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1976;58:195-201. J Bone Joint Surg Am.NK Poppen and PS Walker

Normal and abnormal motion of the shoulder

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References

CORTICAL BONE ATROPHY SECONDARY TO FIXATION 195

VOL. 58-A, NO. 2, MARCH 1976

(2) showed one-to-one correspondence between o . and

P. Hence, the stress calculated when P = maz the ulti-

mate bending strength (or stress crc).

The flexural modulus of elasticity (E) of the bonespecimen can also be calculated using the following

formula :

(3) Yq(4 (L.)() (a +--)

where Y(,( .4 5 the vertical deformation at point A (Fig. 2).

E= Pa 6IY, . \ 2

= 8.64 (-i-- (L\Y(,( A! \bh3

wherea = L = 1.2 cm.

Now atA the Instron cross-head displacement, andthe initial slope ofthe load-deformation diagram (Fig. 2) is

at A- Therefore, E can be calculated from equation (4).

I . AKESON, W. H., Woo. S. L-Y; COUTTS, R. D.; MATTHEWS, J. V. ; GON5ALVES, M.; and AMIEL, D.: Quantitative Histological Evaluation ofEarly Fracture Healing of Cortical Bones Immobilized by Stainless Steel and Composite Plates. CaIc. Tissue Res. , 19: 27-37, 1975.

2. BARDOS, D. L.: An Evaluation ofTi-6Al-4V Alloy forOrthopedic Applications. In Proceedings ofthe Orthopaedic Research Society. J. Boneand Joint Surg. ,56-A: 847, June 1974.

3. BAUMF.ISTER, T.: Marks Standard Handbook for Mechanical Engineers. Ed. 7, chapters 5-31. New York, McGraw-Hill, 1967.4. BYNUM. D. . JR.: ALLEN, G. F.; RAY, D. R.; and LEDBETTER, W. B.: In Vitro Performance of Installed Internal Fixation Plates in Compression.

J. Biomed. Mat. Res., 5: 389-405, 1971.5. CURREY, J. D.: The Mechanical Properties of Bone. Clin. Orthop., 73: 210-231, 1970.6. GODFREY. J. L.: Looking at Bone Plates and Screws. Eng. in Med., 1: 17-18, 1971.7. HICKS, J. H.: The Fixation of Fracture Using Plates. Eng. in Med., 2: 60-63, 1973.8. LINDAHI., OLov: The Rigidity of Fracture Immobilization with Plates. Acta Orthop. Scandinavica, 38: 101-114, 1967.9. ROMANUS, B.: Physical Properties and Chemical Content of Canine Femoral Cortical Bone in Nutritional Osteopenia. Acta Orthop. Scan-

dinavica, Supplementum 155, 1974.

10. UHTHOFF, H. K., and DUBUC, F. L.: Bone Structure Changes in the Dog Under Rigid Internal Fixation. Clin. Orthop., 81: 165-170, 1971.1 1 . Woo, S. L-Y; SIMoN, B. R.; and AKESON, W. H.: Evaluation of Rigidity of Internal Fixation Plate on Long Bone Remodeling. Abstract

published in Proceedings of the Twenty-eighth meeting of ACEMB, p. 150, New Orleans, Louisiana, September 1975.12. Woo, S. L-Y: AKESON. W. H.; LEVENETZ, B.; COUTTS, R. D.; MATTHEWS, J. V.; and AMIEL, D.: Potential Application ofGraphite Fiber and

Methyl Methacrylate Resin Composites as Internal Fixation Plates. J. Biomed. Mat. Res., 8: 321-338, 1974.

Normal and Abnormal Motion of the Shoulder

BY NORMAN K. POPPEN, M.D.*, AND PETER S. WALKER, PH.D.t, NEW YORK, N.Y.

