Screws Flashcards
fine threads along shaft
cortical screw
coarse threads with a smooth, unthreaded portion
cancellous screw
What is a lag screw?
threaded only distally
used to compres fracture fragments together
What is a lag-screw technique?
The application of cortical screws involves overdrilling the near cortex to the external diameter of the screw. When the screw is inserted, it glides through this hole and the threads only engage the far cortex. As the screw is tightened the head of the screw engages the near cortex and the fracture fragments are compressed together.
What technique is shown?
Lag technique
Why are the threads of a Herbert screw different at proximal and distal ends?
“It is cannulated and threaded at both ends. These threads run in the same direction, but the proximal portion has a wider pitch to its thread. Thus, when the proximal threads engage in the bone, they tend to move through the bone faster than the threads at the distal end, causing the two ends of the bone to compress together. “
