Bunion (hallux valgus) affects the big toe joint (1st MTP joint). The proximal phalanx of the big toe moves outwards making the metatarsal head prominent on the inner side of the forefoot. This broadens the forefoot. Shoes therefore rub on this bony prominence creating thickening and inflammation of the bursa. Also increase in the deviation of the 1st metatarsal inwards (metatarsus primus varus) can lead to hallux valgus deformity.
As time goes on, the constant pressure may cause the bone to thicken as well, creating an even largerlump to rub against the shoe.
Bunion is painful and a cosmetic problem. With severe deformities the big toe pushes the second toe upwards creating secondary deformity. These can cause difficulty in wearing fashionable shoes for women.
X-rays are done to quantify the deformity and plan treatment.
Wider shoes reduce the pressure on the bunion. Treatment of hallux valgus nearly always starts with adapting the shoes to fit the feet. In the early stages of hallux valgus, converting from a pointed-toe shoe to a shoe with a wider toe box can arrest the progression of the deformity. Bunion pads may reduce pressure and rubbing from the shoe. Although toe spacers are used to splint the big toe and reverse the deforming forces, they are not effective.
Almost always surgery is required for symptomatic bunions. There are well over 150 surgical procedures described to treat hallux valgus. The objective of correction of the deformity is to remove the bunion, to realign the bones that make up the big toe, and to balance the forces so the deformity does not return.
The angle made between the first metatarsal and the second metatarsal is used to make this decision. The normal angle is around 9-10 degrees. If the angle is 15 degrees or more, the metatarsal will probably need to be cut and realigned.
In some cases, the far end of the bone is cut and moved laterally (distal osteotomy).
This effectively reduces the angle between the first and second metatarsal bones. The bone is held in the desired position with a metal pin or small screw. In other situations, the first metatarsal is cut at the near end of the bone (proximal osteotomy). Nowadays Scarf Akin osteotomy is the preferred treatment. This involves longitudinal cutting and realigning of first metatarsal, cutting the proximal phalanx of the big toe and releasing the tight structure on the lateral side of the first MTP joint. This includes the tight joint capsule and the tendon of the adductor hallucis muscle. As you can see, this muscle tends to pull the big toe inward. The toe is realigned and the joint capsule on the medial side of the big toe is tightened to keep the toe straight. Once the surgery is complete, it will take about 6 weeks before the bones and soft tissues are healed.