16 – Plates and Screws Flashcards
1
Q
What are the forces controlled by bone plates and screws?
A
- *all of them! (as long as you follow the rules)
- Screws alone control TORSION and COMPRESSION to some degree, but NOT strong against bending
2
Q
Interfragmentary screws
A
- Have them partial placed but then will come out when the rest are in place
3
Q
Screw and plate sizes
A
- Classified according to EXTERNAL diameter (distance that the threads project)
o Drill a hole that is the internal diameter (‘inside’ of the threads) - Plates are sized according to the size screws they are bult to accommodate
4
Q
What are the different methods of screw application?
A
- Neutral
- Compression
5
Q
Neutral screw application
A
- POSITIONAL screws
- NO compression added across fracture line by screw
6
Q
Compression screw application
A
- LAG screws
- Squeeze fractures together
7
Q
What is a nonlocking plate?
A
- Force is transferred from bone to plate via FRICTION at each screw site=requires close PLATE-BONE contact
- Screws can be angled relative to plate and can be used to compress fracture
- Screws MUST engage TWO cortices to contribute meaningful strength to the construct
8
Q
What is a locking plate?
A
- Screw heads thread INTO the holes in the plate=makes plate-screw construct mechanically ONE thing (similar to ESF)
- Plate contouring for close bone contact is NOT necessary
- *screws must be perpendicular to the plate and can’t be used to compress the fracture
o Can be monocortical
9
Q
What are the advantages of bone plating?
A
- Anatomic reconstruction of the fracture is NOT always necessary
- Minimal irritation of overlying muscle
- Little intervention required by owner
- Bone fragments can be compressed
10
Q
What are the limitations of bone plating?
A
- Expensive
- Considerable exposure required (unless minimally invasive technique is chosen)
- Even plates can BEND or BREAK with cycling
- Plate removal (usually not necessary) requires a second operations
- NOT always a good choice for fractures with very short proximal or distal fragments
11
Q
Bridging plate
A
- Relies on long distance of plate that is NOT attached to bone and can be more flexible
12
Q
Plate nomenclature
A
- Designated by:
o Screw diameter that fits the holes in the plate
o Shape and purpose of plate
13
Q
What is counting cortices?
A
- How many cortices are engaged by screws in each fragment
- If going across a fragment=1 cortex in upper fragment, 1 cortex in lower fragment
14
Q
What are the principles of plate and screw application?
A
- In order for NON-locking plate to be stable=must be a MINIMUM of SIX cortices captured by screws in each major fragment
- Minimum for LOCKING plate=1 bicortical, 1 monocortical screw per fragment
15
Q
Pin-plate combination
A
- More resistance to cycling forces than plating alone
- Pin is on neutral axis of bending of bone (plates are NOT)
o Pin needs to be at least 30% diameter of bone at thinnest point - *minimum screws per major fragment=one 2-cortex screw, at least one additional monocortical screw
16
Q
Do we meet the minimum requirements?
A
-proximal: 5
-distal: 2
*DOES NOT meet requirements
17
Q
Do we meet the minimum requirements?
A
proximal: 6
distal: 3 (one entering in fracture site)
*bare minimum (might be okay b/c he is young
18
Q
Where should the plate be placed?
A
- Strongest if placed on the TENSION (convex) side of the bone(or the joint) being fused
- *rule is sometimes broken if it is much more difficult to approach the tension side, but then the repair should be protected