From The Hospitalfor Special Surgery, Affiliated with The New York Hospital-

Cornell Unisersitv Medical College. New York Cit

ABSTRACT: The roentgenographic parameters ofmotion in normal and abnormal shoulders, including

the movement of the scapula, arm angle, glenohumeral

angle, scapulothoracic angle, excursion of the humeralhead, and instant center of motion for abduction in theplane of the scapula, were determined in twelve normalsubjects and fifteen patients. The scapula rotated ex-

ternally with abduction. The ratio of glenohumeral toscapulothoracic movement was 5:4 after about 30 de-

grees of abduction. The center of rotation of the

glenohumeral joint for abduction in the plane of the

scapula was located within six millimeters of thegeometric center of the humeral ball. The average ex-

cursion of the humeral ball on the face of the glenoid inthe superoinferior plane between each 30-degree arc of

motion was less than 1 .5 millimeters in normal sub-

jects. Significant previous injury resulting in abnormalmechanics of the shoulder joint was associated withabnormal values for excursion of the instant center and

* 535 East 70th Street, New York, N.Y. 10021.t Reprint requests to Dr. Walker, Codman and Shurtleff, Inc.,

Randolph, Massachusetts 02368.

of the humeral head. An abnormal glenohumeral-to-scapulothoracic ratio was associated with significantpain in the shoulder. The fact that these variousparameters were sensitive indicators of normal and

abnormal motion raises the possibility of diagnostic

clinical application.

Many authors 2,3.4.5.6.7,8,1O.II.I2,13 have pointed out the

complexity of the shoulder and nearly a century ago 2.3 the

interplay of the sternoclavicular, acromioclavicular,

scapulothoracic, and glenohumeral joints was described. It

has been suggested 11.12 that true abduction of the arm

should not be in the coronal plane, but rather in the plane

of the scapula which is angled 30 to 45 degrees anteriorto the coronal plane, because in the scapular plane the in-

ferior part of the capsule is not twisted and the deltoid andsupraspinatus are optimally aligned for elevation of the

arm. Inman and co-workers showed that all of the joints in

the shoulder girdle move simultaneously, and that in the

motion of abduction the glenohumeral joint moves twice

as much as the scapulothoracic joint. Saha described a

zero position of the humeral head on the glenoid basedon how much rolling and sliding takes place at the

I 96 N. K. POPPEN AND P. 5. WALKER

THE JOURNAL OF BONE AND JOINT SURGERY

FIG. I

Reference axes are taken in the humerus: x.y, scapula x,y, and bodyx,Y. The line x is a perpendicular to the true )Fthe axis ofThe humerus)through O. the center of the humeral head. The line v passes through thesuperior and inferior edges of the glenoid and .v is the mid-line of thescapular spine. O is chosen at the center of the glenoid fossa and hence

the x-axis passes through this point perpendicular to the y-axis.

glenohumeral joint. Dernpster applied the concept of treat-

ing the upper extremity as a series of rigid links to measure

the contributions made by each joint of the upper extremity

to bring the hand to a position where it can perform a re-

quired task. Freedman and Munro and Doody and as-

sociates analyzed abduction in the scapular plane and

found a ratio of 3:2 between glenohumeral and

scapulothoracic motion. This ratio was not substantially

affected when there was resistance to movement.

In this study we attempted to measure two other pa-

rameters of motion, as well as the angular movements of

the humerus and scapula when the arm is abducted in the

scapular plane: namely, the centers of rotation of the hu-

meral ball in relation to the scapula, and the excursion of the

ball on the face of the scapula. Using the various mea-

surernents we were able to compare the motion of the nor-

mal and the abnormal shoulder.

Subjects Studied

Materials and Methods

The main motion we studied was abduction ofthe arm

in the plane of the scapula. We had twenty-seven subjects,

of whom twelve were asymptomatic, normal volunteers

twenty-two to sixty-three years old, and fifteen were pa-

FIG. 2

Three sets of x-y axes are taken to define the joints positions. XY isfixed in the thorax, xy is fixed in the scapula, and ,y is fixed in thehumerus. 0A #{176}GH #{176}ST#{149}The arm angle (eA) is the angle formed bythe y-axis of the humerus and a line parallel to the Y-axis of the body.The glenohumeral angle (O(;H) 15 defined as the angle formed by they-axis of the humerus and the y-axis of the scapula. The scapulothoracicangle (O) is the angle formed by the y-axis of the scapula and a lineparallel to the Y-axis of the body.

tients seventeen to seventy-two years old who had lesions

of the shoulder and were about to have arthrography. We

adopted a technique similar to that of Freedman and

Munro to obtain roentgenograms in the plane of the

scapula with the arm in neutral rotation. An anteropos-

tenor roentgenograrn was made of each shoulder with the

patient standing with the torso at a 30-degree angle to the

plane of the roentgenogram. When the arm was abducted

to each of the required positions, the plane of abduction

was parallel to the plane of the roentgenogram and the

amount of abduction was gauged with reference to the axis

of the body.

