Hetherington

Fig. 6-2. (A) Proximal articular set angle. (B) Intraoperative photograph shows deviation of effective articular 

cartilage in a patient with hallux abducto valgus. 

experience has led to the belief that the most reliable 

indicator of an abnormal PASA is to visualize the artic- 

ular cartilage of the first metatarsal intraoperatively 

(Fig. 6-2B). Also, one should recognize that when per- 

forming an osteotomy at the base of the first metatarsal 

to correct an abnormal intermetatarsal angle, the PASA 

may be relatively increased to a point that the first 

metatarsal phalangeal joint is no longer congruous, 

necessitating a second distal osteotomy to connect for 

the relative increase in the PASA. 

 

 

PREOPERATIVE ASSESSMENT IN HALLUX VALGUS    113

 

Tangential Angle to the Second Axis

 

The tangential angle to the second metatarsal axis 

(TASA) is formed by the bisection of the effective artic- 

ular surface of the first metatarsal and its perpendicu- 

lar to the longitudinal axis of the second metatarsal

25 

(Fig. 6-3). TASA is helpful in determining the angula- 

tion of a transverse V osteotomy when performing an 

Austin-type procedure. In fact, TASA actually redefines 

a rectus  hallux because it compares the position of the 

hallux to the second toe angle and not to the shaft of 

the first metatarsal. Ideally, TASA should equal 0°, but 

an acceptable range is ±5°.  A useful equation that may 

be employed preoperatively when assessing TASA is 

TASA = PASA - IM angle. Therefore, the only time it is 

indicated to reduce PASA to 0° is when the intermeta- 

tarsal angle is 0°. Utilizing this formula, one can see 

that TASA concomitantly reflects changes that occur in 

both the proximal articular set and the intermetatarsal 

angle in any given foot.

25

 

Distal Articular Set Angle

 

The distal articular set angle (DASA) represents the 

angle formed by the bisection of the shaft of the proxi- 

mal phalanx and the line representing the effective 

articular cartilage of the base of the proximal phalanx 

(Fig. 6-4). A normal DASA is considered to be less than 

8°. Historically, an abnormal DASA may be corrected 

by employing a proximal osteotomy near the base of 

the proximal phalanx. It should be remembered, how- 

ever, that whenever hallux valgus deformity is present  

clinically and radiographically the proximal phalanx 

will also present with some degree of rotation on x-ray 

examination. This means that one is not viewing the 

true structural medial and lateral borders of the proxi- 

mal phalanx. Therefore, preoperative assessment of 

DASA should be fully compared with the clinical 

amount of valgus deformity if correction at the base of 

the proximal phalanx via osteotomy is to be ad- 

dressed.

26,27

 Another factor to consider in measuring 

the DASA is the length of the proximal phalanx, or the 

presence of a distal angulational abnormality. 

Hallux Abductus Interphalangeus

 

The hallux abductus interphalangeus (HAI) angle is a 

comparison of the longitudinal bisection of the proxi-

 

 

Fig. 6-3. Tangential articular set angle.

 

mal phalanx with the longitudinal bisection of the dis- 

tal phalanx (Fig. 6-5). The HAI angle is usually consid- 

ered normal when it measures within a range of 

0°-10°. An increase i in this angle indicates that the 

level of deformity is present at the interphalangeal

 

 

114    HALLUX VALGUS AND FOREFOOT SURGERY

 

 

Fig. 6-4. Distal articular set angle.

 

joint of the hallux. Correction of this deformity is usu- 

ally addressed at the head of the proximal phalanx.

28 

Although osteotomies at the base of the proximal 

phalanx to correct for an abnormal DASA or hallux 

interphalangeus angle (HIA) have long been used as 

an adjunct procedure in the surgical management of 

 

Fig. 6-5. Hallux abductus interphalangeus angle.

 

hallux abducto valgus deformity, it is our experience 

that the surgeon will get a more satisfactory functional 

and cosmetic result when performing an osteotomy at 

the head of the proximal phalanx if the HIA angle is 

abnormal. 

 

PREOPERATIVE ASSESSMENT IN HALLUX VALGUS    115 

Tibial Sesamoid Position

 

The tibial sesamoid position describes the relation- 

ship of the tibial sesamoid to the bisection of the first 

metatarsal shaft on a weight-bearing dorsiplantar view. 

