e5-01: Bunion

A bunion is one of the most prevalent foot problems seen by foot and ankle specialists. Bunion is a deformity at the big toe joint with abduction and valgus rotation of the great toe combined with a medially prominent first metatarsal head (Figure E5–1A). Bunions form when there is a disruption of the balance of forces on the tendons that cross the big toe joint. The first metatarsal head is susceptible to external forces due to the fact that it has no muscular insertion. As the big toe deviates in a lateral direction, the adductor hallucis and flexor hallux brevis muscles serve as deforming forces as their pull shifts lateral to the longitudinal axis of the big toe joint. As the deformity continues to progress, the lateral soft tissues become contracted while the medial tissues become attenuated. It is considered to be a progressive deformity.

There are five types of conditions that can lead to a bunion deformity: (1) arthritic conditions; (2) biomechanical abnormalities; (3) neuromuscular diseases; (4) genetic disorders; and (5) trauma. Abnormal foot mechanics that may contribute to a bunion deformity include equinus contracture and pes planus. Neuromuscular disease that can contribute to a bunion deformity includes cerebral palsy or cerebrovascular accident. Bunions may be associated with certain types of inflammatory arthritic conditions, such as rheumatoid arthritis. Genetic disorders that may lead to ligamentous laxity and subsequent instability leading to bunion deformity include Ehlers-Danlos syndrome, Down syndrome, and Marfan syndrome. Amputation of the second toe may increase the risk of developing a bunion deformity due to the loss of the lateral buttress that the second toe provides the big toe.

Any disorder that results in excessive amount of pronation can predispose a person to bunion development. Therefore, biomechanical control of the foot is particularly important in both the preoperative and postoperative setting. Patients with this deformity often have a significant family history of bunion deformity. Although bunions tend to run in families, it is the foot type that is passed down and not the bunion. The deformity is more prevalent in women, likely caused by wearing narrow footwear. Controversy remains, however, regarding effects of heredity and shoe gear as precursors to bunion deformity.

A. Symptoms and Signs

Bunions may or may not be symptomatic. Pain varies with the severity of the deformity. When symptoms are present, patients frequently report a dull achy pain, swelling, and redness at the site of the bunion that are exacerbated with walking and narrow shoe gear but relieved with rest. A burning sensation is characteristic of an adventitious bursa that may form on the medial aspect of the big toe joint. Chronic pressure to the outside of the big toe will cause irritation of the first proper digital nerve, leading to paresthesia or neuralgia of the big toe. The clinical examination entails an inspection of the foot type, patient's gait, and the foot (weight bearing and non-weight bearing). There is a variable spectrum of presentation of the deformity from mild bony prominence to severe dislocation of the big toe joint. Painful or limited motion of the big toe joint is indicative of degenerative arthrosis. Other associated signs include intractable plantar keratosis under the second metatarsal head, interdigital neuromas, lesser deformities, and callus.

B. Imaging

Plain radiographs are used to determine the severity of a hallux valgus deformity. Weight-bearing anteroposterior and lateral radiographs of the foot are the most useful images (Figure E5–1B).

Oblique views or sesamoid axial views of the foot may aid with recognition of other deformities of the foot. Plain radiographs in conjunction with the clinical findings are used to determine various angular relationships that allows the clinician to classify the severity of the deformity as mild, moderate, or severe. This classification of bunions can serve as a guideline for treatment of the deformity.

A. Conservative

Conservative care typically entails patient education of the natural history of the deformity and biomechanical support and is often adequate to relieve symptoms. Biomechanical support includes a custom or prefabricated orthotic device or supportive shoes. Orthotics can aid in providing support and improved motion for bunion deformities associated with pes planus or ligamentous laxity. Shoe modifications such as pocketing of the medial shoe counter, soft leather material, or simply wider shoe gear may provide symptomatic relief of pressure points over the bunion. Other palliative forms of conservative management include spacers, pads, and splints that are commercially available.

In the setting of an adventitious bursitis, anti-inflammatory medications such as nonsteroidal anti-inflammatory drugs may provide symptomatic relief.

It is important to note that conservative treatment provides a degree of symptomatic relief but does not reverse the bunion deformity.

B. Surgical

Pain and discomfort unresponsive to conservative care is the major consideration for surgical correction. Over 100 different surgical treatments have been described in the literature to correct bunion deformities.

As a general guideline, the severity of the deformity dictates the type of surgery. Mild to moderate bunion deformities generally can be corrected with distal metatarsal osteotomies. Severe deformities are typically managed with more proximal osteotomies. Fusion of the first metatarsophalangeal (MTP) joint generally is reserved for a bunion deformity associated with significant arthrosis of the big toe joint, severe deformities, or salvage of failed previous bunion procedures.

• If the patient has not responded to conservative treatment.

• There is severe deformity (overriding toes).

• There is severe pain from the MTP joint or bunion.