to eccentric loading. The effect of preparation of the glenoid bone

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Edge displacement and deformation of glenoid components in response
to eccentric loading. The effect of preparation of the glenoid bone
D Collins, A Tencer, J Sidles and F Matsen
J Bone Joint Surg Am. 1992;74:501-507.
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Publisher Information
The Journal of Bone and Joint Surgery
20 Pickering Street, Needham, MA 02492-3157
www.jbjs.org
1992 by T!te Jourttal
Copyright
Edge
EFFEcr
THE
D. COLLINS.
M.D.t.
A.
TENCER.
In vestigation
The
ABSTRACT:
aration
of glenoid
effect
bone
OF
PREPARATION
PH.D4.
performed
of different
at the
PH.D4.
University
methods
on displacement
OF
J. SIDLES.
of the
osseous
displacement
cartilage
surface
was
and deformation
with
a curet.
displacement
and
deficiency
associated
and
of prep-
and
Reaming
with
simple
resulted
deformation.
less
removal
of
in the
Substantial
least
posterior
glenoid
was not
of displacement
deformation.
Glenohumeral
arthroplasty
head
This
that
is commonly
head
glenoid
developed
noid.
articulated
procedure
and function
in
problems
related
humeral
with
used
for the
residual
glenoid
increased
comfort
many
patients.
However,
Neer
to the undisciplined
articulation
component
In most
the
has substantially
on
surface.
As a result,
various
prostheses
systems
a flattened,
degenerated
he, and subsequently
for resurfacing
for glenohumeral
noted
of the
others,
of the gle-
arthroplasty,
joint
capsule
and through
the compressive
scapulohumeral
muscles”.
The glenohumeral
j oint-reaction
force
and it changes
from an inferior
abduction,
to a superior
direction
to an inferior
variable,
and
for
or more
personal
directly
direction
off-center
of glenoid
*One
the
been
tional
of the
authors
funding
dress
requests
VOL.
74-A.
received
or will
is associated.
article.
III.
School
M.D4.
fund.
were
study
of Medicine,
received
reprints
4. APRIL
to Dr.
I9)2
Seattle.
Matsen.
in total
in this
University
educaone
98195.
or
or partial
article.
The
of Arkansas
of Washington
Washington
related
which
for
School
Please
WASHINGTON
Seattle
for
loosening
of high stresses
These
stresses
of the
component.
at the
create
Although
Neer et al. found
no clinical
evidence
series’2,
other
reports
have described
fortunately,
analysis
of these
reports
ofloosening
in their
loosening’4’4.
Unis impaired
by their
inconsistent
of radiographic
definitions
of evidence
and
clinical
loosening
of a glenoid
component,
a problem
was addressed
in detail
by Franklin
et al.
Cofield
found
radiographic
cency
at the
evidence
of loosening
Neer prostheses,
being associated
glenoid
that
of
with fifty-two
of
with some radiolu-
bone-cement
interface.
In a more
detailed
study, Wilde et al. divided
component
into three
zones
and
the stem
measured
of the glenoid
the radiolu-
cency
occurred
near
in each
zone.
Radiolucency
of the
average
stem
in 89 per
width
of the
Wilde
lucency
et al. also reported
a high
immediately
postoperatively,
technical
problems
cent of the
lucent
zone
with
technical
the
Using
strict criteria,
rate
of loosening
prevalence
which
cementing.
problems
with
the
into
of radiosuggested
Bade
et al. susas well.
Barrett
et al. reported
a 10 per cent
of the glenoid
component
within
a
the stability
failure
tests
cemented
base
cementing
follow-up
period
of two to 7.5 years.
Although
a variety
ofdesigns
ofglenoid
are available,
there
have been few studies
influence
performed
the
components,
and the
was 1 .4 millimeters.
components
of factors
that
of the component.
Clarke
et al.
on glenoid
components
that had
scapulae
of cadavera
and
found
that
the torque
to failure
was three
to four times greater
than
that predicted
to occur in the shoulders
of living patients.
