Roentgen examination of the deformed foot

342

}rlll';lliEli(;l'.'ll, l lEIISII AND I IAIIliISON 60

5O

-"

.-,,,

4o

k~ 30

-..,

"%; 9

g

! 9

9

9

9

9

9

i

zc 9

,-

9

-- 9

.-

10

I

2

:3

4

5

G

7

8

9

IO

~i

12

13

YE&RS

Fig. 1.--Talocalcaneal ;ingle measurements f, om AP views of 160 ,~ur,nal feet. (Courtesy of Templet9 A. \V., ~lcAlister, \V. II., and Z i m , I. D.; ~:: vei~roduced with permission of Amer. J. Roe,~tgex:.)

Equinus: Fixed phlntar flexion of the hindfoot. The ealealleus is plantar flexed (anterior end do~m) on the lateral view, ,nakizlg an angle of ,nero t h:m 90 ~ anteriorly with the tibia. Calcaneus deformity: An abnormal dorsiflcxion of the calcanc'us (axltcrior end up). The ealcaneus is in an increased vertical position. Cavus deformity: A high longih~dinal arch of tl~e foot. It is suggested that the reader review these definitions again, with Figure ,~ at ha,td after reading this article. ].{ O E N T G E N

TI~CH.X~QUE

The radiograph must show whether the foot is in equinus or can b 9 normally dorsittexed. The lateral view is dmrefore taken with the foot in dorsifle• XVith an ilffant, someone m.ust dorsiflex the foot by placing a s~nall plywood board on the plantar sm'faee. The older child or adult stands, leaning the ]eg forward tc dorsiflex the foot. The anteroposterior view of the foot should be taken with flae sagittal plane of the leg perpendicular to the fihn. The leg should lean neither medially nor lateralh'. Leaning the leg medially to place a varus deformed forefoot flat on the cassette must be avoided since a true AP view of the hindfoot is desired. Since the roentgen examination will undoubtedly be repeated several times during the course of treatment, keeping the leg straight represents it reproducible method of positioning and allows an accurate comparison of previous and new films. The,'e is no need for an oblique view in the foot examination of an infant. 'l'~m NomxtAl. FooaIn the AP view, tile long axis of the talus falls on Ol- close to tl~e medial border of the first metatarsal and the long axis of the ealeaneus falls at the base of the fot, rth metatarsal. The taloealeaneal angle is approximately 35 ~

342

FBI~IBI~I~GI!:Ii~ I IERSII A N 1) 11A liB[SON

60

50

.'::

u~ 4C

,..j

s

II I I t l

9

"~, 9

q:

II

~-~ 50 t~

Ig

C5

1

20

9 ,

9

9

-o

-

-

-

9

-

I0 0 ---J-I

! ._.J_~t

I.

1

1

I ..... [.

1....... J.......1..... I . . . . .

2

5

G

7

8

I0

:5

4

9

ii

12

13

YEARS

F i g . l . - - T a k ) c a l c a n e a l a n g l e m e a s u r e m e n t s f~om A P v i e w s of 160 n o r m M l:eet. ( C o u r t e s y of T e m p l e t o n , A. W., M c A l i s t c r , \V, H., a n d Z i m , I. D . ; t" r c D r o d u c e d w i t h p e r m i s s i o n of A m e r . J. l:~oentgeP..)

Equinus: Fixed plantar tlexion of the hindfoot. The ealeaneus is plantar flexed (anterior end doxx~) on the lateral view, :making an angle of more th;u~ 90 ~ anteriorly with the tibia. Calcaneus deformiig: An abnormal dorsiflexion of the ealeaneus (anterio~ end up). The ealcaneus is in an increased vertical position. Caous deformity: A high longitudinal arch of tlle foot. It is suggested that the re~'lder review these definitions again, with Figure 8 at hand after reading this article. I~OENTGEN