A numerical sequence of one to seven is described 

with increasing deformity

18

 (Fig. 6-6). A tibial sesa- 

moid position of four or greater represents a signifi- 

cant contraction of the fibular sesamoidal ligament  

and corresponding sesamoid apparatus. Many practi- 

tioners have advocated a fibular sesamoidectomy 

when the tibial sesamoid position is four or greater.

29 

However, with adequate soft tissue release it is often 

possible to realign the fibular sesamoid under the 

head of the first metatarsal. Therefore our criteria for 

performing a fibular sesamoidectomy is when the ses- 

amoid presents with severe arthritic changes or is 

fused to the lateral aspect of the first metatarsal head. 

Also, a fibular sesamoidectomy should be considered 

when one simply cannot relocate the tibial sesamoid 

under the metatarsal head. 

Smith  et  al.

30

  have   recommended  a  simplified 

method of measuring the tibial sesamoid position us- 

ing gradations 0, 1, 2, and 3 rather than the traditional 

seven. They found the four-grade system was adequate 

and easier to apply than the seven-grade system in the 

literature. 

Finally, as mentioned previously, one should not 

use a forefoot axial radiograph to assess the tibial sesa- 

moid position. It should be remembered that when 

the metatarsal phalangeal joint is dorsiflexed to obtain 

the forefoot axial view, the windlass  mechanism is 

activated, which allows the position to appear less 

severe than the deformity actually is. 

Relative Lengths of the First and 

Second Metatarsal

 

Metatarsal protrusion is the comparison of the first 

and second metatarsal lengths. A normal protrusion is 

+2 to -2 mm. The first and second metatarsal shafts  

are first bisected and extended proximally to their 

point of intersection. From this point a compass may 

be used to construct an arc to the most distal point of 

the first and second metatarsals. The distance between 

the arcs is now measured in millimeters (Fig. 6-7). If 

the first metatarsal is longer, a positive value is as- 

signed; if shorter, a negative value.

18

 There exists a 

strong correlation between a long first metatarsal and 

a hallux valgus or hallux limitus deformity. Therefore, 

the practitioner may wish to employ an osteotomy that 

will shorten the first metatarsal as well as correct for 

valgus deformity. In the case of a short first metatarsal, 

we do not recommend a lengthening procedure, be- 

cause jamming may occur at the first metatarsal pha- 

langeal joint and thus cause a limitus deformity. 

Metatarsus Adductus Angle

 

An accurate measurement of the metatarsus adductus 

angle should be made, especially in the preoperative 

planning of correction of juvenile hallux abducto 

valgus deformity. The midway point of both the me- 

dial aspect of the metatarsocuneiform joint and the 

talonavicular joint is first found. Similarly, the midway 

point of the lateral aspect of both the calcaneocuboid 

joint and fourth metatarsocuboid joint is found. These 

medial and lateral midway points when connected 

represent the perpendicular to the long axis of the 

lesser tarsus. A line perpendicular to the long axis of 

the lesser metatarsus is now drawn and compared to 

its bisection of the longitudinal axis of the second 

 

Fig. 6-6. Tibial sesamoid position. 

 

116    HALLUX VALGUS AND FOREFOOT SURGERY

 

 

Fig. 6-7. Relative metatarsal protrusion.

 

metatarsal. The angle formed represents the metatar- 

sus abductus angle

18

 (Fig. 6-8).  The metatarsus 

adductus angle is considered normal when it is less 

than 15° in the rectus foot type. It  has great clinical 

implications in the selection of a  bunion procedure. 

As  a general rule, it should be re membered that the 

greater the metatarsus adductus angle, the greater the 

hallux abductus angle and the   smaller the 

intermetatarsal angle.

31

 

The following formula is quite useful to assess the 

true intermetatarsalangle (IMAp): 

IMAp = M 1 - 2 + (MAA  -  15°) 

 

Fig. 6-8. Metatarsus adductus angle. 

 

PREOPERATIVE ASSESSMENT IN HALLUX VALGUS    117

 

First Metatarsophalangeal Joint 

Articulations

 

The articulating surface between the head of the first 

metatarsal and base of the proximal phalanx in hallux 

abducto valgus deformity may be described as con- 

gruous, deviated, or subluxed. A congruous joint is 

one in which lines representing the effective articular 

surfaces of the metatarsal head and base of the proxi- 

mal phalanx are parallel; to 3° divergence is consid- 

ered normal. The normal first metatarsal phalangeal 

joint should be congruous.  However, a congruous 

joint can be found in hallux abducto valgus deformity 

and may represent a structurally adapted articulation 

(Fig. 6-9A). 

