Hallux Valgus

Anatomy

The articulation of the first MTP joint differs from that of the lesser toes in that it has a sesamoid mechanism. The head of the first metatarsal is round and covered by cartilage and articulates with the somewhat smaller, concave elliptic base of the proximal phalanx. A fan-shaped ligamentous band originates from the medial and lateral metatarsal epicondyles and constitutes the collateral ligaments of the MTP joint ( Fig. 7-3 ). The strong collateral ligaments run distally and plantarward to the base of the proximal phalanx, whereas the sesamoid ligaments fan out plantarward to the margins of the sesamoid and the plantar plate. The two tendons of the flexor hallucis brevis, the abductor and adductor hallucis, the plantar aponeurosis, and the joint capsule condense on the plantar aspect of the MTP joint to form the plantar plate ( Fig. 7-4A ).

Located on the plantar surface of the first metatarsal head are two longitudinal cartilage-covered grooves separated by a rounded ridge (the crista). A sesamoid bone is contained within each tendon of the flexor hallucis brevis and articulates by means of cartilage-covered convex facets on its superior surface, with the corresponding longitudinal grooves on the inferior surface of the metatarsal head. Distally, the two sesamoids are attached by the fibrous plantar plate (sesamoid-phalangeal ligament) to the base of the proximal phalanx; thus the sesamoid complex is attached to the base of the proximal phalanx rather than the metatarsal head. The sesamoids are connected to each other by the intersesamoidal ligament, and this recess conforms to the crista on the plantar surface of the metatarsal head ( Fig. 7-4B ).

The tendons and muscles that move the great toe are arranged around the MTP joint in four groups. The dorsal group is composed of the long and short extensor tendons, with the extensor hallucis longus anchored, medially and laterally, by the hood ligament ( Fig. 7-5 ). The extensor hallucis brevis inserts beneath the hood ligament into the dorsal aspect of the base of the proximal phalanx. The plantar group contains the long and short flexor tendons, with the tendon of the flexor hallucis longus coursing through a centrally located tendon sheath on the plantar aspect of the sesamoid complex. This tendon is firmly anchored by this tunnel within the sesamoid complex. The last two groups are composed of the tendons of the abductor and adductor hallucis, which pass medially and laterally, respectively, but closer to the plantar surface than the dorsal surface. Thus the dorsomedial and dorsolateral aspects of the joint capsule are covered only by the hood ligaments, which maintain alignment of the extensor hallucis longus tendon.

The adductor hallucis, arising from the lesser metatarsal shafts, is made up of two segments, the transverse and the oblique heads, which insert on the plantar lateral aspect of the base of the proximal phalanx and also blend with the plantar plate and the sesamoid complex. The adductor hallucis balances the abductor forces of the abductor hallucis ( Fig. 7-6 ). Acting in a line parallel to this bone and using the head of the first metatarsal as a fulcrum, the abductor hallucis pushes the first metatarsal toward the second metatarsal.

The base of the first metatarsal has a mildly sinusoidal articular surface that articulates with the distal articular surface of the first cuneiform. The joint has a slight medial plantar inclination. The medial lateral dimension is approximately half the length of the dorsoplantar dimension. The joint is stabilized by capsular ligaments and is bordered laterally by the proximal aspect of the second metatarsal, which extends more cephalad and offers a stabilizing lateral buttress to the first metatarsocuneiform (MTC) articulation. ElSaid et al, in a cadaveric evaluation of 239 specimens, observed a facet to be present in 25% of cases; however, these were not specimens with hallux valgus. Coughlin and Jones observed the radiographic presence of a facet between the proximal first and second metatarsals in 7% of 122 cases review with a bunion deformity ( Fig. 7-7 ).

The orientation of the MTC joint may determine the amount of metatarsus primus varus, and the shape of the articulation may affect metatarsal mobility. A medial inclination of up to 8 degrees at the MTC joint is normal. Increased obliquity at this joint can increase the degree of metatarsus primus varus. The axis of motion of the MTC joint is aligned to permit motion in a dorsal-medial to plantar-lateral plane.

The tarsometatarsal articulation is quite stable in the central portion because of interlocking of the central metatarsals and cuneiforms ( Fig. 7-8 ). This is not necessarily the case for the first and fifth metatarsals, where stability is determined not only by the inherent stability of the tarsometatarsal articulation but also by the surrounding capsular structures. Therefore when ligamentous laxity is present, the first metatarsal may deviate medially and the fifth metatarsal laterally in the development of a splay foot deformity ( Fig. 7-9 ).

Blood Supply to the First Metatarsal Head

The blood supply to the first metatarsal passes through a nutrient artery traversing the lateral cortex of the midshaft of the metatarsal in a distal direction. The vessel divides within the medullary canal and sends branches both distally and proximally. Whereas the blood supply through the nutrient artery demonstrates little variation, the blood supply to the metatarsal head and to the base of the metatarsal does demonstrate variability ( Fig. 7-10 ). According to Shereff et al, the primary sources of circulation to the metatarsal head emanate from the first dorsal metatarsal artery, the first plantar metatarsal artery, and the superficial branch of the medial plantar artery. The majority of this blood supply penetrates the capsule in the general area along the dorsal and lateral aspects of the joint. Fig. 7-11 shows the geographic distribution of the intraosseous blood supply to the metatarsal head. Proximally, the blood supply is centered around the area of the old epiphyseal plate region and seems to demonstrate a more uniform pattern. The surgical significance is that after medial capsulorrhaphy and distal metatarsal osteotomy, the vascular supply to the metatarsal head depends on the remaining metaphyseal vessels. Wide soft tissue dissection may imperil the circulation of the capital fragment and lead to avascular necrosis (AVN).

Pathoanatomy

Hallux valgus is a multiplanar deformity arising from a combination of extrinsic forces and an inherent tendency toward instability based on unique anatomic features. Because no muscle inserts on the metatarsal head, it is vulnerable to extrinsic forces, in particular, constricting footwear. Once the metatarsal becomes destabilized and begins to subluxate medially, the tendons about the MTP joint drift laterally. The muscles that previously acted to stabilize the joint become deforming forces because their pull is lateral to the longitudinal axis of the first ray. The plantar aponeurosis and the windlass mechanism contribute significantly to stabilization of the first ray ; with progression of a hallux valgus deformity, their stabilizing influence is diminished ( Fig. 7-12 ). As the hallux valgus deformity progresses, the soft tissues on the lateral aspect of the first MTP joint become contracted, and those on the medial aspect become attenuated. The metatarsal head is pushed in a medial direction by the lateral deviation of the proximal phalanx, thereby progressively exposing the sesamoids, which are anchored in place by the transverse metatarsal ligament and the adductor hallucis muscle. As the metatarsal head continues to deviate medially off the sesamoids, the crista, which normally acts to stabilize the sesamoids, is gradually eroded ( Fig. 7-13 ). These lesions are rarely seen on the plantar surface of the first metatarsal unless an effort is made intraoperatively to inspect this area. Bock et al reported on a large series of patients treated for hallux valgus and found that 57% had significant plantar erosive lesions. Roukis et al, reporting on 166 feet that underwent bunion surgery, noted that almost every joint had some element of articular cartilage erosion on the plantar metatarsal head. In more severe deformities, this erosion becomes more pronounced and extensive. As the sesamoid sling slides beneath the first metatarsal head, the hallux gradually pronates. As this dynamic joint deformity occurs, the medial eminence often becomes more prominent ( Fig. 7-14 ).

The hallux and the first MTP joint play a significant role in the transfer of weight-bearing forces during locomotion. The plantar aponeurosis plays a key role in this process by plantar flexing the first metatarsal as weight is transferred to the hallux. As the hallux is dorsiflexed at the first MTP joint, the first metatarsal is depressed, which results in increased weight bearing beneath the first metatarsal head and stabilization of the medial longitudinal arch ( Fig. 7-15 ).

Certain pathologic conditions, either acquired or iatrogenic, diminish the ability of the first MTP joint and hallux to function as weight-bearing structures. This results in transfer of weight to the lateral aspect of the forefoot, which often leads to the development of a transfer lesion beneath the second or third metatarsal head. As less weight is borne by the first ray, transfer metatarsalgia and lesser toe deformities may develop. Coughlin and Jones reported a 48% incidence of second MTP joint symptoms in a prospective study of adult patients undergoing repair of moderate and severe hallux valgus deformity.

Pathophysiology

The dynamics of the hallux valgus deformity can best be understood by first examining the articulations where the deformity occurs, that is, the MTP and MTC joints. The most stable MTP articulation has a flat articular surface, and conversely, the least stable has a rounded head ( Fig. 7-16 ). Coughlin and Jones and Okuda et al both noted an increased incidence of a rounded first metatarsal head associated with hallux valgus. A congruent MTP joint likewise is more stable than an incongruent or subluxated joint. A congruent joint tends to remain stable, whereas once a joint has begun to subluxate, the deformity tends to progress with the passing of time ( Fig. 7-17 ).

A patient with more than 10 to 15 degrees of lateral deviation of the distal metatarsal articular surface, referred to as increased distal metatarsal articular angle (DMAA), may have a significant hallux valgus deformity that is symptomatic because of the presence of a prominent medial eminence, even though the joint is congruent and tends to be stable.

In some circumstances, alignment of the first MTP joint is normal but a valgus deformity is present because of a deformity within the proximal phalanx, which is termed hallux valgus interphalangeus (HVI) ( Fig. 7-18 ). More than one of the above conditions can be present and contribute to the overall deformity and symptoms in a given patient.

Since no muscle inserts into the first metatarsal head, but several attach to the proximal phalanx, the position of the metatarsal head is necessarily influenced by the position of the proximal phalanx. Because medial and lateral movement of the first metatarsal is to a great extent controlled by the position of the proximal phalanx, a certain degree of mobility at the MTC joint must exist for this to occur. A horizontal orientation tends to resist an increase in the intermetatarsal (IM) angle, whereas an oblique orientation is a less stable articulation.

The pathophysiology of a hallux valgus deformity varies, depending on the nature of the deformity. With a congruent hallux valgus deformity, the basic deformity consists of the prominent medial eminence (the bunion), which results in pressure against the shoe and thus a painful bursa or cutaneous nerve over the prominence. The MTP joint itself is stable, and the deformity does not usually progress in adults.

With an incongruent or subluxated hallux valgus deformity, there is usually a progressive deformity. As the proximal phalanx moves laterally on the metatarsal head, it exerts pressure against the metatarsal head, which pushes it medially and results in an increased IM angle. As this process occurs, there is progressive attenuation of the medial joint capsule, as well as a progressive contracture of the lateral joint capsule ( Figs. 7-19 and 7-20 ). Resulting forces at the medial MTC joint can create laxity that exacerbates the deformity.

While this deformity is occurring, the sesamoid sling, which is anchored laterally by the insertion of the adductor hallucis muscle and the transverse metatarsal ligament, remains in place as the metatarsal head moves medially and thereby creates pressure on the medial joint capsule. The weakest portion of the medial joint capsule lies just above the abductor hallucis tendon, and with chronic pressure, this portion of the capsule gives way; as a result, the abductor hallucis muscle gradually slides beneath the medially deviating metatarsal head. As this process slowly progresses, atrophy of the crista occurs beneath the first metatarsal head, which normally helps stabilize the sesamoids ( Fig. 7-21 ). The sesamoids subluxate from their position, which can lead to abnormal loading and degeneration of the articular surfaces of the sesamoids and plantar metatarsal head (see Fig. 7-13 ).

Once the abductor hallucis slides beneath the first metatarsal head, two events occur. First, the intrinsic muscles no longer act to stabilize the MTP joint but rather enhance the deformity. Second, as the abductor hallucis rotates beneath the metatarsal head, because it is connected to the proximal phalanx, it will rotate the proximal phalanx around on its long axis and give rise to varying degrees of pronation ( Fig. 7-22 ). It has been well established that as the hallux valgus deformity progresses, so does the degree of pronation. Because of this abnormal rotation, calluses may develop along the medial aspect of the interphalangeal (IP) joint.

Ultimately, as the MTP joint becomes less stable, the hallux carries less weight, body weight is transferred laterally in the forefoot, and callus may develop beneath the second, third, or both metatarsal heads. Increased pressure may lead to capsulitis, instability, or deviation of the second MTP joint, followed by other lesser MTP joints.

