Watkins Chapter 24: Fixation
Terms in this set (15)
What screws are fully threaded?
What is the weakest point on a screw?
The run out
What screws have a smaller pitch? What screws have a wider pitch?
Smaller pitch = Cortical
Larger pitch = Cancellous
Describe the lag screw technique for a 2.7mm screw:
1. Drill pilot hole (2.0-mm drill bit) -- near and far cortex
2. Drill glide hole (2.7-mm drill bit) -- near cortex
3. Counter simnk
5. Tap (2.7-mm tap)
7, Insert 2.7mm screw
What part of a screw pulls a cortex up? What part of a screw pushes a cortex down?
The threads pull the bottom cortex up, whereas the head push the top cortex down.
What kind of wire can convert distractive forces into compressive forces?
Tension band fixation
For example, when done properly it can cause the pull of the triceps surae to compress a fracture rather than distract.
What are two bone bioabsorbale fixation devices? What is a risk of fast dissolving?
PGA (polyglycolic acid) and PLA (poly lactic acid)
Risks: Osteolysis and bone cysts formation
Difference between dynamic compression plate, static compression plate, and compression plate?
How do compression plates work?
A compression plate is a plate with screw holes with sloped edges on the side of the hole distal from the fracture site.
As the screw is inserted, the plate moves away from the fracture, thereby compressing the fracture sites.
This allows compression across a fracture osteotomy site as the screws are tightened.
What plates are used to protect bone that is unstable and needs protection from compression or axial loading such as comminuted fractures or bone grafts?
What plates are normal run-of-the-mill plates designed to protect fracture sites from normal bending, rotation, and axial loading forces?
What plates are always used in combination with a lag screw?
What is another name for a buttressing plate?
A tension-band plate is placed on what side of a fracture/osteotomy?
The tension side, which prevents distraction on that side while causing a corresponding compression on the other side.
What is special about a locking plate?
Locking plates have scress that secure to the plate, preventing toggle and providing a more stable fixation. They mmake good bridge plates because they act line "internal external fixators."