Oct 9, 1990 - Administration, and the M. J. Murdock. Charitable. Trust. t Department of Orthopaedics,. RK-lO,. University of Washington,. Seattle, Washington.
Copyright
by The Journal
1990
of Bone
and Joint
Surgery.
incorporated
Translation of the Humeral Head with Passive Glenohumeral BY
KEVIN
J.
DOUGLAS
MCQUADE,
T.
R.P.T.t,
HARRYMAN,
II,
TYLER From
D.
M.D.t,
GIBB,
the Department
JOHN
B.S.t,
A.
AND
of Orthopaedics,
SIDLES,
on the Glenoid Motion*
PH.D.t,
FREDERICK
A.
University
JOHN
M.
MATSEN,
CLARK,
III,
of Washington,
M.D.,
M.D.t,
PH.D.t,
SEATTLE,
WASHINGTON
Seattle
We have demonstrated that certain pasABSTRACT: sive motions of the glenohumeral joint are reproducibly accompanied by translation of the head of the humerus on the glenoid. We investigated the relationship of these translations to the position of the glenohumeraljoint and to applied torques and forces in seven isolated glenohumeral joints from fresh cadavera, using a six-degreesof-freedom position sensor and a six-axis force and torque transducer. Reproducible and significant translation occurred in an anterior direction with glenohumeral flexion and in a posterior direction with extension. We also observed posterior translation with external rotation and anterior translation with cross-body movement. The translation
sition between the late cocking and early acceleration phases of pitching a baseball. Posterior labral tears and calcification of the posterior part of the capsule, which are seen in pitchers, may be a result of these translations. Obligate glenohumeral translations are not the result of ligamentous insufficiency or laxity; instead, they result when the capsule is asymmetrically tight. This observation is consistent with the clinical observation that posterior translation is associated with tightness of the anterior portion of the capsule in osteoarthrosis and with excessively tight anterior repairs for glenohumeral instability.
occurring
head; therefore, translation of the humeral head on the aticular surface of the glenoid is mechanically possible. This is in contrast to the hip joint, where the deeply cupped acetabulum prevents translation of the femoral head. Two groups of investigators have used single-plane radiographs to document that translation occurs in living
with
flexion
was
obligate
in that
it could
not
be prevented by the application of an oppositely directed force of thirty to forty newtons. Operative tightening of the posterior portion of the capsule increased the anterior translation on fiexion and cross-body movement and caused it to occur earlier in the arc of motion compared with the intact glenohumeral joint. Operative tightening of the posterior part of the capsule also resulted in significant superior translation with flexion of the glenohumeral joint. CLINICAL RELEVANCE: Awareness that glenohumeral translation is associated with passive motion of the shoulder is clinically important in attempts to maintam or restore normal kinematics ofthe shoulder. Translations occurring with passive motions represent a departure from pure ball-and-socket mechanics. The obligate translations that we identified are likely to occur during physical examination or physical therapy when the joint is passively moved to the limits of its motion, when part of the capsule becomes tight. We suggest that glenohumeral translation may also be associated with motions in sports, such as the tran-
*
Although
none
of the
authors
has
received
or will
receive
benefits
for personal or professional use from a commercial party related directly or indirectly to the subject of this article, benefits have been or will be received but are directed solely to a research fund, foundation, educational institution, or other non-profit organization with which one or more of the authors are associated. Funds were received in total or partial support of the research or clinical study presented in this article. The funding sources were National Institutes of Health Grant RO1-AM37069-01 , the Rehabilitation Research and Development Service of the Veterans Administration, and the M. J. Murdock Charitable Trust. t Department of Orthopaedics, RK-lO, University of Washington,
Seattle,
1334
Washington
98195.
The glenoid
subjects.
Poppen
translation normal about
cavity
and
during
rotated.
Walker
abduction.
subjects, the four millimeters
ternally
is too shallow
observed Howell
humeral when
They
to capture
the humeral
superior-inferior et al.
found
that,
in
head translates posteriorly the arm is extended and ex-
concluded
that
“normal
tension
of
the capsule or the articular congruencies, or both, and not contraction of the muscular envelope, constitute the mechanism by which this posterior translation is mediated’ and ‘
that contraction placement did
of muscles not correct
on the side the translation.
this posterior translation was absent anterior instability. These observations
away from the disThey found that
in shoulders that have suggest that the pos-
terior translation that they observed in normal a product of tightening of the anterior part
shoulders was of the capsule
in extension
of the
and
external
rotation.
