Bunions are common in adult shoe-wearing populations and usually occur in association with hallux valgus. The exact cause is unknown, but improper footwear, genetic predisposition, and anatomic factors may all contribute. The diagnosis of symptomatic bunion is clinical and is based on the presence of pain in the medial area of the great toe when the patient walks or wears shoes. Symptoms of tenderness and pain must be differentiated from those caused by such disorders as gout, metatarsophalangeal arthritis, and skin irritation. Standing roentgenograms are helpful, especially because they show the functional relationship of the foot structures. Nonoperative care involves proper footwear, exercises, and anti-inflammatory medication. Surgery is reserved for patients who continue to have pain and is aimed at functional restoration, not cosmetic correction.
A bunion is a localized enlargement at the medial portion of the first metatarsal head. It occurs as a result of bony overgrowth or malposition of the first metatarsal head-most often, hallux valgus.
Bunion and hallux valgus can occur in adolescents but are more common in middle-aged and older adults. Although the prevalence of bunion deformity is unknown, the reported incidence of painful hallux valgus among adults in countries where shoes (not sandals) are worn ranges from 20 to 150 per 1000, or 2% to 15%. Women are affected about 9 times more often than men; population-based studies suggest a relationship between wearing “stylish” shoes (with a high heel and narrow toe) and the increased incidence of great-toe problems in women.
Bunion and hallux valgus are common causes for physician visits-not only because of pain but also because of the cosmetic distress and difficulties with shoe fit that they can create. Although they are permanent conditions that do not spontaneously disappear, symptoms may resolve without resorting to corrective (specifically, surgical) measures.5 In this article, I review some of the factors that contribute to the development of bunion and hallux valgus and discuss the anatomic changes that underlie these conditions. I then offer my approach to diagnosis and nonoperative management and discuss when referral for surgery is indicated.
WHAT CAUSES BUNIONS?
More literature exists about the combination of hallux valgus and bunion than about bunion as a primary entity; several mechanical causes of hallux valgus are assumed to also result in painful bunions. Conditions associated with hallux valgus include forefoot pronation, metatarsus adductus (forefoot splaying), cock-up deformity of the second toe, rheumatoid arthritis, stroke, cerebral palsy, and generalized soft tissue laxity (as in Ehlers-Danlos syndrome). Persons with coexisting conditions are more challenging to treat than adults who have hallux valgus but are otherwise normal.
Population studies comparing barefoot with shod persons show a higher incidence of foot deformities-including bunions-among shoe-wearers. External pressure from the shoe along the medial side of the great toe, which can occur if the foot is pronated or otherwise malaligned, increases the tendency for hallux valgus and creates an environment conducive to bunion formation. The narrow toe boxes and high heels often found on women’s stylish shoes contribute to bunions by crowding the forefoot and forcing the hallux laterally.
Anatomic factors can contribute or predispose to bunion formation. A rounded rather than flat metatarsal head makes the toe more prone to valgus deformity. Generalized foot pronation with forefoot abduction-the pes planus (flatfoot) deformity-creates a mechanical environment of high contact pressure between the bunion area and the shoe. Contraction of the Achilles tendon can also cause the patient to walk with the foot externally rotated, stressing the medial side of the foot.
An exceptionally long great toe can be pushed into lateral deviation by a snug shoe. If the intermetatarsal angle is greater than 10 degrees (a condition known as metatarsus primus varus), the hallux will drift laterally and predispose the patient to hallux valgus and bunion. Splayfoot, a condition in which ligamentous laxity allows the first and fifth rays to fan out during weight bearing, similarly contributes to drifting of the hallux.
Bunions and hallux valgus are common in ballet dancers. In women, the combination of body weight and static deforming forces exerted on the toes by pointe shoes is primarily responsible. Men are more likely to have hallux valgus as a result of improper training technique (stressing the medial aspect of the first metatarsophalangeal [MTP] joint and incorrectly stretching the medial ligaments during a grand plie).