With severe hallux valgus deformities, the extensor hallucis longus tendon is displaced laterally as the medial hood ligament and capsule become stretched. As a result, when the extensor hallucis contracts, it not only extends the toe but also tends to adduct it, thus further aggravating the deformity. The abductor hallucis tendon, by migrating plantarward, loses its remaining abduction power. The flexor hallucis longus tendon, which retains its relationship to the sesamoids, moves laterally and also becomes a dynamic deforming force.

In rare circumstances, if the progressive deformity of the MTP joint continues unabated, dislocation of the MTP joint may occur over time, with the fibular and tibial sesamoids becoming dislocated into the first IM space ( Fig. 7-23 ).

The medial eminence develops with lateral migration of the proximal phalanx, but it is not characterized by new bone formation or hypertrophy of the medial first metatarsal head. Normally, a small eminence is present on the medial aspect of the first metatarsal head. The size of the medial eminence varies, and sometimes most of the enlargement is on the dorsomedial aspect of the head and is thus not apparent on anteroposterior (AP) radiographs. Volkmann and Truslow both suggested that new bone formation occurred with bunion formation, whereas Lane and Haines and McDougall suggested that merely a segment of the first metatarsal head had become exposed with lateral deviation of the hallux. Thordarson and Krewer and Coughlin and Jones have both demonstrated that the size of the medial eminence was similar in subjects with and without bunions, and the authors concluded that bony proliferation was not a component of bunion formation. The overall width of the distal metatarsal head does not enlarge with progression of a hallux valgus deformity. Thordarson and Krewer reported an average width of the medial eminence of 4.4 mm, whereas Coughlin and Jones reported the mean width to be 4.6 mm in subjects with bunions ( Fig. 7-24 ).

As the hallux valgus deformity develops, progressive medial deviation of the metatarsal head occurs and becomes symptomatic because of pressure against the shoe. Individuals who wear a broad, soft shoe or sandal are usually less bothered by the enlarged medial eminence, in contrast to persons who wear narrow dress or high-heeled shoes. At times, an inflamed or thickened bursa may aggravate the problem. On rare occasions and usually in older patients, the skin over the medial eminence can break down and result in ulceration or a draining sinus. On other occasions, a ganglion arising from the medial side of the joint can erode the joint capsule and make the eventual hallux valgus repair technically much more difficult (see Fig. 7-1D ).

The splayed appearance of the forefoot in more severe cases of hallux valgus (see Fig. 7-9 ) occurs primarily because the first metatarsal head is no longer contained within the sesamoid sling and is displaced in a medially deviated position. The middle metatarsals do not splay because of the stable articulation at their tarsometatarsal joints. On occasion, the fifth metatarsal lacks stability and drifts laterally, thereby completing the appearance of a splayed foot.

As the hallux drifts laterally, the lesser toes, particularly the second toe, are under increasing pressure. In response to this pressure, the second MTP joint may remain stable, and the great toe may drift beneath the second toe or occasionally on top of it. At other times, progressive subluxation or complete dislocation of the second MTP joint occurs. On occasion, no subluxation affects the second MTP joint; rather, all the lesser toes are pushed into lateral deviation or a “wind-swept” appearance resulting from extrinsic pressure from the hallux.

Demographics

Age of Onset

The development of hallux valgus deformity can occur in childhood, adolescence, or adulthood and probably occurs much earlier than has previously been appreciated. At what age a patient recognizes a hallux valgus deformity is dependent on their understanding of the deformity, the symptoms, the magnitude of the deformity, family history, and keenness of a patient’s observation skills. Piggott reported 57% of the patients treated for hallux valgus recalled an onset of the deformity during their adolescent years, whereas only 5% recalled development of the bunion deformity after 20 years of age. In a long-term review of patients with hallux valgus deformities, Hardy and Clapham reported that 46% of bunion deformities occurred before the age of 20. In contrast, Coughlin et al reported 62% to 65% of patients dated the development of their bunion to the third to fifth decade of life, while only 4% recalled onset in the first decade and 20% in the adolescent years. The incidence of occurrence was almost equal throughout the second through fifth decades.

There is no relationship between the severity of the deformity and the decade of onset, and increasing age is not associated with increasing magnitude of angular deformity. Many deformities can begin in the adolescent years but progress in magnitude in later decades when they become more symptomatic. Although Scranton stated that a hallux valgus deformity rarely develops before 10 years of age, Coughlin reported on a series of juvenile patients with bunions in whom the average age at onset was 12 years; 40% of these patients noted that the onset of their deformity occurred at the age of 10 years or younger.

The date when surgery was performed should not be confused with the age at onset. Coughlin et al noted that although patients recalled the onset of their bunion deformity at a mean age of 31 years, the average age at which surgery was performed was 50 to 60 years.

Of importance is the fact that late development after skeletal maturity occurs in a foot that at one point most likely had a normal structure, whereas an early onset in the juvenile years occurs before maturation in a foot that most likely “never had a normal structure.” Coughlin observed, in a series of patients with juvenile hallux valgus, that early onset of hallux valgus (before 10 years of age) was associated with a much higher DMAA, a finding that would probably alter the choice of operative technique in these patients.

Gender

Although several studies have demonstrated a predilection in the female population for the development of hallux valgus, this may be merely a reflection of a specific person’s choice of footwear. Population-based studies of younger patients, who presumably wear similarly constructed shoes, report prevalence of hallux valgus from near equal to 3 : 1 female to male ratio. Wilkins, in a study of schoolchildren’s feet, reported a female preponderance of 2 : 1. Hewitt et al and Marwil and Brantingham, in investigating male and female military recruits, found a predilection of approximately 3 : 1 in the female population. Akinbo et al, in a study of young Nigerians, reported close to equal female (56%) and male (44%) involvement in an adolescent population.

Studies that focus on symptomatic bunions, or those seeking surgery, find a greater female preponderance. Several studies on adult patients report females make up 90% or more of the patient population. Coughlin and Jones found that the proportion of females in their report on moderate and severe hallux valgus deformities was 92%. Creer and Hardy and Clapham, in reporting statistics from their surgical practices, found this ratio to be approximately 15 : 1 in adult patients. Nery et al also reported a female to male ratio of 15 : 1, finding hallux valgus in males is commonly hereditary in nature and is mainly transmitted by the mother, with early onset and higher severity when compared to women. The reported incidence of females in the juvenile population undergoing surgical correction for hallux valgus deformities varies from 84% to 100%.

Fashion trends entail that shoes worn by women can be less physiologic than those worn by men, and shoes of any type can lead to hallux valgus in susceptible persons; however, it is also likely that heredity plays a substantial role in the development of bunion deformities ( Fig. 7-25 ). On the contrary, Pique-Vidal et al observed that gender did not affect the severity of the angular deformity in his series of 350 subjects.

Bilaterality

Most patients with moderate to severe deformities have bilateral hallux valgus deformities, which may be of differing magnitude and differing symptoms, and may be associated with a familial trait. Coughlin and Jones found that 84% of patients had bilateral hallux valgus deformities. There was no association between bilateral deformities and handedness, family history, or the magnitude of the preoperative deformity. There was a strong correlation between bilateralism and a family history of bunions ( P < 0.01).

Extrapolating the incidence of hallux valgus corrective surgery to the prevalence of bilaterality underestimates the number of bilateral cases. Mann and Coughlin initially suggested that hallux valgus deformities most commonly occurred as unilateral deformities. This notion was based on reports of the results of surgical procedures in which a majority of patients underwent unilateral surgery. However, it is very common for patients to have bilateral deformities yet have surgery performed on only the symptomatic side, or they may only have the index surgery performed during the period of study. In their prospective evaluation of moderate and severe bunion deformities, while Coughlin and Jones found that 84% of patients had bilateral hallux valgus deformities, only 18% had both feet corrected during the study period. The remaining surgery occurred either before or after the reported study. Symptoms and varying magnitudes of deformity may lead a person to desire unilateral correction despite having bilateral hallux valgus deformities.

Etiology

Extrinsic Causes

Footwear

Symptomatic hallux valgus occurs primarily in persons who wear shoes but does occasionally occur in unshod people ( Fig. 7-26 ). The notion of footwear being the principal contributor to the development of hallux valgus was substantiated by a study of Sim-Fook and Hodgson in which 33% of shod persons had some degree of hallux valgus as compared with 2% of unshod persons. Akinbo et al and Owoeye et al reported a very low incidence of hallux valgus in Nigerian youth in a typically unshod population. Hallux valgus deformities were also extremely rare in the Japanese because of the nature of their traditional footwear, the tabi sandal ( Fig. 7-27 ). When the manufacture of fashionable leather shoes greatly exceeded the manufacture of traditional sandals in the 1970s, the incidence of hallux valgus deformity increased substantially. Conversely, physicians in France referred to the development of hallux valgus deformities as early as the 18th century. Before that time, the common footwear was a Greco-Roman style, flat-soled sandal. Studies by Maclennan in New Guinea, Wells in South Africa, Barnicot and Hardy in West Africa, Engle and Morton in the Belgian Congo, and James in the Solomon Islands found some element of metatarsus primus varus and an occasional asymptomatic hallux valgus deformity in the indigenous populations ( Fig. 7-28 ). Cho et al has reported in a study from a rural Korean community, that female subjects in the fourth through seventh decades had a higher incidence of deformity.

One can conclude from these studies that an asymptomatic hallux valgus deformity in an unshod person may be attributed to hereditary causes. In shoe-wearing populations, however, a symptomatic and painful bunion would be expected to develop more commonly. A wide or splayed forefoot forced into a constricting shoe might thus lead to symptoms over the medial eminence.

Although shoes appear to be an essential extrinsic factor in the development of hallux valgus in adults, the deformity does not develop in many people who wear fashionable footwear. Therefore some intrinsic predisposing factors must make some feet more vulnerable to the effect of footwear and likewise predispose some unshod feet to the development of hallux valgus. In most cases, a juvenile hallux valgus deformity does not appear to be influenced by a history of constricting footwear. In a prospective study of adults with hallux valgus, Coughlin and Jones reported that only 34% of patients undergoing surgical correction implicated constricting footwear as a cause of their deformity, while in an earlier report, Coughlin found that 60% of men with hallux valgus who had undergone surgical correction implicated ill-fitting shoes as a cause of their deformity.

Occupation

Cathcart and Creer have implicated occupation as a cause of hallux valgus. Again, objective evidence in the small percentage of patients who claim that their occupation contributed to their hallux valgus deformity is lacking. Coughlin and Jones reported that patients considered occupation an infrequent cause of their deformity, with 17% implicating their job as a cause of their hallux valgus deformity. However, there was not a correlation between the magnitude of the angular deformity and those who attributed their deformity to either occupation or constricting shoewear.

Trauma

Trauma to the forefoot may be a cause of acute deformity or chronic deviation to the MTP joint. Rupture of the medial joint capsule has been recognized as a cause leading to development of a bunion deformity. Johal et al reported a bunion deformity that followed a tibial shaft fracture with entrapment and injury to the medial plantar nerve. Bohay et al reported seven cases in which a Lisfranc joint injury led to first MTC joint instability and later bunion deformity. Surgical correction with a standard bunion correction in several of these cases led to realignment of the first ray.

Intrinsic Causes

Heredity and Genetics

The notion that a hallux valgus deformity is inherited has indeed been suggested by many authors. A positive family history of hallux valgus in 58% to 88% has been reported in five different series of adult patients. Coughlin and Jones stated that 86 of 103 adult patients (84%) reported a family history of hallux valgus deformities in parents or grandparents. In 1956, Johnston reported an in-depth genetic history on subjects with hallux valgus. Based on a single-family case report, he proposed that this trait was autosomal dominant with incomplete penetrance.