Laxity
portion of the capsule in shoulders bility would be expected to eliminate resulting translation. Passive motions important. Passive
anterior
that have anterior instathis tightening and the
of the glenohumeral joint are clinically manipulations of the relaxed shoulder
are used in examination of the shoulder in the clinic and the operating room. Physical therapy of the shoulder often includes forceful passive manipulation of the shoulder to the extremes thesia
of motion.
are used The
goals
Passive
to increase of our
investigation ThE
manipulations
glenohumeral
JOURNAL
under
anes-
motion. were
OF BONE
to determine AND
JOINT
the
SURGERY
TRANSLATION
THE
OF
HUMERAL
HEAD
ON
THE
GLENOID
P =
scapula
FIG.
Photograph field transmitter
of the set-up. F = of spatial sensor.
direction
and
selected
passive
magnitude
of locally icity
tight
of isolated tissues
Eight
and
translation
and not a product
with
is a result of aspher-
and
(from
in dish
of plaster,
fresh
adult
cadavera
were
pre-
of the scapulothoracic, sternoclaThere were three contralateral pairs
individuals
who
were
eighty-seven,
sev-
enty-seven, and seventy-two years old at the time of death), and two left shoulders (from individuals who were sixtyeight and sixty-one years old at the time of death). The skin
GLENOHUMERAL
sensor tronics; and
(Polhemus, Colchester,
positioned
R
and
torques
that
Sources
There
The
vertebral
border
of each
scapula
was rigidly
potted
ular
body
and
the face
The transmitter VOL.
72-A,
NO.
9. OCTOBER
of the glenoid
were
vertical.
coil of a six-degrees-of-freedom 1990
spatial
=
Douglas Electo the scapula
centimeters
lateral
to
applied
to the
scapula,
while
recorded with California).
a Macintosh
II com-
is a time-lag
in the
spatial
sensor,
which
we
for the angular outputs. Angular rotation of order one radian per second will therefore induce translation errors of order 0. 1 L, where L is an
0. 1 second
We
to avoid
Under
the most
made
this
favorable
we have
found
that
of absolute accuracy of better gular accuracy of 0.5 degree with results our studies
conditions
torque
and the the
our
measurements
of error.
(quasi-static
less than transmitter
spatial
than one or better.
sensor
mo-
forty cenand the is capable
millimeter and anThis is consistent
that were reported by An et al. However, in we did not rely on the absolute accuracy of the
sensor. Instead we used systematic errors, as will The force-transducer
known
all
source
tion, no metal in the environment, timeters of distance between receiver),
with plaster of Paris in a five-centimeter-deep plastic dish (Fig. 1). This container was rigidly fixed to a vertically mounted six-axis load-cell (Astek Model FS16OA-600; Barry Wright, Watertown, Massachusetts) so that the scap-
T
of Error
dimension.
Instrumentation
were
cell and the sensor were puter (Apple, Cupertino,
quasi-statically,
that
and
the spatial sensor detected the translation and rotation of the humerus with respect to the scapula. Data from the load-
anatomical
normal on inspection at the dissection at the conclusion of the experiment.
fifteen
sensor,
possible without interfering with a full range of The load-cell permitted accurate resolution of the
without intermittent was stable. A final appeared performed
of spatial
of McDonnell was secured
approximately
to be about
joint was
coil
the humerus. The receiving coil of this sensor was rigidly attached to the humeral shaft as close to the humeral head
measured
or roughness, and the shoulder was that the surfaces of the
receiving
=
Division Vermont)
and subcutaneous tissue were excised, along with the muscle over the medial one-third of the scapula. The criteria for the selection of specimens were that the glenohumeral joint had a full range of motion, the passive motion was smooth catching requirement
1335
MOTION
1 mounted
forces
from
pared by disarticulation vicular, and wristjoints.
PASSIVE
as was motion.
Methods
Preparation
shoulders
of shoulders
occur
head.
Materials and
that
glenohumeraljoints
that glenohumeral
capsular
of the humeral
Specimens
(force-transducer),
of the translations
motions
to test the hypothesis
load-cell
WITH
of 1474
control measurements be described. was calibrated by
newton-millimeters,
with
to correct applying a one-kil-
a
1336
D.
T.
HARRYMAN,
ogram weight on a fifteen-centimeter lever arm relative to the center of the humeral head. It was measured as 1471 ± 0.6 newton-millimeters root-mean-square (100 samples at 0.3 hertz), for an average error of 0.2 per cent. An inferiorly directed force of 9.83 newtons, centered on the humeral head, was measured as 9.50 ± 0. 17 newtons rootmean-square (100 samples at 0.3 hertz), for an absolute error of 3.3 per cent.
II,
ET
AL.
Location
of a Reference
of the Anatomical
All glenohumeral to the
scapula.
