Selecting Cases for Fracture Repair

Question 1

What do you worry about with a highly comminuted articular fracture at distal MT3 and P1?

Answer 1

• Leg can hyperextend
• Suspensory apparatus gives away
• Palmar vessels and nerves can stretch and
• due to endothelial damage

Question 2

Challenges with fracture repair to consider

Answer 2

• Size of the horse
• Disposition of the horse
• Expectations (going back to soundness; breeding stallion)
• Cost

Question 3

What influences prognosis for a fracture?

Answer 3

• Size
• Location
• Open vs closed
• Complete vs incomplete

Question 4

Fractures in a horse <150 kg

Answer 4

• Prognosis will increase
• Treat similarly to large small animals
• Protect joints and growth plates
• Residual lameness not okay in most cases
• Fairly easy to repair

Question 5

Criteria to repair fractures in adults

Answer 5

• Minimal comminution (internal fixation)
• Closed fracture
• Adequate blood supply
• Calm/sensible horse
• Suitable equipment
• Expeditious surgery
• Adequate recovery room/pool

Question 6

Closed vs open fracture prognosis

Answer 6

• Open fracture will get infected 90% of the time

- Decreases your prognosis 50%

Question 7

What are the rules of repairing comminution?

Answer 7

• 6 cortices proximal and distal to the fracture (go across with 3 screws)
• 180 degrees of cortices to carry weight axially

Question 8

P1 fracture requirement

Answer 8

• Must have an intact strut of bone spanning the fetlock and pastern joints for internal fixation
• Otherwise they will crush it down

Question 9

Lag screw fixation

Answer 9

• Drill a hole on the side of the fracture that has the head i nit to the diameter of the OUTSIDE of the thread of the screws (e.g. 5.5 mm, 4.5mm, or 5.0 mm)
• Drill a hole on that side so the screw doesn’t engage there
• On the other side they drill to a core diameter and tap it (create the threads that it will screw into
• Slides through the first part not touching or engaging and twist the screw onto the second part to engage the threads
• As you tighten it,the head of the screw will bring the two pieces together quite nicely

Question 10

Benefits of lag screw fixation

Answer 10

• Minimizes motion at the fracture line

- Anchors the pieces together

Question 11

Lag screw fixation method (short)

Answer 11

• Drill glide hole (outside diameter of the screw, e.g. 4.5, 5.0 or 5.5)
• Drill thread hole (core diameter of the screw e.g. 3.2, 4.0, or 4.3)
• Measure
• Tap (create threads in far cortex)
• Place and tighten screw

Question 12

Core diameter of 4.5 mm screw

Answer 12

• 3.2

Question 13

Core diameter of 5.5 mm screw

Answer 13

• 4.0

Question 14

Core diameter of 5.0 mm locking screw

Answer 14

• 4.3

Question 15

Which screw is the strongest?

Answer 15

5.0 with core diameter 4.3

Question 16

Locking compression plate (LCP)

Answer 16

• These plates are used a lot now
• Tighten it down, the bottom of the screw will engage the bone, and the head of the screw will engage the plate
• Plate is almost like an external fixature (rigid structure that holds itself together and holds the fracture together)
• The plates

Question 17

Dynamic compression plate

Answer 17

• Screws don’t actually attach it to the plate

- They hold it by compressing it against the bone

Question 18

What is “the race” of fracture repair?

Answer 18

• Open fractures (communication of fracture with skin) have increased risk of infection
• Decreased rate of healing
• Increased risk of implant failure
• Majority of horses with open fractures will have implant infection
• Decreases prognosis by at least 50%

Question 19

Adequate blood supply and fracture repair

Answer 19

• No blood no healing
• Fractures through nutrient foramen
• Loss of both palmar digital vessels = loss of the foot

Question 20

Fracture recovery

Answer 20

• Need to have a place to recover the animal
• If they slam their legs down
• Recover long-bone fractures with a pool
• GO in a sling, lower the floor
• Float in the pool until they are awake enough
• Allow the floor to come up until they can get on their feet
• Then they lift them up

Question 21

Indirect bone healing

Answer 21

• Callus formation
• Occurs in fractures that have an unstable mechanical environment caused by motion
• This is how most bones heal

Question 22

What is fracture strain?***

Answer 22

• Ratio of the change in gap width to the total width of the gap
• Motion at fracture site causes change in the width of the gap between fragments
• Particular tissues will not proliferate under strain conditions that exceed the tissues limits of deformation

Question 23

What can decrease fracture strain?

Answer 23

• In a comminuted fracture and move it the same amount, that movement will be equally distributed

Question 24

Stages of fracture healing?

Answer 24

1. Hematoma
2. Granulation tissue (fibroblasts and endothelial cells)
3. Connective tissue (blood vessels regress out of the fibrous stump)
4. Then it will make a jump to fibrocartilage
5. Fibrocartilage will be converted to cancellous bone
6. Then remodeling

Question 25

How much strain can a hematoma handle?

Answer 25

- 100%

Question 26

How much strain can granulation tissue handle?

Answer 26

- 100%

Question 27

How much strain can connective tissue handle?

Answer 27

20%

Question 28

How much strain can fibrocartilage handle?

Answer 28

10%

Question 29

How much strain can cancellous bone handle?

Answer 29

<2%

Question 30

What happens if you have too much strain in a fracture?

Answer 30

- No healing - Will stop at whatever point - Often gets stuck in the progression from granulation tissue to connective tissue - Non-union

Question 31

Biological mechanisms to decrease strain

Answer 31

- Fragment end resorption - Number of fracture lines decreases strain on any individual fracture line - Sequential formation of stiffer tissues in the fracture gap

Question 32

What does fragment end resorption do?

Answer 32

- Increases width of gap which decreases ratio of change thus decreasing strain

Question 33

Which fractures are most difficult to repair?

Answer 33

- Displaced, comminuted fractures of the femur, humerus, proximal tibia and proximal radius - Can heal with conservative treatment (AKA stall confinement with cross ties)

Question 34

What part of the limb has best blood supply?

Answer 34

- Proximal

Question 35

What part of the limb has the worst blood supply?

Answer 35

- Distal

Question 36

Pelvic fractures

Answer 36

- Can do well - Limiting factor is acetabulum - If not involving the acetabulum, they may be lame for 4-6 months and heal on their own - If they do involve the acetabulum, may not be worth putting the horse through that

Question 37

Proximal fractures of the femur and humerus

Answer 37

- Conservative management

Question 38

Arthodesis on a coffin joint?

Answer 38

- Does not arthrodese well

Question 39

P1 fracture

Answer 39

- Need an intact struct of bone | - Absent of that, think about an external fixator to hold it so you don't get crush

Question 40

Lateral condylar fractures

Answer 40

- Quite common - Break out through lateral cortex 3-5 in up the leg - Not often catastrophic - Need to repair quickly so you avoid arthritis - If minimally displaced, pretty good chance of healing

Question 41

What can you have help you if you're unable to get six cortices spanning the fracture line?

Answer 41

- A plate

Question 42

What about a very highly comminuted fracture with significant proximity to the joint?

Answer 42

- Cannot get enough screws in on the proximal bit to hold it together - He would try and put the pieces back together and do a trans-articular pin - Put pins above the joint and below it and rely on external fixator

Question 43

Ulnar fracture

Answer 43

- Non-weight bearing - Just re-establish tension band and re-engage the tricep - Elbow drops so they can't lock the carpus in place - Curve the plate around to engage the top part of the bone