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References

C O RT ICA L BO NE AT R O P H Y S E CO ND AR Y T O F IX AT IO N 19 5

VO L . 58-A N O. 2 M AR CH 1976

(2) show ed one-to-one correspondence betw eeno . an d

P. Hence, the stress calculated w henP = m az t he ulti-

m ate bending strength (or s tress crc).

The flexural m odulus of elasticity E) of the bonespecim en can also be calculated using the follow ing

form ula

(3) Y q(4 L . a +- )

where Y , .4 5 the vertical deform ation at pointA (F ig. 2).

E= P a 6IY . \ 2

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

wherea = L = 1.2 cm .

N ow a t the Instron cross-head displacem ent, andthe initia l slope ofthe load-deform ation diagram (Fig. 2) is a t A - Therefore, E can be calcu lated from equation (4).

I . AKE SON W . H ., W o o. S . L Y ; C O U TTS R . D .;M AT T H E W S J . V . ; G O N5 A LV E S M .; an d AM IE L D .: Q ua ntita tive H isto log ica l E va lua tion ofE arly F racture H ealing of C ortical B ones Im m obilized by S tain less S teel and C om posite P lates . C aIc. T issue R es. 19 : 27-37 , 1975 .

2. B AR DOS D . L.: A n Evaluation o fTi-6A l-4V A llo y forO rthoped ic A pp lica tions.In Proce ed ings o fthe O rthopae dic R esea rch Socie ty. J . B oneand Joint S urg. 56 A: 847, June 1 974.

3. B AUM F. IST E R T.: M a rks S ta ndard H andb oo k for M echa nica l E ng ine ers . Ed .7, chapters 5-31 . N ew Y ork, M cG raw -H ill, 1967.4. B Y N U M . D . . JR .: ALL E N G . F .; RAY D . R .; an d L E DB E T T E R W . B .: In V itro Pe rform a nce of In sta lle d Internal F ixa tion P la te s in C om pression.

J. B iom ed. M at. R es., 5 : 389-405, 1971.5. C U R R E Y J. D .: The M echa nica l P rope rtie s of B o ne . C lin. O rthop ., 73 : 210 -231 , 1970.6. GODFR E Y. J. L.: Looking at B one P lates and S crew s. E ng. in M ed.,1 : 1 7 1 8 1 97 1.7. HIC KS J . H .: The Fixation of Fra ctu re U sin g P la te s. Eng. in M ed ., 2 : 60 -63 , 1973 .

8. LINDAHI. O Lov: The R igid ity o f Fracture Im m o biliza tion w ith P la te s. A cta O rthop. S ca nd ina vica , 38: 101 -114, 1967 .9. R OM ANUS B .: Physical P roperties and C hem ical Content of C anine Fem ora l Cortical Bone in N utritiona l O steopenia. Acta O rthop. Sc

dinavica, S upplem entum 155, 1974.

10 . UHT HOFF H . K ., and D UB UC , F. L.: Bone Struc ture Changes in the D og Under Rigid Internal Fixation. Clin. O rthop.,8 1: 1 65 1 70 1 97 1.1 1 . Wo o S . L - Y; SIMoN B . R .; an d A K E S O N W . H .: E va lua tion of R igid ity of In terna l F ixa tion P la te on Long B one R em odeling . A bstrac

published in Proce ed ings o f the Tw en ty-e ig hth m e eting of A C EM B , p. 150 , N ew O rle ans , Louis iana , S ep tem ber 1975 .12 . Wo o , S. L-Y : AKE SON. W . H .; L E VE NE T Z B .; C O UTTS , R.D .; M AT T H E W S J . V.; an d AMIEL D .: Po te ntia l A pplica tion o fG raphite Fiber a nd

M ethyl M ethacryla te R es in C om posites a s Intern al Fixation P la tes . J. B iom ed . M at. R es., 8 : 321 -338, 1974.

Normal and A bnorm al M otion of the Sh ou lder

BY N OR M A N K. PO PPEN ,M .D. AN D P E T E R S . W AL K E R PH .D.t N E W YO R K N .Y.