Axes
motions
Thus,
were
flexion
and
defined
with
extension
were
respect forward
and backward motions of the humerus about a horizontal axis perpendicular to the face of the glenoid. Abduction and adduction were outward and inward motions about a horizontal axis parallel to the glenoid face. External and internal rotation were outward and inward rotations about a vertical axis parallel to the humeral shaft. A final motion, identified as
cross-body
which
movement,
the humerus
to a position
was
a complex
was brought
where
from
the humerus
and
movement
the neutral
in
were
pa-
allel to the floor and pushed as far across in front of the scapula as possible. These scapula-referenced motions are not the same as motions that are referenced to the plane of the body. Raw data from the spatial sensor were transformed into the defined
anatomical
axes
with
use of transformations
that
were determined from defined manipulations of the shoulder. To specify the anatomical axes, the shoulder was placed in the anatomical neutral position, and its position was recorded.
Then
degrees,
and
the the
shoulder new
was
position
flexed was
approximately
recorded.
The
30 flexion
axis was defined as the axis of the rotation between the two measured points. The arm was abducted and the anterior axis was determined in a similar manner; it was externally rotated and the inferior axis was defined. In each shoulder these measured axes were found to be orthogonal (mutually perpendicular)
to within
then rectified to enforce
5 degrees
with a singular
or less.
The
value decomposition
axes
were
of the
choice
A similar technique was used to specify the defined anatomical axes for the measurements of force. The output from the spatial sensor was recorded with no load applied to the shoulder and with a load of approximately twenty newtons applied along the anterior axis. The measured vector force defined the anterior axis in spatial-sensor coordinates. The medial and inferior axes were similarly determined.
The
force
axes
that
were
determined
in this
-
and
abduction.
load of the shoulder, ported and the output
Similarly,
to determine
the center
point
the center error
on the
humeral
of the head
in the control
head.
is desirable,
measurements.
-
the capsule
remained
lax.
The
reference
point
was
as the point on the humeral head that moved least these maneuvers, as determined by a least-mean-
squares
fitting
algorithm.
averaged A similar
point
of
locate the reference point, the hurneral head was into the glenoid socket, and its position and oriwere recorded in ten positions as the shoulder was extended, abducted, and internally and externally through angles of less than 45 degrees positions
in which
defined during
the motion of the humeral
control measurements ensure translations were independent
reference
near
it minimizes
To pressed entation flexed, rotated
point
point
Head
Residual
0.7 millimeter technique
was
on the humeral
head
motion
of the reference
root-mean-square. used
relative
to locate to the
the
reference
force-transducer.
Several directions of applied force were measured. These forces always had a medial component, to ensure that the head remained centered. The sensor coordinates of the humeral head were defined as those about which the applied forces had a minimum moment-arm, as determined by a least-mean-squares fitting algorithm. Residual momentarms were typically three to four millimeters. Applied forces in this experiment
were
the corresponding
uncertainty
20
newtons
x
of order
twenty
newtons
in torque
4 millimeters
80
=
or less,
so
was on the order
of
newton-millimeters,
which was negligible compared with the 3000-newton-nillimeter torques that were typically applied. Translations
head
were
reference
relative
point
as motions
of the humeral-
axes, been All torques were calculated with moment-arms at the reference point on the humeral head.
to the
determined. originating During
data
the defined
anatomical
passive
made
neutral
movement
three rotations, three torques were displayed time
defined
along
anatomical
position
of the
translations,
joint,
forces,
screen.
to reproduce
had
glenohumeral
three
on the computer
it possible
that
desired
and
three
These
real-
motions
and
to apply a specified torque or force to the joint. Motions were performed manually in a fashion that is similar to passive
clinical
manipulation
was securely pressed motion was performed.
of the joint.
into
the glenoid
The
humeral
socket
head
while
each
way
were orthogonal to within 5 degrees and were rectified as already described. To determine the neutral position of the shoulder, data were recorded from the spatial sensor while the humeral head was manually pressed into the glenoid socket in the that is, 0 degrees of flexion, anatomical neutral position rotation,
by tracking
of the
A reference
technique
orthogonality7.
measured
that approximated
were
point
head. As will be discussed, that measured glenohurneral
position
the forearm
on the Humeral
Translations a reference
because
Definition
Point
the neutral
the weight of the humerus was supfrom the spatial sensor was recorded.
