A hallux valgus (plural: halluces valgi) is a fixed abduction of the first metatarsophalangeal joint of the great toe. It is usually due to metatarsus primus varus which is a medial deviation or adduction of the first metatarsal with an increased first-second metatarsal angle.
A normal first metatarsophalangeal angle is ≤15° on an AP weight-bearing foot radiograph ; anything greater indicates hallux valgus where the head of the first metatarsal is deviated medially. The intermetatarsal angle should be <9° on a weight-bearing foot radiograph .
Other associated radiographic features include:
- lateral subluxation of the base of the first proximal phalanx with respect to the head of the first metatarsal
- the prominence of the medial aspect of the first metatarsal head is referred to as the medial eminence
- dorsal angulation of the first metatarsal (on the lateral projection)
- lateral subluxation of the hallux sesamoids
- secondary osteoarthritis of the first MTP joint, usually with a medial osteophyte
- first MTP joint medial soft tissue swelling representing synovial thickening and bursitis (clinically presents as a bunion)
- second metatarsal dorsal clawing and cortical hyperostosis due to increased stress from altered biomechanics
There is a close association between the degree of metatarsus primus varus and hallux valgus. The combined deformities are present to some degree in most patients. Hallux valgus may be a result of metatarsus primus varus, and surgical correction is often based on this theory.
Treatment and prognosis
Non-surgical treatment involves the use of accommodative footwear. This is usually achieved by the use of soft and wide shoes. While orthoses are sometimes prescribed, there is minimal evidence to suggest their use will prevent the progression of the disease . Non-surgical treatment is deemed to have failed when the pain is no longer controlled with the suggested measures. In this case, surgical management is recommended.
The type of surgical procedure recommended will be determined by the severity of the deformity and the presence of arthritis in the 1metatarsophalangeal joint. In cases of minimal deformity and no arthritis, a distal metatarsal osteotomy of the 1metatarsal +/- proximal phalanx may be considered. A proximal 1st metatarsal osteotomy allows for greater correction thus is used in more severe deformity. In cases where the 1st MTP joint is already degenerate or there is a recurrence of the disease, a fusion procedure may be considered .