Juvenile hallux valgus deformities have also been characterized by their familial tendency. Coughlin reported a family history in 72% of patients in his retrospective study on juveniles and noted that a bunion was identified in 94% of 31 mothers of children with a family history of hallux valgus deformity. Of the 31 patients with a positive family history for the deformity, four females noted an unbroken four-generation history of hallux valgus transmission from maternal great-grandmother to maternal grandmother to mother to patient ( Fig. 7-29 ). Eleven females reported a three-generation history of transmission from maternal grandmother to mother to patient, and 11 patients noted a two-generation history of mother-to-patient transmission. Of three males with hallux valgus in this same series, two reported their mothers to have had a bunion and one reported a three-generation history of maternal transmission to the patient. Thus 29 of 31 patients (94%) with a family history showed a pattern consistent with maternal transmission. The preoperative hallux valgus deformity in these patients was reported to be 5 degrees greater in those with a family history, although the average postoperative hallux valgus correction was similar in patients with and without a family history.

Pique-Vidal et al, in a report of 350 patients with hallux valgus, constructed a three-generation pedigree. The gender ratio was male : female 1 : 15; juveniles comprised only 5% of the series. Ninety percent of the subjects had at least one other relative with a bunion; 70% of the subjects had at least three relatives with bunion involvement. The authors also observed that severity of the deformity was not affected by gender or the magnitude of deformity in other relatives.

Both Bonney and Macnab and Coughlin observed an earlier onset of deformity in patients with a family history of hallux valgus. The high rate of maternal transmission noted in previous reports makes it difficult to avoid a conclusion that there is a genetic predisposition for hallux valgus deformities in the female population. However, the chapter authors believe that although this trait can be associated with X-linked dominant transmission or polygenic transmission, it more commonly is an autosomal dominant transmission with incomplete penetrance.

Genetic mapping strongly suggest a genetic component to risk of developing progressive hallux valgus deformity. A genetic study of 5925 individuals of European Ancestry identified a novel locus in the intronic region of CLCA2 on chromosome 1, an expression quantitative trait locus for COL24A1, a member of the collagen gene family. A genetic study of a Chinese population found susceptibility single nucleotide polymorphisms (SNPs) for hallux valgus located within the promoter region of gene for tumor necrosis factor (TNF), an important cytokine involved in bone remodeling and chronic inflammatory bone diseases. Additional data on genetic loci associated with hallux valgus may ultimately produce a genetic test that may predict risk of progression. However, the complex and multifactorial nature of bunion deformities adds challenge to this task.

Pes Planus

The association of pes planus with the development of a hallux valgus deformity is unclear and difficult to quantify. Mann and Coughlin found a low incidence of advanced pes planus in adults with hallux valgus, suggesting that the occurrence of hallux valgus with pes planus is uncommon in patients without neuromuscular disorders. A 20% incidence of pes planus in the general population was defined in a review of normal adult military recruits by Harris and Beath. Half of these cases represented an asymptomatic “simple depression of the longitudinal arch.” Pouliart et al did not observe any relationship between the degree of pes planus and the severity of hallux valgus. Kilmartin and Wallace found that the incidence of pes planus in the normal population and in those with a hallux valgus deformity was essentially the same. They concluded that pes planus in juveniles had no significant association either with the magnitude of the preoperative hallux valgus deformity or with the postoperative success or failure rate of a surgical repair. This finding was confirmed by Coughlin and Trott and McCluney and Tinley, who all noted no increased incidence of pes planus in juvenile patients.

In general, pes planus may be no more common in those with hallux valgus than in the general population. Studies by Canale et al, Coughlin, and Kilmartin and Wallace have reported no correlation between pes planus and the success rate of surgical repair of a hallux valgus deformity. Coughlin and Jones reported only a 15% incidence of moderate and severe pes planus in their surgical series of 122 feet with hallux valgus. However, Heyes et al found a strong correlation between recurrence of hallux valgus following surgical correction and degree of pes planus.

One challenge is in the definition of pes planus, which is variable in the literature. Arch height has been quantified by both Harris mat imprints and radiographic measurements ( Fig. 7-30 ). Coughlin and Kaz reported good correlation between Harris mat imprints and physical examination and angular measurements, such as the lateral talometatarsal angle, lateral talocalcaneal angle, calcaneal pitch, and the AP talonavicular angle. Grebing and Coughlin used Harris mat imprints to assess arch height and demonstrated that a low arch was significantly more common in an adult group with hallux valgus than in a control group. They reported an 11% incidence of pes planus in a normal control group and a 24% incidence in a group with hallux valgus but also found no correlation between the hallux valgus angle and pes planus or between pes planus and first-ray mobility. Saragas and Becker did not find an increased incidence of pes planus when they examined the calcaneal pitch angle and found no association between the degree of pes planus and the severity of hallux valgus deformity. King and Toolan observed an association between the hallux valgus angle and both the Meary line (lateral talometatarsal angle) and the AP talonavicular coverage angle in those with pes planus.

Other authors have suggested that a hallux valgus deformity tends to develop in a pronated foot. Hohmann was the most definitive and asserted that hallux valgus was always associated with pes planus and that pes planus is always a causative factor in hallux valgus. In attempting to resolve this contradiction, the chapter authors believe that a patient with a pes planus deformity in whom hallux valgus develops will have more rapid progression of the deformity. However, hallux valgus does not develop in most patients with pes planus.

Models and radiographs can demonstrate the role of pronation in the pathophysiology of hallux valgus in a normal foot ( Figs. 7-31–7-34 ). Although an excellent demonstration of the effect of pronation on the foot and hallux, they do not enable determination of what initiates a hallux valgus deformity. In Fig. 7-31 , a pendulum has been attached to the nail of the great toe. As the foot is pronated, rotation of the first ray around its longitudinal axis is clearly seen. In Fig. 7-32 , a skeletal model has been photographed. With longitudinal rotation of the first metatarsal head, the fibular sesamoid becomes visible on the lateral side of the first metatarsal head. Fig. 7-33 shows a dorsoplantar weight-bearing radiograph; with the pronated position of the sesamoids, they appear to have been displaced laterally. The fibular sesamoid is now visible in the interval between the first and second metatarsals, as would be anticipated from the skeletal model in Fig. 7-34 . Tangential or sesamoid views of the foot show that this appearance is caused solely by longitudinal rotation of the first metatarsal, not by actual lateral displacement; the sesamoids remain in a normal relationship with their facets located on the plantar surface of the metatarsal head (see Fig. 7-34 ).

Pronation of the foot imposes a longitudinal rotation of the first ray (metatarsal and phalanges) that places the axis of the MTP joint in an oblique plane relative to the floor. In this position, the foot appears to be less able to withstand the deforming pressures exerted on it by either shoes or weight bearing. No data are available on the relationship between the degree of pes planus and the degree of hallux valgus in the small percentage of unshod persons in whom the condition develops. Furthermore, authors who have noted a relationship between pes planus and hallux valgus in shod people have presented no quantitative data.

To discount pronation entirely, however, is not appropriate because in some cases it can play a substantial role in the development and progression of specific hallux valgus deformities. Pronation of the foot does alter the axis of the first ray. With weight bearing, the first MTP joint assumes an oblique orientation with the ground. In some pronated feet, especially in patients with ligamentous laxity, pressure exerted on the medial capsule of the first MTP joint can lead to progression of a hallux valgus deformity because the soft tissue supporting structures are unable to withstand these deforming forces. In such pathologic situations, a physician should be aware of possible progression of deformity, as well as postoperative recurrence. The use of prefabricated or custom orthoses in these patients may be beneficial. Persons with a mild hallux valgus deformity may experience rapid progression of the deformity if instability of the hindfoot secondary to rupture of the posterior tibial tendon, hindfoot valgus secondary to rheumatoid arthritis, or instability of the first MTC joint develops. Therefore pronation of the foot can be a factor predisposing to hallux valgus in certain conditions because the medial capsular structures offer limited resistance to the strong deforming forces.

Hypermobility of the Metatarsocuneiform Joint

The concept of hypermobility of the first ray was introduced by Morton in 1928. Later, Lapidus suggested an association between increased mobility of the first MTC joint and hallux valgus. It is unclear whether this increased mobility is cause, effect, or somewhere in between. Many reports dealing with correction of hallux valgus implicate first-ray hypermobility as a cause yet offer no proof regarding the magnitude of pre- or postoperative mobility. The notion of this theory has been advanced by Hansen, Sangeorzan, and others.

Others have disputed the significance of first-ray mobility as a cause of hallux valgus. In reports on series involving the treatment of hallux valgus, Dreeben and Mann and others have found no evidence of first-ray hypermobility after surgical correction of a hallux valgus deformity. Wanivenhaus and Pretterklieber reported a 7% incidence of MTC joint instability. Coughlin and Jones reported that 23 of 122 patients (10%) with moderate or severe hallux valgus preoperatively were observed to have increased first-ray mobility.

Clinical assessment of sagittal plane mobility of the first ray was described by Morton, who suggested that with the ankle in neutral position, the examiner stabilize the lateral aspect of the forefoot with one hand and then grasp the first ray with the other hand ( Fig. 7-35 ). The first ray was translated in a dorsal plantar direction until a soft end point was reached. First-ray hypermobility was defined as excess motion on this examination. The biomechanical axis of the first MTC joint is obliquely placed, which permits motion of the metatarsal head to occur in a dorsomedial to plantar-lateral direction ( Fig. 7-36 ). This oblique motion of the joint can indeed be qualitatively observed on physical examination, but attempting to quantify it clinically has been difficult. Although Morton claimed that first-ray hypermobility led to a multitude of foot problems, he concluded that there was no reliable method by which he could quantify the magnitude of first-ray hypermobility. Efforts to quantify MTC mobility have proved difficult, and surprisingly, no report of the results of first MTC joint arthrodesis has provided data on the pre- and postoperative magnitude of first-ray mobility. Attempts to quantify first-ray mobility have measured motion in either degrees or millimeters of either dorsal displacement or total excursion ( Fig. 7-37 ). Efforts to accurately measure first-ray mobility have evolved to the use of external calipers in recent years. Klaue et al described a noninvasive caliper consisting of a modified ankle–foot orthosis and an external micrometer to quantify first-ray mobility. The authors found measurable, repeatable values for both normal and hypermobile first rays and concluded that hypermobility was often associated with the development of hallux valgus. They reported that normal adult patients had approximately 5 mm of flexibility at the MTC joint, and patients with hallux valgus had 9 mm or more of mobility. Although the applied force is not standardized when using this device, both the examination and the position of the foot and ankle are actually quite similar to the manual examination as originally described by Morton. Jones et al have substantiated that the Klaue device is reliable and gives reproducible measurements of first-ray excursion. Glasoe et al demonstrated comparability of both the Klaue device and the Glasoe device for external measurement of first-ray mobility.

Other reports have also demonstrated that external calipers are reliable in quantifying first-ray motion. Klaue et al and others used external calipers to measure first-ray mobility and reported greater mobility in patients with hallux valgus deformities than in control subjects. However, both Glasoe et al and Cornwall et al reported that the manual testing technique, as described by Hansen and others, was quite unreliable and not reproducible when compared with mechanical testing techniques. Using the Klaue device to assess postoperative first-ray mobility after treatment with various hallux valgus surgical techniques, Coughlin et al reported that the measured mobility was 4 mm after MTP arthrodesis and 5 mm after distal soft tissue reconstruction with proximal first metatarsal osteotomy. In both series, no first-ray hypermobility was observed after correction of the bunion. However, in neither of these studies were measurements made before correction of the hallux valgus (because this measurement device had not been available). Since there is no consensus on the magnitude or threshold to define MTC instability, this is simply one of several assessment tools in the decision making for hallux valgus correction.

The position of the ankle and first toe substantially influences the perceived first-ray mobility through their effect on plantar aponeurotic tension. Sarrafian observed that the position of the ankle secondarily affects tension on the plantar aponeurosis ( Fig. 7-38 ). Rush et al suggested that first-ray motion could affect tension on the plantar aponeurosis and windlass mechanism, thus secondarily diminishing first-ray mobility. Grebing and Coughlin defined the position of manual examination by investigating a group of patients with a modified Klaue device that enabled them to dorsiflex and plantar flex the ankle while measuring first-ray mobility ( Fig. 7-39 ). A control group (mean mobility, 5 mm), a group with moderate and severe hallux valgus (mean mobility, 7.0 mm), a group that had previously undergone first MTP arthrodesis (mean mobility, 4.4 mm), and a group that had previously undergone plantar fasciectomy (mean mobility, 7.4 mm) were studied. When the ankle was placed in 5 degrees of dorsiflexion, first-ray mobility was significantly diminished in all four groups. When the ankle was placed in 30 degrees of plantar flexion, there was significantly increased mobility in the first three groups; however, the group that previously underwent plantar fasciectomy did not experience an increase in first-ray mobility. Of interest is that in the hallux valgus group, when examined in neutral position, 21% were considered hypermobile, but when they were examined in plantar flexion, 92% were considered hypermobile. When the ankle is plantar flexed 30 degrees, the amount of first-ray mobility is increased almost twofold.

