiropractor with extensive experience with HVLASM
techniques. Strict sterile technique was maintained
throughout the procedure. The particular HVLASM
maneuver used in this study was the lumbar mammillary push. The prethrust manipulative position
involved the subject lying in the right lateral decubitus position with the left hip and knee flexed. At
first, relatively low offsetting forces were applied to
bring the spinal region to the end range of passive
motion of combined left rotation and left lateral
flexion. Thus, the subject’s pelvis was ultimately
positioned at approximately a 35° angle to the table
surface (Figure 2).
Next, the force of the high-velocity, low­amplitude thrust was generated by an upper extremity thrust and body drop. This procedure has been
well described elsewhere (Peterson & Bergmann,
2002; Triano & Schulz, 1997).
Figure 1 — Fluoroscopic images showing the pressure probe positioned in the center of the L3–4 intervertebral disc. The arrowheads indicate the flexible catheter, and the arrow points to the metal tip.
Disc Pressure During Manipulation 237
Figure 2 — Premanipulative position for the lumbar side-posture high-velocity, low-amplitude procedure.
Results
Baseline pressures in the prone and side-lying
positions were 110 kPa and 150 kPa, respectively.
Pressure rose to 500 kPa when the subject was in
the prethrust manipulative position. During the
administration of an HVLA thrust, the pressure rose
to a peak of 662 kPa over 290 ms. However, this
manipulation did not result in joint cavitation, as
determined by both the intervening chiropractor and
the subject. A second thrust was delivered, resulting
in a pressure peak of 890 kPa over 125 ms, and this
did cause joint cavitation (Figure 3).
Immediately following the second thrust, pressures in the prone and side-lying positions measured
150 and 165 kPa, respectively. After the procedure,
both subjects experienced moderate low back pain
that resolved within 48 hr with analgesics. Approximately 16 months following the procedure, neither
subject has suffered any recurrent back pain or other
adverse effects.
Discussion
To our knowledge, this study presents the first report
of in vivo measurement of lumbar intervertebral
disc pressure during HVLASM. The measurements
we obtained in the prone and side-lying positions
are similar to those recently reported for normal
lumbar discs in vivo. The 500-kPa pressure seen
in the prethrust manipulative position is similar to
pressures recently measured for normal subjects
sitting upright (550 kPa to 623 kPa); and the peak
pressure of 890 kPa during the manipulative thrust
is similar to pressures recently measured for normal
subjects sitting flexed (830 kPa to 1,133 kPa) (Sato
et al., 1999; Wilke et al., 1999). Thus, in the one disc
measured in this subject, the pressures during the
given HVLASM maneuver were similar to physio­
logic pressures and unlikely to reduce or cause a
herniation.
A increase in pressure of 40 kPa in the prone
and 15 kPa in the side-lying positions was seen following the HVLASM procedure. We do not know
the duration of this pressure change, since we only
took measurements for approximately 12 s in each
pre- and postmanipulative position. Since our testing of the device demonstrated measurement error
of approximately ±20 kPa on repeated measures, a
portion of this change may be artifact. If the manipulation did indeed cause the noted pressure change,
the mechanism whereby such change would occur
remains speculative.
Concerns for subject safety led us to perform
this preliminary study on only two highly informed
subjects. We excluded subjects with chronic pain
and/or particular psychometric profiles because
these factors have been shown to be related to
238 Lisi, O’Neill, Lindsey, Cooperstein, Cooperstein, and Zucherman
Figure 3 — Pressure during manipulation: A) Premanipulative positioning (note that this is elevated from the baseline); B) highvelocity, low-amplitude thrust resulting in cavitation; C) release of manipulative positioning and subject’s return to the side-lying
position.
chronic pain after discography (Carragee et al.,
2000). Continued caution is required when considering similar in vivo work in the future because longterm consequences are largely unknown. However,
this study is consistent with other recent in vivo
pressure measurements that were conducted without
significant adverse effects (Polga et al., 2004; Sato
et al., 1999; Wilke et al., 1999).
There are several limitations to this study, the
most significant being the n-of-1 sample size. Data
from more subjects are needed to more clearly
understand the pressure effects of HVLASM on
the lumbar disc.
All measurements were recorded with the sensor
oriented in the sagittal plane. We did not attempt to
take measurements with the sensor arranged in
the transverse plane also; therefore, we could not
confirm the presumed isotropic behavior of the
disc. However, such perpendicular measurements
would not have been technically possible during the
phases we were most interested in measuring, the
manipulative positioning and thrust.
There was no attempt to determine the location
of zygapophysial joint cavitation relative to the disc
being measured. It was not our intention to ensure
that cavitation occurred at L3–4, but merely to measure pressure at that level while it was being targeted
for manipulation. Indeed it is unclear whether singlelevel audible cavitation can be achieved accurately
with HVLASM (Ross, Bereznick, & McGill, 2004)
or whether such cavitation is necessary for clinical
improvement (Flynn, Fritz, Wainner, & Whitman,
2003). Future work measuring intradiscal pressure
changes in the presence or absence of same-level
cavitation may be interesting.
This study was limited to the measurement
of one manipulative maneuver. Variation in subject positioning and load application with various
maneuvers may yield different results. Pressures
were recorded from a normal-appearing disc in an
asymptomatic subject. Results from diseased discs
in symptomatic subjects may be different. Also,
current technology does not allow measurement of a
disc stress profile (McNally & Adams, 1992) during
HVLASM. However, since anomalous stress concentrations seen on profilimetry have been shown to
predict painful discs (McNally, Shackleford, Goodship, & Mulholland, 1996), such measurement may
Disc Pressure During Manipulation 239
be more clinically relevant than the simple pressure
measurement we conducted.
Measuring lumbar intervertebral disc pressure
in vivo during HVLASM was accomplished successfully. The peak pressures measured during the
manipulation positioning and thrust were similar to
pressures previously measured for sitting un­supported
and sitting flexed, respectively. These data do not support the hypotheses that manipulation can reduce a
herniation by decreasing intradiscal pressure or cause
a herniation by raising pressure to failure levels. Further work exploring the pressure changes caused by
different manipulative positioning and the changes
seen in symptomatic subjects may lead to a better
understanding of this treatment method.
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