Principles of fracture management 2 Flashcards
Name some different types of screws
Cortical/Cancellous
Partially/fully threaded
Self tapping/ non self tapping
Locking / not locking
What is the size of the screw mean?
Size of screw = thread diameter
What is the thread of a screw?
a helical structure used to convert between rotational and linear movement or force
Name the 3 different types of screws on this image
Left - locking
Middle - cortical
Right - cancellous
What is a self tapping screw?
A self-tapping screw is a screw that can tap its own hole as it is driven into the material.
What properties does a self tapping screw have?
Thread on screw
Cutting flutes at the end of the screw
Cuts thread into bone as screwed in
What properties does a non self tapping screw have?
No cutting flutes
Use a tap to cut the thread before placing the screw
Thread of profile of tap = thread profile of screw
What type of screw is this -
Self tapping or non self tapping?
Self tapping
It has cutting flutes
What type of screw is this - self tapping or non-self tapping?
Non self tapping
Blunt end
Are self tapping or non self tapping screws faster to place?
Self tapping - faster to place as do not need to tap before hand to place it
Why should you take care when placing self tapping screws?
Care with placement, can fracture bone
If replacing screw, dont make a second thread
Name 3 BONE screws
Lag screw
Positional screw
Name some PLATE screws
Non locking: for axial compression or neutral (no compression)
Locking
What does a POSITIONAL screw do and how is it placed?
Both cortices of the bone are drilled and tapped
Screw holds 2 pieces of bone together i.e. in position
What screw is shown here?
Positional screw
both cortices of the bone are drilled and tapped
screw holds 2 pieces of bone together
What are the order of events for placing a 3.5mm positional screw?
Placing 3.5mm positional screw
- Drill a 2.5mm hole in the cis and trans cortices (using a 2.5mm drill guide)
- Measure the depth of the hole using a depth gauge; add 2mm
- Use a 3.5mm tap in a 3.5mm guide, tap both cortices Not necessary if screw is self-tapping
- Place a 3.5mm screw of the appropriate length
- Screw should be tight but do not over-tighten otherwise strips
Counter-sinking is not necessary for a positional screw.
This applies to a positional screw in a bone, or in a plate.
What are lag screws - how are they placed and what do they do?
The near cortex if ‘over’ drilled to the same diameter as thread
The far cortex is prepared normally - drill to shaft diameter, tap to thread diameter
Screw compresses/squeezes 2 pieces of bone together
What is this screw, how does it work?
Lag screw
Near cortex is over drilled to same diameter as thead
Far cortex is perpared normally
Screw compresses/sqeezes 2 pieces of bone together
When should you use a lag screw?
For oblique fracture only
(oblique fracture = more than 3odegrees to long axis. Apply lag screw perpendicular to the fracture, so the squeezing action is to squeeze the fracture rather than to shear the fracture)
How should a lag screw be placed and in what type of fracture?
Oblique fractures only
Fracture should be help reduced with bone holding forceps
leg screw at 90degree to fracture line - to compress, otherwise it will shear (which we do not want)
It should lead to primary bone union - lag screws are a way of achieving NO gap and absolute stability in oblique fracture
What are the steps involved with placing a 3.5mm lag screw?
How to place 3.5mm lag screw
- Drill a 3.5mm glide hole in the cis cortex (drill guide)
- Place a 2.5/3.5mm insert sleeve into the glide hole
- Drill a 2.5mm hole in the trans cortex
- Remove the insert sleeve
- Countersink the hole (not if placed through a bone plate)
- Measure the depth of the hole using a depth gauge; add 2mm
- Using a 3.5mm tap in a 3.5mm guide, tap the trans cortex
- Choose a 3.5mm screw of the appropriate length
- Place it in the prepared hole and screw it in until tight.
- Do not over-tighten the screw
What happens if you tighten a lag screw too tight?
If tightened too tight - bone fractures or strip the thread in the far cortex, the bone mini fractures around the screw and then do not have intact break
What are the functions of fully threaded bone screws?
Positional screw
Lag screw
Depends on how the ci cortex is prepared - over drill or tap.