First ray mobility is decreased after hallux valgus correction, suggesting hypermobility is an effect rather than a cause of hallux valgus deformity. Sing et al used a Klaue device in two planes and found that 81% of feet with hallux valgus had hyperlaxity (odds ratio 6.7) compared with a 24% occurrence in a control group. However, Coughlin et al, in a cadaver study of specimens with hallux valgus, reported that first-ray mobility as measured with the Klaue device was 11 mm preoperatively. After distal soft tissue repair and proximal osteotomy to correct the deformity, mean first-ray mobility was 5 mm. In a follow-up prospective study in which a similar operative repair was performed on 122 feet with moderate and severe hallux valgus deformities, Coughlin and Jones reported first-ray mobility to have a preoperative mean of 7.3 mm that was reduced to a mean of 4.5 mm after surgical correction. Thus, with the ability to quantify first-ray mobility, the authors concluded that first-ray mobility is an effect of the hallux valgus deformity rather than a cause in most cases. The fact that it is reduced to a normal level after distal surgical realignment or proximal first metatarsal osteotomy that spares the MTC joint makes a strong case for increased first-ray mobility being a secondary rather than a primary cause. First-ray stability is probably a function of first-ray alignment and the effectiveness of the intrinsic and extrinsic muscles and the plantar aponeurosis and not an intrinsic characteristic of the first MTC joint. Coughlin and Jones reported no correlation between first-ray mobility and the magnitude of the hallux valgus angular deformities.

Using second metatarsal cortical hypertrophy or shaft width as an indication for first MTC joint arthrodesis in the treatment of a hallux valgus deformity is unfounded. Although Morton claimed that first-ray hypermobility was characterized by increased mobility on manual clinical examination, he concluded that the most notable structural feature of first-ray hypermobility was hypertrophy of the second metatarsal diaphysis as demonstrated on an AP radiograph (1928) ( Fig. 7-40 ). Prieskorn et al attempted to relate mobility of the first MTC joint to thickening of the second metatarsal shaft and found no correlation. Grebing and Coughlin analyzed second metatarsal shaft width and medial cortical hypertrophy (in a series of 172 patients, with 25,000 data points) and found no association with hallux valgus, first-ray mobility, or first metatarsal length. Opsomer et al, in a later study of second-ray medial cortical thickness after hallux valgus correction, reported osseous diminution of the cortical thickness in as little as 11 months after surgery. In their series of 13 patients in which differences were measured in hundredths of millimeters, their claim that redistribution of weight-bearing patterns led to cortical thinning is questionable. The significance of the preoperative measurement, as well as the postoperative changes, will require a much more rigorous process with a larger study and longer-term follow-up.

Other radiographic parameters have been studied in relation to first-ray mobility. Coughlin and Jones and Cooper et al have reported no correlation between measured first-ray mobility and any radiographic angular measurements defining pes planus’ (Meary line, calcaneal pitch, AP talonavicular coverage, lateral talocalcaneal angle). Myerson and King and Toolan suggested that a radiographic gap on the plantar aspect of the first MTC joint is associated with both hallux valgus and first MTC joint instability. The incidence of this finding is unknown. Coughlin and Jones, in a prospective study of moderate and severe hallux valgus deformities, reported a 23% incidence of plantar gapping. Of those 122 cases, the average first-ray mobility as measured by the Klaue device was 7.2 mm. The mean hallux valgus angle for these cases was 30 degrees. With respect to the preoperative presence of plantar MTC joint gapping, there was no significant difference in first-ray mobility between those with and without gapping. Of interest, one third of those joints with a gap resolved after distal realignment of the bunion deformity. It is likely that the plantar gapping as seen on the lateral radiograph is indicative of sagittal plane instability, just as metatarsus primus varus is indicative of axial plane instability.

King and Toolan, in a small series (25 cases), described the first metatarsal medial cuneiform angle (MMCA) as a possibly being a reliable measure of dorsiflexion or plantar wedging of the first MTC joint ( Fig. 7-41 ). All patients in King and Toolan’s series were considered to have first-ray instability when assessed by manual examination, although the magnitude of mobility was not quantified or reported. They described increased dorsiflexion through the first MTC joint (hallux valgus patients, 2 degrees; controls, 0.2 degree) and concluded that this demonstrated an association between the clinical and radiographic findings of first-ray hypermobility and hallux valgus. In the Coughlin study, in which a much larger cohort was examined, no evidence was found to support King and Toolan’s notion that an increase in first metatarsal-cuneiform angle was associated with increased first-ray mobility.

If increased sagittal motion of the first ray is a primary factor that predisposes to the onset of a hallux valgus deformity, one would not expect a substantial reduction in first-ray mobility after a surgical realignment distal to the first MTC joint. Postcorrection measurements of first-ray mobility (using Klaue device measurements) after a distal realignment procedure (both in vivo and in vitro) demonstrate consistent and regular reduction of first-ray mobility. Sarrafian has suggested that the plantar aponeurosis plays a key role in first-ray stability. The chapter authors believe that realignment of the first ray restores normal anatomic relationships (intrinsic and extrinsic muscles, plantar aponeurosis) and that this, in turn, leads to a diminution in first-ray mobility. Thus the stability of the first ray, in most cases, is a function of the alignment of the first ray and is not an intrinsic characteristic of the first MTC joint.

Ligamentous Laxity

The role of ligamentous laxity in hallux valgus is also a matter of debate. Carl et al observed mild generalized ligamentous laxity in a small series of patients with hallux valgus. Clark et al, in a report on juveniles, noted that 69% of patients in their series had generalized laxity on physical examination. Others have also mentioned ligamentous laxity as an etiologic factor.

Beighton and Bird defined ligamentous laxity with a 9-point scale in which 2 points were awarded for hyperextension of both elbows beyond 10 degrees (1 point for only one elbow), 2 points for hyperextension of both knees beyond 10 degrees (1 point for only one knee), 2 points for extension of the little finger beyond 90 degrees (1 point for each hand), 2 points for extension of the thumb flat with the wrist (1 point for each hand), and 1 point for the ability to place the hands flat on the ground with the knees extended. A total of 9 points can be accumulated on the examination. A score greater than 6 points indicated generalized ligamentous laxity or hypermobility. Beighton noted that most individuals (94% of males and 80% of females) score 2 or fewer points ( Fig. 7-42 ). Although studies have correlated hyperflexibility of the thumb with hypermobility of the first ray, no study has documented the pre- and postoperative laxity of patients with Beighton and Bird’s method. In one retrospective study of a group of patients with moderate and severe hallux valgus deformities treated by first MTP arthrodesis (mean hallux valgus angle, 42 degrees), 17 of 19 patients demonstrated no evidence of any laxity on the 9-point examination (0 points). Although postoperative recurrence may be a concern in treating patients with ligamentous laxity, the incidence is most likely quite low. Grimes and Coughlin evaluated a series of subjects treated with first MTP joint arthrodesis for previously failed hallux valgus surgery. They closely evaluated this series of 29 patients (33 feet) with the Beighton examination and found only 5 of 29 (14%) had confirmed ligamentous laxity. Of interest, only two patients had first-ray hypermobility as confirmed on the Klaue apparatus. Nonetheless, attention should be addressed to ligamentous laxity in any evaluation before correction of hallux valgus. Although the finding of ligamentous laxity is probably uncommon in the typical adult patient with hallux valgus, patients with Ehlers-Danlos or Marfan syndrome may be better treated conservatively because they may have an increased risk of postoperative recurrence.

Achilles Contracture

Morton defined normal ankle dorsiflexion as requiring 15 degrees. Mann and Coughlin and others have suggested that a contracted Achilles tendon can be associated with the development of hallux valgus. In contrast, Coughlin and Shurnas noted an absence of heel cord tightness in their series and found no correlation between ankle dorsiflexion and hallux valgus ( Fig. 7-43 ).

DiGiovanni et al noted that 44% of patients demonstrated “restricted dorsiflexion” when using 10 degrees or less of ankle dorsiflexion as a guideline. When using 5 degrees or less of ankle dorsiflexion as a guideline for surgical intervention, they observed that 8 of 34 normal subjects (24%) had restricted dorsiflexion and recommended surgical lengthening of the Achilles complex.

Grebing and Coughlin studied the incidence of ankle range of motion in normal subjects and patients with hallux valgus. In the control group, the mean ankle dorsiflexion was 9 degrees, and in the hallux valgus group it averaged 11 degrees. They reported that 19% of normal patients they studied had ankle dorsiflexion of 5 degrees or less. In a similarly sized group of patients with hallux valgus, 21% demonstrated ankle dorsiflexion of 5 degrees or less. Grebing and Coughlin noted that 81% of controls and 67% of those with hallux valgus had 10 degrees or less of ankle dorsiflexion. No correlation was found between ankle dorsiflexion and the magnitude of hallux valgus. In the report by Coughlin and Jones, no correlation was demonstrated between ankle dorsiflexion and the hallux valgus angle.

Gastrocnemius lengthening has been recommended for patients with a limitation of 5 degrees or more. However, none of the patients in the series reported by Grebing and Coughlin were symptomatic, and no Achilles tendon lengthening was performed in the course of their treatment. An Achilles tendon contracture secondary to any cause can produce a gait pattern in which the person slightly externally rotates the foot or tends to roll off the medial border of the foot. This repetitive stress against the hallux has been postulated to lead to a hallux valgus deformity. This can be observed in patients with neuromuscular disorders (e.g., cerebral palsy, poliomyelitis) or patients who have had a CVA.

Although DiGiovanni et al suggested that gastrocnemius lengthening be performed in patients undergoing foot surgery with dorsiflexion of less than 5 degrees, the fact that 81% of subjects demonstrated less than 10 degrees of ankle dorsiflexion suggests that this finding may not be abnormal. Furthermore, Coughlin and Jones reported an incidence of 12% to 54% in patients with moderate and severe hallux valgus who had either less than 5 degrees (14 feet, 12%) or less than 10 degrees (66 feet, 54%) of ankle dorsiflexion. Of the 122 feet in the series, in no case was an Achilles tendon lengthening or gastrocnemius slide procedure performed in conjunction with the bunion correction. There was no correlation between the success of surgery and the tightness of the gastrocnemius–soleus complex. Although on occasion a gastrocnemius–soleus contracture may accompany a hallux valgus deformity, the chapter authors believe this to be uncommon, and lengthening is recommended in the uncommon patients with substantial restriction in ankle dorsiflexion.

Other Factors

Obesity or an increased BMI has been shown to present an increased risk factor for tendonitis, plantar fasciitis, and degenerative arthritis of the lower extremity but has not been associated with an increased risk of hallux valgus.

Amputation of the second toe often results in a hallux valgus deformity, probably from loss of the support afforded by the second toe ( Fig. 7-44 ). Mild hallux valgus may be seen after resection of the second metatarsal head.

Syndactylization of the first and second toes has been reported to occur with a hallux valgus deformity.

Cystic degeneration of the medial capsule of the first MTP joint can occur. The resulting ganglion formation may sufficiently attenuate the capsule to permit the development of a hallux valgus deformity (see Fig. 7-1D ).

Hallux valgus has been reported to occur with the development of a space occupying mass in the first IM space ( Fig. 7-45 ).

Radiographic Measures

Angular Measurements

Radiographs of the foot should always be taken with the patient in the weight-bearing position. The basic studies should include AP, lateral, and oblique views. Sesamoid views can be useful to assess metatarsal pronation, sesamoid position relative to the crista, and sesamoid arthrosis. The AP radiographs are obtained with a tube-to-film distance of 1 m and the x-ray tube centered on the tarsometatarsal joint and angled 15 degrees toward the ankle joint, relative to the plantar aspect of the foot.

