Metatarsus primus varus is a foot deformity where the first metatarsal bone, which connects to the proximal phalanx bone of the big toe, is rotated and angled away from the second metatarsal bone. The rotation of the first metatarsal bone causes the head of the bone to push outward, creating a bump on the side of the foot.This condition is related to the condition hallux valgus or hallux abducto valgus, which affects the big toe and is associated with what is commonly known a bunion. A bunion is the painful swelling of the first joint of the big toe, the metatarsophalangeal joint. When pressure is applied to the angled first metatarsal in a foot with metatarsus primus varus, forcing the big toe inward – even to the point of an angular position above or below the adjacent toe – swelling, tenderness, skin irritation, blisters, and pain can result.1
There is a misconception that a bunion is an enlargement of the bone, but this is not usually the case. It is the case that an inflamed bursal sac may develop, however. In rare cases, there can be a bone anomaly in the metatarsophalangeal joint that contributes to the issue.
Causes of Metatarsus Primus Varus
Metatarsus primus varus is most often found in populations where shoes are regularly worn.
Bunion symptoms occur most often in people who wear shoes with a tight or pointed toe box, such as with high heels. Women are affected more often than men, and for these reasons, shoes are often considered a contributor to metatarsus primus varus, hallux valgus and bunions. However, genetics are also considered as a possible cause.
Problems related to metatarsus primus varus and bunions develop over time and do not generally get better without treatment.
Treatment for Metatarsus Primus Varus and Bunions
Initial treatment is generally aimed at addressing the pain and swelling of bunions. They do not, however, correct the metatarsus primus varus or hallux valgus problems. Initial treatments can include2
Changing shoes: Because bunions are aggravated by shoes and shoes are considered a contributor to the underlying deformities, changing to a shoe with a wider toe box and avoiding high heels and other pointed-toe shoes can help relieve the problem.
Applying ice: Ice applied several times a day will help reduce pain and swelling.
Padding: Bunion pain can be eased with padding, which can be found in retail stores or received from physicians.
Adjusting activities: Avoid standing for long periods and other activities that cause bunion pain.
Medication: Anti-inflammatory medications, such as ibuprofen, can help reduce the pain and swelling of a bunion.
Orthotics: A doctor may suggest custom orthotics to help with bunions.
If the nonsurgical treatments for bunions are insufficient and bunions are interfering with normal activity, surgery is an option.3 A surgeon will examine the angle between the first and second metatarsal bones, called the first intermetatarsal angle, to determine which surgical procedure is needed.
Procedures can include the removal of some of the bone that produces the bump in a bunion, adjusting the bone structure of the foot contributing to the condition, and addressing any changes to tissues in the area that may have been affected.