What are partially threaded screws used for?
There are no near threads - functions exclusively as a LAG screw
What is a non locking plate screw?
Screw is placed in the bone through the place
The head of the screw engages the plate
What is this screw here?
Non locking plate screw
screw is palced in the bone through the plate
the head of the scew engages the plate
Have you had a break recently?
probs not
so got get a tea or lucozade (tred) or a hot choc (anna)
What is a lag screw?
A lag screw is used to compress fracture fragments
How can a plate screw be used as a lag screw?
Fracture should be reduced
Lag screw should be placed at 90 degrees to the fracture line
- fracture should be reduced
- plate is applied
- lag screw should be placed at 90 degrees to the fracture line
What are some mechanical functions of a plate?
Compression
Neutralisation
Bridging
Locking - neutralisation and bridging
What does the size of the plate mean?
Size of plate = the size of screws the plate works with
How does a non locking plate work?
Screw is placed in the bone through the plate
The head of the screw engages the plate
Screw pulls/tightens plate down onto the bone
friction between plate and bone maintains stability
What 2 things do you need to happen when using a non locking plate?
Means 2 things - for contact to happen, screws need to be TIGHT and also need CONTACT between plate and bone - cannot generate friction or equal and opposite forced without these 2 things.
What is non locking plate contouring?
Plate - bone friction depends on CONTACT between plate and bone
Plate needs to be contoured
Use bending irons or press
- can contour the plate to the anatomical shape of the bone that you are applying the shape to
What are the 3 mechanical functions of plates
- Compression plate
- Neutralisation plate
- Bridging plate
How does a COMPRESSION plate work?
Compression plate - dynamic
Apply AXIAL compression to TRANSVERSE fracture
Aim for primary bone union - contact healing
Achieved using a DYNAMIC COMPRESSION PLATE
What is the most popular plate used?
Compression plate
What is the difference between these 2 colours of drill guide and what plate are they used with?
- Green and gold drill guide
- Green - gives central drill hole
- Gold - off centre drill hole - allows eccentric, off centre hole or screw in the plate, so as you tighten, the head of the screw will be forced to move down the metal work of the plate in the direction of the fracture and will compress the fracture
Used with a compression plate
What kind of plate can you only apply to a transverse fracture?
Can only apply compression plate to transverse fracture
How do you use a dynamic compression plate i.e. how does it work?
Dynamic Compression Plate
Oval holes
- Screw other side of fracture fixed
- screw inserted eccentrically (away from centre)
- using GOLD drill guide
- guide has ARROW showing direction / amount
- as tightened, head shifted down towards centre
- pulls bone with it -towards fracture
- thereby compresses the fracture site
What is show here in this radiograph - what plate is used for what type of fracture?
Transverse fracture - dynamic compression plate for axial compression
What is a dynamic compression palte neutral screw?
Oval holes, neutral screw
- Screw inserted centrally using green drill guide
- as tightened, screws pulls plate down onto bone
- does not move in plate hole
- does not move the bone
COMPRESSION screws placed first (maximum of 3) THEN neutralisation screws
When placing a dynamic compression plate, do you place the compression screws or the neutralisation screws first?
COMPRESSION screws palced first (maximum of 3) THEN neutralisation screws
What is the maximum number of compression screws that can be placed in a dynamic compression plate?
maximum of 3
What is a neutralisation plate used for?
Something else such as screws or K wires bring the fracture together, but they are not strong enough along to take the forces of weight bearing, so the plate neutralises remaining forces, so patient can weight bare on the bone
What is used along side a neutralisaion plate?
Neutralisation plate
- Other implants are used to reconstruct the fracture
- stabilise it against some forces
- bone takes some load
- However, implants not strong enough alone
- further implants needed
- to neutralise the remaining forces;
- implants take remaining load
Load sharing between bone and implants
What fractures should you use a neutralisation plate on?
Only use neutralisation plates on oblique or spiral fractures usually
When is a bridging plate used?
Fracture is NOT reconstructed
Bone is unable to take any load i.e. unstable to all forces
The plate must take all of the load
Bridging = spans a fracture gap
Which type of plate spans a fracture gap?