Selection of Reference Axes

A study of the motion of the shoulder must start with

a definition of the axes in each of the two moving parts

(humerus and scapula) relative to the stationary part, the

torso (Fig. 1). The geometric center of the humeral head

(Oh) is chosen as one reference point because the curvatureis sufficiently close to uniform for this purpose, and the

center can be found by a simple geometric construction.

The reference point for the scapula (Os) was chosen to be

the center of a line joining the limits of the glenoid fossa.

On each roentgenogram the three sets of axes were drawn;

the axes of the torso were designated X,Y, the axes of the

scapula, x,y, and the axes of the humerus, x,y (Fig. 2).

Because Figure 2 was drawn from a roentgenograrn made

with the subject facing the x-ray source at a 30-degree

angle, in other words in the plane of the scapula, the XY

axes are in this plane and not in the coronal plane of thebody. The arm angle, glenohurneral angle, and

scapulothoracic angle are defined in Figure 2.

Several roentgenograms were made for each subject,

at 30-degree intervals from the dependent arm position up

A2

NORMAL AND ABNORMAL MOTION OF THE SHOULDER I 97

VOL. 58-A. NO. 2. MARCH 976

to maximum abduction in the plane of the scapula. Be-cause of the inevitable minor variations in a sequential set

of roentgenograms, a method was needed to obtain satis-

factory superposition of the sets of roentgenograms. A

master tracing was made of the scapula and humerus at 60

degrees of abduction (mid-range) and the axes were

marked. Each of the other roentgenograms (made at 0, 30,

90, 120, and I 50 degrees and at maximum abduction) was

superimposed over the master tracing as closely as possi-

ble and the individual axes then were drawn. In this way,

sequential patterns of movement were obtained.

Definitions of Parameters

Still referring to Figure 2, various parameters of in-

terest can now be defined. The tnosement ofthe scapula onthe thorax can be defined by following one point and one

angle, that is, O and the scapulothoracic angle (OST). In-

formation on the rotation ofthe scapula can be obtained by

determining the center of rotation of the scapula for each

30-degree interval considered. The directions of measure-

ment must be defined relative to the several axes. Also,

changes in and #{176}ST can be related to the arm angle

(OA) and the ratio OGH:OST can be determined.The excursion or sliding of the hurneral head on the

face of the glenoid (the rise and fall of the geometric center

of the ball, Oh) can be expressed as the parameter e, the

distance on the y-axis that #{176}h lies above or below the

center of the glenoid (Os).

The motion of the humerus on the glenoid can be de-

scribed in terms of the center of rotation. The method for

determining it is shown in Figure 3. For each 30-degree

interval of the arm angle between two sequential

A1

FIG. 3

Two roentgenograms of the same individual with different angles ofabduction can be used to determine the center of rotation for the anglemoved. This is done as follows: Draw the set of axes based on thehumerus for the tWo roentgenograms; select a single arbitrary interval

(OA) which is measured on the four lines of the two axes (A,01, B1,01, BI)4; bisect the lines A,.A and B,B: erect perpendiculars tothose lines: and C (center of rotation) is the intersection of those perpen-

diculars.

roentgenograrns of the same subject, the center of rotation

for that arc of motion is the pivot point about which thehumerus appears to rotate. The center of rotation of the

scapula on the thorax was determined by a similar tech-

nique.

Results

A typical set of sequential roentgenograms from a

normal subject (Fig. 4) illustrates the information ob-

tamed. In the relaxed position of the extremity with the

subject standing, the average arm angle (OA) for the fifteen

normal subjects was 2.5 degrees, with a range of from -3

to +9 degrees. The average scapulothoracic angle (OsT)was -4.7 degrees, with a range of from - I I to + 10 de-

grees. Freedman and Munro obtained a mean value of

-5.3 degrees, although Basmajian and Bazant stated that itinvariably faced somewhat upward.