TI:CtlNIQUE

The radiograph must show whether the foot is in equinus or cml be normall) dorsiftexed. The lateral view is therefore taken with the foot in dorsiflexion With an i~lfant, someone rn.ust dorsiflex the foot by placing a small plywood board on the plantar surface. The older child or adult stands, leaning thr leg forward to dorsiflex the foot. The anteroposterior view of the foot shoulg be taken witll the sagittal plane of the leg perpendicular to the fihn. The le~ should lean neither medially nor laterally. Leaning the leg medially to plae( a varus deformed forefoot tiat on the cassette m u s t be avoided since a tru( AP view of the hindfoot is desired. Since the roentgen ex~mlination will un doubtedly be repeated several times during the course of treatment, keepin~ the leg straight represents a reproducible method of positioning and allows ar accurate comparison of previous and new films. There is no need for an obliqu( view in the foot examination of an infant. THE NOR~IAL F O O T In the AP view, the long axis of the talus Eflls on or close to tile media border of the first metatarsal and the long axis of the ealcaneus l:alls at thq base of the fourth metatarsal. Tile talocaleaneal angle is approximately 3.5'

IIOEN'I'GEN EXA~.I1NAT1ON OF TI.IE DEFOIr

FOO'I."

343

in the adult and greater in the infant':' (Figs. 1 and 8). The metatarsals are almost parallel to each other with only slight fanning out from a somev,,hat narrower proximal base. In tim lateral position, the foot can be dorsiflexed to make an angle of considerably less than 90 ~ with the leg. Dorsiflexion is normally greater in the infant than in the adfllt. \Vith tlm foot in neutral position, the long axis of the calcaneus runs dorsally from posterior to anterior. The long axis of the talus is plantar flexed and is approximately continuous with the first metatarsal. When the foot is forcibly dorsiflexed, plantar flexion of tim talus increases slightly and the long a.~s of the talus and that of the first metatarsal will plantar angn.llate mildly. The taloealeaneal angle averages 35 ~ and its normal rang{: approximates that of the AP viev,,. The metatarsals are superimposed, with the first metatarsal projecting slightly more dorsally than the others. MV.CJLXNICS OF

Foot

DnFomxzrnES

In describing the deformities of the foot, it is simplest to take the ta]us as a p()int of r(,ference. For practical purposes, the talus may be considered part of the leg, postulating that the ankle is a hinge joint xxdthout an), lateral rnoli(n~. Sil~c'c'. the leg is positioned to produce an accurate AP ~dew of the foot. the positioll of the. talus is standardized. Thus, any change in the relationship of the talus and ealeaneus must be the result of motion of flae ealcaneus. Tim caleanetts moves ill t w o planes: transverse and sagittal. \Vhen the anterior portirm r the calc'anetls at;ehmt.r (increased talocaleaneal angle), tim caleaneus als{~ tilts its sagittal plane to slant downward and outward into valgus position: when lhe anterior portion of the caleaneus adducts (decreased talocaleaneal angle), it tilts its sagittal plane into varus position. The size of the taloealcaneal angle is th(}refore an indication of tim valgus or yams tilt of the laeel. The midfoot is displaced with the anterior end of the ealeaneus, so dm nax'ieular subluxes at the rounded anterior articular surface of the talus. This makes it possible to use the relationship of the long axis of the talus to the base of the first metatarsal in the AP view as a rough indicator of the size of the talocaleaneal angle.

Heel Valgus and Ileal Var.s It is not neeessa W for the radiologist to measure the taloealeaneal angle accurately to determine the nature of the deformity. One ean simply ex-tend the long axis of the talus Oll the AP view, and note its relationship to the base of the first metatarsal. Normally, the talar axis falls on the first metatarsal base or near its medial border. In heel valgus, because of abduction of the foot the axis will be markedly medial to the first metatarsal (Figs. 2A and 8). In heel yams, the long axis of the talus falls lateral to the first metatarsal base because of adduetion of the anterior end of the caleaneus and foot. Instead of descrit)ing large or small talocaleaneal angles, it is morc reasonable for the radiologist to use the descriptive terms of heel t~alg,s and heel varus, since the classification of tim various foot deformities and their prognoses are largely based upon these terms.