Measurement
of Force
and
Torque
We chose a maximum torque of 3000 newton-millifor each specified plane of motion because it was sufficient to cause reproducible translation and did not cause failure of tissues or sutures. Strongly coupled moments were characteristic of many motions that were studied. The nature of the shoulder is meters
such
that
obtained
a pure
by applying
rotational
motion
a torque ThE
about
a given
that is not necessarily
JOURNAL
OF BONE
AND
JOINT
axis
aligned SURGERY
is
TRANSLATION
OF
THE
HUMERAL
HEAD
ON
THE
GLENOID
TABLE NET
ANTERIOR
WITH
PASSIVE
GLENOHUMERAL
I
TRANSLATION*
(SEVEN
SPECIMENS)
Paired
Operatively Intact Capsule
-0.44
Flexion Extension External rotation
-4.81 (-1.68
to
1.17
±
1.86)
1.57 (-5.03
to
in millimeters
(range
and
mean net paired differences
to
-5.87
±
l.68)
to 0.35 ± 1.82)1
-4.95 (-1.23
to 0.86 ± 2.01)
0.86 to 6.84 (1.66 ± 2.6)
-
-0.56 to 4.96 (2.15 ± 1.85)1
2.91 2.81)
±
-0.85 (-2.75
±
-4.95
-
-8.39 2.42)1
to
(-2.17
I .47 to 5.64 (1.01 ± 2.4)
-3.92 (-0.14
Measured
*
translation. t The
-9.7 2.63)
±
2.74 to 12.89 (7.27 ± 3.l7)i
1.24 to 11.28 (5.14 ± 3.71)1
to
-
Cross-body movement
10.94 3.8)1
±
1.9 (-4.92
Internal rotation
Tightened Capsule
Vented Capsule
to
(3.79
mean
and
standard
in glenohumeral
translation
an intact capsule. The mean net paired differences in glenohumeral shoulder with a vented capsule. § According to paired t test, 0.01 p 0.05. #{182} According to paired t test, p 0.01.
0.30 to 4. 15 (2.19 ± 1.3) 2.05
(6.63
deviation), between
1337
MOTION
14.5
±
4.01)
Tightened-Vented Capsules
-0.2 to 2.64 (1.35 ± 1.08)*
-0.92
-2.42
to
(-0.11
±
-1.35 (-0.49
to 0.34 ± 0.55)
of 3000
the shoulder
with
1.31 1.17)
(2.30 newton-millimeters.
a vented
(see
text)
± ±
3.84 l.6l)*
to 2.28
2.69
-
±
0.97)
to 2.63
(0.53
±
1.8)
0.99 to 9.63 (4.47 ± 2.66)*
A minus
capsule
0.28 0.28
1.28)
±
to 4.08 ± l.67)
(1.72
(0.92
to 4.09
0.63
at a torque
(2.13
I .02 to 2.03 (0.65 ± 0.9)
-
to
Differences
Vented-Intact Capsulest
sign
indicates
posterior
and the corresponding
shoulder
with
with the axis of rotation. about the lateral axis of 3000 newton-millimeters,
For example, that
-
rotation
at a net
-
applied
2500
were
between
to produce
is, flexion the
and standard deviation) meters (flexion), 1600
translation
torque
moments
(mean
1600 newton-milli-
±
300 newton-millimeters
±
(adduc-
± 700 newton-millimeters (internal tion), and 1000 rotation). Thus, a combined flexion-adduction-internal rotation torsional load was necessary to produce pure flexion
the
shoulder
cross-body
movement,
the
mean
moments
2500
were
newton-millimeters (flexion), 1 100 newton-millimeters duction), and 800 newton-millimeters (internal rotation); external
rotation,
millimeters
the
(external
moments
(flexion), and 1000 The magnitudes rior, and medial-lateral were
tested.
measured
tendinous
standard
deviation) of 0.5
and superior of range Protocols
force
72-A,
accompanying of 9
for
small
connections
force
7 newtons.
forces
Similar
of forces
accompanied
the
motions
(mean
were
of 8
±
loading and
NO. 9. OCTOBER
1990
(flexion,
the
of these
protocols
move-
humeral
head,
was
or anatomical
impingement. For each lation
after
motion
repeated
from
excision
position,
scapula
and control) data motions, a Student
the
humerus.
shoulder
humeral
as osseous
the
net
trans-
(control)
with translation
To demonstrate between these
was used to determine on the
of an oppositely
The
and
direction
load-cell
data.
from
capsule
translation
application determined
such
was
the arm that
the statistical paired (exper-
for the group of shoulders in the paired two-tailed t test was used.
translation
magnitude
the humeral
any apparent
of the
yielding
by the capsule. of the difference
The eighth
with
irregularities
the experimental
identical
to which
were
and
translation of the humeral errors, asphericity of the
in the protocol,
complete
subtracted
by
humerus
into the glenoid socket. Measureafter complete excision of the capsule
served to control for any apparent head that resulted from systematic
glenoid
the degree was obligate
directed
force
of the applied
to the force
Results
motion.
Glenohumeral translations were large and were significantly altered by operative tightening of the capsule (Table I). The direction of the translation for a given motion was consistent
five
and cross-body
anterior
measurements each
between
securely pressed that were made
4 newtons,
Motion shoulders,
head ments
imental various
compared
at torque
flexion
medial ±
were
the applied
3 newton,
and magnitude
In seven VOL.
±
forces
corresponding
measurements).