In moving the extremity, in normal subjects the rela-

tionships among 0A #{176}GH and #{176}STwere different (Fig. 5)

in the arc of motion between 0 and 30 degrees of abduction,as compared with the arc of motion between 30 and 120

degrees. In all of our twenty-seven subjects as well as in

those of Inman and associates, Freedman and Munro, and

Saha results are in reasonable agreement. The averagearm angle measured from our roentgenograms with thearm in approximately 30 degrees of abduction was in fact

24 degrees. For the arm angle range of 2.5 to 24 degrees,

the ratio of the glenohumeral angle to the scapulothoracic

angle was 4.3: 1 . In other words, the scapula moved only

slightly compared with the humerus. The mean regression

lines were drawn for the range 24 degrees to maximum ab-

duction. For the twelve normal subjects, as well as for

three patients who were found to be normal in all respects,

the equations of the regression lines were: #{176}(;H

+ 12.6 and #{176}ST #{176}-40A 12.4. These indicate that in

that range (24 degrees to maximum arm angle) the ratio of

glenohumeral to scapulothoracic motion was actually 5:4

or 1 .25: 1 , meaning that there was not a great deal of dif-ference in the amounts by which they rotated. Freedmanand Munros ratio was 1.35:1 for the range 0 to 135 de-

grees, which is not very different from ours. Saha how-ever, found an average ratio of 2.34: 1 for the range 30 to

135 degrees for abduction in the plane of the scapula. Our

data are in contrast to the findings of Inman and associates

for abduction in the coronal plane; they stated that at the

glenohumeral and scapulothoracic articulations, the ratio,from almost the beginning to the termination of the arc, isrespectively two to one

Typically, as abduction progressed the glenoid face

moved medially, then tilted upward, and finally moved

upward somewhat as the arm was brought to maximum

elevation (Fig. 6). These motions can be expressed in

terms of the center of rotation of the scapula with respect

to the fixed axes in the body. From 0 to 30 degrees, the

scapula rotated about its lower mid-portion, and then from

60 degrees onward the center of rotation shifted towards

the glenoid, so that it was rotating about that area, result-

Sequential roentgenograms made in abduction in the plane of the scapula.

Y

GLtNO-HUStFRA A\C11 OGHSCAPUO-THORACI( A.GF Si

Tfus stud

- - - Inman Sarclers H. Abbott 1H44-.- SaGa 11

U Doodv freedar) Valerland IH7O00 .Freedman \lunro 1%6 7

V/

V

0

60 -

30

800

Fi;. 5

The relationships between the glenohumeral angle (();j) and the armangle (OA) and between the scapulothoracic angle (O) and the armangle. Each letter 0 denotes the O value for a representative individualpatient for the corresponding #{176}A#{149}

x

ARM ANGLE 9

198 N. K. POPPEN AND P. S. WALKER

THE JOURNAL OF BONE AND JOINT SURGERY

ing in a large lateral displacement of the inferior tip of the

scapula.

By plotting the positions of the tips of the acromion

and the coracoid it was clear that the scapula twisted about

its x-axis. Figure 7 shows how this was detected on a plain

roentgenogram. Assume that there is rotation about O in a

counter-clockwise direction. The coracoid tip will move

predominantly upward, while the acromion tip will move

backwards in the same transverse plane in relation to the

face of the glenoid. Hence, by measuring the upward

movement of the coracoid with respect to the face of the

glenoid, the angle of rotation can be calculated. The rota-

tion could, of course, be about the same axis parallel to x.

For all subjects, patients as well as normal individuals, the

acrornion remained stationary with respect to the face of

the glenoid except at high abduction angles when it tended

120

to rotate slightly downwards, as would be predicted (Figs.

6 and 7). This is consistent with a counter-clockwise rota-

tion (twisting) of the scapula on abduction of the arm that

occurs in the plane of the scapula. For the fifteen normal

subjects, the regression line for the twisting was: 0xs =

#{176}590ST with a correlation coefficient of 0.83.This means that the twisting angle was 0.59 times the

FIG. 6

The motion of the scapula in its own plane is defined by the position ofthe glenoid and the centers of rotation relative to fixed XY axes in thebody. The center of rotation of the scapula begins low in the body of thescapula and progresses upwards toward the glenoid. (Asterisk denotes

center of rotation for the specific intervals, 0 to 30 degrees and so on.)The outlines of the scapula corresponding to the 0 and I 50-degree ab-duction positions are shown.