A variety of factors contribute to bunion. Genetic predisposition is likely when bunions appear during childhood or adolescence; inheritance also may play a role in mid-adulthood onset of hallux valgus. Neurogenic causes of hallux valgus include cerebral palsy and stroke.
Pain from a bunion may be increased by crystalline arthropathy-gout being the most common-or painful arthropathy of the MTP joint. True joint sprains, although considered a rare phenomenon of the medial joint capsule and ligaments of the first MTP joint, can cause pain in patients who have an acquired hallux valgus deformity.
ANATOMIC CHANGES IN HALLUX VALGUS
During the initial stages of hallux valgus, the proximal phalanx begins to drift laterally. However, the sesamoid bones are kept in their usual position by the adductor hallucis tendon. As the great toe continues its valgus migration, the first metatarsal head is pushed into a position of varus, off the sesamoids. As the first metatarsal head migrates medially, the medial joint capsule becomes attenuated and the abductor hallucis tendon is pulled in the plantar direction. The base of the proximal phalanx remains firmly attached to the adductor hallucis. As the metatarsal head drifts medially, the pull of the adductor hallucis on the proximal phalanx can cause the phalanx to rotate along its longitudinal axis. This results in pronation of the great toe.
In more severe cases of hallux valgus, the extensor hallucis longus tendon can displace laterally, becoming an adductor and extensor. The abductor hallucis longus tendon, by migrating plantarward, loses any remaining abductor power and becomes a flexor. The flexor hallucis longus retains its relationship to the sesamoids and becomes a deforming force.
Displacement of the proximal phalanx in a lateral direction uncovers the medial aspect of the metatarsal head, causing a bunion. Subsequent hypertrophy of the metatarsal head or an overlying inflammatory bursa or both can increase the size of the bunion.
The visual appearance of a bunion is that of a “bump” over the medial side of the great toe, near the base. The diagnosis of a symptomatic bunion is clinical and is based on 2 coexisting conditions: pain in the medial portion of the first MTP joint when the patient wears shoes or walks and subsidence of pain when the shoes are removed or the patient rests. The associated finding of hallux valgus is not necessary for the diagnosis.
During the physical examination, assess passive range of motion in the MTP joint of the great toe. If this elicits pain, suspect an additional painful condition, such as arthritis. Note the color of the toe and check for adequate capillary refill beneath the nail to get an idea of circulatory status.
Sensation is tested for light touch only.
Usually, I do not grade hallux valgus; however, I do consider the condition to be clinically severe when the great toe is under or over its neighbor and moderate when the great toe is causing the neighboring toe to lean toward the third toe. Roentgenographic grading can help when planning surgical correction: angulation is mild when it exceeds 15 degrees and severe when it exceeds 35 degrees .
The differential diagnosis includes gout (podagra), MTP arthritis, sensory nerve compression, skin irritation, and infection. Some simple findings during the initial physical examination can help make the distinction.
Gout is usually accompanied by dorsal and lateral inflammation near the MTP joint and exquisite pain when the great toe is touched or moved. Toe joint arthritis produces pain during passive or active motion or both, and compression over the bunion area produces minimal tenderness. Patients with sensory nerve compression often have tenderness along the dorsal-medial sensory nerve, which produces a radiating or “shooting” pain that travels toward the toe or ankle.
Skin irritation from shoes spontaneously resolves when the patient wears loose shoes or sandals for a few days. This type of external skin irritation may lead to formation of a subcutaneous bursa near the medial metatarsal head, which, in turn, may enlarge and form a soft tissue “bunion.” Skin infection or ulceration in the area overlying the medial metatarsal head may occur as a result of shoe-induced pressure and friction and, initially, is difficult to differentiate from a more benign form of skin irritation.
Roentgenograms can help in the diagnosis of MTP arthritis (by showing changes in the joint and subchondral bone) and such generalized arthritic conditions as rheumatoid disease. With increasing severity of hallux valgus and bunion, roentgenograms also may show progressive involvement of the sesamoids and MTP joint.