From The Hospitalfor S pecial Surgery , A ffiliated with The N ew Y ork H ospital-

C ornell Unisersitv M edical C ollege. New Y ork C it

A B S T R A C T: The ro entgen og rap hic param eters o f

m otion in no rm al an d ab no rm al sh ou lders in c lud ing

th e m ovem en t of the scapu la arm an gle g leno hu m eral

angle, scapu lo th oracic an gle excu rsion of th e hu m eral

h ead a n d instant cen ter o f m o tion fo r ab du ctio n in th e

plan e of th e scap u la w ere d eterm ined in tw elve no rm al

sub jects and fifteen patients . Th e scapu la ro ta ted ex

tern ally w ith ab du ctio n . Th e ra tio o f glen oh um eral to

scap u lo th o racic m o vem en t w as 5: after ab ou t 30 d e

g rees o f abd uction . Th e cen ter o f ro ta tio n of the

g leno hu m eral jo in t for abd uction in the plan e of the

scap ula w as lo cated w ith in six m illim eters of th egeo m etric cen ter of th e h um eral b all. The average ex

cu rsion of the h um eral b all o n the face o f th e g leno id in

th e su pero inferior p lan e b etw een each 30 d egree arc o f

m o tion w as less th an 1.5 m illim eters in no rm al su b

jects . S ign ifican t p reviou s in ju ry resu ltin g in abn orm al

m ech anics of th e sh ou lder jo in t w as associa ted w ith

ab no rm al valu es for excu rsion o f the in stan t center and

* 535 E as t 70 th S tree t, N ew Y ork, N .Y .10021.t R eprint requests to D r. W alker, C odm an and S hurtleff, Inc.,

R a ndolp h, M a ssa chuse tts 02368 .

o f th e h u m eral head . A n abn orm al glen oh um eral to

scapu lo tho racic ra tio w as asso cia ted w ith sig nificant

pain in th e sho uld er. The fact th at th ese vario us

param eters w ere sen sitive ind icato rs of n orm al and

abn orm al m otion ra ises th e p ossib ility of diag no stic

c lin ic al a pp lic at io n.

M any authors 2 3.4.5.6.7 8 1 O.II .I2 13 have pointed out the

com plexity of the shoulder and nearly a century ago2.3 th e

interplay of the sternoclavicular, acrom ioclavicular,

scapulothoracic, and glenohum eral joints w as described. It

has been suggested 11.12 that true abduction of the armshould not be in the coronal plane, but rather in the plane

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

f er io r p art o fthe capsule is not tw isted and the deltoid andsupraspinatus are optim ally aligned for elevation of the

arm . Inm an and co-w orkers show ed that all of the joints in

the shoulder girdle m ove sim ultaneously, and that in the

motion of abduction the glenohum eral jo int m oves tw ice

as m uch as the scapulothoracic joint. Saha described a

zero position of the hum eral head on the glenoid basedon how m uch rolling and slid ing takes place at the


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I 96 N. K. PO PPEN A N D P. 5. W A LK ER

THE JOU RN AL OF BO NE AN D JO INT SU RG ERY

FIG . I

R efe re nce a xe s are taken in the humerus: x.y, sca pula x,y, andbodyx ,Y. Th e line x is a perpendicular to the true )F he axis ofThe humerus)through O the center of the humeral head. The line v passes throughthesuperior 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

th e x-a xis p s s s t h r ou g h this point perpendicular to the y-axis.

glenohum eral joint. D ernpster applied the concept of treat-

ing the upper extrem ity as a series of rigid links to m easure

the contributions m ade by each joint of the upper extrem ity

to bring the hand to a position w here it can perform a re-

quired task. Freedm an and M unro and D oody and as-

sociates analyzed abduction in the scapular plane and

found a ratio of 3:2 betw een glenohum eral and

scapulothoracic m otion. This ratio w as not substantially

affected w hen there w as res istance to m ovem ent.

In this s tudy w e attem pted to m easure tw o other pa-

ram eters of m otion , as well as the angular m ovem ents of

the hum erus and scapula w hen the arm is abducted in the

scapular plane: nam ely, the centers of rotation of the hu-m eral ball in relation to the scapula, and the excursion of the

ball on the face of the scapula. U sing the various m ea-

surernents w e w ere able to com pare the m otion of the nor-

m al and the abnorm al shoulder.

