Hetherington

6

 

Preoperative Assessment in 

Hallux Valgus 

DAVID M

.

 LAPORTA

 

THOMAS V

.

 MELILLO

 

VINCENT J

.

 HETHERINGTON

 

The goal of any bunion surgery is the elimination of 

pain, restoration of a congruous metatarsophalangeal 

joint, realignment of the hallux into a rectus position, 

and preservation of joint motion. The best method for 

predicting a successful surgical result in hallux valgus 

reconstruction is thorough preoperative planning. 

This helps ensure selection of the appropriate proce- 

dure to attain these goals. Preoperative planning 

should include a thorough history as to the progres- 

sion of the deformity and an adequate clinical and  

radiographic examination. In addition, addressing the 

deformity by the choice of surgical procedures re- 

quires identifying its etiology and pathomechanics. 

This chapter reviews and details pertinent features of 

the preoperative clinical and radiographic examina- 

tion. 

ETIOLOGY

 

The hallux abducto valgus deformity may result from a 

variety of contributing factors. Proper historical and 

clinical assessment of the patient in both a non-weight- 

bearing and weight-bearing manner and a thorough 

biomechanical evaluation, as well as an understanding 

of the microscopic pathologies occurring in and 

around the first metatarsophalangeal joint, will ensure 

a more predictable surgical result by selection of the 

appropriate procedure or procedures. 

A historical review of the various etiologies shows 

that some still believe that shoe choice, excessive ac-

 

tivity, and external environmental factors play a signifi- 

cant role in the development of hallux abducto valgus 

deformities. This belief persists despite historical stud- 

ies that demonstrate these are aggravating factors, not 

primary pathologies. Hereditary factors are known to 

be causative only in that it is the foot type with its 

associated biomechanical abnormalities that is inher- 

ited, not necessarily the resulting pathologic condition 

known as hallux abducto valgus. 

Biomechanical Etiology

 

The biomechanical etiology of hallux abducto valgus 

has its origin in the rearfoot. The subtalar joint range 

of motion when excessive will most often lead to a 

pronated foot. External factors such as limb rotations 

and equinus conditions tend to accelerate the patho - 

logic processes associated with hallux abducto valgus. 

The sequence of events usually commences when the 

calcaneus everts beyond the vertical in an excessively 

pronated foot. The resultant eversion unlocks the mid- 

tarsal joint, allowing the axes of the talonavicular and 

calcaneocuboid joints to become parallel to each 

other and resulting in an unstable midtarsal joint. This 

instability, which persists during stance, allows for hy- 

permobility of the first ray at the time it should be 

most stable for propulsion.

1-3

 

At the same time, the soft tissue musculature around 

the rearfoot and first ray become altered in the prona- 

ted foot. With calcaneal eversion, the pull of the flexor 

107 

 

108    HALLUX VALGUS AND FOREFOOT SURGERY 

hallucis brevis and longus are altered. In addition, 

with an unstable midtarsal joint the route of the pero- 

neus longus muscle tendon is altered, thereby affect- 

ing the motion about the first ray. The peroneus 

longus muscle, coursing around the cuboid, normally 

inserts into the base of the first metatarsal and the  

medial cuneiform and stabilizes the complex at toe- 

off. In a pronated foot, the peroneus longus cannot 

perform this function, and the resultant muscular and 

biomechanical alteration results in a hypermobile first 

ray.

4-9 

With the preceding definition and an understanding 

of the mechanics of hypermobility of the first ray as an 

etiology in hallux abducto valgus deformity, the first- 

ray axis and biomechanics of the subtalar and midtar- 

sal joints can be discussed. The first ray possesses a 

triplane axis that courses in an  anterior, lateral, and 

dorsal direction.

3,10

 Therefore, dorsiflexion of the first 

metatarsal will be accompanied by adduction and 

plantar flexion will be accompanied by abduction. 

Motion about the first ray is dependent on the pero- 

neus longus muscle. As was previously discussed, the 

peroneus longus muscle in turn is dependent on the  

stability of the midtarsal joint because it uses the cu- 

boid as its fulcrum. From the cuboid this muscle 

courses anterior and dorsal to exert its stability on the 

first ray. The triplane stability exerted on the first ray 

in normal biomechanics is one of plantarflexion, ab- 

duction, and a posterior pull. In normal gait therefore 

as the foot progresses from midstance into propul- 

sion, the supinating subtalar joint also locks the mid- 

tarsal joint; this ensures a stable lateral column of the 

foot and provides the peroneus longus muscle with an 

efficient fulcrum at the cuboid to exert a plantar, lat- 

eral, and posterior pull on the first ray. Consequently, 

any pronatory influence that causes an unlocking of 

the midtarsal joint may result in metatarsus primus 

adductus over a period of time.