A

ROENTGEN EX.A~'IINATION O F T]IE I)EFORB,IED FOOT

345

Accurate measurenaent of the talealeaneal angle is neeessa W, though, to follow the course of treatment. These measurements are a more reliable indication of the state of the deformity during treatment than the clinical appearance of the foot. The lateral view shows features that are consistent with the malt~osition of tarsals and forefoot seen on the AP view, In heel valgus and abduction of the anterior ealcaneus (Fig. 2B), support has been withdrawn from the anterior portion of the talus, which is therefore seen in a more p]antar flexed position with sagging of the longitudinal arch. The long axis of the talus and that of the first metatarsal, Which are normally almost continuous, angulate plantarward. In heel varus and adduction of the anterior portion of the calcaneus under the talus, the talus cannot phmtar flex and the axes of the two bones become parallel to each other (Fig. 5B). Rotation of the forefoot into varus position is also visible on the lateral view. FLEXIBLE FLATFOOT

])EFORMtTY

The talocalcal~eal angle on the AP view is greater than normal, and tlm forefoot is i~ abduction, with heel valgus (Fig. 2A). The long axis of the talus falls well medial to the first inetatarsa] while the long axis of the ealeaneus remains near the fourth metatarsal base. The metatarsals are ahnost parallel to each otl~er because of the flattening of the midtarsal transverse arch. In severe /lexil~le flatfoot defomlity, ma]alignment clue to the laxity of the joints may occur at each major joint level. The foot will then abduct at the midtarsal level and adduet at the tarsal-metatarsal joint~, and lines through the axes of the talus, the midfoot, and the metatarsals roughly form a "Z." On the lateral view, the foot dorsiftexes to a normal or greater tllan normal anglo (Figs. 2.B and 8). The talocalcaneal angle is increased because of the plantar flexion of the talus. The long axis of the talus and that of the first metatarsal angulate considerably p]antarward, indicating sagging of the longitudinal arch. ~'[ETATARSUS ADDUCTUS AND VARUS

The heel is either in normal position or in valgus on the AP view (Fig. 3A). The long axis of dee talus therefore falls near the base of the fie'st metatarsal, or, ff there is heel valgus, medial to it. The forefoot is addueted and in varus, as evidenced by overlapping of tile metatarsals. On the lateral view, the foot dorsiflexes to normal or greater than normal. (Figs. 3B and S). (Never equinus]) The talocaleaneal angle is either normal or slightly increased because of plantar flexion of the talus. The varus position of the forefoot will be noticeable on the lateral x4ew." The iaffant with a normal hindfoot usually corrects to a normal foot. Those with marked hindfoot valgus will have a flatfoot after correction of the forefoot deformity. Most metatarsus adduetus and varus feet con-ect quickly and easily. Except-ions ,'u'e die hereditaw tb.'pe and the rigid defonnities of the forepart of the foot. l~adiographs with the foot forcibly held in maximally corTected position

afford prognostic information.

34(J

lq/,ELI~E/1CEII, I-IE/ISI-I

IlARRISON

AND

:, e~,", .t'3~~ . .

":ti~.J..

v.~..

:a.'~.a,.a-

.',.',

.

.

.,.~

.', " 9

Fig. 3.-Meta,'tarsus 'ldcluctus a,ld varus. A. AP. lleel valg~ls. Ir,~refoot ;tdduction and sligllt varlls. B. L;ttcral. "l'lm hindl'oc~t dorsillexes Jmrmally. Tile t.dals is il~ nmdez'ale plantar ttexi+m.

CONGI..NI'rAL VI:~II'rICAI, TALUS (PI::s CONVEX, CONGFNrrAI, PLAN'I;'~Ir IrLI-XI.:I)

TALus FooT, Cox(;ExrraL "I',LOX*VmULaI~ DtSLOC,vrIox) Severe. heel vaigus and forefoot abdlmlion are indicated by an i~mreascd talocalcaneal angle with the talar axis falling far medial to tile first lnciatarsal (Fig. 4A). The heel is in equinus position on the lateral view (Fig. 41.I). Tim long axis of tile calcaneus is tilted plantarward, front end down. axld maxinnum dorsillexion of the fool does not dorsitlex the ]mel. The talus is in extrelne plantar tlcxion, producing a markedly increased lalocalcaneal angle. The forefoot dorsillexes at the lnidtarsal level causing the plantar surface to be convex. This results in a rockerbotlom, delormity. The rear part of the rocker is formetl by the plantar flexed calcaneus, tho front by the dorsillexed forefoot. A dorsally dislocated navieula and dorsally shifted posterior tibial tendon lock the talus into its planlnr llexed position. ~" The talonavieular disloeationl IJeeo,nes visil)le in the Older child after Ihe ossificationl center for tile navicula~" has appeared (Fig. 4C). This is at serious and disabling foot deformity. Treatment is sttx'gieal. ])o not coxlftnse tile congenital vertical talus rockerl)ottom foot deformity with the severe ordinmr3, llatfoot which has a vertical tah,s but m~t equinus, or v,'ith rockcrbottom treated clubfoot which has persistent heel equinus but not a plantar flexed talus (Fig. 5C).

