Selecting Cases for Fracture Repair Flashcards
What do you worry about with a highly comminuted articular fracture at distal MT3 and P1?
- Leg can hyperextend
- Suspensory apparatus gives away
- Palmar vessels and nerves can stretch and
- due to endothelial damage
Challenges with fracture repair to consider
- Size of the horse
- Disposition of the horse
- Expectations (going back to soundness; breeding stallion)
- Cost
What influences prognosis for a fracture?
- Size
- Location
- Open vs closed
- Complete vs incomplete
Fractures in a horse <150 kg
- 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
Criteria to repair fractures in adults
- Minimal comminution (internal fixation)
- Closed fracture
- Adequate blood supply
- Calm/sensible horse
- Suitable equipment
- Expeditious surgery
- Adequate recovery room/pool
Closed vs open fracture prognosis
- Open fracture will get infected 90% of the time
- Decreases your prognosis 50%
What are the rules of repairing comminution?
- 6 cortices proximal and distal to the fracture (go across with 3 screws)
- 180 degrees of cortices to carry weight axially
P1 fracture requirement
- Must have an intact strut of bone spanning the fetlock and pastern joints for internal fixation
- Otherwise they will crush it down
Lag screw fixation
- 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
Benefits of lag screw fixation
- Minimizes motion at the fracture line
- Anchors the pieces together
Lag screw fixation method (short)
- 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
Core diameter of 4.5 mm screw
- 3.2
Core diameter of 5.5 mm screw
- 4.0
Core diameter of 5.0 mm locking screw
- 4.3
Which screw is the strongest?
5.0 with core diameter 4.3
Locking compression plate (LCP)
- 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
Dynamic compression plate
- Screws don’t actually attach it to the plate
- They hold it by compressing it against the bone
What is “the race” of fracture repair?
- 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%
Adequate blood supply and fracture repair
- No blood no healing
- Fractures through nutrient foramen
- Loss of both palmar digital vessels = loss of the foot
Fracture recovery
- 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
Indirect bone healing
- Callus formation
- Occurs in fractures that have an unstable mechanical environment caused by motion
- This is how most bones heal
What is fracture strain?***
- 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
What can decrease fracture strain?
- In a comminuted fracture and move it the same amount, that movement will be equally distributed
Stages of fracture healing?
- Hematoma
- Granulation tissue (fibroblasts and endothelial cells)
- Connective tissue (blood vessels regress out of the fibrous stump)
- Then it will make a jump to fibrocartilage
- Fibrocartilage will be converted to cancellous bone
- Then remodeling
How much strain can a hematoma handle?
- 100%
How much strain can granulation tissue handle?
- 100%
How much strain can connective tissue handle?
20%
How much strain can fibrocartilage handle?
10%
How much strain can cancellous bone handle?
<2%
What happens if you have too much strain in a fracture?
- No healing
- Will stop at whatever point
- Often gets stuck in the progression from granulation tissue to connective tissue
- Non-union
Biological mechanisms to decrease strain
- Fragment end resorption
- Number of fracture lines decreases strain on any individual fracture line
- Sequential formation of stiffer tissues in the fracture gap
What does fragment end resorption do?
- Increases width of gap which decreases ratio of change thus decreasing strain
Which fractures are most difficult to repair?
- Displaced, comminuted fractures of the femur, humerus, proximal tibia and proximal radius
- Can heal with conservative treatment (AKA stall confinement with cross ties)
What part of the limb has best blood supply?
- Proximal
What part of the limb has the worst blood supply?
- Distal
Pelvic fractures
- 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
Proximal fractures of the femur and humerus
- Conservative management
Arthodesis on a coffin joint?
- Does not arthrodese well
P1 fracture
- Need an intact struct of bone
- Absent of that, think about an external fixator to hold it so you don’t get crush
Lateral condylar fractures
- 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
What can you have help you if you’re unable to get six cortices spanning the fracture line?
- A plate
What about a very highly comminuted fracture with significant proximity to the joint?
- 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
Ulnar fracture
- 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