3,5

 

Finally, it should be remembered that the first meta- 

tarsal head is firmly bound to the sesamoids by the  

tibial and fibular sesamoidal ligaments.

11,12

 In the early 

stage of hallux abducto valgus deformity, these two 

ligaments firmly hold the sesamoids to the metatarsal 

head. Therefore, the early radiographic view of the  

deformity is actually dorsiflexion, adduction, and in- 

version of the first metatarsal. As the deformity prog- 

resses over time, the tibial sesamoidal ligament be- 

comes functionally elongated as it adapts to stress 

placed on the medial side of the first metatarsophalan- 

geal joint. The fibular sesamoidal ligament, con- 

versely, functionally shortens along with the other lat- 

eral soft tissue structures. The first metatarsal rotates 

slightly at the metatarsal cuneiform articulation. In a 

pronated foot, this slight rotation of the metatarsal al- 

lows for an inversion or varus rotation of the first 

metatarsal head relative to the sesamoids. The hallux 

now moves in the opposite direction of the first meta- 

tarsal head, which accounts for the valgus or rotational 

component of the deformity. As the amount of hallux 

eversion increases over time, the tibial, intersesa- 

moidal, and fibular sesamoidal ligaments continue to 

adapt functionally to the deformity. The surgical im- 

portance of the soft tissue adaptation lies in the fact 

that if valgus rotation of the hallux is a component of 

the deformity and if transection of the fibular sesa- 

moidal ligament is not accomplished, there will still 

be some degree of valgus rotation left in the great toe. 

With the advent of biomechanics and a more de- 

tailed radiographic evaluation of the deformity, the 

etiology in hallux abducto valgus deformity has be- 

come more refined and may be categorized as fol- 

lows

3

 : 

1.

 

Hypermobility of the first ray 

2.

 

Instability of the midtarsal joint 

3.

 

Calcaneal eversion beyond vertical 

4.

 

Instability of the peroneus longus 

Metatarsus Primus Varus

 

The first metatarsal articulates proximally with the first 

cuneiform via their articular surfaces and strong liga- 

mentous support. As a result, any deviation or abnor- 

mality in this articulation can give rise to deformity. 

Some of the terms used to describe this relationship 

between the first metatarsal and the cuneiform, as well 

as the relationship between the first metatarsal and the 

second metatarsal, are metatarsus primus varus, meta- 

tarsus primus adductus,  and an  increased intermeta- 

tarsal angle.  Quite often, and erroneously, these 

terms are used interchangeably. In reality, the term 

metatarsus primus varus classically is used to describe 

a condition in which both medial and lateral cortices 

of the metatarsal are of equal length, but there is an 

increase in the measurable angle between the first and 

 

PREOPERATTVE ASSESSMENT IN HALLUX VALGUS    109

 

second metatarsal that is secondary to a deviation at 

the first metatarsocuneiform joint. 

Additionally, there exists a difference in the margins 

or sides of the cuneiform such that the lateral margin 

as compared to the medial margin of the first cunei- 

form is longer, causing an oblique angulation of the 

first metatarsocuneiform joint.

13,14

 The clinical and ra- 

diographic effect is an increased intermetatarsal angle 

measurement on radiographs, and a pronounced first 

metatarsal medially on palpation. This type of cunei- 

form has often been termed  atavistic  and was origi- 

nally discussed by Lapidus

15

 in the surgical correction 

of hallux abductor valgus deformity. Klienberg in 

1932

16

 believed that such obliquity at the first metatar- 

sophalangeal joint represented a medial cuneiform 

that was an atavistic remnant of a period when the 

hallux had a prehensile thumb-like function. 

The alternative concept of an os intermetatarsum as 

the proximate cause of a true metatarsus primus varus 

was a poor attempt to explain its occurrence. Objec- 

tive studies by Wheeler

17

 failed to demonstrate the 

correlation between the presence or absence of an os 

intermetatarsum and the development of metatarsus 

primus varus. 

The radiographic diagnosis of metatarsus primus 

varus may be demonstrated by comparing the longitu- 

dinal bisection of the first metatarsal with the longitu- 

dinal bisection of the medial cuneiform.  If the angle 

formed between this intersection is greater than 25°, a 

metatarsus primus varus deformity is said to exist 

within the first ray.

18

 However, it should be empha- 

sized that the obliquity seen on radiographic images 

may quite possibly represent a positional alteration 

produced by the imaging technique. In short, metatar- 

sal primus varus is a true structural deformity that lies 

within the first metatarsal cuneiform relationship. 