A bridging plate
What is the problem with using a bridging plate and what can you do to prevent or help this?
Potential for plate to fail mid section
Use a larger plate or auxillary fixation device e.g. intradeullary pin. need something to strengthen the bridging plate and this usually means using an additional plate or a bigger plate. Plate is weak at resisting bending so could use an IM pin to help it also.
What are some negatives associated with plate application?
Has a biological cost:
requires dissection
trauma to the none
disruption of soft tissue attachment/bloody supply
What are locking plates?
Screw head locks into plate
- implant stability = locking mechanism
- stability does not depend on bone quality
- Security of screw no longer dependent on quality of bone
If you have poor quality bone, which plate are you best to use?
Locking plates where screw head locks into plate hole rather than being dependent on holding into the bone
Does not compress plate onto bone: no periosteal vascular distubrnace and exact contouring not necessary
Does locking or non locking internal fixation NOT require accurate contouring?
Locking internal fixation does NOT require accurate countouring necessary
What are some properties of NON LOCKING plates as an internal fixation:
- Friction or no friction?
- Accurately contoured?
- How tight should screw be?
- What does the plate do?
Non-locking plate
–Friction between plate & bone
–Plate is accurately contoured
–Screw needs to be tight = close to stripping
–Plate can pull fracture into / out of alignment
What are some properties of NON LOCKING plates as an internal fixation:
- Friction or no friction?
- Accurately contoured?
- How tight should screw be?
- Any chance of stripping?
- What does the plate do?
Locking plate
- No friction between plate and bone (internal fixator)
- Plate is approximately contoured
- Screw tightness does not depend on bone thread quality
- No chance of screw/thread stripping
- Plate holds fracture in alignment / malalignment
What can cause plate failure?
Plate failure
- Plates inherently strong and prevent rotation, compression and bending
- However, will bend if exposed to cyclical loading •if trans-cortex is not intact
- Non-reconstructed fracture = bridging plate
- Plate fails generally through a screw hole
- Screw hole = weakest point / stress concentrator
Where is the weakest point on a plate?
screw whole = weakest point/stress concentrator
How can you avoid plate failure?
Having an intact trans cortex or combine with an IM pin to avoid the problem
What makes plates weak to bending?
Plates are weak against bending if cyclically loaded
What is an external skeletal fixator?
- A device that Fixes bones (the Skeleton ) using pins that are inserted into the bone
- It is External to the skin and bone
- The frame maintains bone position and consists of:
- bars
- clamps / putty / expoxy resin
What are some external skeletal fixator frame types?
Linear
Circular
Free form (putty / epoxy)
Hybrid
What kind of external skeletal fixator is this?
Linear ESF
What is a linear external skeletal fixator?
Longitudinal connecting bars
Clamps
Pins into bone
Many applications
versatile
Which type of external skeletal fixator (IA, IB, IIA, IIB, III) is the strongest and which is the weakest?
What is a type 1A external skeletal fixator?
What is a type 1B external skeletal fixator?
What is a type IIB external skeletal fixator?
What is a type IIA external skeletal fixator?
What is a type 3 external skeletal fixator?
What is a circular external skeletal fixator?
Thin wire suspended by rings
More versatile
More applications
More complex
More demanding
What is a circular external skeletal fixator useful for?
Good for complex fracture applications
What is this?
Circular external skeletal fixator
What kind of fixator is this?
Free form Epoxy Putty
Clamps and bars replaced by resin or epoxy putty
What are some pros and cons of free form epoxy putty external skeletal fixators?
Pros:
- Very adaptable
- Infinite combinations
- Bespoe frame
Cons:
- Messy
- Cannot adjust post-op
- Tricky to de-stage
Is secondary or primary bone healing faster?
Secondary bone healing is much faster than primary
Can external skeletal fixators be combined with other things?
ESF can be combined with other techniques to overcome their limitations e.g. IM pin tied in ESF
What is external skeletal fixator basic application?
