THE ANATOMY OF HALLUX VALGUS

1. The anatomy of the forefoot in hallux valgus is compared with the normal, with a review of the literature and descriptions of anatomical preparations, observations at operation and radiographs. 2. The early and essential lesions are stretching of the ligaments on the medial side of the metatarso-phalangeal joint that attach the medial sesamoid and basal phalanx to the metatarsal, and erosion of the ridge that separates the grooves for the sesamoids on the metatarsal head. 3. In established hallux valgus a sagittal groove, formed where the cartilage is free from pressure by either the phalanx or the ligaments, cuts off a medial eminence, which articulates with the stretched ligaments, from a restricted area for the phalanx. 4. Apart from osteophytic lipping which squares off the outline of the eminence as it is seen in radiographs and a small amount of lipping of the ridge on the metatarsal there is no evidence of new bone growth. In chronic cases the eminence may degenerate or disappear. 5. The articular surfaces at the cuneo-metatarsal joint become adapted to the changed positions of the metatarsal without gross pathological change. 6. The four deep transverse ligaments that bind together the five plantar pads of the metatarso-phalangeal joints are not unduly stretched, so that as the metatarsals spread it is the ligaments that bind the pads to the heads of the metatarsals that give way. 7. The plantar metatarsal artery to the first space pursues a tortuous course between the two heads of the flexor hallucis brevis. In hallux valgus the course becomes still more tortuous and part of the pain experienced may be due to ischaemic effects.