Subjects Studied

Ma te ria ls a n d Me th o d s

The m ain m otion w e s tudied w as abduction ofthe arm

in the plane of the scapula. W e had tw enty-seven subjects,

of w hom tw elve were asym ptom atic , norm al volun teers

tw enty-tw o to sixty-three years old, and fifteen w ere pa-

FIG. 2

Thre e se ts of x-y axes are ta ke n to define the joints positions. X Yfixe d in the thora x, xy is fixe d in the scapula , and y is fixed in thehumerus. 0A {176}GH { 176} ST { 149}he a rm angle eA ) is the angle forme d bythe y-a xis of the hume rus and a line para lle l to the Y -a xis of the body.The gle nohume ral angle (O (;H )15 define d as the angle forme d by they-a xis of the hume rus and the y-axis of the sca pula . The sca pulothoracicangle (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-tw o years old w ho had lesio

of the shoulder and w ere about to have arthrography.

adopted a technique sim ilar to that of Freedm an a

M unro to obtain roentgenogram s in the plane of

scapula w ith the arm in neutral rotation. A n anteropos-

tenor roentgenograrn w as m ade of each shoulder w ith

patient standing w ith the torso at a 30-degree angle to

plane of the roentgenogram . W hen the arm w as abducte

to each of the required positions , the plane of abduction

w as parallel to the plane of the roentgenogram and

am ount of abduction w as gauged w ith reference to thea x i s

of the body.

S e l e c t i o n of eference xes

A study of the m otion of the shoulder m ust start w

a definition of the axes in each of the tw o m oving pa

(hum erus and scapula) relative to the stationary part,

torso (Fig . 1). The geom etric center of the hum eral h

(Oh) is chosen as one reference point because the curvatureis suffic ien tly close to uniform for this purpose, andth e

center can be found by a sim ple geom etric construction.

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

the center of a line joining the lim its of the glenoid fosO n each roentgenogram the three sets of axes w ere draw

the axes of the torso w ere designated X ,Y , the axes of

scapula, x,y, and the axes of the hum erus, x,y (Fig.

Because Figure 2 w as draw n from a roentgenograrn m

w ith the subject facing the x-ray source at a 30-degree

angle, in other w ords in the plane of the scapula, the

axes ar e in this plane and not in the coronal plane of tbody. The arm angle, glenohurneral angle, a

scapulothoracic angle are defined in Figure 2.

Several roentgenogram s w ere m ade for each subjec

at 30-degree intervals from the dependent arm position


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A2

N ORM A L A N D A BN ORM A L M OTION OF TH E SH OU LD ER I 97

VOL. 58-A . N O. 2. MA R C H 976

to m ax im um 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, 1 20, 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.

D efinitions o f Param eters

Still referring to Figure 2, various parameters of in-

t e r e s t can now be defined. Thetnosem ent ofth e scapula onthe thorax can be defined by following one point and one

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

formation on thero tatio n 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. A lso,

changes in and {176}STcan be related to the arm angle

(OA) and the ratio O G H : O S T can be determ ined.Th e 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}hlies 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. T he method for

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

interval of the arm angle between two sequential

A

F I G 3

Tw o ro e ntg e no g ra m s of th e s a m e ind ivid ua l w ith d iffe re nt a n g le s o fa bduc tio n ca n be us e d to de te rm ine the ce nte r o f ro ta tio n fo r the a ng le

m o ve d. This is d o n e a s follows: D ra w th e s e t o f a xe s b a s e d o n thehum e rus fo r the tW o ro e n tg e no g ra m s ; s e le c t a s ing le a rbitra ry inte rva l

(O A) w hic h is m e a s ure d o n the fo ur line s o f the tw o a xe s (A,0 1 , B 1 ,0 1 , B )4; b is e c t the line s A,.A a nd B,B e re c t pe rpe nd ic u la rs totho s e line s : a nd C (ce nte r o f ro ta tio n) is the in te rs e c tio n o f tho s e pe rpe n-

d i c u l r s

roentgenograrns of the same subject, thecenter 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.

R e s u l t s

A typical set of sequential roentgenograms from a

norma l 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 M unro 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}G H 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 M unro, 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 of2. 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 actually5: 4

or 1 .25: 1 , meaning that there was not a great deal of dif-ference in the amounts by which they rotated. Freedmanand M unros 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-


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S e q u e n tia l ro e n tg e n o g ra m s m a d e in a b d u c tio n in th e p la n e o f th e s ca p u la .