Hallux Valgus Angle

On an AP weight-bearing radiograph, middiaphyseal axes are drawn on the first metatarsal and proximal phalanx, bisecting metaphyseal reference points in the proximal and distal metaphyseal regions. The angle created by the intersection of these axes forms the hallux valgus angle (HVA). A normal angle is less than 15 degrees, mild deformity is less than 20 degrees, moderate deformity is 20 to 40 degrees, and severe deformity is greater than 40 degrees ( Fig. 7-46 ).

1–2 Intermetatarsal Angle

On an AP weight-bearing radiograph, reference points are placed bisecting the proximal and distal metaphyseal regions of the first and second metatarsals. The angle created by the intersection of these axes forms the 1–2 IM angle. Normal IM angle is less than 9 degrees, mild deformity is 11 degrees or less, moderate deformity is greater than 11 and less than 16 degrees, and severe deformity is greater than 16 degrees ( Fig. 7-47 ).

Hallux Interphalangeal Angle

On an AP weight-bearing radiograph, reference points are placed bisecting the proximal and distal metaphyseal regions of the proximal phalanx and the axis drawn connecting these points. Reference points are placed at the center of the base of the distal phalanx and at the tip of the distal phalanx, and a second axis is drawn. The intersection of these two axes forms the hallux IP angle ( Fig. 7-48 ).

Distal Metatarsal Articular Angle

On an AP weight-bearing radiograph, the DMAA defines the relationship of the distal first metatarsal articular surface to the longitudinal axis of the first metatarsal. Points are placed at the most medial and lateral extent on the distal first metatarsal articular surface. A line connecting these points defines the lateral slope of the articular surface. Another line is drawn perpendicular to this articular line. The angle subtended by this perpendicular line and the longitudinal diaphyseal axis of the first metatarsal defines the DMAA. Normal is regarded as 6 degrees or less of lateral deviation ( Fig. 7-49 ).

Metatarsophalangeal Joint Congruency

On an AP weight-bearing radiograph, the congruency of the MTP joint is determined by inspecting the relationship of the articular surfaces of the base of the proximal phalanx and the first metatarsal head. Individual reference points are placed at the most medial and lateral extents of the phalangeal articular surface and the distal metatarsal articular surface. With a subluxated (noncongruent) hallux valgus deformity, the corresponding points on the proximal phalanx migrate laterally in relation to the corresponding points on the metatarsal head. With a nonsubluxated (congruent) hallux valgus deformity, concentric apposition of these points on the corresponding metatarsal and phalangeal joint articular surfaces occurs. No lateral shift of the proximal phalanx takes place with a congruent hallux valgus deformity ( Figs. 7-50–7-52 ).

Medial Eminence

One of the key components of a hallux valgus deformity is the size of the medial eminence. It is frequently this prominence that is the focus of pain and footwear intolerance by patients. The size of the medial eminence is measured by drawing a line along the medial diaphyseal border of the first metatarsal. A perpendicular line is then drawn at the widest extent of the medial eminence and measured in millimeters (see Fig. 7-24 ).

Both Haines and McDougall and Lane suggested that the medial eminence was not a new growth but merely a portion of the metatarsal that had become exposed with lateral deviation of the proximal phalanx. The size of the articular surface diminishes as the sagittal sulcus migrates lateralward. The sagittal sulcus forms a border between the medial eminence and the remaining articular surface. Volkmann and Truslow suggested that there was actually new bone formation with development of a bunion. Thordarson and Krewer reviewed a series of feet and reported that the size of the medial eminence is similar in patients who undergo bunion surgery and those without a hallux valgus deformity ( Fig. 7-53 ). They concluded that bone proliferation did not occur with bunion formation. Thordarson and Krewer reported that the mean thickness of the measured medial eminence was 4.4 mm in those with hallux valgus and 4.1 mm in those with normal feet. The mean difference was 0.2 mm. Coughlin and Jones also concluded that the medial eminence does not reflect new bone formation. Resection of the medial eminence is a standard component of most hallux valgus repairs. Reducing a prominent medial eminence does aid in narrowing the forefoot; however, it is important to stress that the sagittal sulcus is not a reliable landmark for gauging resection of the medial eminence and may lead to excessive resection and subsequent hallux varus if a disproportionate amount of bone is removed.

Metatarsus Primus Varus

The simultaneous occurrence of hallux valgus and metatarsus varus has been noted frequently in the literature ( Fig. 7-54 ). Hardy and Clapham and others have reported a correlation between the degree of hallux valgus and the size of the IM angle. Of all the variables considered in their study, Hardy and Clapham noted that the highest correlation was between metatarsus primus varus and hallux valgus ( r = 0.71). The question of cause and effect between medial deviation of the first metatarsal and valgus of the great toe continues to be debated, but the findings indicate a combined deformity to a greater or lesser extent in most patients. Truslow proposed the term metatarsus primus varus to describe a congenital anomaly that, if present, “inevitably resulted in hallux valgus” when the person was forced to wear shoes. Others have also supported his notion that the primary deformity is an increased 1–2 IM angle.

Studies by Hardy and Clapham and Craigmile, in contrast, indicate that metatarsus primus varus is secondary to the hallux valgus deformity. Others have supported this notion that lateral migration of the hallux leads to medial deviation of the first metatarsal. A close relationship exists between the degree of metatarsus primus varus and hallux valgus, which must be considered in any corrective surgery. Metatarsus primus varus may predispose a foot at risk, and poor footwear may enhance the development of a hallux valgus deformity.

The authors believe that metatarsus primus varus is more frequently associated with the juvenile form of hallux valgus than the adult form and is probably a strong predisposing factor. In adults, metatarsus primus varus is probably more often a secondary change. Metatarsus primus varus can be associated with an adducted forefoot as well. Based on our analysis of available information, the authors are unable to conclude which is the primary deformity and can assert only the correlation between the two.

Hallux Valgus Interphalangeus

The relationship between the proximal and the distal phalanx of the hallux demonstrates that a line drawn perpendicular to the articular surface of the base of the proximal phalanx will usually not deviate laterally more than 10 degrees. When this line deviates more than 10 degrees laterally as it passes through the proximal phalanx, it gives rise to an HVI deformity (see Fig. 7-18A–C ). On occasion, the distal articular surface of the proximal phalanx deviates in a lateral direction, which creates a more severe HVI deformity (see Fig. 7-18D and E ). An epiphyseal injury can lead to deformity as well (see Fig. 7-18F and G). At times, an HVI deformity coexists with a hallux valgus deformity and must be considered when correction of hallux valgus is carried out or the correction is incomplete. Park et al has suggested that the interphalangeus angle may be artificially reduced because of pronation of the hallux associated with increasing deformity. They reported an average HVI angle of 13 degrees and advocated an Akin osteotomy for those with a great HVI angle.

Sorto et al suggested that there is an inverse relationship between the hallux valgus angle and the hallux valgus interphalangeal (HVIP) angle. They concluded that an increased hallux valgus angle indicates MTP joint instability, whereas a decreased angle indicates joint stability. Sorto et al reported that in a normal foot the HVIP angle averages 13 degrees. They concluded that an increase in the HVIP angle is dependent on transverse plane stability at the MTP joint. An increase in the HVIP angle is associated with a low hallux valgus angle and increased transverse plane stability. Conversely, decreased stability (hallux valgus) is associated with a high hallux valgus angle and a low HVIP angle.

Barnett reported that a normal value for the HVIP angle was 10 degrees or less. Bryant et al reported that the average HVIP angle was 5 degrees for those with hallux valgus and 15 degrees for those with hallux rigidus. Coughlin and Shurnas reported that the average HVIP angle was 18 degrees in those with hallux rigidus. They hypothesized that as the MTP joint becomes more resistant to a transverse plane deformity, the hallux becomes predisposed to an increase in the HVIP angle. In a report by Coughlin and Jones, the average HVIP angle in this group with hallux valgus was 6.7 degrees. There were only 13 of 122 subjects with an HVI angle greater than 10 degrees. The current authors suggest that in those with hallux valgus there is less resistance to transverse plane deformity, thus explaining the decreased HVIP angle.

First Metatarsal Length

The length of the first metatarsal relative to the second metatarsal, with regard to a possible association with hallux valgus, is controversial. Based on minimal supporting data, both a short and a long first metatarsal have been implicated as essential factors in the development of hallux valgus deformities. Munuera et al reported that in comparing males and females with hallux valgus both genders had a first ray that was longer (mean, 3.6 mm) than normal. Males characteristically had a longer hallux and first metatarsal, although females only had a long first metatarsal.

The method of metatarsal measurement appears to influence the measured frequency of a long or short first metatarsal, as some methods are erroneously influenced by the degree of hallux valgus. Morton suggested drawing a transverse line between the distal extent of the first and second metatarsals to compare their relative lengths ( Fig. 7-55A ). Hardy and Clapham thought that this method was influenced by angular deformities (hallux valgus, metatarsus primus varus, metatarsus adductus) ( Fig. 7-55B ). Using the arc method, Harris and Beath reported 32% with short first metatarsals, 37% with equal lengths of the first and second metatarsals, and 31% with long first metatarsals in the general population. In his evaluation of juvenile patients with hallux valgus, Coughlin reported short first metatarsals in 28%, first and second metatarsals of equal length in 42%, and long first metatarsals in 30%—data closely concurring with that previously reported by Harris and Beath.

When using appropriate measurement methods, the relationship between metatarsal length and the development of hallux valgus seems to be incidental, with decreased first metatarsal length playing essentially no role and increased length being of questionable significance. Mancuso et al reported that 77% of patients with a hallux valgus deformity had a first metatarsal length equal to or longer than the second metatarsal. Mancuso et al and Grebing and Coughlin recognized that Morton’s method of measurement had inherent problems ( Fig. 7-56 ). As the 1–2 IM angle increases, there is apparent shortening of the first metatarsal. Grebing and Coughlin compared the two methods of measurement in a control group and in a group with hallux valgus. In the control group, 30% of the first metatarsals were short with the arc method and 53% were short with Morton’s method of measurement. In the group with hallux valgus, only 5% had a short first metatarsal with the arc method, whereas 63% were short when Morton’s method was used. The normal group compared closely with results previously reported by Hardy and Clapham. The authors believe that the notion of first metatarsal shortness, as suggested by Morton, is largely an artifact based solely on his novel measurement technique. In fact, when the arc method of measurement is used, rarely is a short first metatarsal associated with a hallux valgus deformity.

Slight shortening of the first metatarsal typically occurs after many surgical procedures involving first metatarsal osteotomies. This may be an acceptable development because of the incidence of long first metatarsals in patients with hallux valgus.

Metatarsophalangeal Joint Shape

The shape of the head of the first metatarsal varies considerably from a round dome-shaped structure to a flat articular surface. The orientation and shape of the metatarsal and phalangeal articular surfaces have an important effect on the intrinsic stability of the first MTP joint. These respective articular surfaces may resist or predispose the hallux to deformity. The association of a curved metatarsal articular surface with hallux valgus has been proposed by several authors, the variability of specific joint shapes in the general population is thought to be substantial. Okuda et al, in a comparison of a control group and a group with hallux valgus, found a 78% incidence of a rounded metatarsal head in a cohort (76 feet) with a bunion and 2% in the control group (60 feet) ( Fig. 7-57 ). Schweitzer et al reported no difference in the shape of the MTP joint when they compared patients with hallux valgus or hallux rigidus. DuVries and others have suggested that a curved surface is less stable and more prone to progressive hallux valgus deformity. Patients with hallux valgus have been shown to have a high incidence of rounded metatarsal heads, varying in frequency from 71% to 91%.

A flat or chevron-shaped MTP articulation (see Fig. 7-16A–C ) is stable, tends to resist increased progressive valgus deformation, and is associated with hallux rigidus. Coughlin and Shurnas found that only 29 of 110 (26%) MTP joints in a group of patients with hallux rigidus had an oval or curved articular joint surface (see Fig. 7-16D and E ). Coughlin and Jones reported that a curved articulation was present in 71% of those with a moderate or severe hallux valgus deformity. The current authors believe that a flattened or chevron-shaped articulation is more stable and tends to resist subluxation and that a curved joint shape is less resistant to transverse plane deformity and predisposes to a hallux valgus deformity.