I{OEN'I'CI,;N EXAS, IINA'I'JON Oi: T I l E I)EIrOII,~I|~I) FOOT

347

CLuBFoo'r

The tcl'lla chtbfoot should refer only to tua equilloeavus varus foot deformity with hindfoot varus, it serious abnormality requiring long treatment and ofteff surgie~fl procedures, h t the AP view (Figs. 5A arid 8), the talocalcaneal ~lngle is nl~t,'kedly reduced and tile long axes ot7 the t~tlus and calcaneus may be p~lr~llel. The forefoot is in x,arus ~lllcl ~ldductcd. :.['he base of the metatarsals will be greatly lmrrowed and the forefoot may apl?eur in laterttl profile if tho degree ol5 varus is severe.

Fig. 4.-Congenital vertical tah,s (rockerb~ttom fool). A. AP. Extreme heel valg~is. B. Lateral. Eqttili~,s, extreme l~hmtar flexion c~f tile talus, dorsiflexed forefoot, and rockerlJr C, Seven years late,'. Equinu:~ heel, plantar flexed talus, and r~ckerbdttom. The talus is h~ckcd'lJ,," the dc~rsailv tlisl~catcd n-lvicular, J,~w ossified.

348

Flll,.:I]31'~llGEI:I, ]IEFiSII A N D I1AI:IHISON

, .r.

9

,.

9

1

)~ "-.'

9" . ' - ,

,

.

. , . : . ,

.

.

:

..

-

.

Fig. 5.-Clubfoot. A. AP. l leel varus, forefoot adduction, aml v a r u s . 1~. Lateral view. Equizlus, forefoot vart~s, and ca.vus. C. Treated clubfoot with roekerbottom, equinus heel, dorsillexed forefoot. The talus is not plantar tlexed. D. Treated clubfoot, tarsal deformity. Flat topped talus.

Oil the lateral view (Fig. 5B), the heel is ill equinus position and tile forefoot is plantar flexed (cavus) to all evell greater degree than tile ]findfoot, despite forced dorsiflexion. The long axes of the talus and calcaneus are parallel to each oOmr. The cavus tlefonnity, ordinarily seen on a lateral view, may not be apparent because of marked rotation of the forefoot in varus. The cavus is seen radiographically whenever the X-ray lwam is parallel to the true plantar mlrface of the foot.

IIOEN'I'CEN FXAMINATION OF "1"111..~I)I'2I,'OIlM~EI) FOOT

349

Posttreatment and Other Late Ch~bfoot Deformities Bockerbottom deformity (Figs. 5C and 8) occurs when dorsi/lexion of the foot by plaster east treatment is attempted before the equinus deformity at the heel is corrected. The varus and adchtetus of the calcaneus lnust ]')e corrected to allow talar plantar flexion. "l'here must be suflicient capsular and ligamentous llexibility at the ankle joint and resiliency of the Achilles tendon to allow dorsiflexion of tim hindfoot. Soft-tissue contractt~res at the ankle joint and at the medial aspect of the foot, as well as shortening of the Acl~illes tendon, may prevent rapid and adequate reduction of tire deformities by cast treatment alone. Soft-tissue rdlease operations are oftell required. 7'arsal deJormities. Because, of rapid growth of the bones of the foot, the articular surface of tlm" plantar flexed talus adapts itself to its al)normal t?osition :rod flattens along its area of corltact with the til~ia. This flalto 1) l,hts de[ormilll is of importance since it causes incongruity of the ankle joillt (Fig. ,519). Otl~er deformities of tile talus and tarsal bones occur and generally intcrl'cre with rlornlal growth, so tlmt the. clut~foot is" smaller than the opposite ~ornmi foot. In order to ;tvoid signifieaJlt tarsal deforn~ities, rapid correction of tire positional almornmlity of the foot is desired. Soft-tissue r/elease operations of the mlkle joirlt and tl~e nmclial asl?ect of the foot and also tendon Acl~illes lengthening are l)erfor~ned i~l a large percentage of C~luinoeav'~ts \'ares clul~feet treated in our clir~ic.~ CAVUS FOOT ])EFOmXtrru

