Εμβιομηχανικές Άρχες Κηδεμόνων
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Transcript of Εμβιομηχανικές Άρχες Κηδεμόνων
Γεώργιος Χ. Κελάλης
Ορθοπαιδικός Χειρουργός
Κλινική Σπονδυλικής Στήλης
Metropolitan Hospital
Εμβιομηχανικές Άρχες Κηδεμόνων
Without intervention, a curve is likely to progressbetween the time of detection and the time of
skeletal maturity
The risk of progression
• increases as the degree of curvature increases
• increases with the magnitude of the curve at the time of detection
• decreases with increased age at the time of detection
Nachemson et al, 1982
Younger girls (ten, eleven, or twelve years old) who had a curve of at least
30o at the time of detection had the highest likelihood of progression,
ranging from 90% to 100%.
Curves that are 20o
or less before the time
of skeletal maturity
are considered mild
and generally are
re-evaluated
every six months.
Curves that
• progress 5o to 10o in 6 months
• that are more than30o at the time of diagnosis
usually are treated with a brace, as early and intensive bracing is believed to preclude the need for an operation in most instances.
Ideally, braces should be prescribed
to patients with idiopathic scoliosis
with curves between 30o and 40o, or with curves less than 30o
who have a history of curve progression with a high risk for
continued progression
Edgar et al, JBJS, 1985
Kehl et al , Clin Orth, 1988
Lonstien et al. JBJS(Am), 1994
Nachemson et all, JBKS(Am), 1995
1894DARK AGES
MANY TYPES
OF BRACESMilwaukee
Boston
Stagnara
Chenneau
Charleston
Michel
Lyonese
DDB
ΠΕΠEtc.
21 EXPERTS
19 TLSO
2 MILWAUKEE
Combination of pressures applied to
the torso over a prolonged
period, brace treatment attempts to modify mechanically
the scoliotic spine morphology
and to control progression of spinal
curvature
Peterson et al, JBJS, 1995
The degree of spinal correction is related to many parameters such as • The flexibility of the spinal
curves
• The shape and stiffness of the brace shell
• The location, size and thickness of brace parts
• The strap tension adjustment
• The biomechanical properties of truncaltissues to transmit the brace forces to the spine
• The duration of brace forces applied on the torso
Pressure distribution and forces generated by braces on the scoliotic deformities were measured to characterize bracing biomechanical action on the torso
A flexible tissue matrix was developed, composed of thin circular sensors that measure the pressures generated at the entire skin-brace interface.
It was suggested that Boston brace action is limited mainly to specific regions of pressure
Measuring mean brace forces exerted locally by the brace found that correction of curves was not solely depended on the level of force applied by the braceThe patients with the greatest curves achieved little correction despite significant levels of applied force
Chase et al, Spine 1989
Measurement of
• magnitude,
• location
• and direction of pressures
generated by the brace and the forces present in the straps while the pts assumed different positions, proved that :posterior thoracic pads provided scoliotic correction and derotation and that brace interface pressure were present in all positions.
Low strap forces had scoliotic curves that progressed while in the brace, whereas those with high strap forces had a reduction in curvature.It was concluded that although high strap forces are necessary to ensure lateral and derotationalforces on the spine they also cause undesirable forces that induce lordosis.
An increase in strap tension by 50% resulted in an increase of 20% in the mean force exerted through the compression pads
Therefore it would seem that the effectiveness of the brace depends to a certain extend on how tightly it is adjusted and fastened Currently, there is no standardized strap tension at which the brace should be fastened to obtain optimal results
A great deal of variability in the strap tension also was found the patients were taking different positions regardless of how tightly the straps were originally fastened
Even when the
patients returned in
the standing position
after having
performed other tasks
these were also
significant decreases
in strap tension
Several authors
believe that the
Heuter-Volkmann
principle contributes
to the development
of adolescent
idiopathic scoliosis
(A.I.S.)
Machida et al, Spione, 1999
Dickson et al, JBJS, 1984
Stokes et al, Spine, 1996
Briefly stated, asymmetric loading or compression of the growth plates on the concave side of the curves inhibit growth leading to wedging of the vertebral bodies
Bracing a scoliotic
curve should, in
theory, unload the
growth plates on the
concave side of the
vertebral bodies
near the curve’s
apex
Growth stimulation leading to structural remodeling of the vertebral bodies, on the curve’s concave side may explain the improvement or lack of curve progression, as measured by Cobb angles, reported with successful brace management of A.I.S.
