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Abstract from the SRS 2001 Annual Meeting
Daniel Odermatt, MscA
Pierre A. Mathieu, PhD
Marie Beauséjour, MscA
Carl-Éric
Aubin, Ph.D
Hubert Labelle, MD Institut de génie biomédical, Université de Montréal/École
Polytechnique; Research Center,
Ste-Justine Hospital., Montréal, Canada PURPOSE:
Despite knowledge on the clinical outcomes of the Boston brace (BB) treatment,
there is a lack of understanding of its action mechanisms. To reduce the pressures
exerted by the brace pads, the patient could actively induce specific trunk muscle
recruitment patterns capable of correcting the scoliosis [1]. Although simulation
models identified trunk muscles on the convex side of the lumbar curve as being
potentially able to reduce the magnitude of the scoliosis, there is no clinical
evidence to support this [3,4]. This study was conducted to investigate the immediate
muscular reaction in response to bracing in scoliosis patients. METHODS: We collected
data from 11 female adolescent idiopathic scoliosis patients (King I or II type)
treated with the BB. Surface electromyographic (EMG) signals from 22 trunk muscles
were obtained with and without the brace under 4 controlled isometric tasks: 1)
maintaining an upright stable posture; 2) resisting a trunk flexion moment; 3)
resisting a right lateral trunk bending moment; 4) resisting a left lateral trunk
bending moment. A motion analysis system was also used to evaluate the magnitude
of the load-induced trunk movements during the execution of the last 3 tasks.
ANOVA tests were conducted with p ‹ 0.05. RESULTS: When the brace was worn, an increase
in back muscles EMG activity was observed in 93% of individual observations (43%
statistically significant) but no significant effect on the EMG of abdominal muscles
was observed. Individual significant braced/unbraced EMG ratios for back muscles
ranged from 1.28 to 2.34 while significant group ratios varied from 1.49 to 1.61
for tasks 1), 3) and 4). When specific muscular regions were analyzed, larger
increases were found for muscles spanning the convex side of the lumbar curve.
CONCLUSIONS: Our results indicate that BB has a stimulating effect on back muscle
activities particularly on muscles on the convex side of the lumbar curve. As
previously suggested, the recruitment of this muscle group could have a beneficial
effect on the scoliosis [3]. It thus seems that by seeking to reduce the pressures
exerted by the brace pads, the patient could actively recruit back muscles that
can have a corrective effect on the spinal deformity. References:
[1] Emans, J.B.,
Brace manual. Scoliosis Research Society, 1988.
[2] Katz D. et al., Spine, 22(12),
1302-1312, 1997.
[3] Schultz A., Haderspeck K., Takashima S., Spine, 6(5), 468-476,
1981.
[4] Wynarsky, G.T., Ph.D. thesis, University of Michigan, 1988.
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