title: The first tarsometatarsal joint and its association with hallux valgus.
abstract: BACKGROUND
  The aetiology of hallux valgus is almost certainly multifactoral. The biomechanics of the first ray is a common factor to most. There is very little literature examining the anatomy of the proximal metatarsal articular surface and its relationship to hallux valgus deformity.
  
  
  METHODS
  We examined 42 feet from 23 specimens in this anatomical dissection study.
  
  
  RESULTS
  This analysis revealed three distinct articular subtypes. Type 1 had one single facet, type 2 had two distinct articular facets, and type 3 had three articular facets one of which was a lateral inferior facet elevated from the first. Type 1 joints occurred exclusively in the hallux valgus specimens, while type 3 joints occurred exclusively in normal specimens. Type 2 joints occurred in both hallux valgus and normal specimens. Another consistent finding in regards to the proximal articular surface of the first metatarsal was the lateral plantar prominence. This prominence possessed its own articular surface in type 3 joints and was significantly flatter in specimens with hallux valgus (p < 0.001) and the angle with the joint was significantly more obtuse (p < 0.001).
  
  
  CONCLUSIONS
  We believe the size and acute angle of this prominence gives structural mechanical impedance to movement at the tarsometatarsal joint and thus improves the stability.
authors.affiliation: Foot and Ankle Unit, Royal Gwent Hospital, Cardiff Road, Newport NP20 2UB, UK.
authors.forename: L W
authors.initials: LW
authors.lastname: Mason
authors.forename: H
authors.initials: H
authors.lastname: Tanaka
keywords: 1st metatarsal joint; 1st metatarsal joint morphology; Aetiology; First metatarsal biomechanics; Hallux valgus; Medial cuneiform; Tarsometatarsal joint; Tarsometatarsal joint instability