Acromion

30600

150 150..120.90

60.

0-Coracoid

x

up

FIG. 7

30#{176}to Max.Glenohumeral to

Scapulothoracic RatioInstantCenter

(nun)

Excursion of

Ball on Glenoid(in,i)

Clinical Findings

VARIOUS PARAMETERS AND CLINICAL DETAILS OF THE PATIENTS AND Two NORMAL VOLUNTEERS (SUBJECTS K AND N)

MaximumSubject Arm Angle

Average of Normals

(Degrees)

Normal volunteersISO .25 0.25 6.0 1.85 1.09 0.475

K I 56 1.00 8.7 A* 1.2 Old GH dislocation (normal volunteer)

N 150 1.87 4.4 1.2 Normal volunteer

CL 112 1.00 7.1 4.OA Rotator-cuff tear

E 150 0.99 A 4.8 1.0 Shoulder pain; normal arthrogram

H 137 1.14 6.5 0.8 Rotator-cuff tear

J 147 1.36 6.6 1 .0 Painful shoulder; previous injury

M 155 1.15 10.7 A 2.OA Shoulder pain; normal arthrogram

0 156 1.38 1 1.2 A 1.45 Rotator-cuff tear

Q 137 0.99 A 4.2 0.8 Rotator-cuff tearR 152 2.24 A 8.2 1.1 Shoulder pain; normal arthrogram:

arthritis in cervical spine

T 128 0.68 A 4.0 0.6 Rotator-cuff tear

U 99 0.72 A 4.9 1.0 Shoulder pain; normal arthrogram:degenerative arthritis GH joint

V 123 0.83 A 12.1 A 2.7 A GH dislocation

W 164 0.93 A 10.8 A 2.2 A Rotator-cuff tear

x 129 1.41 14.2 A 4.OA Rotator-cuff tearY 99 0.236 A 13.25 A 2.2 A GH dislocations

z_ 148 0.826 A 12.7 A 2.2 A Painful shoulder; previous injury_______

* Designates a value outside of one standard deviation of the normal.

NORMAL AND ABNORMAL MOTION OF THE SHOULDER 199

VOL. 58-A, NO. 2. MARCH 1976

Rotation or twisting of the scapula about the x-axis is shown by theupward movement of the coracoid and little shift in the acromion relativeto the face of the glenoid (left). If the scapula is viewed in the lateralprojection (right), the coracoid would be seen to move upward with theacromion remaining on the same horizontal plane relative to the glenoid.

scapulothoracic angle. The mean amount of twisting at

maximum abduction was 40 degrees ( 9 degrees standard

deviation).

This twisting can be described as the superior angle of

the scapula moving away from the body wall and the in-

ferior angle moving into the body wall, that is, external ro-

tation of the scapula. This is of significance when con-

sidered with the external rotation of the humerus which

often occurs after 90 degrees of abduction. It now is evi-

dent that the humerus and the scapula move synchronously

to some extent, so that the relative amount of rotation may

be small, depending on how much the humerus rotates.

instant centers of rotation and ball excursion: In all

of the normal subjects, although there was some variation,

the instant centers lay quite close to each other and to the

center of the hurneral ball. In contrast to this, many of the

patients displayed centers of rotation which deviated con-

siderably from the center of the ball (Table I, Subjects K,

0, V, W, X, Y, and Z).

In order to assign a value which was descriptive of the

instant center patterns, the center of the humeral head was

located and the distance from it to each instant center was

measured. The distances were then averaged and scaled up

or down to correspond to an average humeral-head diame-

ter of forty-four millimeters. The average instant centervalue for the normal subjects was 6.0 1 .8 millimeters.

An abnormal value for instant center was one that was lo-

cated ten millimeters or more from the center of the ball.

The ball excursions showed an interesting feature.

From 0 to 30 degrees, and often from 30 to 60 degrees, the

humeral ball moved upwards on the glenoid face by about

three millimeters. Thereafter it remained constant, moving

only one millimeter or at most two millimeters upward or

downward between each successive position. For the

normal individuals the average movement from position to

TABLE I

200 N. K. POPPEN AND P. S. WALKER

THE JOURNAL OF BONE AND JOINT SURGERY

position was only 1 .09 0.47 millimeters. It was ex-

pected that there would be a correlation between the in-

stant center and the ball excursion, and this was borne out

when the abnormal values were compared (Table I).