Joint Congruity

Congruity is the term used to describe the relationship of the metatarsal and phalangeal articular surfaces. A congruent hallux valgus deformity occurs when the corresponding articular surfaces of the metatarsal and phalanx are concentrically aligned (see Fig. 7-16A–C and F ). When the proximal phalanx has migrated laterally off the metatarsal articular surface, the deformity is deemed an incongruent or subluxated articulation ( Fig. 7-58 ; see Fig. 7-16D and E ). Piggott suggested that mild subluxation of the first MTP joint can progress to significant subluxation and leave the medial metatarsal articular surface uncovered (see Figs. 7-20, 7-44B , and 7-51C ). Congruency of the first MTP joint was initially described by Piggott, who noted that a congruous joint was typically stable, and hallux valgus did not appear to increase with time ( Fig. 7-59 ). Thus the valgus orientation of the hallux can be caused by either joint subluxation or sloping of the metatarsal articular surface or the phalangeal articular surface in relation to the diaphyseal axis of their respective bones. With a congruent hallux valgus deformity, the magnitude of hallux valgus is determined by the magnitude of the DMAA. Piggott, in an analysis of 215 adult feet with hallux valgus, determined that 9% had a congruent joint (see Fig. 7-52A ). Significant hallux valgus can occur with a congruent joint. In a patient with a symptomatic hallux valgus deformity and a congruent MTP joint, who requires surgical intervention, intraarticular MTP joint realignment may create an incongruent joint. This sloping of the joint articular surface may predispose the patient to a recurrent hallux valgus deformity or the development of postoperative degenerative joint disease ( Fig. 7-60 ).

Chi et al reported great difficulty in consistently and accurately assessing joint congruity, whereas Pique-Vidal et al reported a much higher accuracy. Others have reported varying degrees of accuracy in quantifying the DMAA. Coughlin and Freund found variable accuracy in their much larger study, with differing accuracy by some reviewers, and also found some radiographs more difficult to assess. Radiographs of skeletally immature feet are much more difficult to assess regarding congruency. Although some feet are difficult to assess, others are clearly congruent, and it is these particular feet that warrant careful and specific surgical treatment ( Fig. 7-61 ).

In a study dealing just with juveniles with hallux valgus, Coughlin demonstrated that 47% were noted to have a congruent joint with a laterally sloping DMAA ( Fig. 7-62 ). For those with a subluxated first MTP joint, the average DMAA was 8 degrees. For congruent joints, the average lateral slope or DMAA was 15 degrees. The DMAA was noted to be significantly higher in patients with a positive family history, in those with early-onset of hallux valgus (younger than 10 years), and in those with a long first metatarsal. The DMAA was not affected by the presence of metatarsus adductus. An increased DMAA is the defining characteristic of many juvenile hallux valgus deformities.

Coughlin reported that a congruent joint was present in 37% of males with hallux valgus; the measured DMAA was twice as high (21 degrees) as in congruent joints than in subluxated joints. When the postoperative hallux valgus angle was compared in the two groups, in those with a congruent joint, the preoperative DMAA and postoperative hallux valgus angle closely correlated.

Distal Metatarsal Articular Angle

On an AP radiograph, the DMAA (or proximal articular set angle) defines the relationship of the articular surface of the distal first metatarsal to the axis of the first metatarsal (see Fig. 7-49 ). The radiograph may demonstrate that the articular surfaces of the distal first metatarsal and the proximal phalanx are not oriented at right angles to the long axis of the metatarsal and phalanx (see Figs. 7-51B and 7-52A ). Slight valgus alignment allows lateral inclination of the great toe, and thus a hallux valgus angle of 15 degrees or less is considered normal.

To measure the DMAA, a point is placed on the most medial extent of the metatarsal articular surface and a second point on the most lateral extent of the metatarsal articular surface. A line is then drawn connecting these two points. The angle subtended by the longitudinal axis of the first metatarsal and a line drawn perpendicular to the distal metatarsal articular surface defines the magnitude of the DMAA. The reported normal value of the DMAA in adults varies in the literature (6.3–18 degrees). Lateral sloping of the articular surface of the distal first metatarsal or the base of the proximal phalanx may be the cause of a static valgus orientation of the great toe (see Fig. 7-59A ). As the DMAA increases, the magnitude of the hallux valgus angle increases.

Piggott stated that over time, this congruent orientation can lead to pain but that it is unusual for a deformity of this type to progress to a more severe abnormality. Measurement of this angle is extremely important when evaluating a patient with a hallux valgus deformity because it will in part determine what type of operative procedure should be performed. Richardson et al demonstrated in adults that the DMAA can be reliably quantified on an AP radiograph, although others have had difficulty in measuring the DMAA. Robinson et al has observed variation in the measurement of the DMAA with both rotation and inclination of the first ray. Pontious et al observed that it is much more difficult to measure the DMAA in a young person before bone maturation. Coughlin observed that in juvenile patients younger than 10 years with hallux valgus, the DMAA averaged 15 degrees, and in those older than 10 years, it averaged 9 degrees. In a series of juvenile hallux valgus deformities treated with a soft tissue realignment of the first MTP joint, lack of recognition of the DMAA resulted in suboptimal correction of the deformity. Coughlin and Jones, after eliminating all congruous hallux valgus deformities from their study, analyzed the remaining deformities, which were all deemed incongruent or subluxated, and they measured the magnitude of the DMAA in these cases. The mean DMAA for these subluxated joints was 10.6 degrees. Coughlin noted that the DMAA averaged 16 degrees in those with a long first metatarsal and 6.0 degrees in those with a short first metatarsal ( P = 0.002). Of interest is that Breslauer and Cohen observed that an increased DMAA greater than 15 degrees was associated with erosion of the plantar metatarsal articular surface.

The proximal phalangeal articular angle (PPAA; or the distal articular set angle) defines the orientation of the proximal phalangeal articular surface in relation to the long axis of the proximal phalanx (see Fig. 7-18 ). Although slight valgus inclination is often present in the proximal phalanx, it rarely exceeds 5 degrees. When this angle exceeds 5 degrees, an HVI deformity occurs. HVI as a separate entity occurs infrequently (3%).

A static hallux valgus abnormality can develop as a result of an abnormally large DMAA or PPAA or a combination of both. Hallux valgus deformities caused by angulation of the articular surfaces are considered a static structural abnormality; although symptoms may develop, these deformities are unlikely to progress over time. Coughlin and Shurnas confirmed earlier findings that the preoperative DMAA measurement correlated with the magnitude of postoperative hallux valgus correction in men with hallux valgus deformities. The DMAA has not been linked with the magnitude of preoperative hallux valgus or with 1–2 IM or HVI angles.

First Metatarsocuneiform Joint

The first MTC joint is a key factor in the development of both an enlarged 1–2 IM angle and an increased hallux valgus angle, though its exact contribution to development of hallux valgus remains incompletely understood. The shape of the MTC joint has a variable medial deviation. The orientation and flexibility of the MTC joint play an important role in development of the deformity at the MTP joint. On an AP radiograph, the angle formed by the intersection of the longitudinal axes of the first and second metatarsals defines the 1–2 IM angle. Metatarsus primus varus or a 1–2 IM angle of 9 degrees or greater is considered abnormal (see Fig. 7-47 ). The proximal articular surface of the first metatarsal articulates with the distal articular surface of the first cuneiform. This elliptic concave joint surface is oriented in the transverse (coronal) plane. Normally, it is deviated medially, but in some cases, it may have a marked degree of medial inclination, which is thought to result in joint instability. Both Ewald and Berntsen observed that when the first MTC joint was obliquely oriented, the first metatarsal was inclined medially and a hallux valgus deformity was much more prevalent. The MTC joint is difficult to visualize on plain radiographs. It is questionable whether a horizontal orientation, oblique orientation, or curved MTC articulation correlates with an increased 1–2 IM angle ( Fig. 7-63 ). Simon and Brage et al have questioned the “apparent orientation” of this joint and suggested that some of the apparent radiographic findings were indeed artifacts. After anatomic dissection of the MTC joint, Haines and McDougall and Truslow concluded that a hallux valgus deformity is often associated with an oblique orientation of the first MTC joint. Haines and McDougall hypothesized that an abnormality in the first metatarsal base leads to a metatarsus primus varus deformity. First MTC joint orientation is the major factor associated with an increased magnitude of the 1–2 IM angle. Mitchell et al concluded that an increased 1–2 IM angle is the result of an abnormal first MTC joint articulation. The chapter authors have observed the complex nature of this facet in dissections. The distal first cuneiform articular surface is typically convex dorsally ( Fig. 7-64 ) and flat or concave plantarward. There is a medial inclination of this joint that is variable. Depending upon the angle of the radiographic beam, the joint may appear rounded or flat or oblique. Further investigation of this joint is important in defining what is obviously a key joint in the development of hallux valgus deformities.

Inman and Piggott suggested that with subluxation of the MTP joint a simultaneous concomitant increase occurs in the 1–2 IM angle ( Fig. 7-65 ). DuVries stated that in juveniles, the increased 1–2 IM angle was responsible for the development of hallux valgus, whereas in adults, the increased 1–2 IM angle was a secondary change after first MTP joint subluxation. The belief that in juveniles an increased 1–2 IM angle is a primary deformity and the hallux valgus deformity is a secondary or acquired deformity is not new.

When a hallux valgus deformity occurs with a concomitant increase in the 1–2 IM angle, inherent flexibility at the first MTC joint may be present. In this situation, adequate correction of a hallux valgus deformity can be achieved by performing a distal soft tissue realignment without metatarsal osteotomy. Antrobus hypothesized that after a distal soft tissue repair (without a first metatarsal osteotomy) to correct a hallux valgus deformity, if the 1–2 IM angle corrected to a normal range, the metatarsus primus varus deformity was secondary to the distal hallux valgus deformity. The inherent flexibility of the first MTC joint plays an integral role in the success of any hallux valgus surgical correction. MTC joint flexibility, however, can often be assessed only intraoperatively.

Most distal first metatarsal osteotomies, MTP joint arthroplasties, and soft tissue realignments achieve correction of the 1–2 IM angle by realignment of the MTP joint. Mann and Coughlin reported an average decrease in the 1–2 IM angle of 5.2 degrees after a modified McBride procedure in adults (without a first metatarsal osteotomy). Hawkins et al reported an average 5.2-degree decrease in the 1–2 IM angle after the Mitchell procedure. One can infer from these studies that sufficient flexibility often exists at the MTC articulation and allows a reduction in the 1–2 IM angle after either a distal first metatarsal osteotomy or distal soft tissue realignment. This is an important issue because flexibility of the MTC joint can influence both the development of hallux valgus and the appropriate type of surgical repair used to achieve a successful outcome.

Intermetatarsal Facet/Os Intermetatarseum

An IM facet located between the proximal lateral base of the first metatarsal and the proximal medial base of the second metatarsal ( Fig. 7-66 ) may create a rigid MTC articulation that is resistant to surgical reduction after a distal osteotomy or distal soft tissue procedure. Likewise, the presence of an os intermetatarseum ( Fig. 7-67 ) may create a rigid MTC articulation that resists correction of the 1–2 IM angle. The presence of an IM facet or os intermetatarseum in the proximal interval between the first and second metatarsals has been suggested to be incompatible with successful distal soft tissue repair because it is an impediment to diminution of the 1–2 IM angle. On the contrary, Ellington et al have suggested that the presence of an os intermatarseum is associated with first-ray hypermobility although they present no evidence to substantiate this claim (see Fig. 7-7C ). Coughlin and Jones demonstrated that the incidence of os intermetatarseum was 7% and that of an IM facet was 7%.

