Bunion (Hallux Valgus)
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- Lateral deviation of the great toe (Hallux abducto valgus derives from the Latin for “big toe askew.”)
- Associated with medial deviation of the 1st metatarsal, leading to a medial prominence of the 1st metatarsophalangeal (MTP) joint (also known as “Bunion”); progressive subluxation of the 1st MTP joint is common.
- System(s) affected: musculoskeletal/skin
- Predominant age: more common in adults
- Estimated 23% in adults aged 18 to 65 years
- Estimated 35.7% in elderly >65 years
- Predominant sex: female > male by ~2:1
- Prevalence increases with age particularly in females.
- Juvenile hallux valgus
- More common in girls (>80% of cases)
- Commonly bilateral
- Pain is not usually the presenting symptom.
Etiology and Pathophysiology
Multifactorial. Contributing factors include the following:
- Valgus deviation of the hallux promotes varus position of the 1st metatarsal.
- Medial MTP joint capsule stretches and attenuates, whereas the lateral capsule contracts.
- Metatarsal head moves medially, shifting the sesamoid bones to a more lateral position.
- Extensor hallucis longus deviates laterally.
- Lateral and plantar migration of abductor hallucis moves the great toe into plantar flexion and lateral pronation.
- Medial collateral ligament stretches and eventually ruptures due to this deviation, decreasing stability and causing progressive subluxation of the 1st MTP joint.
- Familial predisposition
- Abnormal biomechanics (i.e., flexible flat feet)
- Joint laxity; pronation of hindfoot; Achilles tendon contracture; pes planus (fallen arches)
- Metatarsus primus varus
- Amputation of second toe
- Inflammatory joint disease
- Neuromuscular disorders
- Improper footwear, narrow toe box
Proper footwear may decrease the progression of the disease.
Commonly Associated Conditions
- Medial bursitis of the 1st MTP joint (most common)
- Hammertoe deformity of the 2nd phalanx
- Plantar callus
- Degeneration of 1st metatarsal head cartilage
- Pronated feet; ankle equinus
- Onychocryptosis (ingrown toenail)
- Entrapment of the medial dorsal cutaneous nerve
- Synovitis of the MTP joint