Evidencedemonstrating the biomechanical effects of the Hueter-Volkmann on the vertebral body growth in spinal deformities is lacking
The threshold and limit of the force magnitudes necessary for the Hueter-Volkmann principle to apply in A.I.S. have not been delineated
Frank et al Spine Journal, 2003
The purpose of this
investigation was to
determine whether
long-term brace
treatment stimulated
asymmetric
chondrogenesis in the
apical three vertebrae
Curve flexibility is an important predictor of successful brace
outcome.
Brace application
was a successful
treatment when
the initial
vertebral body
derotations were
maintained until
skeletal maturity
The efficacy of
brace treatment
in patients with
rigid curves was
strongly
questioned
The Prevalence and Natural History Committee of the Scoliosis Research Society decided to compare, with use of meta-analysis, the results of non-operative treatment of idiopathic scoliosis
The type of brace had a significant
effect on the outcome
although this effect was small compared
with the effects of other variables
The daily duration for
which the brace was
worn also had a
significant effect on the
outcome
Bracing for twenty-
three hours per day
was associated with
the highest rates of
success
The goal of brace treatment is to
prevent progression of the
scoliosis by:1. Correcting the lateral curve
2. Correcting the malrotation
3. Returning the torso to a balanced
position over the sacrum
4. Properly aligning the spine in the sagittal
plane
Trochanter PadLumbar Pad
•The length and position of the lumbar pressure pad is determined by applying
•pressure to the paraspinal muscle at the level of the lumbar apex of the curve and
every vertebral body with a segmental vertrebral tilt towards the curve.
•Added length must be estimated for patients with increased lumbar lordosis as this
results in an apparently shorter lumbar spine.
•If L4 and L5 are to be included in the lumbar pad, the pad thickness should be
tapered in this area so that a bridging effect between the gluteus and the upper
lumbar region do not occur
•A trochanter pad is
used to correct a stiff
lumbo-sacral curve and
to act as a lever arm for
the lumbar pad and/or
the axilla extension.
•It is usually placed on
the same side that L5
tilts toward.
•The length and position of the thoracic
pressure pad is determined from the
ribs which project downward from the
thoracic curve.
•The pad is positioned from the mid-illiac
crest roll level and extends superiorly to
include the rib of the apex vertebra.
•The pad should not extend above the
•rib of the apex vertebra.
•The thickness of the pad should not
extend to the posterior vertical
•trim line to avoid worsening thoracic
hypokyphosis.
•The thickness of the thoracic pressure
pad is determined by the severity of the
thoracic curve and the extent to which the
thorax is displaced from the center line.
•The pad should provide superior medial lift
to the ribs under the apex, thus the pad is
thicker at the bottom than at the top (a
triangle in cross section).
Thoracic Pad
Derotation PadAxial rotation is most efficiently corrected by using force
couples, that is using a pair of forces directed in opposite
directions working on opposite sides of the axis
majority of derotational corrective forces are built-in to
the brace.
Just as the lateral forces require a relief area
opposite the correcting force, rotational
forces require an area of relief so that the
spine can migrate axially to derotate.
These relief areas can be created by an
adjacent pad which draws the brace away
from the body as seen anteriorly or by
bending the brace away from the body as
seen posteriorly on the right
Anterior Lumbar
Derotation Pad
ASIS Derotation Pad
Because the ribs slope downward from back to
front, the anterior thoracic derotation pad will be
inferior to the posterior derotation pad on the
thorax to give the appropriate force.
Thoracic posterior derotational pads are not
recommended in patients who present with a
hypo-kyphotic or lordotic
thoracic spine.
Anterior Thoracic Derotation Pad
In order to keep the brace from twisting on the
pelvis, pads may be needed, in a force-couple
arrangement,opposite to the ones used for
derotation of the lumbar spine.
This can be accomplished by a pad anterior to the
ASIS on one side and by bending inward the
lower margin of the module posteriorly
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