Abstract
The aetiology of hallux valgus is well published and largely debated. Hypermobility at the TMTJ was initially described by Morton, but it was not till Lapidus that its association with hallux valgus was hypothesized. However, little has been published on the anatomy of the tarsometatarsal joint. Our aim was to determine whether there was an anatomical basis for the coronal hypermobility in hallux valgus.
Method
Anatomical dissection was completed on 42 feet from 23 bodies. Presence of hallux valgus was noted (displacement of sesamoids). Measurements and photographs were taken of the first tarsometatarsal joint and all differences noted.
Observations
The TMTJ articular morphology is variable. There were 3 separate subtypes identified of the metatarsal articular surface.
Results
The articular subtypes identified were called called A, B and C. Type A, was uni-facet with a single flat articular surface, Type B was bi-facet with two distinct flat articular surfaces, and Type C was tri-facet, with the presence of a lateral eminence on inferolateral surface of metatarsal. Type A was found exclusively in bodies with Hallux Valgus and Type C exclusively in bodies without Hallux Valgus. Type B was found in both groups. Type C was more common in males and type B was more common in females.
The third facet was much more common in men. Another anomaly was found; measurements taken from the lowest to highest point of joint surface (mm) revealed a significantly flatter joint surface in bodies with hallux valgus.
Conclusion
Coronal plane motion in varus is a consistent feature of hallux valgus. The lateral eminence acts as a sliding dovetail joint and prevents coronal plane motion and rotation. We believe we have identified a joint type that is protective of the development of hallux valgus.