Y

G LtN O -H U StFR AA\C 1 1 O G HS C A P UO -TH O R A C I( A GF S i

T fu s s tu d

In ma n S a rc le rs H. Ab bo tt 1 H4 4 S a G a 11

U D o o d v fre e d r ) Va le r la n d IH 7 O

00 .F re ed ma n \lu nro 1 % 6 7

V

/

V

0

60

-

30

80 0

F i;. 5

Th e re la tio n s h ip s b e twe e n th e g le n o h u m e ra l a n g le(() a n d th e a rma n g le (O A) a n d b e tw e e n th e s ca p u lo th o ra c ic a n g le (Oa n d th e a rma n g le . E a c h le tte r 0 d e n o te s th e O va lu efo r a re p re s e n ta tive in d ivid u a lp a tie nt fo r th e c o rre sp o nd in g { 176} A { 149}

x

AR M AN G LE 9

198 N. K. P O P P E N A N D P. S. W A L K ER

TH E JOU RN A L OF B ON E A N D JOIN T SU RGER

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 w as clear that the scapula tw isted about

i ts x-axis. Figure 7 show s how this w as detected on a plain

roentgenogram. A ssume that there is rotation about O in a

counter-clockw ise di rection. The coracoid tip w i l l move

predominantly upward, w hile the acromion tip wil l move

backw ards in the same transverse plane in relation to the

face of the glenoid. H ence, by measuring the upw ard

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 paral lel to x .

For all subjects, patients as w ell as normal individuals, the

acrornion remained stationary with respect to the face of

the glenoid except at high abduction angles w hen it tended

12 0

to rotate sl ightly downwards, as would be predicted Fi

6 a n d 7) . This is consistent with a counter-clockw ise rot

tion tw isting) of the scapula on abduction of thearm that

occurs in the plane of the scapula. For the fif teen norm

subjects, the regression l ine for the tw isting w as: 0xs=

{176 }590 ST w ith a correlation coeff icient of 0.83.T h i s means that the tw isting angle w as 0.59 times th

FIG. 6

Th e m o tio n o f th e s c a p u la inits o w n p la n e is d e fin e d b y th e p o s itio n oth e g le n o id a n d th e c e n te rs o f ro ta tio n re la tive to fixe d XY a xe s inb o d y. Th e ce n te r o f ro ta tio n o f th e s ca p u la b e g in s lo w in th e b o d y o f

s ca p u la a n d p ro g re s s e s u p w a rd s to w a rd th e g le n o id . (As te ris k d e n o t

c e n te r o f ro ta tio n fo r th e s p e c ific in te rva ls , 0 to 3 0 d e g re e s a n d s oT h e o u tlin e s o f th e s c a p u la c o rre s p o n d in g to th e 0 a n d I 50 -d e g re ed u c tio n p o s itio n s a re s h o w n .


6/8

Ac r o mi o n

30600

150 150..120 9

6

0-Coraco id

x

up

FIG. 7

3 0 { 1 7 6 }o Ma x.

G le no h um e ra l to

S ca pu lo tho ra c ic R atio

Ins tant

Ce n t e r

n u n )

Excursion of

Ba ll o n Gle no id

in , )

C linic al F indin gs

VA R I O U S P A R A M E T E R S A N D C L IN IC A L D E T A IL S O FT H E P A T IE N T S A N D Tw o N O R M A L V O L U N T E E R S S U B J E C T S K A ND N )

MaximumSubjec t Arm Angle

Ave ra g e o f N o rm a ls

De g re e s )

Norma l volunteersS O .2 5 0 . 2 5 6. 0 1 . 8 5 1 . 0 9 0 . 4 7 5

K I 5 6 1 .0 0 8 .7 A* 1 .2 O ld G H dis lo c a tio n (no rm a lvolunteer )

