Normal Talar–1st Metatarsal Angle Size on Radiography
The talar–1st metatarsal angle (also called Meary's angle on the AP projection) is measured on weight-bearing or simulated weight-bearing foot radiographs and reflects the alignment between the long axis of the talus and the first metatarsal. In the pediatric foot, this angle quantifies forefoot abduction relative to the hindfoot and changes predictably with skeletal maturation. Accurate measurement is essential for evaluating flatfoot deformity, metatarsus adductus, and post-treatment foot alignment in children.
Normal Reference Values
| Orientation | Age | Measurement |
|---|---|---|
| Anteroposterior | Newborn | 20¡ |
| Anteroposterior | 2 y/o | 13¡ |
| Anteroposterior | 4 y/o | 10¡ |
| Anteroposterior | 4-9 y/o | -9-31¡ |
Clinical Significance
In the normal foot the talar–1st metatarsal angle decreases progressively as the longitudinal arch develops: approximately 20° at birth, falling to 13° by age 2 and 10° by age 4, with a wide but defined reference range of −9° to 31° across ages 4–9 years. A persistently elevated (positive) angle indicates forefoot abduction and planovalgus deformity, while a negative value suggests forefoot adduction or metatarsus adductus.
Deviation beyond age-adjusted norms warrants correlation with clinical examination and dynamic weight-bearing assessment. Serial measurements are more informative than a single study, particularly when monitoring conservative treatment or surgical correction.
- Flexible flatfoot (pes planovalgus): increased positive angle with weight-bearing, typically corrects on toe-rise
- Rigid flatfoot: persistently elevated angle on and off weight-bearing; consider tarsal coalition
- Metatarsus adductus: negative talar–1st metatarsal angle with medial deviation of the forefoot
- Clubfoot (talipes equinovarus): markedly negative angle on AP view; used to monitor surgical or casting correction
- Post-surgical over-correction: angle swinging to opposite polarity following flatfoot or clubfoot repair
Reference: Vanderwilde R, Staheli LT, Chew DE et al. Measurements on radiographs of the foot in normal infants and children. J Bone Joint Surg Am. 1988;70(3):407–15.
Imaging Notes
On the anteroposterior (AP) foot radiograph, the talar axis is drawn through the center of the talar head and neck, and the first metatarsal axis is drawn along the midshaft of the first metatarsal. The angle formed at their intersection is the talar–1st metatarsal angle; a positive value indicates the metatarsal deviates laterally (abduction), and a negative value indicates medial deviation (adduction). In children old enough to cooperate, a weight-bearing or simulated weight-bearing position is preferred to reflect functional alignment.
Technique consistency is critical: even minor rotation of the foot alters the measured angle. Both feet should be imaged in identical positioning to allow side-to-side comparison. In infants where ossification is incomplete, the metatarsal shaft axis remains reliable, but the talar axis may require estimation from the partially ossified talar body.