Locomotor - Diaphyseal Bone Fracture Healing Flashcards Preview

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Flashcards in Locomotor - Diaphyseal Bone Fracture Healing Deck (14)
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1
Q

Describe the forces acting on a fractured diaphyseal bone (the middle of the bone, the shaft of a long bone, for example).

A

Since bones are curved generally & not straight, they bend to resist normal weight-bearing and pulling-action from muscles. Bending thus generates the greatest force on curved bones, causing them to break more easily at the diaphyseal site than pulling.

Compression & Tension - caused by bending loads from weight-bearing

Shear - ie., displacement of fracture perpendicular to long axis of bone; caused by bending loads from weight bearing and asymmetrical twisting loads from muscles pulling on bone

Torsion - Twisting forces from muscular contraction

2
Q

Say you have a diaphyseal fracture ie., a fracture in the middle of a long bone. What is an example of:

External Coaptation / Coaption

What are the basic rules of application?

A

Bandages & casts

Basic rules of application:

  • only works if there is still some partial stability in bone
  • should be minimally displaced fractures in thick periosteum
  • minimal malalignment
  • for fractures of radius where ulna still intact
  • for fractures of tibia where fibula still intact
  • for fractures of metacarpals or metatarsals
    where some still intact
  • animal is skeletally immature so fast-healing
    potential high
3
Q

What are the advantages and disadvantes of using external coaption ie., bandages and casts?

A

Advantages:

  • no open surgery - cheap
  • easy to apply

Disadvantages:

  • gives little control/stability to fracture
  • can result in further severe malalignment
  • cannot apply to fractures proximal to elbow or stifle
  • cast-associated injuries in 60% of cases; expensive to fix these
4
Q

What are the two main techniques used in internal fixation of a diaphyseal fracture?

A
  1. Plates & Screws
  2. Interlocking Nail
5
Q

How do plates and screws work? What are the basic rules of application?

A

How it works:

Plate held flush against bone, held in place by screws driven in perpendicularly through width of bone

Basic rules of application:
Can be used to achieve primary or secondary union:

  • compression (primary/direct)
  • neutralisation (secondary/indirect) - fracture is re-constructed so plates & screws protect the reconstruction, allowing for callus formation
  • buttress (secondary) - transfers all the weight to the buttress (plate) to allow for callus formation
6
Q

What are the advantages and disadvantages of using the plates and screws method of internal fixation of a diaphyseal fracture?

A

Advantages:

  • can achieve perfect reduction
  • no bulky external element (“hidden inside animal”)
  • big range of implants avail.
  • minimally invasive

Disadvantages:

  • large equipment range required
  • large skill base required
  • normally needs open surgery
7
Q

How is the Interlocking Nail technique of internal fixation used in diaphyseal fracture healing?

A

Medullary nail is driven through centre of bone along axis and held in place (“interlocked”) by perpendicularly inserted screws that span width of bone.

8
Q

What are the advantages of the Interlocking Nail and what are the disadvantages of the procedure?

A

Advantages:

  • can be used semi-closed
  • very strong when used in simple & comminuted fractures, esp. resisting bending

Disadvantages:

  • limited skill base (not used in UK)
  • implants must match bone
  • only tibia & femur
  • requires specialist equipment
9
Q

What type of equipment can augment plates and screws and other fixations?

A

Orthopaedic wire aka cerclage wire - Strong piece of wire only used in completely reconstructable fractures; paired wires twisted outside of bone to stabilise long oblique fractures. Must be very tight.

K-wire aka Kirschner wire - Stainless steel pins driven into bone percutaneously for pin fixation. Not “screws” so do not pull distal bone toward proximal for compression.

10
Q

What is an Intramedullary Pin?

A

Same as the medullary pin of the Interlocking Nail technique but isn’t locked into position; smooth pin driven through medullary cavity & exits cortex at one end

** should always be combined with another fixation method eg., ESF, cerclage wire, plate.

Advantages:

  • can place in humerus, ulna, femur & tibia
  • partial resistance to major loading forces such as bending (shear)

Disadvantages:

  • cannot place in radius
  • does not resist compression or rotation
11
Q

What is a type of External Fixation?

A

External Skeletal Fixation (ESF)

12
Q

What is the External Skeleton Fixation? How does it work?

A

Three parts:

1) Pins drive into skin to penetrate bone
2) Clamps connect pins & connecting bar
3) Connecting bar (ext. frame)
- semi-rigid, allowing small movement that’s stimulatory for callus formation
- usually used for secondary union, callus formation
- can be used in neutralisation mode, taking on some torsional & shearing force from fracture eg, in comminuted, reconstructable tibial fracture where tibia is shattered into large fragments

13
Q

What are the advantages and disadvantages of using the External Skeletal Fixator for fixing a diaphyseal fracture?

A

Advantages:

  • quick & easy to apply
  • relatively cheap - don’t need a lot of equipment
  • can do it closed, without surgery
  • similar technique can be used with a wide variety of patients

Disadvantages:

  • pins can loosen (pin-tract infection)
  • difficult to apply compression
  • cannot achieve perfect reduction
14
Q

What is a lag screw and when is it used?

A

Squeezes two bone fragments together for direct union, placed at right-angle to fracture line. Does create compression as it screws distal end to proximal (unlike a pin).

Can augment plates & screws & other fixations but it will not resist loading forces.

Shouldn’t be used alone.

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