Bunions (Hallux Valgus)
A bunion is a prominence over the joint where the big toe joins the rest of the foot (1st metatarsophalangeal joint). A bunion usually develops due to a hallux valgus deformity, which is when the 1st metatarsal bone gradually deviates inwards, towards the opposite foot. The big toe moves in the opposite direction, towards the lesser toes, and this leaves the head of the 1st metatarsal bone prominent under the skin.
As a hallux valgus deformity progresses, the lesser toes can start to deform as a result. The most common sequelae are hammer toes, usually of the 2nd or 3rd toes. In addition, the skin under the balls of the foot (specifically under the 2nd and 3rd metatarsal heads) can become sore and thickened due to increased and abnormal weight going through them. As the deformity worsens, the big toe can move under or over the second toe.
What is the cause?
There is no single cause of hallux valgus. It often runs in families, but the genetic link has not been identified. The most common cause is imbalance of forces on the toe, which is probably present from early in life, and this results in a gradual progression of deformity over time. Other causes include neuromuscular disorders like polio and cerebral palsy, ligamentous laxity, and joint destruction associated with arthritis.
High-heeled pointed-toe shoes have not been shown to cause hallux valgus deformities, but they can make it painful and exacerbate the condition. Pressure from tight fitting shoes can cause bunions, corns and calluses to develop in the setting of hallux valgus.
The diagnosis of a bunion by an orthopaedic surgeon includes taking a full medical history, and performing a thorough physical examination to assess the extent of deformity and damage to the soft tissues. Weightbearing X-rays (ie x-rays taken when you are standing up) help determine the degree of the hallux valgus and lesser toe deformities, the extent of any arthritis, and whether any concomitant problems exist.
It is important to exclude other causes of big toe pain, which include osteoarthritis, rheumatoid arthritis, infection and gout. Circulatory problems may not only cause pain, but can also lead to serious complications if surgery is undertaken. Cigarette smoking and diabetes significantly impair healing potential and increase the risk of infection.
Conservative treatment should be trialled initially. The goal of non-surgical treatment is to relieve pressure on the foot in order to alleviate pressure sores, ulcers and bursitis (painful inflammation). Such measures include wearing properly fitting shoes with wide toe boxes, custom prescribed orthotic inserts, padding, or taping of bunions.
Surgery can correct painful bunions. The severity of the bunion deformity and the presence of any associated problems (eg arthritis, 1st TMT joint hypermobility) will determine the type of surgery that is recommended.
Most bunion correction operations involve bone cuts (osteotomies) in order to re-align the deformed bones. The ultimate goal of any bunion surgery is restore the normal shape and mechanics of the foot in order to reduce pain and discomfort and allow return to normal shoe wear.