Tills is ~t~ alJnorlnally lriglr longitudilml arcl~ of tl~e foot and may exist witll :t heel vartts or laccl w~lgus, and with equinus or ealemleus deformity. AItllough lzioderate cav,~s dr, fortuity ~lay occllr withorJt known cause, it is often assor with Jmurolnuscular disease. RIG/D J?I.A'I'FOOT, 1)EItONF, AL SPASTIC

]?I.,ATIrOOT~, ']"AI.~SAI., COAI.ITION

Tile ordinary flatfoot is flexible and usually painless. Ill rigid flatfoot, pronation and supination are severely limited, and tlm patient often complains of pain in tile foot and calf. This condition is seen in older chi!dfen and young adults. Peroneal .STJaslic flatfoot is usually caused l~v a tarsal coalition: a bony, cartilaginous, or fibrous bridging of either the c~Icaneus and tlle nax,icular or the calcaneus and talus.' Subtalar coal'ffion is most frequent at tlm sustcntaeular talar joint and less frequently posteriorly near the os trigonmn. A clue that should lead to the search for a coalition is tile presence of a smooth spur on tile anterior superior aspect of the talus at the talonavicular joint (Fig. 6A). The calcanconavicular eoalition is easily recognized on conventional radiographs, particularly when one remenabers that normally no articulation or fusion exists between the calcaneus and tim navicada (F'ig. 6A). Sustcntacuhun talar coalition is much more difficult to detect since the subtalar joint cannot be adequately evaluated on tim routine AP, lateral, or ohliqu6 views of the foot. The tangential view of the heel (llarris view) is

-

,

..", _

r

.~

.r'-"

," ~ ;.- %'.'~.~,'. "

~

"J

" . L r.

9

I

f"

"jr

IIOEN'I'(;EN EXA~I[NATION OF" TJIE I)I,'.FOIiM~I:]I) FOOT

...

3~].

..

.V, 9 '....

. m

.r ', : ~.-

:.

9

i

.- -...>--

i';'.~ ... - ; . . . . ,

"~

Fig. 7.--Calc~ineonavicul~lr eoalitioll. A. Arl al)tlorm~tl joint (arrow) between the alltcrior process of tile c~tlc'al~e~s ;~(1 the i~tvicular i~ ~t~ / l yc~r t~ld patient, l~. S;~,~e foot 3 ),e~tvs pvevi(~usly. The [avsal e~);tlitit)~ is not visible ~tl)pare~tl.v beca~se it is c~trtih~gi~)()us. us(flu[ for this purpose (Fig. 6I]). Ilowr fih~ls with the eentlu[ rely itt x';U')'illg angles to the horizolltal (35 ~ 45 ~ ~tnd 55 ~ must be ta]
Triple Arlhrodesis There are a number of reasons for this operative procedure: (1) To give the foot hatcral stability in palicnts with nct~roznuscul~:r disease; (2) to provide correction of a sex,ere and recurring foot deformity; (3) to relieve pain cruised by artllritic changes in tile hil~dfoot joints or by tarsal coalitiol~.

3~

l:~tl~lBl:.l{Gl.:]l~ ]II,:RSII AND IIAHII[SON

o

.--4 0 e-

0 0

0

d 'ID

I ~J

iJ 0

,r

I.~

0

U

:>

U I 0

4.; 0 0

D~ 0 r~

0 0 b,

0

0 U

0

0 r

*N

~'~

E k.

0

9 o

~~

oo

'10

u.

