The simple bunion: anatomy at the metatarsophalangeal joint of the great toe.

The pathomechanics for the development of the hallux valgus deformity takes place at the first metatarsophalangeal joint--the sesamoid complex. The sesamoid complex consists of seven muscles, eight ligaments, and two sesamoid bones. When the first metatarsal escapes the complex and drifts medially, the sesamoids remain twisted in situ, several of the ligaments "fail," and others contract. The authors propose reduction of the metatarsus primus varus by first metatarsal osteotomy and appropriate ligament releases and plications to restore alignment. A detailed understanding of the pathomechanics is essential for proper interpretation of the problems and anticipated lasting surgeries.