Metatarsus Adductus

On an AP radiograph, the longitudinal axis of the lesser tarsus is used to measure the magnitude of metatarsus adductus. A line is drawn on the lateral aspect of the foot between two points marking the most lateral extent of the calcaneocuboid joint and the most lateral extent of the fifth metatarsocuboid joint ( Fig. 7-68 ). A second line is drawn along the medial lesser tarsus between two other points: the most medial extent of the talonavicular joint and the most medial extent of the first MTC joint. At the midpoint of these separate lines, a connecting line is drawn that bisects the lesser tarsus. Then a line is drawn perpendicular to the lesser tarsus bisection line. The angle that this line forms with the longitudinal axis of the second metatarsal determines the relationship of the forefoot to the lesser tarsus and thus the magnitude of metatarsus adductus. A normal value is 0 to 15 degrees, mild metatarsus adductus is 16 to 19 degrees, moderate metatarsus adductus is 20 to 25 degrees, and severe metatarsus adductus is greater than 25 degrees. In the presence of metatarsus adductus, a hallux valgus deformity is characterized by an abnormally low 1–2 IM angle resulting from medial deviation of both the first and second metatarsals.

The incidence of metatarsus adductus in the general population is 1 in 1000. Griffiths and Palladino found no relationship between hallux valgus and the metatarsus adductus angle with regard to gender. Ferrari and Malone-Lee found that all women in their series with an abnormal metatarsus adductus angle had an increase in the hallux valgus angle. Men with metatarsus adductus, on the other hand, had a normal hallux valgus angle. Coughlin and Shurnas and others have found no association with hallux valgus in men ( Fig. 7-69 ), and Coughlin and Jones also reported that there was no correlation between preoperative hallux valgus and metatarsus adductus in a series that was largely female.

Most reports observe an increased incidence of hallux valgus with metatarsus adductus, mainly in the juvenile population, though others have not. Coughlin reported a 22% incidence of metatarsus adductus in his series of patients with juvenile hallux valgus, and Banks et al reported a linear correlation between an increasing hallux valgus angle and an increased incidence of metatarsus adductus. Mahan and Jacko reported an increased recurrence rate after hallux valgus repair when metatarsus adductus was present, but Coughlin was unable to substantiate this finding.

Metatarsus adductus associated with a hallux valgus deformity is a difficult condition to treat because there is little room to realign the first metatarsal laterally. Coughlin reported no significant increase in the metatarsus adductus angle in patients with a positive family history of juvenile hallux valgus. Martinelli et al have advocated a multiple metatarsal osteotomies in combination with a hallux valgus repair as a means to correct the forefoot deformity.

Role of Weight-Bearing CT Scan

The recent advance and proliferation of weight-bearing CT (WBCT) technology has produced a relatively inexpensive tool to evaluate the loaded foot in three dimensions. WBCT has improved our understanding of hallux valgus deformity in ways not easily seen on radiographs. This includes more reliable measurements of HVA, IMA, sesamoid position, pronation angle, and a better understanding of the multiplanar relative positioning of the first and second rays. Kimura et al evaluated medial column mobility using WBCT and found significantly greater dorsiflexion of the navicular at the TN joint, significantly greater eversion and abduction of the medial cuneiform relative to the navicular at the NC joint, and greater dorsiflexion, inversion, and adduction of the first metatarsal at the MTC joint in hallux valgus patients compared with the control group. While some suggest that WBCT will supplant traditional foot radiographs for evaluation of deformity, the technology remains available in a limited number of foot and ankle practices.

Juvenile Bunions

Open Physes

A juvenile hallux valgus deformity is complicated by the presence of an open epiphysis at the base of the proximal phalanx and first metatarsal ( Fig. 7-70 ). Postoperative recurrence of a hallux valgus deformity attributable to further epiphyseal growth has been speculated as a cause of recurrence and has led to the recommendation that surgical intervention be postponed until skeletal maturity has been achieved. Helal and Bonney et al have cautioned against early surgery because of the poor prognosis, but Goldner and Gaines stated that “early surgery” may allow for remodeling of the articular cartilage. These authors and others have noted no contraindications to early surgery. Coughlin observed that patients who underwent surgical correction with an open epiphysis had greater correction of the hallux valgus angle.

The high recurrence rate in patients with an open epiphysis may be explained not only by a more severe deformity in those who undergo early surgery but also by a corresponding increased DMAA in younger patients with severe deformity. Coughlin noted that in patients with an onset of hallux valgus before the age of 10, the average hallux valgus deformity was 32 degrees; in patients 10 years or older, the average preoperative deformity was 25 degrees. Significantly greater correction was achieved in patients with early onset of deformity. The average hallux valgus correction in the younger group was 24 degrees, and the average correction in the older group was 15 degrees ( P = 0.0001). The average DMAA of patients who underwent correction of hallux valgus in the presence of an open epiphysis was 21 degrees, whereas the average DMAA of those who underwent correction after the epiphysis was closed was 10 degrees. Greater deformity may have been a factor influencing early correction of a hallux valgus deformity with an open epiphysis. Luba and Rosman hypothesize that medial inclination of the first metatarsal epiphysis causes tension forces to develop on the lateral aspect of the epiphysis and compression forces to develop on the medial aspect of the epiphysis, thereby leading to increased growth of the lateral epiphysis with subsequent increased medial inclination of the first metatarsal. They further hypothesized that the surgical correction achieved by a first metatarsal osteotomy distal to an open first metatarsal epiphysis may decrease with time because of lateral epiphyseal overgrowth. However, no evidence supports the premise that “epiphyseal overgrowth” of the proximal first metatarsal is the cause of recurrent hallux valgus in juvenile patients.

A large DMAA in juvenile hallux valgus deformities treated by intraarticular correction (i.e., a distal soft tissue procedure) is associated with a high recurrence rate. An increased DMAA may have led to the previous conclusion that surgery in the presence of an open epiphysis is contraindicated. Rather, in the presence of a large DMAA (often associated with severe deformity at a younger age), intraarticular correction is contraindicated.

A partial lateral first metatarsal epiphyseal arrest procedure in the early adolescent years may theoretically achieve gradual diminution of the 1–2 IM angle. Ellis and others have proposed partial lateral epiphyseal arrest to achieve a gradual decrease in metatarsus primus varus. Ellis, in reporting on 20 cases of partial epiphyseal arrest, noted a high failure rate; others report only anecdotal short-term experience with this technique. Davids et al reported on a 4-year follow-up on 11 feet treated with lateral epiphyseodesis. Although they concluded that no foot clinically worsened, and that they achieved a significant correction in 6 of 11 feet, the average angular correction was mediocre at best (hallux valgus angle correction of 3.5 degrees, 1–2 IM angle correction of 2 degrees). The efficacy of this technique remains hypothetical and is not recommended.

The possibility of an epiphyseal injury at the base of either the first metatarsal or the proximal phalanx after an osteotomy must be considered when surgery is to be performed on a growing child, and this is probably the major reason for delaying surgical intervention. Anderson et al analyzed the rate of growth in the female foot and determined that full foot growth is usually achieved by 14 years of age. At 12 years of age, an average of less than 1 cm of total longitudinal foot growth remains. Less than 50% of this growth occurs at the proximal first metatarsal epiphysis, and thus a relatively small amount of growth occurs in the first ray after 12 years of age. In adolescent boys, completion of growth tends to occur at an average age of 16 years. By age 12, however, boys still have almost 3 cm of total longitudinal foot growth remaining. Again, with an estimated 50% of the remaining longitudinal foot growth occurring at the first metatarsal epiphysis, approximately 1.5 cm of metatarsal growth remains.

The presence of an open epiphysis is not a contraindication to either surgical correction or an osteotomy in either the proximal phalanx or the proximal first metatarsal. At surgery it is important to determine the exact location of the phalangeal or metatarsal epiphysis to avoid causing an iatrogenic epiphyseal injury ( Fig. 7-71 ). Reconstruction of a short first metatarsal may be a complex and difficult salvage.

Correction of hallux valgus in a juvenile patient frequently requires an osteotomy to achieve complete correction. When either a phalangeal or a metatarsal osteotomy is planned in a patient 10 years or younger, it is important to ascertain the amount of growth that can be expected postoperatively, not only in the foot but also in the first metatarsal. If an iatrogenic epiphyseal injury does occur, one can then hypothesize its effect on ultimate phalangeal or metatarsal longitudinal growth. In an older juvenile patient, iatrogenic epiphyseal arrest or partial epiphyseal plate closure after surgery will have little effect on first-ray length at this age. Surgery in a younger child is not contraindicated and may allow adaptation or remodeling of the MTP articular surfaces postoperatively.

Juvenile Hallux Valgus

To qualify as a juvenile hallux valgus deformity, the onset of the deformity must occur in the preteen or teenage years. Despite development during this period, however, a patient may choose to seek medical treatment later in life. Coughlin and Mann and others have observed that in adults, certain hallux valgus deformities are much more difficult to correct surgically than others. These same patients appear to have a much higher risk of postoperative recurrence of deformity ( Fig. 7-72 ). The authors hypothesized that these bunions occur in adults because of specific anatomic characteristics that developed during the juvenile and adolescent years.

Juvenile and adult hallux valgus deformities can be differentiated by several characteristics. Degenerative arthritis of the first MTP joint is rarely associated with a juvenile hallux valgus deformity but is more often associated with an adult bunion ( Fig. 7-73 ). Likewise, whereas bursal thickening over the medial eminence is typically found in older patients, it is rarely present in a juvenile with hallux valgus. The epiphyseal growth plates at the base of the first metatarsal and proximal phalanges are frequently open in early adolescence. In juveniles and adolescents with hallux valgus, the prominence of the medial eminence is of lesser magnitude and the magnitude of the 1–2 IM angle is often increased, but the hallux valgus angle is typically of lesser magnitude. Pronation of the hallux is much less common in juvenile patients. Hypermobility of the first MTC articulation may be associated with a juvenile bunion. However, a very rigid MTC joint articulation may also occur and make surgical repair resistant to correction without a metatarsal osteotomy.

Classification of Hallux Valgus Deformities

The primary purpose of classifying hallux valgus deformities is to facilitate the decision-making process on how to treat the deformity. No one classification is perfect, and the numbers used to define a mild, moderate, or severe deformity are not definitive given the complex nature of hallux valgus deformities. Classifications are meant as a guideline. With experience, the clinician will be able to appreciate which procedures and which patients will have a satisfactory outcome with a certain procedure performed past the numerical limits of the classification scheme. As with any surgery, the technical skill and judgment required to carry out a successful bunion procedure can be gained only through clinical experience and careful following of patient outcomes.

With a mild bunion deformity, the hallux valgus angle is less than 20 degrees, and part of the deformity may result from an HVI deformity. The MTP joint is often congruent, and the IM angle is usually 11 degrees or less ( Fig. 7-74A ). These patients typically complain of a painful medial eminence that frequently has a sharp ridge along the dorsomedial aspect. Radiographs generally demonstrate that the sesamoids are maintained in anatomic position. On occasion, however, about 50% subluxation of the fibular sesamoid may be present.

A moderate hallux valgus deformity usually demonstrates subluxation of the MTP joint, unless the DMAA is abnormal. The hallux valgus angular deformity is 20 to 40 degrees, and the great toe may exert some pressure against the second toe ( Fig. 7-74B ). The hallux is typically pronated. The IM angle varies from 11 to 16 degrees. The fibular sesamoid is usually displaced 75% to 100%.

A severe hallux valgus deformity has greater than 40 degrees of lateral deviation of the hallux, and this often results in an under- or overriding deformity of the second toe. The hallux is moderately or severely pronated. Because of the functional loss of the first MTP joint with a severe deformity, a painful transfer lesion may develop beneath the second metatarsal head. Radiographic examination demonstrates significant subluxation of the MTP joint and usually 100% lateral subluxation of the fibular sesamoid. The IM angle is generally 16 to 18 degrees or greater ( Fig. 7-74C ).

A secondary point of classification for hallux valgus deformities groups those that have normal DMAA and those with increased DMAA. The feet with normal DMAA may have subluxated MTP joints with moderate or severe degrees of deformity, while feet with an increased DMAA may have congruently reduced joints despite greater hallux valgus and IM angles. This distinction will lead to different approaches for surgical correction.

Patient Evaluation

Evaluation of hallux valgus begins with a careful history of the patient’s condition. This should include the chief complaint, which is pain over the medial eminence in 70% to 75% of patients. A symptomatic intractable plantar keratosis beneath the second metatarsal head was present in about 40% of patients. Symptomatic metatarsalgia was present in 48% of patients. Other associated problems include instability of the lesser MTP joints, interdigital neuromas, lesser toe deformities, corns, and calluses ( Fig. 7-75 ). Information should be obtained regarding the patient’s level of activity, occupation, athletic inclinations, preference for specific types of footwear, and reasons for choosing surgery. The patient’s medical history should be obtained as well.