N 1 5 0 1 .8 7 4 .4 1 .2 N o rm a l vo lunte e r

CL 1 1 2 1 . 0 0 7 .1 4 .O A R o ta to r-cuff te ar

E 1 5 0 0 .9 9 A 4 .8 1 .0 S h o u lde r p a in; no rm a l a rthro g ra m

H 1 37 1 . 1 4 6 .5 0. 8 Rotator-cuff tea r

J 1 4 7 1 . 3 6 6. 6 1 .0 P ain fu l s ho ulde r; p re vio u s in ju ry

M 1 5 5 1 .1 5 1 0 .7 A 2 .O A S h o u lde r p a in; no rm a l a rth ro g ra m

0 1 5 6 1 .3 8 1 1 .2 A 1 .4 5 Ro ta to r-c u ff te a rQ 1 3 7 0 .9 9 A 4 .2 0 .8 R o ta to r-c ufft e a rR 1 5 2 2 .2 4 A 8 .2 1 .1 S ho ulde r pa in ; n o rm a l a rthro g ra m :

a rthritis in ce rvic a l s pine

T 1 2 8 0 .6 8 A 4 .0 0 .6 Ro ta to r-c uff te ar

U 9 9 0 .7 2 A 4 .9 1 .0 S h o ulde r pa in ; n o rm a l a rthro g ra m :

de ge ne ra tive a rthritis GH jo int

V 1 2 3 0 .8 3 A 1 2 .1 A 2 .7 A G H d is lo c atio n

W 1 6 4 0 .9 3 A 1 0 .8 A 2 .2 A R o ta to r-cuff te a rx 1 2 9 1 .4 1 1 4 .2 A 4 .O A R ota to r-c uff te ar

Y 9 9 0 .2 3 6 A 1 3 .2 5 A 2 .2 A G H dislocations

z_ 1 4 8 0 .8 2 6 A 1 2 .7 A 2 .2 A P a infu l s ho ulde r; pre vio us inju ry_ __ __ __

* De s i g n a t e s a va lue o u ts ide o f o ne s ta nda rd de via tio n o f the no rm a l.

N O R M L N D N O R M L M O T I O N O F T H E S H O U L D E R 199

V OL. 58-A , N O.2. M R C H 1976

R o ta tio n o r tw is ting o f the s c a pu la a bo ut th e x-a xis is s h o w n by th eu pw a rd m o ve m e n t o f the c o ra c o id a n d little s h ift in th e a c ro m io n re la tiveto the fa c e o f th e g le n o id (le ft). If the s c a p ula is vie we d in the la te ra lp ro je c tio n (rig ht), the c o ra c o id wo uld b e s e e n to m o ve u pw a rd with th ea c ro m io n re m a in ing o n the s a m e ho riz o nta l p la n e re la tive to the g le n o id .

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. I t now is evi-

dent that the humerus and the scapula move synchronously

to some extent, so that therel tive amount of rotation may

be small, depending on how much the humerus rotates.inst nt centers of rot tion nd b ll 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 ofthe

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. T he average instant centervalue for the normal subjects was 6.0 1 .8 mi ll imeter s.

A n 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


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N O R M A L A N D A B N O R M A L M O T IO N O F T H E SH O U L D E R 201

VOL. 58-A N O . 2 M AR C H 1976

6 . D O O D Y S . 0 .; FR E E D MA N , LE O N A R D ; a n d WATER LA N D , J . C .: S ho u ld e r M o v e m en ts D u rin g A b d u c tio nin th e S c a p u la r P la n e . A rch . P h y s . M e d .a n d R eh a b . 5 : 5 9 5 6 0 4 1 9 7 0 .

7 . FISK, G H. : S o m e O b s e rv a tio n s o f M o tio n a t th e S h o u ld e r Jo in t. C a n a d ia n M e d . A s s n . J . 5 0: 2 13 -2 16 , 1 9 4 4 .8 . FR E ED MA N , LE O N A R D , a n d MU N R O , R . R .: A b d u c tio n o fth e A rm inth e S c a p u la r P la n e : S ca p u la r G le n o h u m e ra l M o v e m e n ts . J . B o n e a n d J o in t

S ur g . 8 A: 1 50 3 1 51 0 De c. 1 96 6.9 . G R AV E S , W . W .: T h e T y p e s o f S c a p u la e . A C o m p a ra tiv e S tu d y o f S o m e C o rre la te d C h a ra c te ris tic s in H u m a n S ca p u la e . A m . J . P h y s .

