Hallux Valgus

KEY FACTS

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Hallux valgus is defined principally by the intermetatarsal angle; the distal metatarsal articular angle can also weigh on treatment decisions; the hallux valgus angle is the least relevant to treatment.
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Etiology is likely multifactorial with genetics playing a large role.
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Associated symptoms (metatarsalgia, hammer toes, etc.) are very relevant and can sway treatment decisions.
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Surgery is ultimately done in order to relieve pain; the goals of surgery should always be made explicitly clear to patients.
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Various operative treatment options exist, all with relative merits and downsides.
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Generally speaking, metatarsal osteotomies have the advantage of relatively rapid healing allowing early weight bearing, although they can be limited in terms of their deformity correction capacity.
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Tarsometatarsal fusion, or the Lapidus procedure, allows for maximal deformity correction and potentially protecting the 2nd ray, although it is a bigger operation with a longer recovery and a greater risk of nonunion.

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The term bunion is a colloquial one for the medial prominence of the big toe. Bunion comes from the old French word buigne, which literally meant swelling.
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While the term bunion is often used in lay parlance, surgeons more appropriately refer to the deformity as hallux valgus with hallux referring to the 1st ray and valgus referring to the deformity seen at the 1st metatarsophalangeal (MTP) joint.
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Hallux valgus can be broken down into its component parts and is typically described by a set of radiographic angles, all from a standing anteroposterior radiograph.
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  The principle defining angle that defines hallux valgus is the intermetatarsal angle. This angle essentially describes the metatarsus primus varus or the inclination of the 1st metatarsal away from the 2nd. The intermetatarsal angle is typically < 9°. Surgery for hallux valgus most often seeks to address an elevated intermetatarsal angle.
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  The hallux valgus angle is used less frequently in clinical decision-making. It is measured as the angle subtended by the long axes of the 1st metatarsal and the 1st proximal phalanx and is normally < 15°.
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  The final, and perhaps most subtle, angle that defines the deformity is the distal metatarsal articular angle (DMAA). This angle essentially measures the degree to which the articular surface is offset from the longitudinal axis of the 1st metatarsal.

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There is a female preponderance with many studies quoting over 90% female patients, although there is significant variability in the literature with regard to the male:female ratio. Shoewear may account for this difference to some degree, although the overt causes are not entirely clear.
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  In 1 study of 600 elderly patients, the rate of hallux valgus was found to be 58% in women and 25% in men. The development of hallux valgus was correlated with low BMI and high heel use between ages 20-64 in women; it was correlated with a high BMI and pes planus in men.
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  Another study noted a 15:1 female:male ratio with males generally having more severe deformity and more commonly having an increased DMAA, while a 3rd study noted little sex difference between groups of elderly patients with 58.0% of males having hallux valgus and 66.5% of females.
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  It is possible that these studies, despite their widely disparate numbers, are simply assessing different patient populations in which the incidence is quite different.
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There is not a direct correlation between the degree of deformity and pain; some patients can have severe deformity with little pain, while others have mild deformity and significant pain. For most surgeons, pain is a strict indication for any surgery.

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Influence of shoes
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  Sim-Fook and Hodgson looked at shoewearing and nonshoewearing groups of Chinese patients in the 1950s, noting a 33% rate of hallux valgus in the shod group vs. < 2% in the unshod.
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  Other studies in various indigenous peoples have noted that hallux valgus certainly occurs, although it is much less apt to be symptomatic.
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  To what degree shoes play a role in the development of hallux valgus is a subject of some debate. However, that shoes in general, and certain shoes especially, can make hallux valgus more symptomatic is generally accepted.
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Prolonged weight bearing over time
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  No overt correlation has been found between the development of hallux valgus and excessive walking or occupation.
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It is very possible that hallux valgus represents a grouping of conditions that all have a similar endpoint. There may be several disparate mechanisms that all end at more or less the same point, although this theory remains to be tested.

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At a basic level, metatarsalgia simply implies pain associated with the metatarsals. Practically speaking, this term is meant to represent pain in the forefoot underneath the metatarsal heads. This pathology can exist ± symptomatic pathology in the 1st ray, although they will often be concomitant and related. If the 1st ray bears insufficient weight for any number of reasons, then that weight can be transferred typically to the 2nd or 3rd metatarsal heads, a phenomenon termed transfer metatarsalgia.

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Hammer toes are defined by a combination of flexion at the proximal interphalangeal joint (PIP) and extension at the distal interphalangeal joint. Pain can come from either the prominence of the PIP on the top of the shoe or from the end of the toe contacting the ground or the shoe.

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