17 – Bone Healing and Fracture Management Strategies Flashcards
1
Q
What is strain?
A
- *CHANGE in length
- Some cells can handle strain better than others
- More pieces=lower strain at each individual fracture site
- Bigger gap=lower strain
2
Q
Examples of different tissues handling strain
A
- Granulation tissue: 100%
- Fibrous tissue: 15%
- Chondrocytes: 10%
- Osteoblasts: 2%
3
Q
What types of fractures are these?
A
- Short, simple oblique
- Comminuted (likely multiple fracture lines)
4
Q
What does the type of bone healing depend on?
A
- Size of the gap between fragments
- Amount of motion at the fracture site
5
Q
What are the types of bone healing?
A
- Secondary (indirect) healing
- Primary (direct) healing
o Contact healing
o Gap healing
6
Q
Secondary healing
A
- Indirect healing, endochondral ossification, healing by callus formation
- *healing via a sequence of tissue types that make progressively stiffer matrix
- Occurs in fractures that have some movement and/or more than a 1mm gap
7
Q
Secondary healing: ‘steps’
A
- Fracture
- Hematoma followed by fibrin clot
- Fibrous tissue formation
- Fibrocartilage formation
- Cartilage mineralization and blood vessel ingrowth
- Bone formation
- Remodelling
8
Q
What is Wolff’s law
A
- Bone remodels in response to STRESS
o It is laid down where it is needed and resorbed where it is NOT needed
9
Q
What are some growth factors influencing bone healing?
A
- Bone morphogenetic proteins (BMPs)
- Insulin-like growth factor
- Transforming growth factor beta
- Platelet-derived growth factor
- Fibroblast growth factors
- Vascular endothelial growth factors
10
Q
Primary (direct) healing
A
- Formation of bone WITHOUT intermediate tissues coming first
- *Requires close apposition of fragments, blood supply and rigid stability
11
Q
Primary healing: contact healing
A
- Requires direct contact between fragments
- Bone multicellular units (led by cutting cones) form spot welds
- Then remodelling of laminar bone occurs
12
Q
Primary healing: gap healing
A
- Gap of 1mm (or less) b/w fragments and fracture is rigidly stabilized
13
Q
Primary healing: gap healing ‘steps’
A
- Hematoma
- Connective tissue/blood vessels
- Osteoblasts lay down lamellar bone in gap
- Cutting cones go across new bone (‘spot welds’)
14
Q
Blood supply to bone
A
- Nutrient artery: medullary canal and endosteum
- Metaphyseal blood vessels
- Periosteal blood vessels
- Extraosseous blood supply of healing bone
o *comes from muscle attachments (try to NOT to disrupt them when fixing a fracture) - *some forms of fracture repair disrupt blood supply more than others
15
Q
Anatomic repair
A
- Perfect alignment and apposition of fragments is the GOAL
- Some early weight transmission may be possible through reconstructed bone, sparing the apparatus
- Usually requires generous exposure and direct manipulation of fragments
- *disrupts blood supply/early healing response to some extent
16
Q
When might you do anatomic repair/when is it appropriate?
A
- ONLY for fractures which CAN be reconstructed
- When you expect fracture to heal slowly under the best circumstances
- When callus is undesirable
17
Q
Biologic repair
A
- No big attempt to reconstruct the fractured bone
- Minimal disruption of blood supply
- Hardware bears all the forces until fracture heals
- Either closed or ‘open but do not touch’ (OBDNT) approach to fracture reduction
- Limb is pulled out to length and angular and rotational deformity are corrected
- Bone heals more rapidly, but until healing has occurred the hardware bears all forces of weightbearing
18
Q
When might you do biologic repair/when is it appropriate?
A
- Fractures with a good blood supply that you expect to heal rapidly
- Fractures you can’t reconstruct
- NOT good in situations where callus is NOT your friend