(control
was induced significance
For example,
the
ening of the posterior portion of the capsule (two-centimeter overlapping of the posterior part of the capsule by mattresssuture technique), and after severance of all capsular and
in the
superior-infefor all motions
rotation,
and
were studied with the capsule intact, with the capsule to air with an 18-gauge needle, after operative tight-
(adduction); and were 2500 newton(adduction).
and external
capsule
internal
newton-millimeters
of anterior-posterior, forces were reviewed
The
newton-
newton-millimeters
newton-millimeters
with the weight of the arm. of 3000 newton-millimeters, force
1600
rotation),
2000
were
and 700 newton-millimeters rotation, the mean moments (internal rotation), 700
(extension), for internal millimeters
that
mean
(adfor
tightened
sion,
Each
The greatest component of torque that was applied for each specified motion was always in the primary direction of loading. The mean moments for extension were 2700 newton-millimeters (extension), 600 newton-millimeters (adduction), and 600 newton-millimeters (internal rotation);
an operatively
ment) vented
moment.
for
with
exten-
among
for all the shoulders, individual specimens.
but the magnitude varied This substantial variability
1338
D.
1.
HARRYMAN,
II,
ET
AL.
20
I 1o
Net
z 0 I-. 4
5
1
Cl)
0
I.-
-5
z4
Control
Control
-10 -80
-P100
-60
-40
-20
0
20
FLEXION FIG.
Representative indicate
flexion
Through the range caused
among our Intact
graph of the relationship and negative
mid-range anterior
shoulders
Table
between
extension;
flexion and extension
positive
arc of motion (for this shoulder, and
posterior
translation,
is reflected
ANGLE
Through applied
the mid-range torque
motions
-
deviations
in
generated
(degrees)
and glenohumeral
tension
Extension
arc of motion,
was
lax), no translation caused the humeral
and
120
translation.
Positive
numbers on the abscissa numbers, posterior translation. and extension out of this mid-
respectively.
by the standard
Flexion
100
on the ordinate indicate anterior translation and negative 35 to 55 degrees), no significant translation occurred. Flexion
Joints
during
80
numbers
intact
Glenohumeral
60
2-A
I.
Translation imurn
numbers,
40
(the
occurred. Flexion beyond head to translate anteriorly,
the head Excision
eliminated
glenohumeral
difference
between
shown
where capsule
caused capsule).
only mm-
The
this range while ex-
of the
angle
intact
(Fig.
capsule
in Figure
of flexion
translation
posteriorly
varied degrees
it was
approximately
55
mately
35 degrees
of extension.
2-A, tissue
2-A, control). and
the
The
control
is
2-A.
at which
began
(Fig.
capsuloligamentous
translation the
as net translation
posterior
remained
to translate
anterior
among of
translation
or
the shoulders,
but
flexion
and
approxi-
20 Intact
Net
Control
115 E
z
10
0 -J Cl)
Control
z 4 I-
-5 10 -100 -80
-60
-40 -20
0
FLEXION FIG.
The same data as in Fig. The translations are grossly unaffected.
2-A, but re-analyzed with the reference distorted relative to those of Fig. 2-A;
20
ANGLE
40
60
80
100 120
(degrees)
2-B
point on the humeral head however, the net translation
deliberately located eccentrically (value for intact capsule minus
ThE
JOURNAL
OF BONE
by one centimeter. value for control)
AND
JOINT
SURGERY
is
TRANSLATION
OF
THE
HUMERAL
HEAD
ON
THE
GLENOID
Intact Capsule Flexion
-4.08 (-0.97
Measured
*
shoulder
to
with a vented
§ According #{182} According
Control
(range
several
reasons,
itself,
eccentricity
differences
to
Paired
translation
at a torque
between
-0.75
translation
the
shoulder
The
the translations
-2.91
0.46)
±
newton-millimeters.
a vented
with
capsule
an operatively
text)
sign
to
-0.14
±
1.07)
indicates
inferior
and the corresponding
tightened
capsule
l.l9)*
±
-3.26 (-1.15
A minus (see
to 0.15
(-1.60
-0.41 to 2.09 (0.84 ± 0.84)J
with
between
Tightened-Vented Capsule$
to 0.67
(0.18
of 3000
the shoulder
Differences
Vented-Intact Capsulest
-1.70 to 3.88 (1.02 ± 1.85)
deviation),
1339
MOTION
SPECIMENS)
0.00 to 4.94 (2.13 ± 1.68)1
2.23 1.52)
±
in glenohumeral
t test,
0.01 p p 0.01.
t test,
shoulder
and
the
corresponding
0.2
millimeter
0.05.
in flexion
and
extension:
(Fig. 2-A) enabled us to correct for that could have occurred for one of
such
as systematic
error
of the humeral
head,
that was not the center
of the humeral
systematic
always
errors,
(SEVEN
Operatively Tightened Capsule
and standard
in glenohumeral
GLENOHUMERAL
capsule.