Fukuda
et al. found
that glenoid
components
had subin a direction
We suggest
that, in contrast
to a pull-out
mechanism
of failure,
an important
mode
of loosening
of the glenoid
component
is rocking
of the component
in response
to
glenohumeral
loads that are not centered
on the compo-
benefits
foundation.
with
presented
Surgery.
party
SEATTLE.
stantial
resistance
to failure
by pull-out
perpendicular
to the face of the glenoid.
fixabenefits
In addition,
organization
Funds
receive
Components
BONE*
MATSEN.
a potential
been
large,
small
for
a commercial
of this
to a research
1959 N.E. Pacific,
NO.
is available
Little
Rock,
Arkansas
72205.
of Orthopaedics,
University
for
is substantial,
that
from
non-profit
of Orthopaedic
Science,
Department
of Medicine.
use
research
or clinical
was DePuy.
tDepartment
Medical
has
subject
or will be directed
of the
source
support
authors
to the
or other
of the
direction
at 0 degrees
of
at 60 degrees,
and back
stock
or professional
institution.
more
the
effect
at 150 degrees’3.
These
loads,
coupled
with
the
bone
of
or indirectly
have
GLENOID
F.
pected
humeral
head is not captured
by the glenoid
component,
but rather
it is stabilized
on the concave
glenoid
by the
amount
THE
AND
eight of seventy-three
the other
prostheses
treatment
of pain
and loss of function
resulting
from
destruction
of the surfaces
of the glenohumeral
joint.
P#{233}an
is credited
with developing
the first total shoulder
prosthesis9.
More
recently,
Neer’
developed
a prosthetic
bone.
Incorporattd
tion, contribute
to the development
glenoid
component-bone
interface.
deforma-
associated
than
of the bone of the reamed
with significant
increases
humeral
Surgery.
of Washington
tion ofa glenoid component
under eccentric
loading was
investigated
in a series of scapulae
of cadavera.
Handburring
a,tdJoint
Displacement
and Deformation
of Glenoid
in Response
to Eccentric
Loading
BY
.
ofBotte
ad-
nent.
Such
unbalanced,
when
loads
such
capsular
There
preparation
glenoid
methacrylate
may occur
when
as when
the rotator
tightness
While
neutralizes
forces
is torn
are
or
is unbalanced7.
is little published
of the glenoid
component.
muscle
cuff
information
bone
on
it is possible
the
effect
the
on the effect
of
stability
of the
that
polymethyl-
of imperfect
prepa501
502
D.
COLLINS.
A.
TENCER.
J. SIDLES,
FI;.
Photograph
glenoid
ofthe
hone
ration
layer
(D).
of the
of this
fragmentation.
preparation
specimen
apparatus.
cup
glenoid
material
(E).
and
showing
linear
bone,
it is also possible
is subject
to fatigue
without
We tested
the surface
the perpendicular
variable-differential
Theoretically,
this risk can
of the bone
so that it directly
component
of
experimental
an interposed
the hypothesis
of the glenoid
layer
that a thin
failure
and
be avoided
supports
by
the
component.
component
the
reduces
disand deforma-
The
specific
hypotheses
the
component.
to be tested
component
component
(2) increasing
ous surface
to the
creases
displacement
were
(1) eccen-
results
in displaceand deformation
of
conformance
of the
osse-
undersurface
of the prosthesis
deand deformity,
and (3) posterior
insufficiency
of the glenoid
bone (such as is often seen in
patients
who have degenerative
disease
of the glenohumeral joint)
contributes
to local deformation
of the component
under
eccentric
These
hypotheses
experimental
transverse
mounted
nor
loading.
were
tested
with
the
use
of
an
apparatus
in which
combined
axial
and
loads
were
applied
to a glenoid
component
in the scapula
of a cadavera
while
the dis-
placements
edges
combination,these
of the
of the
anterior,
posterior,
component
measurements
III
plunger
(A).
at the
ment
and
of the
load
plunger
glenoid
deformation
Preparation
and
lateral
edges
were
superior,
measured.
reflected
and
infe-
Taken
of the
the displace-
component
(C).
(F).
component
under
load.
of the Specimen
the E.vperimental
Apparatus
scapulae
ders
of
distorted
were
human
glenoid
removed
cadavera.
and was
specimens
had
These
specimens
no
from
One
of
not used.
five
pairs
unconstrained
evidence
of glenohumeral
were
selected
because
the
deformation,
of shoul-
the scapulae
The remaining
had a
nine
arthritis.
surface
of
covered
by the prosthetic
The glenoid
and scapularwere potted
in a specimen-
support
cup with fast-setting
potting
plaster
Buff: Columbus
Dental,
St. Louis,
Missouri).
we used
a specially
(Labstone
To permit
designed
non-clinical
all-polyethylene
glenoid
component
with a
radius
of curvature
of thirty
millimeters
and only one
four-millimeter-diameter
central
fixation
peg. The component
had a rounded-rectangle
shape,
as do components that are used most commonly
in the clinical
setting,
and it was three
millimeters
thick.