An important part of the patient database is standing (weight-bearing) roentgenograms-primarily, the anteroposterior, lateral, and pronated (internal) oblique views. Compared with the supine position, the standing position offers the advantage of showing the foot structures in their position of function and enables roentgenograms to be obtained more reproducibly.
The alignment of the first metatarsal and the MTP joint has received much attention in the orthopedic literature. Normally, the angle between the first and second metatarsal is less than 10 degrees . As this angle increases, forefoot splaying causes greater pressure from the shoe overlying the metatarsal head and creates a mechanical environment suitable for progressive hallux valgus.
The normal angle of the great toe with respect to the metatarsal is 10 degrees to 20 degrees of lateral deviation. As this angle becomes larger, the pressure on the medial first metatarsal increases, which may compound the medial deviation of the first metatarsal. Rarely, an enlargement of the metatarsal head will be seen on x-ray films to be the source of the bunion deformity.
Begin therapy by advising the patient to wear shoes that have a wider, deeper toe box. For instance, you might discourage a woman from wearing pumps-especially those with higher heels-as an everyday work shoe; if they are necessary, suggest styles that have a low heel and a rounded toe. For both men and women, sports shoes or “walking shoes” appear to offer advantages over styles that tend to fit snugly over the medial great toe.
The patient also can take an anti-inflammatory medication as needed for pain relief. In my experience, exercises to stretch the great toe passively are helpful. They should be done twice daily, 1 minute per foot (10 to 15 repetitions) for the first month, then once daily for 3 months. The additional measure of wearing a bunion splint at night may further reduce soft tissue tension on the medial joint and ease discomfort. The patient who has excessive pronation may benefit from wearing a custom insole orthosis, which provides mechanical support and relieves contact pressure or forces at the bunion site.
Intra-articular injection is reserved for the patient with a painful joint, not just a tender bunion. To reduce the potential for drug-induced weakening of the joint capsule, proceed cautiously and give a low volume of corticosteroid (0.5 to 1 mL of a mixture of 50% plain 1% lidocaine and synthetic corticosteroid). These injections, which can be repeated up to 3 times a year, are helpful for as long as several months but are not curative.
If the patient responds to treatment, encourage him or her to continue whatever measures (shoes, splint, and exercises) have helped. It also may be necessary to modify certain sports activities that aggravate discomfort. For example, a canoeist who customarily kneels to paddle might change to a sitting position.
Bunion surgery is usually reserved for patients who do not obtain significant pain relief after at least 3 months (perhaps a shorter time if hallux valgus coexists) of nonoperative care. Surgery provides the opportunity to reduce deformity (conservative care does not do this) and remove chronically painful tissue in an effort to improve the function of the foot.
There are literally scores of surgical procedures to correct bunion problems and hallux valgus deformity, none of which can cure all bunion problems. An article by Coughlin provides an excellent synopsis of the anatomic features that can lead to symptomatic bunion as well as the current surgical approaches to correction of this condition. Surgery is directed at removing the medial bunion and reducing forefoot width. This usually reduces the hallux valgus and provides stable support for the toe.
The goal is to create a less painful foot that fits into most shoes and provides acceptable support for a full day of standing and walking. In 2001, a Finnish study reported that in patients with bunion pain, outcomes were better with bunionectomy than with observation and orthotic treatment. Bunion surgery rarely enhances athletic performance or produces a cosmetically appealing foot. Patients usually ask whether the bunion will grow back after surgery. The answer is no. The bunion will not grow back, but the great toe may gradually drift over toward the second toe.
Failure to provide stable support for the toe and to maintain alignment are the primary reasons why surgery is sometimes unsuccessful. Secondary to this is reappearance of the bunion symptom. Another unwanted outcome is excessive stiffness of the MTP joint of the great toe because of scarring. Some limits on stylish footwear and athletic activity are needed after successful bunion surgery to avoid recurrence of hallux valgus. In other words, hallux valgus may recur with failure to maintain the correction that is achieved by surgery.