Bone Screws and Plates - Betance Flashcards
Cancellous screws are used in
softer/spongey bone
- metaphyseal or epiphyseal bone
Cortical screws are used in
harder bone
- cortex, diaphyseal
Shaft screws are used when/how/where?
used for lag application in diaphyseal bone
Cannulated screws are used when?
used in more difficult fractures
Locking head screws are used when?
used in locking compression plates
What is a self tapping screw?
it’s a cortical screw that has a head at the tip like a drill bit. It allows screw placement without predrilling a hole and tapping.
What kind of pitch/thread does a cancellous screw have?
a larger pitch and a deeper thread. It can be partially or fully threaded
What kind of pitch/thread does a cortical screw have?
smaller pitch and shallow threads. This allows for more threads per inch. It’s fully threaded
what kind of thread does a shaft screw have?
partially threaded (AT THE DISTAL END). It’s a cortical screw!!!!!!
Tell me about the structure of a cannulated screw
it has a central hollow core. K-wire holds reduced fx and acts as a guide
what would you use a compression plate on?
a transverse or nearly transverse fracture
what would you use a neutralization plate on?
an oblique or communicated fracture
What would you use a bridging (buttress) plate on?
they basically bridge diaphyseal fractures
What does a compression plate do, exactly?
allows compression of bone at the fracture site
- compression is applied by the spherical gliding principle and occurs with an eccentric loaded screw
- the plate needs to be shaped to bone
- allows for compression of the opposite cortex
What does a neutralization plate do, exactly?
- anatomical reduction is accomplished with the use of lag screws or cerclage wires
What forces does a neutralization plate protect against?
- rotation
- bending
- shearing forces
Where is a bridging plate secured to?
proximal and distal fracture fragments. It spans the comminuted part of the fracture
what does a bridging plate prevent?
prevents axial deformity as a result of shear or bending forces
How can a dynamic compression plate be used?
- neutralization
- compression
- bridge plating
Limited Contact Dynamic Compression Plates can be used in 3 different ways:
- compression
- neutralization
- bridging functions
LC-DCPs do what to cortical perfusion?
improves it!!! it has decreased plate to bone contact. It also reduces stress concentration at screw holes
what functions can a Locking Compression Plate have?
- compression
- neutralization
- bridging function
what else can a locking compression plate be called?
an internal fixator
What specific ortho thing is the LCP good for?
Minimally invasive plate osteosynthesis (MIPO)! It has a tapered tip.
which type of plate would you use in an area that requires complex plate contouring such as the mandible?
A reconstruction plate! It allows for contouring in an additional plane. It’s not as strong as a DCP though.
What plate would you use in super thin bones?
A VCP (veterinary cuttable plate). It’s relatively week, can be stacked, and does not have any compression function
What plate would you use in a chihuahua thing?
miniplates! They are teeny tiny and have self-tapping screws
What plate classification is a string of pearls?
A locking plate. It can contour in any direction
What screws would you use for a string of pearls plate?
unicortical screws.
Does the string of pearls compress?
Nope! It neutralizes or bridges
What kind of plate would you use in a hip dysplasia patient?
Triple Pelvic Osteotomy plates. It changes the angle
What kind of plate would you use in an area with little soft tissue covering?
tubular plates
Where do you place the bone plate on the bone?
On the tension side of the bone. Plates will likely fail on the compression side
What do plates achieve?
They convert distracting/tension forces into compression forces with weight-bearing
How many cortices on each side of the fracture line should you engage when bone plating?
at least 6! (at least 3 screws)
Where should the bone plate span?
the diaphysis of the bone if possible
How far from the fracture line should screws be placed?
at least 5mm
When do you place screws in a fracture line?
ONLY if a lag/position screw!
Where is an interlocking nail placed?
a stainless steel nail placed within the MEDULLARY CAVITY. (it gets locked to the bone by screws that cross the bone and pass through holes in the nail)
What are interlocking nails used for?
mid diaphyseal fractures of the humerus, femur, and tibia
How do you place interlocking nails, retrograde or normograde?
NORMOGRADE
what forces do interlocking nails resist?
bending, shearing, and rotational forces
