And thanks to the threads, the rod can't back off on its own. A number of the most common clamps are screw clamps, including ...

A 23-year-old from Maldives with neuromuscular scoliosis underwent a surgery with 38 screws and special rods to sit upright.

And so it was that his as-yet-unnamed Screw With No Slot came to be. A brass rod pushes down to reveal the keyed center section. The screw’s disc-like appearance looks as if it’s a metal trim ...