Metatarsus primus adductus or increased intermetatar- 

sal angle are indeed the same entity, and represent a 

deformity characterized by an increased angulation 

from a long axis bisection of the first and second meta- 

tarsals. The presence of metatarsus primus adductus is 

an important consideration in understanding the osse- 

ous pathologies associated with hallux abducto valgus. 

This change may be the result of long-standing biome- 

chanical pathologies as opposed to inherent structural 

deformity, but in either event if any of the deformities 

of metatarsus primus varus or metatarsus primus ad- 

ductus are pathologic, they must be corrected. In fact, 

Hardy and Clapman

9

 were the first to demonstrate that 

in younger patients it is an increase in the metatarsus 

primus adductus of the first ray that initiates the trans- 

verse plane rotation of the great toe. Of 78 patients 

who developed adult hallux valgus deformity, it was a 

consistent finding that the initiating factor in the osse- 

ous structure was an increased intermetatarsal angle, 

which was later followed by the hallux moving away 

from the midline of the body. 

CLINICAL EVALUATION

 

The podiatric surgeon should never base the selection 

of a surgical procedure solely on any one set of find- 

ings or evaluations. It is only after a thorough history 

and clinical examination in conjunction with assess- 

ment of standardized radiographs that one may con- 

sider the appropriate surgical procedure that will 

yield the best long-term result. All too often the preop- 

erative clinical examination of the deformity is limited 

to the patient seated in the chair. It should be remem- 

bered that hallux abducto valgus is a dynamic propul- 

sive phase deformity that obligates both non-weight- 

bearing and weight-bearing examination, as well as 

palpation and gait analysis. 

The practitioner should first obtain a thorough his- 

tory of the patient's chief complaint. One should note 

the exact location of the pain as being deep within the 

first metatarsophalangeal joint or solely confined at 

the medial eminence, and if there is coexisting second 

metatarsal pain. One should inquire as to the duration 

of the pain. A long-standing deformity that has only 

recently worsened may be indicative of erosion of the 

plantar crista, which has now allowed the sesamoids to 

drift laterally unimpeded. It is equally important to 

establish any functional limitations resulting from the 

deformity. The practitioner should inquire if there is 

pain at rest, only in shoe gear, or on vigorous activity. 

Another important consideration in the preopera- 

tive assessment in hallux abducto valgus reconstruc- 

tion is the age of the patient. The practitioner should 

select the procedure that will yield a functional and 

cosmetic long-lasting result. In addition, associated de- 

formities such as ankle joint equinus may also be ad- 

dressed at this time in the younger patient. Finally, the 

podiatric history is no different from the standard for- 

mat utilized in the medical arena. A thorough systemic 

 

 

110    HALLUX VALGUS AND FOREFOOT SURGERY 

history should be obtained on every patient contem- 

plating any surgical procedure. 

As mentioned previously, the clinical examination 

should be performed in both the non-weight-bearing 

and weight-bearing attitudes. It should be remem- 

bered that the physical examination should include a 

thorough assessment of vascular, dermatologic, neu- 

rologic, and musculoskeletal systems. 

The examination of the bunion deformity should 

begin with thorough palpation of the bunion and first 

metatarsophalangeal joint to localize the exact area of 

tenderness. This preferably is done while placing the 

joint through an entire range of motion. Pain through- 

out range of motion at extreme dorsiflexion or plantar 

flexion may indicate synovial or cartilaginous changes. 

Although there is often a dorsomedial prominence, 

the presence of a bursal swelling should be noted. In 

addition, many patients exhibiting hallux valgus de- 

formity may actually present with a chief complaint of 

a paronychia of the fibular nail border, which results 

from the abutment of the hallux against the second 

toe. The sesamoids and plantar crista should also be 

palpated for localized tenderness. 

Examination of the first metatarsophalangeal joint 

range of motion is vital for a successful surgical out- 

come. First, the quantity of the range of motion should 

be noted. The normal first metatarsophalangeal joint 

should exhibit at least 65° of dorsiflexion and 15° of 

plantar flexion. Any decrease in the quantity of motion 

may be indicative of arthritic changes predisposing the 

joint to a hallux limitus deformity. Severe arthritic 

changes with cartilaginous erosions would make any 

attempt at osseous and soft tissue realignment futile in 

hallux valgus reconstruction. 

The quality of motion within the first metatarsopha- 

langeal joint should likewise be carefully evaluated. 

This evaluation should be performed with the joint in 

both the deviated and rectus position. Again, it should 

be noted if pain is elicited at the endpoint of the range 

of motion or throughout range of motion. Any crepita- 

tion should be noted as this may indicate articular 

damage or structural adaptation within the joint. 