measurements
measurements translations
-2.35 (-0.13
and mean
differences
to paired to paired
control apparent
LATION*
-2.86 to 2.52 (0.52 ± 2.01)
1.64 2.00)
±
in millimeters
translation. t The mean net paired with an intact capsule. 1: The mean net paired
TRANS
Vented Capsule
-2.89 to 3.27 (0.35 ± 2.22)
Cross-body movement
SUPERIOR
PASSIVE
II
TABLE
NET
WITH
we
in the spatial
sensor
or a reference
point
head.
tabulated
To control
the
were
the two sets of data reference
points
identical
to within
(Figs.
were
2-A and 2-B),
one
that the net translations the reference point.
centimeter
were
even
apart,
insensitive
for
though
the
demonstrating
to the selection
of
for Translation
glenohumeral
during
Internal
and
External
Rotation
that is, from the translation at any given translation position, we subtracted the control translation at the same position. As a test of this method, we re-analyzed the data (Fig. 2-A) by tracking motion of a reference point that was
For the measurements of internal and external rotation, the arm was placed in 0 degrees of flexion and abduction.
intentionally shifted one centimeter away from the original reference point near the center of the head. Relative to the newly designated reference point, the humeral head was
compared
-
grossly
eccentric.
translations large and
This
(Fig. 2-B): angle-dependent
was even
apparent
control apparent
in the
Translation
(Table
not
of shoulders with
dramatic
the translations
that
I). The displacements
internal nificant
showed However,
during
rotation. difference
internal
that had an intact
order of two millimeters, rection for external rotation
re-analyzed
measurements translations.
was
rotation
with and
induced
by flexion
small,
typically
trends in the in the anterior
Venting of the joint in the translation.
external
especially
were
were
and
capsule,
on the
posterior direction
did not make
difor
a sig-
14 12
Tight
capsule
10
le E
z
6
0
Cl)
o
Control
-2 -4
-20
0
20
40
60
60
100
120
FLEXION ANGLE (degrees) FIG.
Representative graph comparing operative tightening of the posterior with an intact or vented capsule.
VOL.
72-A,
NO. 9, OCTOBER
1990
translation during flexion in shoulders part of the capsule, anterior translation
3
with an occurred
intact capsule, a vented capsule, at lesser angles and to a much
and a tightened greater
extent
than
capsule.
After
m shoulders
1340
D.
T.
HARRYMAN,
II,
ET
AL.
30 25
Resisted
20
Translation
z
15
Ui
0
10
0
U.
5
0 -5 0
1
I
I
I
I
.
10
20
30
40
50
60
FLEXION Representative during flexion.
example of an attempt The magnitude of this
Translation
Before due
during
the joint
to cross-body
the
largest
Cross-Body
was vented,
movement
in direction (Table anterior translation
at manual resistance force increased with
were
also
the translations small
and
that
venting
produced
that were
were
I). Venting of the joint to a mean of 2.2 millimeters,
change
4-A
to translation by the application the angle of flexion, as measured
Movement
ever,
of force in a direction by the load-cell.
a concomitant this
superior
excursion
was
any
Translation
the was of the
during
Anterior earlier
and
displacement to a greater
part
Operatively
Capsule
during
tightening
Flexion
translation
of the posterior
portion
of the
occurred at smaller angles intact (Fig. 3). There was
was
of tightening
capsule resulted in a significant increase (from a mean of 5 . 1 to 7 .27 millimeters) in anterior translation with flexion
(Table I). The anterior translation of flexion than with the capsule
posterior
of the
contrast to the minimum the same motion with
Operative
displacement
(Table
(mean,
II);
how-
2. 13 millimeters).
observed
(Table
Translation
The
internal
after
capsule
Rotation
rotation
operative
(Table
displacement the capsule during
External
I). This
that intact.
external
occurred
tightening
of
was
in
was noted No change
rotation
for in
as a result
I).
during
humeral
millimeters
and
during degree
the
Translation
to the observed
displacement small
lnternal
motions. Tightened
opposite
variable
increased which for
80
(degrees)
ANGLE FIG.
70
head
of anterior
Cross-Body
Movement
exhibited
between
translation
with
2.05 cross-body
and
14.5 move-
5 4
I 3
Unresisted
z
0 I-.
Translation
2
4 -I
Cl)
z
I
I-
0
Resisted Translation
4
-1
0
10
20
30
40
FLEXION FIG.
The application of a resisting force did not significantly obligate. Refer to Fig. 4-A for corresponding forces.
change
50
ANGLE
60
70
80
(degrees)
4-B
the translation.
