Meary angle, also known as (lateral) talus-first metatarsal angle, has been used to identify the apex of deformity in patients with pes cavus and pes planus on lateral weight-bearing foot radiographs.
Measurement
It is the angle between a line drawn along the longitudinal axes of the talus (mid-talar axis) and the first metatarsal (first metatarsal axis).
Interpretation
In the standard weight-bearing foot, the midline axis of the talus is in line with the midline axis of the first metatarsal. Typically, Meary angle is 0º, with abnormal values considered 3:
angle >4º convex upward: pes cavus
angle <-4º convex downward: pes planus
It can be used to classify the severity of deformity 3:
mild: <15º
moderate: 15-30º
severe: >30º
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