Only seven shoulders from our series of twenty-seven

subjects showed distinctly greater instant centers and ex-

cursions than the remainder. Analysis of the seven abnor-

mal and one borderline abnormal shoulder was revealing

(Table I). All had either a previous glenohumeral disloca-

tion (Subjects V and Y), a rotator-cuff tear (Subjects CL,

W, and X), or significant shoulder pain associated with a

previous history of injury (Subjects M and Z).

Three (Subjects H, Q, and T) of the seven patients

with rotator-cuff tears documented by arthrogram did not

have abnormal values for ball excursion and instant center,

and one of these (Subject Q) was also noted to have a sig-

nificant tear of the rotator cuff at the time of surgery.

All of the three patients with a previous glenohumeral

dislocation (Subjects K, V. and Y) had abnormal values

for the instant center and only one had a normal value for

ball excursion. This sixty-one-year-old patient had been

asymptomatic for thirty-six years following a glenohum-

eral dislocation.

In the analysis of the ratios of glenohumeral to

scapulothoracic angle in the ten individuals with abnormal

ratios, none were patients. Two had had previous

glenohumeral dislocations (Subjects V and Y), three had

rotator-cuff tears (Subjects Q, T, and W), and one had

roentgenographic changes compatible with degenerative

arthritis of the glenohumeral joint (Subject U), one had

cervical osteoarthritis (Subject R), and two had significant

shoulder pain associated with a history of injury to the

shoulderjoint (Subjects Z and E). One individual with an

abnormal value was an asymptomatic volunteer (Subject

N). All but one of these ten subjects had significant shoul-

der pain or neck and shoulder pain. The five subjects with

abnormal glenoh umeral-to- scapulothorac ic ratios , butnormal values for instant center and ball excursion, in-

cluded one with degenerative osteoarthritis of the

glenohumeral joint (Subject U), two with rotator-cuff

tears, and one with no known shoulder symptoms (Subject

N).

A normal value for the glenohumeral-to-scapulo-

thoracic ratio was not significant because four subjects

with rotator-cuff tears (Subjects CL, 0, W, and X), one

subject with previous glenohumeral dislocation (Subject

K), and one with normal motion values and a painful

shoulder (Subject M) had normal glenohumeral-to-

scapulothoracic ratios.

It may be concluded that if a patient has an abnormal

instant center value (more than ten centimeters) and in ad-

dition an abnormal ball excursion (more than I .5 millime-

ters), a significant previous injury has occurred resulting in

abnormal mechanics of the shoulder joint.

An abnormal glenohumeral-to-scapulothoracic ratio

was associated with significant disease, but a normal ratio

of this kind did not rule out significant disease of the

shoulder joint.

Discussion

The measurements which have been described de-

pended primarily on the selection of reference axes drawn

in the thorax, scapula, and humerus. With careful

roentgenographic and graphic techniques these axes could

be drawn accurately and reproducibly. The glenohumeral-

to-scapulothoracic ratio in abduction motion was found to

be 5:4 after 30 degrees of abduction was reached. It is

emphasized that for a given arc of motion, this means that

the humerus moves 5 degrees on the glenoid, while the

scapula moves 4 degrees on the thorax. In contrast, a study

of Figure 5 reveals that the absolute angles O; to #{176}STare

in about a two-to-one ratio. The reason for this difference

is that from 0 to 30 degrees most of the movement is

glenohumeral, elevating that line, while there is lowering

of the scapulothoracic line for the motion from 30 degrees

upwards. This may explain the discrepancy mentioned at

the outset.

There is a surprising degree of conformity between

the humeral head and the glenoid in the frontal scapular

plane. Therefore, as long as there is a compressive force

acting, the glenohumeral articulation would be expected to

be stable, and the humeral head will rotate on a more or

less fixed center with little, if any, excursion. For the nor-

mal shoulder this was found to be the case. The upward

excursion occurring in the early range of motion would

probably be due to an initial sag of the ball in the depen-

dent position. Excessive excursion. along varying centers

of rotation, would occur if the conformity of the joint were

lost or if the component of shear force acting upward or

downward were excessive. The latter situation could arise

due to an imbalance of forces caused by muscle tears or if

pain disturbed the muscle coordination.