The component
was
mounted
on the glenoid
bone after each sequential
step
ofthe
preparation
of the osseous
surface.
The central
peg
fit snugly
into a hole drilled
into the center
of the face of
the glenoid:
this
cement
or other
fixation.
in
(B). glenoid
component
each one could
be completely
component,
without
overhang.
neck portions
of each scapula
Methods
tric loading
of the glenoid
ment of the edges
of the
load
Ten
of cement.
F. MATSEN.
I
transducers
that optimum
preparation
bone,
so that
it fits
undersurface
of the glenoid
placement
of the edges
of the
tion or warp of the component.
AND
ing and
The
The
prevented
grouting
peg
provided
sliding
substance
minimum
of the component.
No
was used for glenoid
restriction
to rock-
no resistance
to deformation
of the component.
load was applied
to the glenoid
through
a harTHE
JOURNAL
OF
BONE
AND
JOINT
SURGERY
EDGE
DISPLACEMENT
AND
DEFORMATION
OF
GLENOID
503
COMPONENTS
in any of eight orientations:
posterior,
posterior-inferior,
anterior,
and
placements
nor edges
with
the
anterior-superior.
of four
(model
New
posterior-superior,
inferior-anterior,
At each
of the anterior,
of the glenoid
use
ducers
sauken,
superior,
inferior,
posterior,
component
linear
position,
inferior,
were
the
dis-
and supedetermined
variable-differential
trans-
050-DCD:
Shaevitz
Engineering,
Jersey),
as shown
in Figures
1 and
Penn2. The
core of each linear
variable-differential
transducer
was
suspended
from
the edge of the glenoid
component
at
the location
of measurement.
Each
core floated
freely
within
the barrel
of the corresponding
transducer,
which
was
attached
bone rigidly.
the glenoid
to the
fixture
that
Displacements
were measured,
analog
digital
lation,
Marlborough,
converter
Schematic
diagram
showing
the magnitudes
loads
applied
to the glenoid
component
through
of the linear
variable-differential
transducers
tached
to the glenoid
component.
dened
radius,
steel
ball-bearing,
centered
on the
with
glenoid
and directions
of the
the loading
ball. One
(LVDT)
is shown
at-
(model
preparations
removal
with
glenoid
DT-2801;
Data
within
of
Trans-
a personal
corresponding
to a reso-
hole was drilled
in the center
of the
The stability
of the glenoid
component
for each
glenoid
after
five different
of the
first
bone.
stage
of the
of the
articular
only
subchondral
glenoid
bone
was
a twenty-five-millimeter
component
(Fig. 1 ). This
the
to the face
of a twelve-bit
Sequence
The fixation
glenoid
surface.
was determined
The
held
Massachusetts)
computer,
to within
0.001 volt,
lution
of 0.000125
millimeter.
Experimental
also
perpendicular
with the use
its attached
preparation
of the
cartilage
with
bone
remained.
performed.
The
linear
glenoid
a curet,
was
so that
No shaping
of the
glenoid
component.
variable-differential
transducer
slight
degree
of mismatch
between
the radii of the ball
and the glenoid
was selected
to avoid
the inadvertent
loading
of the rim of the glenoid
component
that results
cores,was
mounted
on the glenoid
bone. With the loading
ball resting
on the glenoid
component,
a set of zero-load
readings
was recorded
from each of the linear
variable-
from
minimum
humeral
and
differential
verse
loads
displacements
glenoid
radii.
in perfectly
conforming
A force
of 196 newtons
(30
were
per cent
of average
body
weight)
was applied
to the
loading
ball in a direction
perpendicular
to the glenoid
surface.
The load was maintained
at a constant
196 newtons with
the use of a servohydraulic
materials-tester
(Bionix,
model
nesota)
set
glenoid
connected
face
cylinder
tester.
828;
on
MTS
Systems,
Minneapolis,
A
transverse
load-control.
was applied
to a load-cell
load
the
component
to the ball by a second
plunger,
and a pneumatic
cylinder.