th ropo l . 4 : 1 1 1 1 2 8 1 9 2 1 .1 0 . INMAN, V. T.; S A U N D E R S , J . B . D EC . M.; a n d A B B O T T, L. C .: O b s e rv a tio n s o n th e F u n c tio n o fth e S h o u ld e rJ o in t. J . B o n e a n d Jo in t S u rg .. 2 6 :

1 3 0 J a n. 1 94 4.1 1 . J O H N S T O N , T . B .: T h e M o v e m e n ts o f th e S h o u ld e r Jo in t. A P le a fo r th e U s e o f th e P la n e o fth e S c a p u l a a s th e P la n e o f R e fe re n c e fo r M o v e

m e n ts O cc u rrin g a t th e H u m e ro s ca p u la r Jo in t. B ritis h J . S urg . 2 5 : 2 5 2 2 6 0 1 9 3 7 .12. SAHA, A. K.: M e c h a n is m o f S h o u ld e r M o v e m e n ts a n d a P le a fo r th e R e co g n itio n o f Z e ro P o s itio n o f G le n o h u m era l Jo in t. In d ia n J . S urg . 1 2:

1 5 3 1 6 5 1 9 5 0 .1 3 . S A HA , A . K. : T h e o r y o f th e S ho u ld e r M e c h a n is m: D e sc rip tiv e a n d A p p lie d. S p rin g fie ld I llin o is C h a rle s C T h o m as 1 9 6 1 .

E lectr om yogr a p h y b efor e a n d a fter Su r ger y for H ip D efor m ity

in C h ild r en w ith C er eb r a l P a lsy

A C O M P A R ISO N O F C L IN IC A L A N D E L E C T R O M Y O G R A P H IC F IN D IN G S

B Y J A C Q U E L IN PE R R Y M .D . M . M A R K H O F F E R M .D . D A N IE L A N T O N E L L I M .5 .

J OH N PL UT M .D . G OR DO N L EW IS M .D . A N D R ON G RE EN B E RG R .P .T . D O WN E Y C A L IF O RN IA

A B S T R A C T: Tw e n ty -th re e a m b u la to ry c h ild re n w ith

s pa s tic d ip le g ic c e re b ra l p a ls y w e re e v a lu a te d c lin ic a lly

a n d b y e le c tro m y o g ra p h y b e fo re a n d a fte r h ip -m u s c le

s u rg e ry . Th e s tre tc h te s ts o rig in a lly d e s ig n e d to d is tin -

g u is h s p e c ific m u s c le tig h tn e s s a n d s p a s tic ity w e re

fo u n d to b e n o n -s p e c ific w h e n te s te d b y e le c tro m y o -

g ra p h y . A m b u la to ry e le c tro m y o g ra m s u s in g n e e d le

e l e c t r o d e s a n d te le m e try g e n e ra lly s h o w e d d e c re a s e d

a c tiv ity in th e re le a s e d m u s c le s a n d , o n o c c a s io n ,c h a n g e s in a c tiv ity in m u s c le s n o t o p e ra te d o n . Th e s e

u n a n tic ip a te d c h a n g e s a fte r re le a s e m a y e x p la in s o m e

o f th e u n p re d ic ta b ility o f re s u lts o f s u c h p ro c e d u re s in

c ere bra l p a ls y.

Currently children with cerebral palsy and a spastic

gait are evaluated by observation of their gait and by a

series of stretch tests 1 5 , 8 U nfortunately, surgical treat-

ment based on these criteria may produce unpredictable re-

sults. W e hoped that electromyography during the stretch

t e s t s 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 doneby Sutherland and associates.

Me th o d s a n d C lin ic a l Ma te ria l

From January 1971 to A ugust 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 gait6 and use of apparatus as well

T h e P ro fe s sio n a l S ta ff A s s o c ia tio n R an ch o L o s A m ig o s H o s p ita l

7 4 13 G olo nd rin a s S tre et D o w ne y C alifo rn ia 9 0 24 2.

as the findings by clinical stretch tests, gait examination,

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

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 of

the psoas and hence representative of the activity of the

iliopsoas. Our testing system permitted only eight muscletests per run. W e 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) T h e s e

t e s t s 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

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