The displacement
of the humeral
THE JOURNAL
head represented
OF BONE
AND
in this graph
JOINT
SURGERY
is
TRANSLATION
ment
after
OF
the posterior
HUMERAL
portion
operatively
tightened
(Table
translation
occurred
at lesser
than
THE
it had in the same
HEAD
ON
of the capsule
had
I). In all shoulders,
angles
shoulders
GLENOID
WITH
PASSIVE
GLENOHUMERAL
1341
MOTION
been
the anterior
and to a greater
when
THE
degree
the capsule
had been
intact. The
Obligate
To
determine
Nature whether
forced
by asymmetrical
being
associated
the observed
tightness
with
to prevent the anterior flexion of shoulders
laxity
translations
of the capsule,
were
rather
of the capsule,
than
we attempted
translation of the humeral that had an intact capsule
an oppositely directed We found that forces affect lation
of Translation
head during by applying
(posterior) force to the humeral head. of more than thirty newtons did not
the translation was obligate.
(Figs.
4-A
and
4-B).
Thus,
the trans-
Discussion
An important aspect measurement of all spatial ponents
of applied
is the
first
force
time
such
for
the
problems
that
traditionally
shoulder.
are not quantifiable permits
and torque.
information methodology
this
has
been
solves
two
been associated with manfirst, that hand manipulations
have
and
second,
viewing
accurate
To our knowledge,
Our
of the joints:
ible. Real-time
study is its simultaneous of freedom and all corn-
comprehensive
gathered
ual positioning
of this degrees
ofthe
that
they
of any desired
motion
or load-
ing condition. it permits
important
aspect
the measurement
in a manner
that
landmarks.
Furthermore,
measurements
of this methodology
that
translation
of any choice
of anatomical
the technique
head
we used
is that
of net glenohumeral
is independent
that the humeral
requires
head
certain
are thus
passive
joint and that mentous tissue
neither
be spherical.
to locate
assumes
nor
The kinematic
the reference
point
on
capsule,
lation
from
away
local
eliminated
servations translation
by
we refer
intact
glenohumeral
Glenohumeral
of the capsule, of the
entire
that translation
translation
of the joint
siderable
variation
VOL.
NO.
9. OCFOBER
1990
and
capsule.
con-
it can These
may accompany
may
surfaces.
in the radius
of trans-
as the capsular
can be increased in at earlier angles of motion
to occur
tightening
sectioning
suggest
to the phenomenon
manipulation of glenohumeral is even greater when there
and flexibility
72-A,
ofthe
the side of the joint (Fig. 5). Translation
straint mechanism magnitude and made by selective
not a critical
movements
constraint
head and glenoid fossa9. be almost flat or slightly
Rotations of the huoperatively tightened opposite to the tightdisplacement that are head on the glenoid translatory motion is
mechanism.
joints and is a tightened be affected
of curvature
be ob-
passive that this capsule.
by the shape
Saha demonstrated
appearance.
con-
of the humeral
The contour of the glenoid may curved, or it may have a definite In addition,
perfectly
spherical3’8”#{176}.Anatomical
variance
in the congruity
conformity glenoid
this translation is induced by capsuloligaof the glenohumeral joint. In a joint that has
a tightened
clinical
to as the capsular
yet anatomical
part of our protocol. They merely locate the point that is least sensitive to angulation errors in the control measurements. This is advantageous in reducing systematic errors, but our results are independent of the reference point. Our results demonstrate that translation of the humeral head on the glenoid reproducibly and predictably accomthe humeral
panies
referred
socket-like
A second
5
of asymmetrical tightening of the capsule. meral head that produce tension in the tissues of an capsule predictably cause translation in a direction tissue constraint. This constraint opposes loads and directed toward itself and acts to translate the humeral in a direction away from itself. This mechanism of
are not reproduc-
data on load and displacement
reproduction
FIG.
Effect
sections
of the (Figs.
studies
of the glenoid
and
surfaces
6-B).
The
head
have
is not
suggested
and humeral
and computerized
articular
6-A
the humeral
head3’8,
tomography
of the profile
show
humerus of
the
and glenoid
labrum changes and can practically disappear with rotation of the humeral head4. These observations suggest that cornpliance of the cartilage and labrum could help the articular surfaces to conform during translation of the humeral head. By contrast, the bearing-surface of total shoulder-prosthesis components is not compliant. Furthermore, in many prosthetic designs, the humeral and glenoid surfaces are congruent so that translation cannot easily take place. It is important to emphasize that we studied isolated glenohumeral
motion,
glenohumeral whenever this
capsule. The joint assumed
position
of the scapula
glenohumeral
translation,
phenomena the indicated
was not relevant
and
the
were observed position. The
to the observations.
