First ray measuring instrument

General characteristics:
• Connected by their vertical branches with a millimeter scale
• The curvature of the horizontal arms allows the instrument to be adapted to the dorsal surface of the metatarsal heads
• The curvature of the vertical branches reflects the inversion and eversion movement of the first ray during dorsiflexion and plantar flexion.
• Designed based on a mathematical calculation
• Its validity and reliability have been scientifically demonstrated