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November chiropractic research:
Research Article of the Month
Colloca CJ, Keller TS. Stiffness and neuromuscular reflex response of
the human spine to posteroanterior manipulative thrusts in patients with
low back pain. J Manipulative Physiol Ther 2001;24(8):489-500.
ABSTRACT
BACKGROUND: Studies investigating posteroanterior (PA) forces in spinal
stiffness assessment have shown relationships to spinal level, body type,
and lumbar extensor muscle activity. Such measures may be important
determinants in discriminating between patients who are asymptomatic and
those who have low back pain. However, little objective evidence is
available concerning variations in PA stiffness and their clinical
significance. Moreover, although several studies have assessed only load
input in relation to stiffness, a more complete assessment based on
dynamic stiffness measurements (force/velocity) and concomitant
neuromuscular response may offer more information concerning mechanical
properties of the low back.
OBJECTIVE: To determine the stiffness and neuromuscular characteristics
of the symptomatic low back. Study Design: This study is a prospective
clinical study investigating the in vivo mechanical and muscular behavior
of human lumbar spinal segments to high loading rate PA manipulative
thrusts in research subjects with low back pain (LBP).
METHODS: Twelve men and 10 women, aged 15 to 73 years (mean age of 42.8
+/- 17.5 years) underwent physical examination and completed outcome
assessment instruments, including Visual Analog Scale, Oswestry Low Back
Disability Index, and SF-36 health status questionnaires. Clinical
categorization was made on the basis of symptom frequency and LBP
history. A hand-held spinal manipulation device, equipped with a preload
control frame and impedance head, was used to deliver high-rate (<0.1
millisecond) PA manipulative thrusts (190 N) to several common spinal
landmarks, including the ilium, sacral base, and L5, L4, L2, T12, and T8
spinous and transverse processes. Surface, linear-enveloped,
electromyographic (sEMG) recordings were obtained from electrodes (8
leads) located over the L3 and L5 paraspinal musculature to monitor the
bilateral neuromuscular activity of the erector spinae group during the
PA thrusts. Maximal-effort isometric trunk extensions were performed by
the research subjects before and immediately after the testing protocol
to normalize sEMG data. The accelerance or stiffness index (peak
acceleration/peak force, kg-1) and composite sEMG neuromuscular reflex
response were calculated for each of the thrusts.
RESULTS: Posteroanterior stiffness obtained at the sacroiliac joints,
transverse processes, or spinous processes was not different for subjects
grouped according to LBP chronicity. However, in those with frequent or
constant LBP symptoms, there was a significantly increased spinous
process (SP) stiffness index (7.0 kg-1) (P <.05) in comparison with SP
stiffness index (6.5 kg-1) of subjects with only occasional or no LBP
symptoms. Subjects with frequent or constant LBP symptoms also reported
significantly greater scores on the visual analog scale (P =.001),
Oswestry (P =.001), and perceived health status (P =.03) assessments. The
average SP stiffness index was 6.6% greater (P <.05) and 19.1% greater (P
<.001) than the average sacroiliac stiffness index and average transverse
process stiffness index, respectively.
CONCLUSIONS: This study is the first to assess erector spinae
neuromuscular reflex responses simultaneously during spinal stiffness
examination. This study demonstrated increased spinal stiffness index and
positive neuromuscular reflex responses in subjects with frequent or
constant LBP as compared with those reporting intermittent or no LBP.
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