In addition to the first metatarsophalangeal joint, 

the entire first-ray range of motion should be evalu- 

ated. The first ray normally has an axis of motion ap- 

proximately 5 mm toward dorsiflexion and plantar 

flexion. An increase in motion around the first-ray axis 

may indicate hypermobility, which may affect the 

selection of the appropriate surgical procedure. 

Any callous formation should be noted as to its loca- 

tion around the bunion deformity. The callous pattern 

should be noted as plantar first metatarsal, plantar me- 

dial interphalangeal joint, or underneath the second 

metatarsal. 

18-20

 

RADIOGRAPHIC EVALUATION

 

Proper radiographic evaluation of the hallux abducto 

valgus deformity requires standard preoperative 

weight-bearing views taken in the angle and base of 

gait.

21

 It cannot be overemphasized that hallux valgus 

represents a dynamic deformity on which ground re - 

active forces exert a direct pronounced effect. 

Standard preoperative views should consist of 

weight-bearing dorsiplantar, lateral, forefoot axial, and 

medial oblique projections. Dorsiplantar and lateral 

views together will allow the practitioner to accurately 

measure traditional relationships and identify posi- 

tional and structural components of the deformity. A 

45° medial oblique projection demonstrates hypermo- 

bility from lack of parallelity between the first and 

second metatarsals. The medial oblique projection 

will also act as a standard for assessment of pre - and 

postoperative correction of the deformity. The fore - 

foot axial projection will aid in evaluating degenera- 

tive changes noted within the sesamoid apparatus. The 

plantar crista of the first metatarsal head may also be 

viewed and evaluated for erosive changes that may 

accelerate the deformity. We do not recommend eval- 

uating the tibial sesamoid position on the forefoot ax- 

ial view, because it should be remembered that activa- 

tion of the "windless mechanism" will cause the 

deformity to appear less severe than it actually is.

3

 

Finally, the preoperative radiographic evaluation 

must be combined with a thorough history of the pa- 

tient's chief complaint and proper clinical examina - 

tion in both the non-weight-bearing and weight-bear- 

ing stance. 

Intermetatarsal Angle

 

The intermetatarsal angle is formed by the angle pro- 

duced at the intersection of the longitudinal bisection 

 

PREOPERATIVE ASSESSMENT IN HALLUX VALGUS    111 

of the shafts of the first and second metatarsal (Fig. 

6-1). A normal range for the intermetatarsal angle in 

the rectus foot is considered to be 0°-14°. In the ad- 

ducted foot type, 0°-12° may be considered normal. 

An abnormally increased intermetatarsal angle may be 

termed  metatarsus primus adductus.

22

  This transverse 

plane relationship is one of the most important in 

selecting the appropriate surgical procedure. As the 

intermetatarsal angle approaches values greater than 

15°, one may wish to consider a more proximally 

based osteotomy for greater correction. A metatarsal 

head or neck osteotomy may be considered when the 

intermetatarsal angle is mild to moderately in-  

creased.

23

 Scott et al.

24

 reported that when comparing 

the intermetatarsal angle, metatarsus primus varus, the 

metatarsal cuneiform angle, and the metatarsus omnis 

varus  angle in patients with hallux valgus, medial 

deviation  of the first metatarsal was measured 

differently by all four angles. Therefore, it appears the 

best measure of  deviation of the first metatarsal is the 

intermetatarsal angle.

24

 

Hallux Abductus Angle

 

The hallux abductus angle or  hallux valgus angle is 

formed by the intersection of a line drawn through the 

long axis of the first metatarsal and the long axis of the 

proximal phalanx (see Fig. 6-1). A normal hallux ab- 

ductus angle is one that measures less than 16° in the 

rectus foot type. Mild deformity is present when this 

angle measures between 17° and 25°. The deformity is 

categorized as severe when the angle measures up to 

35°. Finally, a subluxed joint is usually apparent when 

this relationship measures more than 35°.

24

 

Proximal Articular Set Angle

 

The proximal articular set angle (PASA) is another 

valuable measurement of structural deformity within 

the metatarsal head. This angle is formed by a line 

representing the effective articular cartilage of the first 

metatarsal head and a perpendicular line to the bisec- 

tion of the shaft of the first metatarsal

18

 (Fig. 6-2A). An 

abnormal increase in PASA may demonstrate the loca- 

 

Fig. 6-1. A. Intermetatarsal angle; B. hallux abductus angle.

 

tion of a structural deformity in the head of the meta- 

tarsal, and it may progressively increase secondarily to 

structural adaptation of the articular cartilage surface 

as the deformity progresses. A normal PASA is one that 

measures less than 8° in the rectus foot. However, our 

 

112    HALLUX VALGUS AND FOREFOOT SURGERY

 

 

A 

B