The fact that these various parameters seem to be sen-

sitive indicators of motion means that they can be of diag-

nostic use. For instance, as an adjunct to arthrography, a

motion study may indicate whether or not there is a

rotator-cuff tear producing abnormality of motion.

NoTF: Wt. ire gratelul fir a grant mm Sir. and Mrs. Skcn C. Clarke. Jr .. in support ofthus ork. and 0 Dr. Rohc L. Paucrson. Jr. . for hi guidance. S5.. faflk Sir. Ray Scafea andDr. Bernard Ghcfman for carrysng out the radiography . Mrs. Margaret Erkrnan greatfy a%sisted% oh the Organl/att()n and analysis of the materiaf

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Electromyography before and after Surgery for Hip Deformity

in Children with Cerebral Palsy

A COMPARISON OF CLINICAL AND ELECTROMYOGRAPHIC FINDINGS

BY JACQUELIN PERRY, M.D.*, M. MARK HOFFER, M.D.*, DANIEL ANTONELLI, M.5.*,

JOHN PLUT, M.D.*, GORDON LEWIS, M.D.*, AND RON GREENBERG, R.P.T.*, DOWNEY, CALIFORNIA

ABSTRACT: Twenty-three ambulatory children with

spastic diplegic cerebral palsy were evaluated clinically

and by electromyography before and after hip-muscle

surgery. The stretch tests originally designed to distin-

guish specific muscle tightness and spasticity werefound to be non-specific when tested by electromyo-graphy. Ambulatory electromyograms using needle

electrodes and telemetry generally showed decreasedactivity in the released muscles and, on occasion,

changes in activity in muscles not operated on. These

unanticipated changes after release may explain some

of the unpredictability of results of such procedures incerebral palsy.

Currently children with cerebral palsy and a spastic

gait are evaluated by observation of their gait and by a

series of stretch tests 15,8 Unfortunately, surgical treat-

ment based on these criteria may produce unpredictable re-

sults. We hoped that electromyography during the stretch

tests and and during gait might clear up some of the confu-

sion and aid in planning operative procedures that would

give predictable results. Initial work in this area was done

by Sutherland and associates.

Methods and Clinical Material

From January 1971 to August 1974, twenty-three

ambulatory children (Cases 1 to 23) with spastic diplegic

cerebral palsy, five to eighteen years old, were evaluated

and treated for their crouched walking posture (walking

with flexed hips and knees and internally rotated thighs).

Their functional class of gait 6 and use of apparatus as well

* The Professional Staff Association, Rancho Los Amigos Hospital,

7413 Golondrinas Street, Downey, California 90242.

as the findings by clinical stretch tests, gait examination,

and gait films were recorded (Table I and Chart VI).

In each patient, electrodes of fifty-micrometer

nylon-shielded copper wire were inserted in the rectus

femoris, gluteus maximus, gluteus medius, lateral ham-

strings, medial hamstrings, gracilis, adductor longus, and

iliacus , assuming iliacus activity to be similar to that ofthe psoas and hence representative of the activity of the

iliopsoas. Our testing system permitted only eight muscle

tests per run. We therefore selected the eight muscles that

we considered to be the most significant hip or knee mus-

des affecting gait. Prior to the selection, we tested four

children with cerebral palsy and found that the activity of

the tensor fasciae femoris roughly paralleled that of the

gluteus medius during gait and that of the hip flexors dur-

ing stretch tests. Furthermore, this preselection study

showed that the activity of the vastus muscles roughly

paralleled that of the rectus femoris during gait. Precise

definition of the contribution of these and other muscles

should, of course, await testing systems with twelve or

more testing channels.

The following stretch tests were carried out while re-

cordings were made: straight-leg-raising, hip flexion with

knees flexed, adductor stretch with hips and knees flexed,

Thomas test , external rotation of the extended hip, ex-ternal rotation of the flexed hip, Phelps-Baker gracilis

test 18 (extension of the knee with the hip flexed in exten-

sion and abduction), and prone flexion of the knee with the

hip extended (prone rectus test of Duncan or Ely) . These

tests were carried out in a standardized fashion for both the

clinical and the electromyographic evaluations. Each pa-

tient was first positioned in the testing posture and then

slow stretch was applied for four seconds as indicated by a