The
was mounted
By adjustment
on one side-post
of the pressure
of the materialsof the cylinder,
seous
surface
approximate
a
transverse
load of forty-nine
newtons
could
be maintamed.
These
two applied
loads may also have had frictional
shear
components
ball. If friction
is ignored,
the
glenoid
was
202
at the surface
the approximate
newtons
at
perpendicular
to the glenoid
surface
tude of this load was close to that
vivo
at both
30 and iSO degrees
unweighted
arm”.
By rotation
of the
respect
ponent
VOL.
to the transverse
could
be loaded
74.A.
NO.
4. APRIL
glenoid-holding
load
with
1992
of the
net
14 degrees
loading
load on
from
the
(Fig. 2). This magnipredicted
to occur
in
of abduction
of the
apparatus
plunger,
the
the transverse
with
glenoid
comcomponent
recorded
from
each
Then
perpendicular
while
the net
of the
linear
and transdisplacements
variable-differen-
tial transducers.
This procedure
was repeated
with the
transverse
component
of the load oriented
in each of the
eight different
directions.
For the second
stage of the preparation,
the glenoid
Mmto
transducers.
were
applied
and
loading
ball
were
removed,
of the glenoid
was carefully
the shape
of the back of the
and
the
contoured
glenoid
os-
to
com-
ponent
by an experienced
shoulder
surgeon
using
a
hand-held
power-burr.
The glenoid
component
and the
cores of the linear
variable-differential
transducers
were
reinstalled
and the measurements
were made as they had
been
for the first preparation.
In the third
stage,
the subchondral
bone
of the
noid
was reamed,
with
the use of a custom-designed
gle-
thirty-millimeter-radius
reamer,
so that it corresponded
to the radius
of the back of the glenoid
component.
The
measurements
were repeated.
For the fourth
stage of the preparation,
the posterior
25 per cent of the previously
reamed
glenoid
bone
was
measured
and was removed
The testing
was repeated.
along a straight
The fifth stage
vertical
consisted
line.
of
504
D.
COLLINS.
A.
TENCER.
J. SIDLES.
TABLE
DIsPl.AcIs.i1NI
OF
EDGE
TIlE
OF TIlE
GLENOID
AND
F
MATSEN.
III
I
COMPONENT
(IN
MILLIMETERS)
IN RESPONSE
TO
LOADING*
Comparison
Method
of Glenoid
Cartilage
Removed
Directiont
Superior
0.16
Preparation
HandBurred
± 0.14
0.22
Reamed
± 0.23
0.16
Cartilage
Removedl
Hand-Burred
± 0.13
Hand-Burred!
Reamed
= -1)51
t
0.31
±0.27
0.15±0.15
0.13±0.06
0.62
Posterior
0.39 ± 0.30
*Values
tThe
INS
removal
after
are given
direction
0.49
± 0.17
0.21
0.15 ± 0.10
as average
of the
± 0.19
NS
I =0.36
t
NS
p
t
NS
= 4.30
p < 0.001
t=2.24
t=0.26
I = 2.23
p
NS
p
t
and standard
transverse
load
± 0.19
1.28
=
1.29
t=
0.14 ± 0.08
= 0.04
t
NS
NS
Anterior
Removed!
Reamed
t =0.67
NS
Inferior
Testedt
Cartilage
<
t
0.05
= 2.01
<
0.05
= 4.44
p<0.001
<
0.05
deviation.
and
the
edge
of the
glenoid
component
at which
the
displacement
was
measured.
not significant.
=
of the
posterior
33 per
which
the testing
This
sequence
of
cent
was done
experiments
of the glenoid
bone,
again.
was
performed
on
each of the nine glenoids.
Although
it would
have been
desirable
to quantitate
the quality
ofeach
preparation
of
bone,
we did not have access
to a method
with which
to
do this.
of the
Displacement
Edges
of the
resulting
ent preparations
of the glenoid
on the
each edge of the component
in response
rected
toward
that edge
(for example,
the superior
I). Because
Results
Displacement
edge
toward
the bone
(a positive
value),
and in most
instances
hand-burring
and reaming
progressively
diminished
the displacement
of the component.