The physical examination is carried out by observing the patient’s gait and then carefully observing the foot with the patient both standing and sitting. The magnitude of the deformity of the hallux and lesser toes is noted and the longitudinal arch and hindfoot position observed. The magnitude of pronation of the hallux is assessed ( Fig. 7-76 ). Typically, with more severe deformities, the magnitude of pronation increases.

With the patient sitting, range of motion of the ankle, subtalar, transverse tarsal, and MTP joints is examined. Ankle range of motion is carefully assessed while the knee is both flexed and extended, with attention directed to gastrocnemius–soleus muscle tightness (restricted ankle dorsiflexion) (see Fig. 7-43 ). Care is taken to ensure that the foot is held in a neutral position (with the talonavicular joint reduced to eliminate transverse tarsal or subtalar motion) with respect to the forefoot and hindfoot during assessment of the gastrocnemius–soleus. Ankle joint motion is measured by placing a goniometer on the lateral aspect of the foot and ankle and using the fibula and plantar lateral border of the foot as landmarks for each limb of the goniometer. A right angle is considered a neutral position.

The posture of the forefoot is assessed (e.g., forefoot varus, valgus, neutral). The first MTP joint is carefully palpated for evidence of synovitis and crepitus, as well as for specific areas of pain.

Active and passive range of MTP joint motion is assessed with the patient sitting and measured with a goniometer by using the plantar aspect of the foot and the medial axis of the proximal phalanx as points of reference. A neutral position is recorded as 0 degrees, and dorsiflexion and plantar flexion are measured from this point. Joseph reported that the average passive range of motion of the first MTP joint in adults older than 45 years was 87 degrees (67 degrees of dorsiflexion and 20 degrees of plantar flexion). It is important to note pain or crepitus with MTP motion as this may suggest underlying arthrosis.

Palpation over the dorsomedial cutaneous nerve often demonstrates irritability if there is a large medial eminence. Attention should also be directed to the plantar-medial hallucial nerve, which courses over the dorsal border of the medial sesamoid. While gently dorsiflexing and plantar flexing the first MTP joint, an attempt is made to manually reduce the deformity to determine how much correction can be achieved. At times, particularly with a long-standing hallux valgus deformity, a reduction in dorsiflexion occurs as the great toe is brought out of lateral deviation. This suggests that the distal metatarsal articular surface may be laterally deviated or that the articular cartilage has deteriorated to such an extent that dorsiflexion may be reduced after surgical realignment.

The mobility of the first MTC joint is also evaluated. This examination is performed with the patient sitting, the knee flexed, and the ankle positioned at a 90-degree angle or in neutral position. The forefoot is stabilized with one hand, and the first metatarsal is grasped between the thumb and index finger of the opposite hand. The first metatarsal is then moved from a dorsomedial to a plantar-lateral direction and compared with the opposite side (see Figs. 7-35 and 7-36 ). In our experience, pathologic hypermobility exists in approximately 10% to 15% of patients with a hallux valgus deformity; however, mobility may be substantially treated and reduced with realignment merely of the first MTP joint. The plantar aspect of the foot is then examined for the presence of an intractable plantar keratosis, which most frequently is located beneath the second metatarsal head. On occasion, one can form beneath the tibial sesamoid because of its centralized position beneath the metatarsal head. The IM spaces are carefully palpated for evidence of neuritic symptoms. The lesser toes are then examined for evidence of lesser MTP joint instability, hammer toes, mallet toes, or interdigital corns.

During the examination, it is important to identify areas of pain on palpation. Bunion patients frequently have tenderness to palpation over the medial eminence. However, pain with ROM of the MTP or MTC joints can indicate arthrosis. It is also important to load the sesamoids with MTP motion to detect sesamoid arthrosis, which has a high prevalence and can impact outcome.

Vascular evaluation includes palpation of the dorsalis pedis and posterior tibial pulses, observation of capillary filling of the toes, and assessment of the skin and hair pattern. If there is any question regarding the circulatory status of the foot, a Doppler evaluation or vascular surgery consultation is obtained.

The neurologic examination focuses on sensation, vibratory sense, and strength of the intrinsic and extrinsic muscles. Often, a sensory deficit may develop with reduced sensation over the medial eminence and medial hallux ( Fig. 7-77 ). This is likely due to either traction on or pressure from the bunion on the dorsal medial sensory nerve to the hallux. Careful attention to this nerve during the surgical dissection is important; the sensory deficit often diminishes during the postoperative period.

Weight-bearing radiographs are obtained and analyzed as outlined above. WBCT scan may be considered when available.

Conservative Treatment

Conservative care in most patients with a bunion deformity is adequate to relieve symptoms. A symptomatic mild hallux valgus deformity should be periodically examined and radiographs obtained to evaluate any progression in the magnitude of the deformity. A custom or prefabricated orthotic device may assist in the treatment of a flexible flatfoot deformity or in a patient with ligamentous laxity and hallux valgus associated with pes planus ( Fig. 7-78A ). Groiso recommended the use of bunion night splints and exercises and noted a 50% improvement in hallux valgus deformities in a 7-year study of juvenile patients. Others have tried physical therapy and night splints, and even injections of botulinum toxin, but there are no long-term studies that conclusively demonstrate successful long-term correction of a deformity.

Modification of footwear is probably the most important factor in achieving symptomatic relief of pain in a patient with a bunion deformity. Constricting footwear increases symptoms in patients with a hallux valgus deformity. Shoes with a low heel, an adequate toe box, and a soft upper tend to diminish symptoms. The physician should encourage the use of wide toe-box footwear to reduce pressure over the medial eminence. A soft leather shoe with a wide toe box and preferably a soft sole may give significant relief of symptoms. A pedorthist can modify shoes by stretching and relieving pressure points over the bunion. On occasion, custom-made footwear may help patients with severe hallux valgus deformities who are reluctant to undergo surgical correction. The use of bunion pads, night splints, bunion posts, and other commercial appliances may also help in relieving symptoms ( Fig. 7-78B–D ). Unfortunately, it is difficult to achieve compliance in any patient with regard to wearing roomy footwear.

The use of prefabricated or custom orthotics is controversial in the treatment of a patient with hallux valgus. An orthotic device may be uncomfortable for a patient because it occupies space within the shoe. It may place increased pressure against the medial eminence and result in increased symptoms rather than relief of pressure on the first metatarsal head. Moulodi et al found, in a randomized controlled trial, that the use of both static and dynamic orthoses can reduce the hallux valgus angle up to 2° to 3°, and that dynamic orthoses increases the passive range of motion of the first MTP joint and are effective during walking. Durman and others recommend use of orthotics postoperatively, but Canale et al and others have not used them. Kilmartin et al, curiously, found that the hallux valgus angle increased more in patients who used orthotics and concluded that orthoses did not prevent progression of a hallux valgus deformity.

If conservative care has not led to symptom improvement, or the deformity has progressed, surgical correction can be carefully considered. Rapid progression of a hallux valgus deformity is unusual, and frequently a hallux valgus deformity can be observed over a lengthy period (see Fig. 7-20 ). In general, cosmesis should not be a primary indication for surgery. Pain, discomfort, and imbalance should be the major considerations for surgical correction. It may be difficult on occasion to distinguish between a patient’s concern for cosmesis and actual discomfort. It is difficult for a surgical procedure to improve upon a pain level of 0.

Nonsurgical care should also be considered in patients with hyperelasticity, ligamentous laxity, or neuromuscular disorders because of the high recurrence rate. Surgery is not urgent. When contemplating surgery, careful decision making may decrease the incidence of postsurgical recurrence of a hallux valgus deformity. Radovic and Shah have reported the use of botulinum toxin A to temporarily diminish the strength of the adductor hallucis and secondarily the angular deformity of the hallux and first metatarsal in a nonsurgical candidate with small corrections noted in the hallux valgus and IM angles. Whether this modality will have a place in future therapy remains to be seen.

Perioperative Considerations

Factors Impacting Outcomes

Healing of soft tissue and osseous structures may be affected by cigarette smoking. Krannitz et al reported that the healing time of a distal first metatarsal osteotomy was delayed in primary smokers, taking 1.73 times longer to achieve bony consolidation. Time to healing in nonsmokers averaged 69 days compared with 120 days in smokers. Of interest, in those who were exposed to secondhand smoke, the average time to bony healing was 78 days. Patients with a smoking history or a history of someone who smokes in their presence should be alerted to the increased risk of delay healing.

The issue of bilateral versus unilateral surgery is a controversial topic in hallux valgus surgery. The age of a patient, his or her dexterity, the particular procedure being performed, and the quality of assistance for each patient plays a role is the decision-making process. Coughlin and Jones reported virtually all 122 cases were done separately as unilateral procedures. Fridman et al and Lee et al have noted no substantial difference in complications, angular correction, or clinical outcomes with unilateral or bilateral bunion surgeries.

Postoperative physical therapy is likewise a decision that is best individualized by the treating physician for each patient. Jones et al, in a cadaveric study, reported a mean loss of MTP motion of 23 degrees after a distal soft tissue realignment with proximal first metatarsal osteotomy. Most of the loss of motion occurred with dorsiflexion of 22 degrees, with minimal reduction of MTP joint plantar flexion. Thus attention must be directed early to the patient who has difficulty with regaining MTP joint motion. Schuh et al reported a significant increase in postoperative range of motion, especially MTP joint dorsiflexion, after a 4- to 6-week course of physical therapy. Improved weight bearing, gait, and range of motion were noted in this group of 30 patients.

Attention to lesser toe deformities associated with a hallux valgus deformity may identify the presence of lesser toe malalignment, necessitating realignment of one or more lesser toes. Please refer to Chapter 9 for more detail on these procedures.

Surgical Decision Making

The decision-making process in hallux valgus surgery must begin with the understanding that not all hallux valgus deformities are equal. If one repair is attempted for all types of hallux valgus deformities, failures are likely to occur.

The following factors should be considered in the decision-making process for hallux valgus correction:

• The patient’s chief complaint(s), occupation, and athletic interests

• Physical findings

• Radiographic evaluation, which should include:

  • Magnitude of the hallux valgus, IM, and interphalangeal angles

  • Magnitude of the DMAA

  • Degree of pronation of the hallux

  • Presence of a congruent or incongruent MTP joint

  • Extent of MTC instability

  • Extent of MTP, sesamoid-metatarsal, and MTC joint arthrosis.

• The patient’s age

• Neurovascular status of the foot

• The patient’s expectations

• Patient resilience (as measured by BRS or similar metric).

Most of these issues can be quantified, but a patient’s expectations of the procedure cannot. Patients who undergo bunion surgery often do not fully appreciate what outcome to expect, nor the process of recovery. Many patients are unhappy after bunion surgery, mainly because they did not realize that they may not be able to return to their previous level of activity. Some patients are not made fully aware of the potential postsurgical complications or fail to comprehend or remember preoperative discussions. Shurnas and Coughlin reported that, after preoperative discussion of risks and complications, recall of individual risks averaged 10% or less. Nonetheless, an attempt must be made to educate the patient, sometimes extensively, about the benefits as well as the risks of surgery. A patient must be informed that some residual stiffness, pain, or recurrent deformity may occur after surgery. It does not necessarily require revision surgery, but these factors can cause some disappointment with outcomes. Some patients have bunion surgery only because they believe that they will then be able to wear a more fashionable shoe and are subsequently disappointed when this goal cannot be achieved. In reviewing more than 300 bunion cases, Coughlin et al have observed that a third of patients could wear the shoes that they wanted before surgery and that two thirds could after surgery. Unfortunately, this still leaves a third of patients unable to wear their shoe of choice, and this should be explained to the patient during the informed consent process.

Another group of patients who deserve important consideration are those in professional sports or dance, who rely on their feet for their livelihood. Until it is no longer possible to perform in their chosen field, deferral of bunion surgery should be considered. There are of course exceptions to this, including the athlete with a bunion deformity that is causing functional limitations that might be corrected with surgery. If patients can eventually resume their previous level of activity after surgery, they will be much more satisfied with the outcome.