The metatarsophalangeal joint is deviated when the 

lines representing the effective articular surface of the 

head of the first metatarsal and base of the proximal 

phalanx intersect at a point outside the joint (Fig. 

6-9B). A normal range of deviated first metatarsopha- 

langeal articulation is 4 percent to 25 percent. In the 

subluxed joint, effective articular lines of the first 

metatarsophalangeal joint intersect within the joint it- 

self (Fig. 6-9C). The angle formed is usually greater 

than 25 percent. The subluxed first metatarsophalan- 

geal articulation represents a stage of deformity 

with rapid progression. A common example would be 

in the patient with rheumatoid arthritis. 

Shape of the First Metatarsal Head

 

The shape of the first metatarsal head when viewed on 

an anteroposterior (AP) radiograph may be described 

as round, square, or square with a central ridge. A 

normal first metatarsal head demonstrates a smooth, 

continuous, circular pattern (Fig. 6-10A). It is often 

considered as the least stable of first metatarsophalan- 

geal joint articulations. In the younger patient with a 

flexible deformity, the round first metatarsal head is 

the most amenable to soft tissue procedures.

32

 

The square first metatarsal head is rarely found in 

hallux abducto valgus deformity (Fig. 6-10B). It is visu- 

ally indicative of a hallux limitus or hallux rigidus de- 

formity. The metatarsal head that is square with a cen- 

tral ridge is perhaps the most stable of the metatarsal 

head shapes (Fig. 6-10C). The central ridge is probably 

the plantar crista, which becomes more important 

when the first metatarsal is dorsiflexed (Fig. 6-10B). In 

a study of 6,000 school children, Kilmartin and Wal- 

lace

33

 did not find statistical evidence to validate these 

beliefs. They concluded that "while the shape of the 

 

 

 

Fig. 6-9. Metatarsal joint articulation. (A) Congruous; (B) deviated; (C) subluxed. 

 

 

 

 

118    HALLUX VALGUS AND FOREFOOT SURGERY

 

 

 

Fig. 6-10. Metatarsal head shape. (A) Round; (B) square; (C) square with central ridge. 

 

metatarsal head may be an interesting radiological ob- 

servation, it has little to contribute to the scientific 

assessment of first metatarsophalangeal joint pathol- 

ogy."

33

 

Metatarsocuneiform Joint

 

The metatarsocuneiform joint should also be assessed 

in hallux abducto valgus deformity. This articulation 

may be described as square, oblique, or round. As 

with the first metatarsal head, a rounded first metatar- 

socuneiform joint may be considered the most flexi - 

ble and it is also most amenable to soft tissue correc- 

tion. The most commonly observed shape in hallux 

abducto valgus deformity. A flat articulation is proba- 

bly  most clinically significant in the preoperative as- 

sessment of the deformity. An oblique metatarsocu - 

neiform joint may represent an etiologic factor in the 

metatarsus primus varus deformity of the first metatar- 

sal. In this instance, the practitioner may wish to select 

a basal osteotomy to reduce the intermetatarsal angle. 

An articulation between the first and second metatar- 

sals may also exist blocking reduction of the interme- 

tatarsal angle without metatarsal ostoetomy (Fig. 6-11). 

Radiographic Angular Relationships

 

After the practitioner has assessed all the pertinent 

traditional angular values, certain angular relation- 

ships may be gathered to aid one in the selection of 

the surgical procedures.

 

 

Fig. 6-11.  Articulation between the first and second meta- 

tarsals that would resist a positional change in the intermeta- 

tarsal angle by soft tissue procedure alone.

 

 

PREOPERATIVE ASSESSMENT IN HALLUX VALGUS    119 

A structural deformity is present when PASA + 

DASA = HA with PASA or DASA exhibiting an abnor- 

mal value. Joint evaluation will reveal a congruent 

joint. It should be remembered that it is not the abso- 

lute numbers that are important but their relationship 

to each other. In this situation, an osteotomy is indi- 

cated as part of the corrective procedure. 

A positional deformity exists when PASA + DASA < 

HA with PASA and DASA both being normal. This is a 

soft tissue deformity and the joint position will be 

deviated or subluxed. Finally, a combined deformity is 

present when elements of both soft  tissue and osseous 

structure contribute to the deformity. 