A comparison
was done of the effects
of three
differ-
Component
from
loading
(toward
in eight
direc-
from
edge in response
we considered
the
the
glenoid)
and
glenoid)
to be
displacement
to loading
displacement
to superior
both
positive
negative
loading)
(Table
displacement
displacement
undesirable,
of
diof
we
(away
calculated
the
tions was measured
at each of the four edges
of the nine
glenoid
components
after each of the five stages
of preparation.
Displacement
was recorded
in millimeters,
with
positive
values
indicating
downward
displacement
(to-
means
and standard
deviations
on the basis of the absolute values
ofthe
displacements.The
paired
Student
t test
was used to calculate
significance
of the differences
resulting
from different
glenoid
preparations.
The greatest
ward
displacements
nor loading,
were
followed
nor loading
In general,
and the
the mean
the glenoid
surface).
The displacement
ofthe
component
was
calculated
anterior
edge
for each
of the
ofthe
nine
after each of three
different
stages
of preparation
glenoid
bone (Fig. 3). It was found
that anterior
almost
always
produced
displacement
of the
glenoid
shoulders
of the
loading
anterior
hand-burring
tilage
and
seen at the anterior
by the posterior
inferior
edge
displacements
edge with anteedge with poste-
with inferior
loading.
were diminished
by
in comparison
with simple
removal
of carby reaming
in comparison
with hand-burring.
Cartilage
Displacement
(mm)
0.40
of the anterior
types
of preparation
away
from
the
glenoid
of the
hone.
edge
glenoid
Note
Hand Burred
0
FIG.
Displacement
of the glenoid
bone.
that
the
Positive
displacement
component
values
indicate
of the
3
in response
to anteriorly
displacement
component
Removed
toward
was
0 when
directed
the
the
loads
glenoid
first
THE
in nine glenoids
bone
glenoid
JOURNAL
and
was
tested
OF
after
negative
BONE
three
values,
in the
AND
reamed
JOINT
different
displacement
state.
SURGERY
EDGE
DISPLACEMENT
AND
DEFORMATION
TABLE
DIsPI.AIMIsr
FOR
RE,\smI
OF liii
GI.INoIos
AND
Method
PosrtRIoR
R)k
Etxw
REAMED
OFFIIE
Gl.INoIDs
MADE
Reamed
± 0.08
GLENOID
TwENTY-FIVE
(IN
AND
MILLIMETERS)
ThIRTY-THREE
Deficient
Deficient
Deficient
0.17
0.16
t =
± 0.18
C’Errr DEFICIENT
25 Per
The
when
mean
the
(Fig.
displacement
tangential
calculated
for
each
4). The
sponse
rendered
was
of the
three
cent
and
of the
four
toward
different
after
then
-I .14
reamed
glenoid
did
not
edge
reamed
did not
significantly
cent
significantly
increase
in response
to anterior
We were
interested
nent
the
from
table.)
reflected
the
the glenoid
Warp
after
the
cartilage
bone.
The
greatest
(mm)
NS
the displacement
had
been
displacements
at the
under
Ifthe
anterior
and
and inferior-anterior
in whether
the
the
loads
glenoid
were
applied
under
anterior
to the
at
We
defined
warp
placement
posterior
in this
the
for
in this
a given
and posterior
vector
sum
(This
relative
difference
a given
of the
in these
loading
of the anterior
edge)
(displacement
displacement
removed
edges
loading.
glenoid
compo-
did not deform
vector
sum of the
would
be equal
that
posterior
disthe
of
can be verified
to the top of a
The extent
to which
these
sums
were
not equal
the deformity
induced
in the component
by the
Thus,
the reamed
collected
from each of the four edges
of
with eight different
directions
of loading.
as an example,
the effect
of eight direcon the displacement
at the four edges of
component
Deficient
superior
and inferior
displacements.
with a piece of cardboard
moved
load.
from
deformed
load, the
placements
deficient
increase
occurred
investigation.
had
the posterior
edge
in response
to posteriorly
directed
loads
(Table
II). We calculated
the means
and standard
deviations
on the basis of the absolute
values
obtained
from the nine glenoids.The
paired
Student
t test was used
for the statistical
comparisons.
Data
were
the component
Figure
5 shows,
tions of loading
Reamed
33 Per Cent
NS
preparation
in re-
glenoid
33 per
displacement
at the posterior
edge.
A substantial
loss of posterior
bone
glenoid
AsPIr*
t=0.25
edges
at its posterior
aspect
was calculated
also (Fig. 4). Again,
the greatest
displacements
were seen with anterior,
postenor,
and inferior
loading.
