ΕΜΒΙΟΜΗΧΑΝΙΚΗ (BIOENGINEERING)

1. Εμβιομηχανικές Άρχες
Κηδεμόνων
Γεώργιος Χ. Κελάλης
Ορθοπαιδικός Χειρουργός
Κλινική Σπονδυλικής Στήλης
Metropolitan Hospital

2. Without intervention, a curve is likely to progress
between the time of detection and the time of
skeletal maturity

3. 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
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%.
Nachemson et al, 1982

4. Curves that are 20o
or less before the time
of skeletal maturity
are considered mild
and generally are
re-evaluated
every six months.

5. Curves that
• progress 5o to 10o in
6 months
• that are more than
30o 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.

6. 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

7. 1894
DARK AGES

8. MANY TYPES
OF BRACES
Milwaukee
Boston
Stagnara
Chenneau
Charleston
Michel
Lyonese
DDB
ΠΕΠ
Etc.

10. 21 EXPERTS
19 TLSO
2 MILWAUKEE

14. 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

15. 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 truncal
tissues to transmit the
brace forces to the spine
• The duration of brace
forces applied on the torso

16. Pressure
distribution and
forces generated by
braces on the
scoliotic deformities
were measured to
characterize
bracing
biomechanical
action on the torso

17. 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

18. 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 brace
The patients with the
greatest curves
achieved little
correction despite
significant levels of
applied force
Chase et al, Spine 1989

19. 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.

20. 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 derotational
forces on the spine they
also cause undesirable
forces that induce
lordosis.

21. An increase in
strap tension
by 50%
resulted in an
increase of 20%
in the mean
force exerted
through the
compression
pads

22. 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

23. 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

24. Even when the
patients returned in
the standing position
after having
performed other tasks
these were also
significant decreases
in strap tension

25. 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

26. 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

27. Bracing a scoliotic
curve should, in
theory, unload the
growth plates on the
concave side of the
vertebral bodies
near the curve’s
apex

28. 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.

29. Evidence
demonstrating
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

30. 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

31. Curve flexibility is an
important predictor
of successful brace
outcome.

32. Brace application
was a successful
treatment when
the initial
vertebral body
derotations were
maintained until
skeletal maturity

33. The efficacy of
brace treatment
in patients with
rigid curves was
strongly
questioned

34. 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

35. The type of brace
had a significant
effect on the
outcome
although this effect
was small compared
with the effects of
other variables

36. The daily duration for
which the brace was
worn also had a
significant effect on the
outcome

37. Bracing for twenty-three
hours per day
was associated with
the highest rates of
success

39. 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

45. Lumbar Pad Trochanter Pad
•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 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

47. Thoracic Pad
•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).

49. Derotation Pad
Axial 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.
Anterior Lumbar
Derotation Pad
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

50. ASIS 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
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

52. ΕΥΧΑΡΙΣΤΩ