ESF basic application
- Many different types of fixator available
- Pins are designed for the purpose and can have both positive and negative profile
- Two are placed at either of bone and an external connecting bar is placed
- Pins are clamped in position whilst examining the limb for length and orientation of the two joints
- Further pins are placed to strengthen the construct with two close to the fracture
- Some limited ability to alter alignment after the pins have been placed
Label the following image of a bone physis
What are some considerations of treating fractures in skeletally immature animals
Considerations
- Occur only in immature animals
- soft bone
- very rapid healing (3-4 weeks)
- Cartilage is weaker than bone so fractures first
- Physis usually shaped to ‘fit together’ –> stable following reduction (except when there is an intra-articular component)
- Physis is quite wide, and in SH types I and II, fracture line is transverse –> good contact and ability to load share when reduced
- Occur at ‘ends’ of bones rather than middle, therefore less bending forces act on fracture
- Able to use smaller, less rigid implants in most cases
What should you avoid when treating fractures in skeletally immature animals?
Avoid implants that exert compression accross the physis during other respairs
What can happens to limbs in skeletally immature animals with fractures?
Most of the growth will stop due to the original injury
Limbs may end up shorter than normal if the animal is very young e.g. 4-5 months compared to 8-9 months
Limbs may deviate during growth if damage to growth plate it asymmetrical, or one of a ‘paired’ bone set is damaged
What is the Physeal Fracture-Separations Salter-Harris classification (I-V)?
How can you treat a Salter-Harris type III or IV fracture?
Compress with lag screw
When does a Salter-Harris Type V occur?
What can it lead to?
Common or rare?
Salter-Harris Type V
- Type 5 occur when the growth plate undergoes compressive damage without separation of the physis
- This can lead to premature closure of the growth plate and angular limb deformities
- The conical shaped distal ulna growth plate is particularly prone to this injury
RARE
Which Salter-Harris Fracture types are relatively stable when reduced, with resistance to compression and moderatley good resistance to bending and rotation?
I and II
Which Salter-Harris Fracture types have an articular component and so must be treated with anatomic reduction and alignment, and rigid stabilisation?
III and IV
Which Salter-Harris Fracture type predominantly invovles the ulna and is likely to result in angular limb deformities due to prevention of synchronous paired bone growth
What are some specific considerations with regards to articular fractures?
E.g. what will animals develop and what can make this worse? What is the problem with this area for a fracture?
Specific considerations:
- animals will develop traumatic (secondary) osteoathritis
- any incongruency (step or gap) in articular surfaces will make OA worse
- articular surfaces are subject to compressive loads
When you repair the fracture, have to get perfect reduction - essential
With an articular fraction, what do you NOT want in the joint and why?
Do not want callus in the joint as will restrict amd upset joint movement
With articular fractures, do you want primary or secondary bone healing?
Must be primary bone healing - no callus
With an articular fracture, what must the repair facilitate?
Repair must facilitate early limb use or will develop joint stiffness and eventual fibrosis with poor range of motion
What is an inevitable consequence of an articular fracture?
Arthritis
What are the 3 golden rules for articular fractures and repair?
- Accurate anatomic alignment
- Rigid internal fixation - compression. So primary bone union = no callus
- As rapidly as possible; max 1-5 days
What is arthrotomy?
An arthrotomy is the creation of an opening in a joint that may be used in drainage
Approaching an articular fracture will usually require an arthrotomy
What should you do during an arthrotomy?
Need good surgical approach to ensure:
- adequate visualisation
- perfect reduction
- optimal implant placement
Protect cartilage - dab, lavage
Flush joitn throughly before closer
How can compression of articular fracture be achieved?
- Lag screw
- Dynamic compression plate
- Reduction forceps then
- position screws
- +/- locking plate
How can you use a lag screw to fix an articular fracture?
When using a lag screw to fix an articular fracture, what must you add?
Must add an anti-rotational K wire (or screw)
Small locking plate = much better stability
If perfect reconstruction/compression not possible with an articular fracture, what else can you consider?
Arthroplaty e.g. hip replacement
Arthrodesis e.g. pancapral arthrodesis
Amputation as final resort