JUVENILE HALLUX VALGUS

 

Hallux valgus as it occurs in the juvenile is a deformity 

of the first  metatarsophalangeal joint that may present 

with pain, is progressive in nature, and may lead to 

future degenerative changes and serve as source of 

embarrassment to the older child and young adult. 

The incidence of juvenile hallux valgus has been ad- 

dressed by several authors. Craigmile

1

 in 1953 studied 

children in the 12- to 15-year-old group; 22 percent of 

female and 4 percent of male children exhibited some 

degree of bunion deformity. Cole

34

 in 1959 found that 

39 percent of female and 21 percent of male school 

children between the ages of 8 and 18 displayed mild 

to severe hallux valgus. Gould and others

35

  reported 

in 1980 the incidence of bunions in the 4-  to 14-year- 

old  group to be rare; however, they found it to be five 

times more frequent in blacks. The male to female 

ratio was reported as approximately 1:1. Hardy and 

Clapman

36

 in 1951 and Piggott

37

 in  1960 reported a 

history of onset of the deformity before the age of 20 

in adult patients with hallux valgus. Johnston

38

 re- 

ported on a family with a seven-generation pedigree 

of hallux valgus and felt that it was attributable to an 

autosomal dominant trait with incomplete penetrance 

of the gene. 

The etiology of juvenile hallux valgus is multifacto- 

rial with both genetic and environmental components. 

There is no doubt that the biomechanics of the child's 

foot contribute to the development of hallux valgus. 

The pathomechanical problems most often associated 

with juvenile hallux valgus are abnormal pronation 

associated with flexible flatfoot deformity. Juvenile 

hallux valgus may also be the presenting complaint of 

a child or adolescent with metatarsus adductus.

15

 In 

this situation, the intermetatarsal angle will not be as 

large when compared with a juvenile hallux valgus, 

but will present with a prominent bunion deformity. 

In this deformity, there is an increase in adduction of 

all the metatarsals as opposed only to the first in juve- 

nile hallux valgus. Serious consideration must be 

given to the management of the metatarsus adductus 

deformity in conjunction with the hallux valgus de- 

formity. 

Neurologic disorders such as cerebral palsy and 

Down syndrome have  also been associated with the 

development of hallux valgus in the juvenile. In Down 

syndrome, the primary foot deformity has been re- 

ported to be hypermobile flatfoot with laxity of the 

soft tissues, which readily leads to the development of 

the juvenile hallux valgus deformity. 

Inflammatory arthritis, of which juvenile rheuma- 

toid arthritis is an example, may also result in this 

deformity.  Goldner and Gaines

39

 described a congeni- 

tal hallux valgus with a short first ray, skin contracture, 

and severe deviation of the toe. They considered  

that this should be treated early, and that soft tis- 

sue releases and skin grafting may be necessary 

as well as osteotomy and bone graft to elongate the 

first ray. 

First-ray deformity in juvenile hallux valgus may be 

considered as dynamic or static. Dynamic hallux 

valgus is a result of first-ray hypermobility with devel- 

opment of metatarsus primus abductus secondary to 

deviation of the great toe. It may also be associated 

with an abnormally long first metatarsal and hallux 

interphalangeus. Hardy and Clapman

36

 suggested that 

some factors caused a lateral displacement of the distal 

phalanx of the great toe. They proposed that the pull 

of the extensor hallucis longus tendon is transferred 

laterally to the axis of the great  toe in a bowstring 

effect, and that once this process has started lateral 

displacement of the first digit must increase. They 

stressed that the deformity was caused primarily by 

displacement of the great toe and widening of the 

intermetatarsal angle secondarily. Lundberg and 

Sulja

40

 found increased relative protrusion of the first 

metatarsal was positively correlated with the develop- 

ment of hallux valgus. 

Hardy and Clapman

9

 in 1951 found the first metatar- 

sal, in cases of hallux valgus, to have a greater relative 

metatarsal protrusion than that of the controls. They 

noted that with a high degree of valgus of the hallux 

 

120    HALLUX VALGUS AND FOREFOOT SURGERY 

and a low intermetatarsal angle, the first metatarsal 

tended to have a greater protrusion relative to the 

second metatarsal as opposed to cases with a low de- 

gree of valgus and a high intermetatarsal angle in 

which the second had the greater relative protrusion. 

