Comparing Maximum Tolerable Pressure
BCI spinal orthoses are the easiest and most consistent to use among 10 braces tested
(2014) Andreas Kannenberg, Ph.D., Executive Medical Director North America, Otto Bock HealthCare LP
• They physically restrict movement
and motion of the lumbar spine and help
the wearer to achieve proper posture.1,2
• By splinting the lower trunk (lumbar
spine and pelvis), spinal orthoses
reduce the activity of the
paraspinal musculature.2,3
• By increasing the intra-abdominal
pressure, they push on the diaphragm
and pelvic floor, resulting in a reduction
of spinal load with widening of the
dorsal intervertebral disc space, facet
joints, and intervertebral foramina.2,4,5
To achieve these effects, clinicians often
recommend that patients tighten spinal
orthoses to their subjective maximal tolerable
pressure. Patients who suffer from reduced
muscle strength and osteoarthritis of the finger
joints, may have limited ability to tighten
an orthosis and reach maximum tightness.
Thus, the easier a spinal orthosis can be
tightened to the maximal pressure, the easier
it is for the patient to use and the greater the
possible clinical effects. Therefore, a study was
conducted by Syprosoft Engineering, Irvine, CA,
to investigate the pull force required to tighten
10 commonly available spinal orthoses to the
maximal tolerable pressure.
Methods
Ten spinal orthoses, five fitting the descriptor
of L0631 (Passport [BCI], Horizon [Aspen],
Miami [Össur], M-Spine 584 [M Brace], Sleeq
[Quinn Medical], and five fitting the descriptor
of L0637 (Protégé [BCI], Horizon [Aspen],
Miami [Össur], M-Spine 574 [M Brace], Sleeq
[Quinn Medical]) were repeatedly tightened to
subjective tolerance by five healthy volunteers.
Tightness-to-tolerance (T3) is defined as
the maximum tightness that the user can
comfortably tolerate while using the brace.
To get to T3 the user has to apply force on the
pull handles. The force required to reach T3
was measured using a Dillon Force Gauge,
Model GS. Applied force data was collected
three times each day for three days from each
volunteer to ensure any natural variations
can be properly averaged out. The force
measurements were averaged for each subject
and brace.
Results
The average pull force required to reach T3
differed between subjects and braces.
None of the volunteers were able to reach T3
with the two M-Spine braces tested. Thus, no
data can be presented for the M-Braces. Out of
the other eight spinal orthoses, the BCI Passport
and Protegé demonstrated the lowest pull force
required to reach T3 (Fig. 1).
Figure 1: Pull force required to reach tightness to tolerance (T3).
NOTE: M-Brace not shown as no one reached T3 with it.
Pull force needed to reach T3 (Newtons)
Spinal orthoses stabilize and relieve the lumbar
spine using three mechanisms of action:
Volunteer
The data for the two BCI braces showed not only
the lowest pull force necessary to reach T3, but
also that the pull force required to reach T3 was
the most consistent in each brace and across
subjects. Each subject needed about the same
pull force to tighten the Passport or Protégé,
respectively, to tolerance. This consistency
was not seen in the other braces tested. The
order of subjects from lowest to highest pull
force required to reach T3 varies considerably
between orthoses.
Discussion
The pull force required to tighten the BCI
Passport and Protégé to individual tolerance
is the lowest across all subjects. Moreover,
based on the consistency of the pull force
measurements, the pull mechanism of the BCI
orthoses appears to be the most consistent
and predictable. Assuming that the tolerable
abdominal pressure is more or less constant in
each individual and the translation of pull force
into abdominal pressure is consistent in every
brace, the pull force curves of all braces across
subjects should be largely parallel. As this is
not the case, it can be concluded that the BCI
Passport and Protégé are the easiest and most
reliable spinal orthoses to use for the patients,
ensuring the lowest and most consistent pull
force to reach maximum stabilization and relief
of the lumbar spine.
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1) Koes BW, van Den Hoogen HMM. Efficacy of bed rest and orthoses on low back pain. A review of randomized clinical trials. Eur J Phys Med Rehabil 1994;4:86–93.
2) van Poppel MN, de Looze MP, Koes BW, et al. Mechanisms of action of lumbar supports: a systematic review. Spine 2000;25:2103–2113.
3) Vad V, Lee M. Quantitative electromyography analysis of disc unloader brace. Pain Physician 2003;6:419-420.
4) Nachemson A, Schultz A, Andersson G. Mechanical effectiveness studies of lumbar spine orthoses. Scand J Rehabil Med Suppl. 1983;9:139-149.
5) Hodges PW, Eriksson AE, Shirley D, Gandevia SC. Intra-abdominal pressure increases stiffness of the lumbar spine. J Biomech 2005;38(9):1873-1880.