treatment options for small animal fractures

Question 1

what are the common options for fracture repair?

Answer 1

Intramedullary pin and cerclage wire
Plating ( +/- compression)
Intramedullary nail
External fixator
Pin and tension band
Various combinations of these including a pin and plate (plate rod combination) and an IM pin with tied in external fixator

Question 2

What is the function of an intramedullary pin?

Answer 2

good at counteracting bending forces as it is in center of bone
poor at axial compression unless bone column is reinstated
Increasing pin diamater => disproportional increase in strenght
rotation can occur if fracture is transverse (plate used in addition to prevent)

Question 3

What is the function of cerclage wires?

Answer 3

draw fragments to their normal position and fix them to produce stability

Question 4

describe the normograde placement of an intramedullary pin

Answer 4

placed from proximal end of proximal fragment and pushed into distal fragment

Question 5

describe the retrograde placement of an intramedullary pin

Answer 5

pin enters proximal fragment distally (from fracture site)
leaves proximal bone fragment and exits skin
Pin then redirected and driven into distal fragment

Question 6

What is the function of an external fixator in a transverse fracture?

Answer 6

prevent rotation and collapse due to axial compression

Question 7

What is the function of intramedullary interlocking nails

Answer 7

prevents rotation and bending
can only be used in straight bones (e.g., tibia and femur)
not used commonly

Question 8

Describe the function of an external fixator

Answer 8

series of pins into bone through skin and connected to a connecting bar via clamps or epoxyresin
Versatile repair
counteracts all forces (particularly if combined with IM pin)
good for open fractures where open wound management may be required

Question 9

What are the complications of external fixators

Answer 9

prone to infection
discharge
frequent examinations and re-application of loose pins
may need staging down to change the load bearing from fixator to bone
several follow up radiographs needed

Question 10

describe plate fixation

Answer 10

allow reconstruction of comminuted (multi-fragmented fractures
protect against axial and rotational forces (less good at bending as not positioned along central axis)
can be locking or non-locking

Question 11

Describe non-locking plates

Answer 11

require plate to be adhered to screws by friction (also applied to plate and bone)

Question 12

Describe locking plates

Answer 12

thread in plate where screw engages as well as in the bone

Question 13

What are the types of plate structures?

Answer 13

buttress
neutralisation
compression

Question 14

What is the function of a buttress plate?

Answer 14

strong central section that bridges a comminuted section of the fracture. In this arrangement the plate takes all the load

Question 15

what is the function of a neutralisation plate

Answer 15

allows reconstruction of the fracture and acts as a scaffold, taking some of the load, the rest being taken by the reconstructed bone

Question 16

what is the function of a compression plate

Answer 16

compresses the fracture by making use of eccentrically placed screws in an oval screw hole. The screw starts its flight at the top of the slope and when tightened it moves down the slope and shifts the one fragment towards the fracture hence compressing it. When used this way the bone takes all of the load.

Question 17

What causes plates to fail?

Answer 17

cyclical (repetitive) loading

Question 18

How can plate failure be prevented?

Answer 18

an IM pin (rod plate combination) manages the bending of plates

Question 19

Describe avulsion/tension fractures

Answer 19

Caused by distractive forces generated internally

Question 20

How can avulsion/tension fractures be repaired?

Answer 20

leg screws or tension bands

Question 21

Describe lag screws

Answer 21

Near hole is drilled to have same diameter as the thread so it doesn’t grip
The screw is tightened => pulling far fragment towards near causing compression

Question 22

Describe tension band

Answer 22

Fracture is reduced
A figure of 8 wire is applied in the opposite direction to distractive force
This provides a compressive force

Question 23

What factors need to be considered when dealing with avian fractures

Answer 23

pneumatised (air filled) bones with periosteal blood supply
avian bone is brittle
heals primarily from endosteum
healing is rapid
anatomical abnormalities due to flight adaptation
primary wing feathers originate in periosteum of ulna and tail feathers in the pygostyle
fractures in joint of within 10mm of joints carry a poor prognosis
IM pins and external fixators used over plates due to brittleness