The big toe is commonly referred to as a bunion. A bunion is a deviation of the bunion to the lateral side at the first metatarsophalangeal joint. Bunions are a complex anatomical deformity that is most commonly seen in middle-aged and older women and most often occurs in people with a genetic predisposition combined with prolonged wear of ill-fitting shoes. The prevalence of bunion deformity is 15 times higher in the shoe-wearing population than in the non-shoe-wearing population. Shoes that tightly bind the forefoot appear to be the primary causative factor for bunion deformities. However, not all people who wear such shoes develop bunions, so there must be other predisposing factors as well. Genetics is an important factor in the development of bunions, especially in adolescent patients; a positive family history of bunions has been reported in many studies. First metatarsal inversion, in which the first metatarsal bone is turned inward at an angle at the metatarsocuneiform joint, may also be a predisposing factor for the development of bunions, with a high incidence especially in adolescent bunion patients. Bunions are also common in patients with systemic joint disease, such as synovitis in rheumatoid arthritis, which causes destruction of the metatarsophalangeal joint capsule, resulting in bunion deformity. In addition, flat feet with incongruent first metatarsal relationships, such as a rounded first metatarsal head and a long or short first metatarsal. The posterior tibial tendon stops are variant and some fibers extend to the oblique head of the bunion and the peroneal part of the thumb flexor, thus increasing the contraction force of the joint tendon of the posterior biceps, and the abnormal bony prominence between the bases of the 1st and 2nd metatarsals play a role in the development of bunion. Rheumatoid arthritis and neuromuscular disease can also be associated with bunions, and there is a familial tendency for bunions to develop in adolescents. Bunions are classified according to severity: (1) Mild bunion: bunion angle less than 30° and intermetatarsal angle less than 13°. The joints are often matched and the deformity may be caused by an interphalangeal bunion. (2) Moderate bunion: bunion angle of 30° to 40°, intermetatarsal joint angle of 13° to 20°. The metatarsophalangeal joint is often mismatched (subluxation), and the bunion rotates forward and often causes compression of the second toe. (3) Severe bunion: The bunion angle is greater than 40° and the intermetatarsal grip angle is 20° or greater. The bunion is rotated anteriorly and often overlaps the second toe with a mismatch of the metatarsophalangeal joint. There is often metastatic pain under the second metatarsal head, and there may be arthritic changes. Treatment 1. Conservative treatment is possible for patients with only deformity without symptoms or with mild symptoms. Wearing looser or open-toed shoes can reduce friction on the medial eminence as well as delay the degree of bunion deviation and further aggravation of the rest of the toe deformity by reducing compression on the forefoot. Placing soft padding inside the shoe can reduce pressure on the painful area of the plantar foot. Application of bunion pads, night splints, and interdigital toe pads may temporarily relieve pain and slow the progression of the deformity. Physiotherapy and hot compresses can be done for bunions. 2.Surgical treatment If conservative treatment cannot relieve the symptoms of bunion deformity, surgery can be recommended to correct the bunion. The appropriate surgical method should be chosen according to the specific situation of the patient. For mild to moderate bunion, if the angle between the first and second metatarsal bones is less than 15°, the medial phalanx of the metatarsal head can be excised and the bunion tendon can be cut or excised. The severed end of the bunion tendon is displaced to the lateral side of the metatarsal head and neck or the metatarsal head and neck is osteotomized and displaced. If the angle between the first and second metatarsals is greater than 15°, the first metatarsal trunk or basal osteotomy is usually used more often. In patients with existing osteoarthritis of the first metatarsophalangeal joint, the first metatarsophalangeal joint fusion is more often used in younger patients; in older patients, the Keller procedure or artificial joint replacement may be used. Patients should also be informed of the possible problems of limited movement, decreased strength, residual discomfort or postoperative recurrence. Prevention Avoid wearing shoes with too narrow a front toe and high heels. Patients with flat feet, rheumatoid arthritis or neuromuscular disorders should avoid deformities by adjusting shoes and choosing appropriate braces.