Bunion A bunion is a deflection of the bunion to the lateral side at the first metatarsophalangeal joint. Bunions are a complex anatomical deformity and can be extremely challenging to treat. A bunion is a distinct medial protrusion present in a bunion deformity, but the two terms are generally used interchangeably. Bunions are the most common lesion involving the bunion and are most commonly seen in middle-aged and older women, most often in those with a genetic predisposition coupled with prolonged wear of ill-fitting shoes, which can exert abnormal pressure on the bunion. Etiology The occurrence of bunions may have an important relationship with wearing improper shoes. The prevalence of bunion deformity is 15 times higher in those who wear shoes than in those who do not. Shoes that tightly bind the forefoot appear to be the primary causative factor for bunion deformity. 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 diseases can also be associated with bunions, and there is a familial tendency for bunions to develop in adolescents. Clinical manifestations Bunion stiffness is generally manifested by the lateral deviation of the bunion at the first metatarsophalangeal joint and the appearance of an obvious bony flap on the inside of the joint. In some patients, the soft tissues at the bony flap become red, swollen, and fluid-filled due to long-term shoe friction and extrusion, called a bunion. Patients with severe bunions may develop deviation and riding across the other toes. Patients with bunions do not always have pain, and the deformity is not proportional to the pain. The main cause of pain is acute bunions due to pressure and friction after the medial bulge of the bunion metatarsal head. Long-term abnormality of the bunion joint, osteoarthritis causing pain and callus under the 2nd to 3rd metatarsal head causing pain. Examination 1. Evaluation of the degree of bunion, other toe deformities and the arch of the foot in the standing position. The morphology of the forefoot and hindfoot is evaluated in the sitting position. Evaluation of the bunion includes the mobility of the first metatarsophalangeal joint, the degree of swelling, the prominence of the medial projection and the presence of callus or painful bunions, and the presence of limited seed bone pain on the plantar surface of the foot; evaluation of the other toes includes the presence of hammertoes, instability or dislocation of the metatarsophalangeal joint, and plantar pain or callus. The angle between the first metatarsal and the midline of the proximal phalanx, the normal value is less than 15°. (2) Intermetatarsal angle The angle between the midline of the first and second metatarsal stems, with a normal value of less than 9°. (3) Distal metatarsal articular surface angle (DMAA) The angle of intersection between the articular surface of the first metatarsal head and the long axis of the first metatarsal: the normal value is less than 10° for the lateral inclination of the articular surface of the metatarsal head. (4) Joint match Whether the joint surface of the first metatarsal head and the proximal phalanx is semi-dislocated; if the sides of the joint are tilted, the joint is mismatched. (5) Angle between toe bones The angle between the midline of the proximal and distal phalanges of the first toe is normally less than 10°. 3. Classification of bunions according to severity (1) Mild bunion The bunion angle is less than 30°, and the intermetatarsal pinch angle is less than 13°. The joints are often matched and the deformity may be caused by the interphalangeal bunion. (2) Moderate bunion The bunion angle is 30° to 40°, and the intermetatarsal joint angle is 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 joint 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 remaining toe deformity by reducing the 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. There are various surgical methods, but no one surgical method is suitable for all bunion patients. The appropriate surgical method should be chosen based on the patient’s specific situation. In mild to moderate bunions, 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 removed. 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, fusion of the first metatarsophalangeal joint is more often used in younger patients; in older patients, Keller surgery 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.