Translation of the Humeral Head on the Glenoid with ...

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.