Fracture Healing

Question 1

What is a fracture?

Answer 1

Disruption in the cortical continuity of a bone

Question 2

How does direct trauma cause a fracture?

Answer 2

• The force is applied at or near to the point of fracture.
• The degree and direction of the force determine the fracture pattern
• Increased soft tissue damage as a result of impact and energy dissipation following fracture

Question 3

Name some example causes of pathological fractures

Answer 3

• Neoplasia
• Incompletely healed fracture
• Systemic disease e.g. Osteopenia, Hyperparathyroidism

Question 4

What are some characteristic features used to classify fractures?

Answer 4

• Open/closed
• Bone
• Position
• Fracture line
• Degree of displacement
• Reconstructable?

Question 5

Position of a fracture is can occur at what points?

Answer 5

• Articular
• Epiphyseal
• Growth plate
• Diaphyseal

Question 6

What are the 5 different fracture line types?

Answer 6

• Transverse
• Oblique
• Spiral
• Comminuted
• Segmental

Question 7

How is a transverse fracture classified?

Answer 7

Any fracture across the bone up to an angle of 30 degrees

Question 8

Describe the 3 classifications of an open fracture

Answer 8

• Grade I - bone ends have pierced skin and retracted
• Grade II - Fracture ends exposed
• Grade III - Major soft tissue loss and trauma

Question 9

70-80% of the blood supply to bone is provided by which vessel?

Answer 9

Medullary artery

Question 10

20-30% of the blood supply to bone is provided by which vessel?

Answer 10

Periosteal arteries

Question 11

How is the blood supply to bone different when there is a fracture?

Answer 11

• • Extraosseous arteries
• From tissues around the fracture
• Can be disturbed by fixation method

Question 12

Describe the features of primary (direct) fracture healing

Answer 12

• Gap less than 1mm
• Rigid stabilisation
• Cutting cones
• No/limited callus
• Works at a cellular level
• No intermediate cartilage stage
• Reduced and compression fractures only

Question 13

Describe the features/steps of secondary (indirect) fracture healing

Answer 13

• Haematoma
• Granulation tissue
• Connective tissue
• Fibrocartilage
• Bone formation-callus
• Callus remodelling

Question 14

Does primary or secondary fracture healing work faster?

Answer 14

Secondary

Question 15

What are the positive healing influencing factors for fracture healing?

Answer 15

• Young patient
• Healthy
• Closed fracture
• Low energy
• Single injury
• Closed reduction
• Non articular

Question 16

What are the negative healing influencing factors for fracture healing?

Answer 16

• Old patient
• Systemic/local disease
• High energy
• Open
• Multi-trauma
• Open reduction with implants
• Articular (OA/fracture disease)

Question 17

What are some complications which may lead to failure of a fracture to heal in the time or manner as expected?

Answer 17

• Infection
• Instability- unsuitable fixation
• Implant failure
• Vascular compromise

Question 18

Complications in fractures healing are nearly always due to..?

Answer 18

Poor surgical technique

Question 19

Why are young dogs (under 8 months) favourable for fracture repair?

Answer 19

Bone has a high rate of turnover

Question 20

What is external coaptation?

Answer 20

Casts

Question 21

When is it suitable to use a cast?

Answer 21

• Small/medium size, non-performance, young dogs (some cats)
• Diaphysis of long bones
• Transverse fractures
• Simple, inherently stable, closed fractures
• Distal limb (but not near joints)
• MUST be reducible to >50% bone contact in two planes (demonstrated radiographically)

Question 22

What are the advantages of using IM pins?

Answer 22

• Good at resisting bending (only force they oppose)
• In neutral axis of bone
• Often relatively inexpensive
• Should be used with other fixation devices e.g. plate

Question 23

What are the disadvantages of using IM pins?

Answer 23

• Poor at resisting rotation
• Poor at resisting shear
• Interferes with medullary blood supply
• Difficult in chondrodystrophic dogs

Question 24

What are the two techniques of IM pinning?

Answer 24

Indirect and direct

Question 25

What is cerclage wire used for?

Answer 25

Used in combination with IM pins for long oblique fractures

• Must be tight to provide compression: primary bone union
• Can slip along diaphysis

Question 26

What are the 3 uses of positional screws?

Answer 26

• To maintain relative position of two bone fragments
• To hold plate to bone
• To anchor wire or suture to bone

Question 27

What are the advantages of using lag screws?

Answer 27

• Lag screw produces static interfragmental compression

- Lag screw is the most efficient method of creating compression

Question 28

What are external skeletal fixators?

Answer 28

• Pins placed within the bone which span the fracture
• Pins are connected by a thick connecting bar
• External scaffold
• Can transverse joints to stop motion of the joint

Question 29

What are the advantages of external skeletal fixators?

Answer 29

• Negates all the fracture forces
• Rigid fixation with minimal invasion of injured area
• Allows access to open wounds during fracture repair
• Can maintain limb length, if bone defects exist, while secondary bone healing occurs
• Allows for gradually increasing loads to be applied to the healing bone
• Materials are inexpensive

Question 30

What are the disadvantages of external skeletal fixators?

Answer 30

High complication rate:
• Iatrogenic interference
• Catches on clothing/furniture
• Pin tract infections
- Can weaken/loosen over time

Question 31

What are some principle points of articular fractures?

Answer 31

• Common e.g. single humeral condylar fracture
• Require primary bone healing
• Require rigid fixation
• Early return to full function

Question 32

What are some principle points of avulsion fractures

Answer 32

• Associated with strong avulsion force at a muscle/tendon/ligament attachment to bone
• Tibial tuberosity = Quadriceps
• Lateral malleolus = Lateral Collateral Ligament
• Unique challenges of negating avulsion force