U

o ~J

0 0

,C

zo

~

o

X

~

0

~

~

~~

0 0

I

I:PO

m

o

.2

IIOEN'I'CI~;N FXA~XIINA'I'ION O1: "I'111'~ DI~FOI:I,\tEi) FOC)T

35~.~

Since it is possible to place the heel in either valgus or rants position by roniovii-lg b o n o w e d g e s either from il~o slll)talar joint or f r o m the os ealcis, tllo evaluation

0[:

heel valgus

o r v~il'llS

I.)y llSO of

tile l a l o e a l e a l l e a ]

,qngie is no

longer wdid. After relnovil~g the cast, an evaluatioii of bony fusion of the three joints (subtalrtr, talonavicular, and caleaileoeuboid) is possible. All attempt is ot:teli lnade to reduce pl:.tntar tlexion by Wedgirig the anterior talus and placing the apex of the wedge into the iriferior aspect of tim navieular 1.,one. "J'his causes the liavicular to project dorsal to the talus. The radiologist must i'ecogliize this as a desired correction. lqgure 8 is a diagminrnatie sulnmary of tim vnl'ious foot deformities tlisctlssed i~ Ihis prest~li'tatioia as they relate to heel position. REFEIIENCir~S 1. ])avis, L. e't., alid J[att', *A:. S.: Coil" gellit:ll alal~,i'lnalities of the feet. ltadic~logy, (; 1:8J8, 1055. :29. lrz'ipl-~. A. 'J'., alJd Slmw, N. E.: CII,I~ l;r~ot. Edinlmrgh, E. & S. l'Jvingstm'l ]_,td., 1 .tJ(J7. :3. Cianimslrits. N. J.: F{,ot I)is~irders. Xledical lillC[ Siil~iC;.ll i'kl;.iilagl.,lliCli(, lqlihlc!t::lpilia, l.c.':l & Fcl//cr, I.t)(i7. 91. Jtarris, R. I., alltl l{cath, T.: i~lit)logy ~d pcrcJzmal spastit' llalloot. J. l~tme .loillt Surg..~()l~:(l~-l, It.)lS. 5. |l,ttl, \V. S., hli([ I_)aVis, I.,. A.: Analysis ~ll" the t'~ot ill ilifallts: "l'l,e radiogral~hic criti:ria and t.lillical aspeuts. Smltllc'rll ~led. J. 50:720, 1.q57. (J. lllulser, lg. !). \v.: ('ml,~:llil',ll Clul,tllot. Sp,'iligfi~4~l, 111., Charles C Thom;:is, 1960. '7. lfaveson, S. B.: Ciliigl,iiila] tlait'l~i~t duo to tal(mavicliliir disloc;ilion (vcrtic-nl

tah,s), l{adiology 72: 19, 1.959. 8. lIersh, A.: The role of smgery ilJ tlJe tt'catlJicJlt of (:!111) feet. J. ]3mle J~iillt St,rg. .IOA : 1084, 1,067. ,0. Kite, J. 11.: Tlle Clld~ lgout. New Yurk, (.;rulie & Stratl(ni, 19{J,t. ](). l,oNnir, J. 1_,., II1: (:on u,t.nital Idi(> patlfic Talipes. Sprillgfield, II1., Cliarh'.s C "l'hc)~j~as, i 966. 11. l.:nsted, L. B., and Keats, T. E.: Atlas ~f l{oevltgcl,ograpliic ~leasltrc,uent. Clfieagcl. Year BorJk hlcdical lhd)lishcrs, 11959. ]2. l{itclJie, (;; \V., anti Keiln, II. A.: A r;idiol.(rapiiic: alial)'sis of llnljilr foot defnrnlities. (Taliad. ~led. Ass..I. 9J[:84(i, J.tJ(J-t. 13. 'l'enipletlnl, A. \V., ~lo<~isicl', \V. I!., iillcl Zilii, i. l).: ~tnlldardizltli()li of torillilill]ogy illill OVil]ll;.l[iOIl Of tlsseoilfi lelatill:lsiiips ill coiigellitally lliliiOl'lii;il feel, Alil~.'l', [. tlol'illTeli. {):3::37-I, 1,qf$5-