Preparation
of the glenoid
diminished
the displacements,
and posterior
deficiency
of the
Cent!
Deficient
it was
preparations
posterior
the
L()AI)S
PosmRI0R
deviation.
oriented
of the
loading
25 per
standard
at each
vector
displacement
to posterior
been
and
AT TIlE
33 Per Cent
NS
*Values
are given
as average
tNS = not significant.
TO PosTERIoR
IN RESI)NSE
PER
Reamed
25 Per Cent
33 Per Cent
± 0.12
505
COMPONENTS
II
COMPONENT
of CilenoidPreparation
25 Per Cent
0.14
GLENOID
OF
edge
inferior
sums
condition
as warp.
equals
displacement
of the superior
+
(disof the
edge
+
edge).
Our
data
suggested
that
the displacements
of the
anterior
and posterior
edges
of the glenoid
component
were not always
reciprocal
and that these displacements
were not always
accompanied
by corresponding
similar
displacements
of the
superior
and
inferior
We calculated
shoulder
for
the warp ofthe
glenoid
each
loading
condition
preparation.
We
substantially
under
found
that
certain
the
edges
component
and each
component
5).
in each
glenoid
deformed
circumstances.
0.30
(Fig.
Since
U
Cartilage
0
Hand burred
any
Rem.
#{149}Reemed
Superiorinferior
AnteriorPosterior
Posterior25%
Direction
of
FIG.
74-A,
NO.
4. APRIL
1992
Posterior33%
Def.
loading
4
Displacement
of each of the four edges
of the glenoid
component
in response
three
different
preparations
of glenoid
bone
and for the reamed
glenoid
bone
posterior
aspect.
The results
are the means
of the absolute
values
for the nine
from those
recorded
after only the cartilage
had been
removed
are designated
VOL.
Del.
to loads
directed
toward
after
it had been
rendered
glenoids.
The values
that
with an asterisk.
that edge. The results
are shown
for
25 and 33 per cent deficient
at the
are significantly
different
(p < 0.05)
506
D.
COLLINS.
A.
TENCER.
J. SIDLES.
TABLE
WARP
OF lIIE
GI.lNoIo
COMPONENT
FOR
Direction
Superior
- .Cartilage
Removed
0.41
Inferior
Posterior
0.44 ± 0.50
*Values
tNS
MethodofGlenoidPreparatiori
HandBurred
0.44
0.27
± 0.58
are given
IN RlsIoNsE
I’() Fot
III
Mu.t.Is1IIERs)
DIFFERENT
III
GI.lNoID
DIREIIoNs
IR
OF
L0ADIN;
PREPARATIONS*
ComparisonTestedt
0.5 1 ± 0.70
0.45
THREE
F. MATSEN.
Cartilage
± 0.49
Anterior
(IN
AND
as average
0.56
Reamed
0.30
± 0.40
0.36
± 0.62
standard
± 0.38
± 0.42
Removed!
Reamed
t = 1.51
t
NS
NS
p
t = 1.53
t = 2.11
I
NS
p
0.05
p
I = 1.40
t
NS
NS
NS
I = 2.58
t = 0.69
p
NS
t = 2.31
p < 0.05
-0.2()
=
I =
0.18 ± 0.24
Cartilage
Hand-Burred!
Reamed
t
0. 1 7 ± 0. 1 1
± 0.58
0.24 ± 0.28
and
Removed!
HandBurred
<
-0.67
0.05
<
=
<
2.26
0.01
3.73
=
<
=
0.005
0.70
deviation.
= not significant.
FIG.
I
Interior
0
Superior
D
Anterior
.
Posterior
5
The displacements
at each
of the four edges
of the glenoid
components
superior
(PS). posterior
(P). posterior-inferior
(P1). inferior
(I). iliferior-anterior
the means
of the values
for the nine glenoids
that had been
prepared
with
in response
to loading
(IA),
anterior
(A).
removal
of the cartilage
in eight
directions:
and anterior-superior
only.
Displacement
(mm)
superior
(AS).
(S),
The
R
Cartilage
0
Hand burred
posteriorresults
are
Rem.
Reamed
Superior
Inferior
Direction
Anterior
Posterior
to
Posterior-
25% Def.
33%
Def.
of loading and displacement
FI;.
