Principles of ESF Application Flashcards
When applying an ESF - What diameter should be pre-drilled?
Predrilling with a drill of diameter 0.1 mm less than the pin core diameter
What speed are pins inserted?
A slow (<140 rpm) power drill
What MUST be used during drilling?
Saline cooling
What interface is an important concept in application of an ESF?
Pin-bone interface
What is the consequence of excessive stress at the pin-bone interface?
Bone resorption; resulting in premature pin loosening
What factors does stress at the pin-bone interface depend on? (4)
Degree of load sharing between the bone and the frame
Number and size of fixation pins
Pin design
Spacing and angle of the pins in relation to the fracture site.
The stiffness of the overall construct depends on some factors. Have a look at the sentences below and select the correct ones.
A) Increasing pin number (up to four pins per bone fragment) doesn’t change the frame stiffness.
B) Increasing pin number (up to four pins per bone fragment) increases frame stiffness.
C) Pin stiffness is related to the radius to the fourth power, and thus a small increase in diameter markedly increases stiffness.
D) Pin stiffness is related to the radius to the fourth power, and thus a small increase in diameter markedly decreases stiffness.
B) Increasing pin number (up to four pins per bone fragment) increases frame stiffness.
C) Pin stiffness is related to the radius to the fourth power, and thus a small increase in diameter markedly increases stiffness.
What are “safe corridors”
They are considered longitudinal regions overlying bone that do not contain important neurovascular or musculotendinous structures.
What are “hazardous corridors”
are those containing musculotendinous units but no important neurovascular structures
How should the patient be position for ESF placement if the fracture is on the proximal femur?
Lateral
How should the patient be position for ESF placement if the fracture is on the crus?
Dorsal
How should the patient be position for ESF placement if the fracture is on the distal humerus?
Dorsal
How should the patient be position for ESF placement if the fracture is on the femur including distal femur?
Dorsal
How should the patient be position for ESF placement if the fracture is on the antebrachium?
Dorsal
How should the patient be position for ESF placement if the fracture is on the Proximal humerus?
Lateral
What are the advantages to suspending the affected limb? (4)
Avoid large muscle masses/vessels/nerves
Aids in fracture reduction and limb alignment
Facilitates limb preparation
Allows 360° access to the limb, facilitating pin placement.
When choosing pin location:
A) Soft tissue area?
B) What size incisions created through intact skin?
C) Soft tissue positioning?
A) minimal
B) Small (approx 1cm)
C) Ensure current anatomical position
When choosing pin location:
A) With open/contaminated wounds?
B) How to prevent soft tissue damage during drilling/placement?
C) Which “areas” should be used where poss?
A) NOT to be used
B) Tissue protectors
C) Safe corridors
Pins can, if required, be placed within the surgical incision, what are needed to allow wound apposition without tension?
Perpendicular incisions
If an unsafe corridor is unavoidable - what should be considered?
Small surgical approach
Accessing the bone
A) What should be used to bluntly dissect soft tissue from the tract prior to drilling?
B) What can Holding the haemostats open against the bone aid?
A) Haemostats
B) Aid correct position for drilling
Accessing the bone:
A) What is used to centre a pin within the clamp + protect soft tissue?
B) What can be used to assess bone position? (2)
A) Drill guide
B) Needle or k wire
Drilling:
A) What speed for pre drill?
B) What size drill bit?
C) What MUST be used during drilling?
A) Full speed
B) 0.1mm smaller than pin core diameter
C) Fluid irrigation
Drilling:
A) What speed are pins placed at?
B) What happens if you reverse a pin?
A) Low speed <140 rpm
B) Weakens pin-bone interface
Pin placement:
A) With respect to the fracture site, what order are they placed in?
B) Where are the first 2 pins placed to establish the limb and frame alignment and helps to stabilise the fracture reduction?
A) far- far, near-near
B) First 2 pins remote from # site
Pin placement:
A) Following on from the first 2 pins, where are the next 2 placed and what is the role of these?
Placement of the two pins nearest to the fracture then further stabilises the major fragments against rotation.
Pin placement:
A) Where in the bone?
B) How are they spread?
C) How many cortices should be engaged?
A) Central
B) Evenly
C) 2
For a correct pin positioning:
A) Three or four pins should be placed in each major fragment, absolute minimum of two pins in each fragment.
B) Place a minimum of 60% of bone diameter away from the fracture line.
C) Select pin diameter to be 50% of bone diameter.
D) Positioning of pins on alternate sides of the connecting bar results in a decrease in resistance to bending and axial compression.
A) Three or four pins should be placed in each major fragment, absolute minimum of two pins in each fragment.
How far away should a pin be placed away from # line?
50%
What is the pin diameter compared to bone?
20-30%
What does positioning pins on alternative sides of connecting bar result in?
Increase in resistance to bending + axial compression
Clamps:
A) Where are they placed compared to connecting bar?
B) How far away from skin surface and why?
A) Inside of
B) 10mm, allow for soft tissue swelling
What should be added with fractures with significant bone defects where prolonged healing is to be expected.?
Bone graft
Additional side bars can be used to link multiple frames (e.g. a second parallel bar, or “A)” applied at the same side of the fracture or “B)”, crossing the fracture site. This C) construct stiffness in the early stages of fracture healing and allows easy D) as healing progresses.
A) Articulation
B) Diagonal
C) Increases
D) Downstaging
Using IM pins with ESF:
A) What does it improve resistance to?
B) Type I fixators combined with an intramedullary pin are mechanically equivalent to..?
A) Bending
B) Type II constructs utilising equivalent numbers of transcortical pins.
IM pins with ESF:
A) What pin diameter of medullary canal diameter?
B) How to improve construct rigidity, prevent pin migration and facilitate removal?
A) 35-40%
B) Tied-in
What post op bandaging should be used after ESF; including time frame?
Entire limb first 7 days (include distal limb to reduce swelling risk).
Frame only after 7 days.
What should be used directly post op around pins/on the skin to control movement/inflamm/swelling?
Sterile gauze/allervyn
When do change bandages after ESF?
Day after surgery.
After 3-7 days (healthy tissue).
Daily (unhealthy tissue).
What aftercare is needed daily? (2) by who?
BY OWNER:
Clean surrounding skin with dilute chlorhexidine (avoid removing developing granulation tissue immediately adjacent to the pins)
Instruct owners on signs of possible complications.
How often for re-checks at vet?
Weekly
When should post operative radiographs be performed?
Adult vs young
Adult: 6-8 weeks, and a further recheck after 12-16 weeks,
Younger animals, earlier timing of recheck radiographs 3-4 weeks postoperatively may be indicated.
As # healing progresses what should be considered with the ESF?
Downstaging
What does downstaging allow?
Increase loading and stimulate osteogenesis
When is an ESF removed?
- Bone healing on xrays
- Manual palp of # site is possible after opening clamps and removing side bar
Steps to remove an ESF (6)
- Deep sedation or short general anaesthesia.
- Removal of clamps and connecting bars.
- Cut full pins close to the skin surface on one side to minimise the length of contaminated pin pulled through the bone during removal.
- Clean and disinfect pins.
- Remove pins with Jacob’s chuck.
- Allow pin holes to heal by second intention.
Following ESF removal how long to bandage for?
24-72 hr
How long to lead walk for after ESF removal?
3-4 weeks
