What are the principals of plate fixation of a radial fracture? (12)
- use appropriately sized plate
- make screws tight; retighten them after last screw is inserted
- don't put a screw in the fracture plane
- place at least 3 screws proximal and distal to the fracture plane; engaged 6 cortices
- don't leave empty screw holes, ESPECIALLY at the fracture plane
- contour the plate to the bone
- apply plate to tension side of bone (convex surface)
- avoid intra-articular implants
- don't bridge open physes with plates
- avoid radial-ulnar fixation
- use long plates
- consider cancellous bone autografts to fill defects
Why is it so important to use an appropriate sized plate for radial internal fixation?
- too small- risk for implant failure
- too large- predisposes to stress protection (need some degree of loading to stimulate bone formation; stress protection leads to non-union)
Why should you use long plates in internal fixation of radial fractures?
directs stress into the cancellous bone of the metaphysis
Why should you avoid implanting a screw in a fracture plane?
it will cause a comminution
If a plate fails, it will tend to fail at the __________; ___________ is protective against this; therefore...
screw holes; screw occupancy; don't leave empty screw holes, and definitely don't leave a screw hole at the fracture plane
Why should you avoid radial-ulnar fixation?
you eliminate the ability of the limb to supinate and pronate, and the screws will tend to loosen over time (trying to supinate/ pronate--> loosening)
What is the purpose of scalloped plates/ limited contact plates?
- less contact with the bone surface--> reduces periosteal crushing, reduces stress riser at plate holes
- if you disrupt the periosteum, you will limit its ability to form a callous, which is necessary for healing
What are methods of fixation of radial fractures? (3)
- Cranial plate fixation: buttress plate for comminution
- Double plate fixation: used to engaged limited bone stock distally (ie. a very distal fracture and not much distal bone fragment to fixate)
- Cranial radial plate/ ulnar IM pin: locking plate on radius; used in large dogs with limited proximal radial bone stock
What is the order of events when using a cranial radial plate/ ulnar IM pin to repair a proximal radial fracture? Why?
Place the IM pin first to align the ulna, then you can align the radius; if you plate the radius first and have the slightest mal-alignment, then you will not be able to place the IM pin in the ulna
Describe the pathophysiology and clinical aspects of radial fractures in toy breed dogs. (3)
- Low-energy fracture (jump down fracture)
- usually oblique fractures of distal radius and ulna w/ compromised blood flow to the distal radius
- DO NOT treat with coaptation/ sling or IM pins!!
What is the standard method of repairs radial fractures in toy breed dogs? (2)
cranial plate fixation (T-plate to engaged limited bone distally) and external fixation (minimize soft tissue trauma around the fracture site)
Describe the pathophysiology and clinical aspects of lateral humeral condyle fracture. (3)
- most common humeral fracture
- low energy fracture (jump down fracture)
- commonly salter-harris type IV (metaphysis, physis, and epiphysis involved) in large breed dogs
Why is the lateral condyle almost always affected in humeral condyle fractures, not the medial condyle?
the medial condyle is MUCH larger, so when the dog jumps down, there is a tendency of the radial head to be driven into the capitulum and shear off the lateral portion of the condyle
What are orthopedic exam findings with fracture of the lateral humeral condyle?
palpation of the elbow- lateral condyle is proximal to medial (they should be at the same level)
Describe the repair of a lateral humeral condyle fracture? (3)
- lag screw: to achieve interfragmentary compression; larger glide hole on the lateral portion and smaller hole that the screw can thread on the medial portion--> when screw engaged medial condyle, there is fracture compression
- antirotational K-wire: screw does not provide stability with regard to bending in the sagittal plane; K wires provide this stability
- intra-articular fracture repair (to avoid OA and progressive DJD): make sure articular surface of medial condyle is reduced to be parallel to semilunar notch
What is incomplete ossification of the humeral condyle?
- failure of humeral condyle to ossify, which predisposes to fracture from a jump down injury
- trabecular sclerosis decreases fracture healing
What are complications of fracture of the medial humeral condyle?
- cartilage trauma
- delay to repair
- overweight/ large dog
- no physical rehab
- ultimately, osteoarthritis