In arcs of motion when the capsular tissues were not tight, there was no significant translation of the humeral head. The direction (relative to the scapula) ofthe translations that we observed during glenohumeral motion were anteriorsuperior translation during flexion, posterior translation during extension and external rotation, and anterior translation during internal rotation and cross-body movement. The greatest extent of glenohumeral translation for the motions cross-body
that
were movement.
tested
was Anterior
evident translation
during
flexion
and
of the humeral
1342
D.
Horizontal-plane (Courtesy of Chris
section Jobe.)
through
the
glenohumeral
joint,
T.
HARRYMAN,
showing
the
II,
flatness
FIG.
Double-contrast of the
computerized
tomographic
view
through
the
glenohumeral
ET
AL.
of the osseous
glenoid
fossa,
an architecture
that
allows
translation.
6-B joint.
The
cartilage
and
labral
elements
of the joint
conform
to the
head
humerus.
head during flexion could oppositely directed forces. Operative more
rotation,
anterior
tightening translation
and cross-body
not be prevented of the capsule in the motions
movement
by moderate,
caused of flexion,
than was noted
earlier
and
internal
in shoul-
ders that had an intact capsule. Venting the joint to air led to slightly translation and
of the humeral
cross-body
Significant
head
during
increased
the motions
anterior of flexion
movement.
superior THE
displacement JOURNAL
occurred
OF BONE
AND
with flexion JOINT
SURGERY
TRANSLATION
and cross-body capsule
OF
movement
was
tightened.
THE
when
HUMERAL
HEAD
the posterior
However,
only
ON
portion
a small
THE
GLENOID
WITH
as a ball
of the
and
apy. they et al.
reported
tions
bined
abduction,
internal
rotation,
and
cross-body
movement. place
during
When
translation
indicate passive
that glenohumeral motions
occurs,
of the
the joint
translation
Such
translations
would
be expected
The obligate nature of these translations suggests that may also occur with active motions. In fact, Howell
normal
Our results
socket.
1343
MOTION
-
We were interested in the effects oftightness of the posterior portion of the capsule because it frequently occurs in patients who have impingement syndrome5, as indicated by limitsflexion,
GLENOHUMERAL
to occur in certain clinical situations for example, during passive examination of motion and stability, examinations with the patient under anesthesia, and passive physical ther-
magnitude
of superior translation of the humeral head was anatomically possible because of the presence of the coracoacromial arch.
of forward
PASSIVE
takes
glenohumeral
joint.
is not functioning
strictly
evidence
that
extension,
translation
is reduced
translation
occurs
and external or eliminated
when
glenohumeral instability. Continued analysis meral translation will add to our understanding anisms
of motion
and
stability
with
rotation
corn-
and that there
is
of glenohuof the mech-
of the glenohumeral
joint.
References I. AN, K. N.; Biomech. 2. 3. 4.
,
JACOBSEN,
M.
C.;
BERGLUND,
L.
J.;
and
CHAO,
E.
Y.:
Application
of a Magnetic
Tracking
Device
to Kinesiologic
Studies.
HOWELL, S. M.; GALINAT, B. J.; RENZ1, A. J. ; and MARONE, P. J. : Normal and Abnormal Mechanics of the Glenohumeral Joint in the Horizontal Plane. J. Bone and Joint Surg. , 70-A: 227-232, Feb. 1988. MAKI, S. , and GRuEN,T.: Anthropometric Studies of the Gleno Humeral Joint. Trans. Orthop. Res. Soc. , 1: 173, 1976. MOSELEY, H. F. , and OVERGAARD, B.: The Anterior Capsular Mechanism in Recurrent Antenor Dislocation of the Shoulder. Morphological and Clinical Studies with Special Reference to the Glenoid Labrum and the Gleno-Humeral Ligaments. J. Bone and Joint Surg. , 44-B(4): 913-927,
1962.
5. 6. 7. 8. 9.
10.
VOL.
J.
21: 613-620, 1988.
NEER,
C. S. , II: Impingement POPPEN, N. K. , and WALKER, PREsS, W. H.; FLANNERY, B.
Lesions. Clin. Orthop. , 173: 70-77, 1983. P. S.: Normal and Abnormal Motion of the Shoulder. J. Bone and Joint Surg. , 58-A: 195-201, March P.; TENKOLSKY, S. A.; and VETTERLING, W. 1.: Numerical Recipes: The Art of Scientific Computing, New York, Cambridge University Press, 1986. SAHA, A. K.: Theory of Shoulder Mechanism: Descriptive and Applied. Springfield, Illinois, Charles C Thomas, 1961. SAHA, A. K.: Dynamic Stability of the Glenohumeral Joint. Acta Orthop. Scandinavica, 42: 491-505, 1971. TESTUT, J. L.: Trait#{233} d’anatomie humaine. Tome I. Osteologie, arthrologie, myologie. Ed. 7, pp. 503-504. Paris, Doin, 1921.
72-A,
NO.
9, OCTOBER
1990
1976. pp. 52-59.