The Distal Metatarsal Articular Angle: Fact or Fiction?
Updated: Dec 29, 2021
The popularity of first tarsometarsal joint fusion, commonly referred to as the Lapidus procedure, has continued to grow in recent years, largely due to patient-centric marketing campaigns which have emphasized the 3-D rotational correction.
As a result, the fall from grace has continued for traditional bunion procedures.
From a birds-eye view…
Many patients with hallux valgus deformity have valgus rotation of the first metatarsal, appreciated on 2-D images by visualization of the lateral round sign and increased distal metatarsal articular angle (DMAA).
With varus correction, the lateral round sign disappears and DMAA decreases, leading surgeons to conclude that both are simply radiographic consequences of the deformity.
Not so fast
In their recent study on distal metatarsal articular angle in hallux valgus deformity, Matthieu Lalevée et al. compared DMAA in patients with and without hallux valgus deformity on both 2-D weightbearing radiographs and 3-D weightbearing computed tomography (WBCT), before and after computer correction of first metatarsal’s valgus rotation, for the latter.
2-D imaging overestimated the DMAA compared to 3D-WBCT, prior to correction.
DMAA correction was observed on both modalities.
DMAA was higher in patients with HV deformity compared to control on 3D-WBCT, after correction, meaning true valgus deformity of the distal first metatarsal surface may persist in bunion correction, despite coronal plane correction of the first metatarsal.
As with so many topics in foot and ankle, more research has given us more questions than answers.