Iselin's apophyseal fragment runs parallel to which structure?

Iselin's apophyseal fragment runs parallel to which structure?

• A. 5th metatarsal diaphysis
• B. 5th metatarsal head
• C. 5th metatarsal base
• D. 5th metatarsal neck

Answer: (A)

Iselin's apophyseal fragment aligns with the long axis of the bone because the traction from the peroneus brevis pulls on the tuberosity where the apophysis sits. The apophysis at the base of the 5th metatarsal develops separately and, when avulsed, the fragment tends to run along the shaft, so its long axis is parallel to the diaphysis. On radiographs this appears as the base fragment following the direction of the metatarsal shaft rather than crossing perpendicular to it.

Iselin's apophyseal fragment aligns with the long axis of the bone because the traction from the peroneus brevis pulls on the tuberosity where the apophysis sits. The apophysis at the base of the 5th metatarsal develops separately and, when avulsed, the fragment tends to run along the shaft, so its long axis is parallel to the diaphysis. On radiographs this appears as the base fragment following the direction of the metatarsal shaft rather than crossing perpendicular to it.