BACKGROUNDThere are no unified theories as to the anatomical changes that occur with hallux valgus, we investigated the radiological characteristics and anatomical risk factors for hallux valgus deformity in Chinese adults.

METHODSWe reviewed 141 patients with hallux valgus (206 feet; 15 males, 126 females; mean age, 58.5 years). These patients attended Peking University People's Hospital from April 2008 to March 2014. All feet had intact radiological data, obtained using the Centricity RIS/PACS system. We measured hallux valgus angle (HVA), 1-2 intermetatarsal angle (IMA), proximal articular set angle (PASA), distal articular set angle, hallux interphalangeal angle, metatarsocuneiform angle, size of the medial eminence of the distal first metatarsal, tibial sesamoid position, and joint congruity of the first metatarsophalangeal joint (MTPJ).

RESULTSWe found positive correlations between the HVA and IMA (r = 0.279, P < 0.01) and HVA and PASA (r = 0.358, P < 0.01), but not for IMA and PASA (P > 0.05). Feet were divided into three groups based on HVA severity. IMA (P < 0.05) and PASA (P < 0.05) in the mild group were significantly lower than that in the moderate and severe groups, with no significant difference determined for IMA or PASA between the moderate and severe groups (P > 0.05). Feet were then grouped based on the shape of the first metatarsal head. Using this grouping, HVA was significant higher in the rounded shape (19.92°) than in a flat shape (17.66°). The size of the medial eminence of the distal first metatarsal was positively correlated with HVA (r = 0.185, P < 0.01). The medial eminence in the moderate and severe groups was significantly larger than that in the mild group; moderate and severe groups were not significantly different.

CONCLUSIONSPASA enlargement is an adaptive change during early hallux valgus formation, and decompensation leads to subdislocation in the first MTPJ. A rounded first metatarsal head would thus predispose a foot to hallux valgus. Furthermore, bone proliferation at the medial eminence may also lead to early hallux valgus development.