Static hallux valgus is associated with deformity of the 

medial cuneiform, possibly a  congenital defect that 

results in metatarsus primus varus as the primary de- 

formity. It may also be caused by a metatarsal devia- 

tion or widening of the epiphysis of the first metatarsal 

proximally on its lateral aspect. 

Jones

41

 though the primary deforming force in ado- 

lescent hallux valgus is adduction of the first metatar- 

sal. He stated that a deformity of considerable severity 

may develop concurrently with the quick growth of 

the foot, and is associated with an adducted first meta- 

tarsal that was present at birth. He suggested that the 

metatarsal adduction was atavistic and related to evo- 

lutionary development. Bohm

42

 described the early 

stages of embryologic development of the first meta- 

tarsal. Early in normal development, the first metatar- 

sal is at the medial border of the first cuneiform and 

forms an angle of 50° with the long axis of the foot, 

obviously being in marked adduction. This adduction 

is seen in the fetus and up to fourth month of gesta- 

tion, gradually reducing until birth. 

Hawkins and Mitchell

43

 believed that there was a 

tendency to underestimate the significance of a con- 

genital metatarsus primus varus in the development of 

a juvenile hallux valgus deformity. Shoe deformity 

forces were felt to be secondary to the congenital 

metatarsus primus varus. Simmonds and Menelaus

1

" 

also associated metatarsus primus varus with juvenile 

hallux valgus. They noted, as did Bonney and Mac- 

Nab,

45

 that metatarsus primus varus was the most im- 

portant aspect needing correction in the adolescent if 

recurrence of the deformity was to be avoided, and  

believed it was a major factor contributing to the  

breakdown of the forefoot. Lapidus

15

 classified hallux 

valgus into three groups with the most predominant 

group showing a congenital predisposition to metatar- 

sus primus varus. Truslow

46

 thought the primary de- 

formity was a wedging of the medial cuneiform or the 

proximal end of the metatarsal. The outward deviation 

of the toe was secondary to this primary deformity. 

As alluded to earlier, Piggott

37

 in his studies on ado- 

lescent hallux valgus classified the metatarsophalan- 

geal joint into three groups. These classes were con- 

gruous, deviated, or subluxed. In his study he could 

produce little or no evidence that metatarsus primus 

varus was the underlying cause of hallux valgus. He 

concluded that the structural prognosis of hallux 

valgus in the adolescent is as follows: Congruity of the 

joint surfaces can be considered as normal and indi- 

cates that a progressive deformity will not occur, but 

subluxation  indicates that deterioration is likely; the  

deviation may or may not progress to subluxation. He 

noted subluxation of the first metatarsophalangeal 

joint was seen before closure of the metatarsal and 

phalangeal epiphysis. However, in support of metatar- 

sus primus varus, Durman

14

 found a significant varia- 

tion in shape of the first cuneiform. In his study, cunei- 

form deformity was present in 47 percent of patients 

with hallux valgus. 

Thus we see that juvenile hallux valgus can be 

dynamic in nature, with deviation of the great toe 

resulting in an increase in the intermetatarsal angle, or 

a static deformity in which  the primary etiology is 

more proximal,  or  a congenital  effect, such as 

deformity of the medial cuneiform or  base of the 

metatarsal. It is interesting to note that  Luba and 

Rossman

47

 show that preoperative compression and 

tension forces may act to perpetuate or stimulate 

active deformity by applying compression force 

to the epiphyseal plate medially and a tension force 

laterally, which may result in an asymmetric growth of 

the first metatarsal (Fig. 6-12). One could only specu- 

late how this relationship interplays with the develop- 

ment of a structural metatarsus primus varus. In a 

study of 6,000 school children, Kilmartin et al.

48

 failed 

to provide significant correlations between adduction 

of the first metatarsocuneiform joint, intercuneiform 

angle (an estimation of the alignment of the medial 

and intermediate cuneiforms), metatarsus adductus 

angle, or differentiation of growth patterns of the first 

metatarsal.

34

 

Clinical evaluation of the juvenile patient with hal- 

lux valgus deformity should be complete and thor- 

ough, including integrity of the soft tissue, examina- 

tion for liagmentous laxity, joint status, and mobility, 

complete neuromuscular evaluation, and biomechani- 

cal evaluation. 

When considering surgery in the child with juvenile 

hallux valgus, several areas are important. As with the 

adult hallux abducto valgus deformity, the correct pro- 

cedure is chosen after careful examination, both clini- 

 

PREOPERATIVE ASSESSMENT IN HALLUX VALGUS    121