The warp of the glenoid
components
in response
the means of the absolute
values of warp. The values
been removed
are designated
with an asterisk.
Posterior-
different
directions
that are significantly
6
of
loading
different
after
(p
<
different
0.05)
THE
from
preparations
those
JOURNAL
recorded
OF
of
the
after
BONE
hone.
only
AND
The
the
JOINT
values
cartilage
SURGERY
are
had
EDGE
warp
the
is undesirable.
warp
DISPLACEMENT
we considered
in our
statistical
the absolute
analysis.
in four different
of preparation
different
states
ciency
of the
(Fig.
in the
conformance
of the
component
deficiency
significantly
under
6 and
posteriorly
directed
III).
An
surface
warp,
in the reamed
glenoid
increase
the warp ofthe
that
of
design
of the
ance,
the
prosthesis,
cementing
tor cuff, and
prostheticjoint.
The
only the effect
the displacement
adequacy
of the preparation
of the
and warp of the glenoid
this component
metal
backing,
pegs.
It was
integrity
only
glenoid
bone
component.
mechanism
is rocking
Thus, our
nent
benefits
a keel,
by the single
of loosening
of the
produce
an
off-center
on
To
little
resultant
force.
In
whereas
with
to warp
was
in the
direction.
glenoid
approxianterior,
is common
in
arthroplasty,
or
espe-
arthritis
that
part
of the capsule
of recurrent
instability.
loss
of a bone
graft
of
bone
for
at the posterior
to a posteriorly
cent
may
support
edge
directed
by a 25 per
was
In
posteriorly
complete
It is difficult
to know
merits
bone-grafting.
by posterior
results
deficiency
of this study
how
of
much
In this
of the compoload was not
or even
a 33 per
of the
reamed
glenoid.
that
careful
prepara-
suggest
so that it matches
component
helps
the contour
to stabilize
of
the
against
the eccentric
loads
that are encounthe daily use of a prosthesis.
A substantial
degree
of stability
of the glenoid
be achievable
even without
the
metal
backing.
or a keel.
the
only
the
of the reamed
glenoid
bone. Similarly,
the
glenoid
component
was not significantly
component
tered
during
our
the
excessive
tion of the glenoid
bone
the back of the glenoid
loads.
compo-
load,
component
is osteoarthrosis
increased
cent deficiency
warp
of the
component
experimental
system,
this type of loading
displaced
glenoid
component
as much as 0.62 millimeter
when
use
significantly
The
when
it conformed
under
the
to be treated
diagnosis
study,
displacement
nent in response
increased
or eccentric
a transverse
are
the glenoid
component.
of an osseous
deficiency
by virtue
and
cent
so that
prosthesis.
allows
after
the anterior
for the treatment
to the
bone.
that an impor-
peg
that
patients,
lead
of cement,
or multiple
glenoid
in response
to off-center
mode
of loading
included
to
deforms
support
if the
these
and warp, we
that had only
peg. Therefore,
of the quality
of the fit against
the glenoid
Our clinical
experience
has suggested
tant
component
developed
tightened
rota-
50 per
prepared
of the
load. The warp
of the component
one-half
millimeter
with loading
cially
applies
to the
was to explore
displacement
component
fixation
did not have
the
fixation
with screws,
stabilized
than
glenoid
bone.
and inferior
ofthe
polyethylene
component
permitted
obserof deformation
in response
to loading.
A perfectly
shoulders
bal-
of the
the patient
of this study
enhance
our ability
to detect
used
a thin, all-polyethylene
one small,
central,
uncemented
of a
the
of soft-tissue
the
loads
that
objective
stability
include
from the
posterior,
by more
posterior,
superior,
or inferior
Posterior
deficiency
of
technique,
the
removed
anterior,
had been
undersurface
non-conforming
under
mately
been
the
reduced
supported
did not
component
to the clinical
of these
factors
the
bone
to the
Use
loads.
contribute
Some
at
were
507
COMPONENTS
had
glenoid
better
vation
Discussion
Many
factors
glenoid
component.
GLENOID
edges
increase
to the shape
and posterior
preparation
glenoid
OF
the cartilage
Displacements
warp
directions
after
and for posterior
of posterior
defi-
Table
of the glenoid
diminished
the
DEFORMATION
value
We found
occurred
under
loads
three
different
stages
loading
with the two
glenoid
AND
component
use of cement,
appears
screws,
to
a
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