Bone Growth and Fracture healing Flashcards
What is the role of the medullary cavity?
> Lightens bone
Haematopoeitic centre
Contains blood vessels
What is the role of spongy bone?
Acts to absorb excessive mechanical stress/load
Bone growth?
1) Hyaline cartilage “model”
2) Primary ossification centre
3) Secondary ossification centre
4) Epiphyseal plate
5) Compact bone and spongy bone
What is the name of the shaft of a bone?
Diaphysis
What is the name of the end of the shaft of a bone?
Metaphysis
What type of bone makes up the diaphysis?
Cortical bone
What type of bone makes up the metaphysics?
Cancellous/spongy bone
What does cortical bone resist?
Bending and torsion
What does cancellous bone/spongy bone resist?
Compression
Which type of bone is more biologically active?
Cancellous bone
How is cortical bone laid down ?
Circumferentially
How is cancellous bone laid down?
Site of longitudinal growth (Physis)
What is a fracture?
> Break in structural continuity of bone
> May be a crack, break, split, crumpling, buckle
What does # indicate?
Shorthand for a fracture
Why do bones fail/fracture?
> High energy transfer in normal bones (Takes a lot)
> Repetitive stress in normal bones (Stress fracture)
> Low energy transfer in abnormal bones:
- Osteoporosis
- Osteomalacia, metastatic tumour
- Other bone disorders
How many stages are there in bone repair?
Four stages:
1) Inflammation
2) Soft callus
3) Hard callus
4) Bone remodelling
What occurs during stage 1 (Inflammation) of bone repair?
> Hematoma and fibrin clot
Platelets, PMN’s, Neutrophils, Monocytes, Macrophages
Fibroblasts
Mesenchymal & Osteoprogenitor cells
Angiogenesis
What is required for angiogenesis to occur in stage 1 on bone repair?
Low oxygen gradients, hypoxic conditions stimulate macrophage to produce angiogenic factors
What can affect stage 1 (inflammation) in bone repair leading to slowing of bone repair?
> NSAID’s
> Loss haematoma
- Open fractures
- Surgery
> Extensive tissue damage
- Poor blood supply
What can be used to affect stage 1 (inflammation) in bone repair aiding bone repair?
Inject platelet concentrates into the fracture site:
> Buffy coat”
> Platelet-derived growth factor (PDGF)
> Transforming growth factor-beta (TGF-B)
> Insulin like growth factor (IGF)
> Vascular endothelial growth factor (VEGF)
When does stage 2 (Soft callus) of bone repair begin?
When pain and swelling have subsided
When does stage 2 (Soft callus) of bone repair last until?
Lasts until bony fragments are united by cartilage or fibrous tissue
What is the gold standard in aided repair of bone in stage 2 (soft callus) of repair?
Autogenous Cancellous bone graft:
> Osteoconductive = Bone grows through it
> Osteoinductive = Stimulate bone growth
Best from the patient themselves
Options in spending up/aiding stage 2 (Soft callus) of bone repair?
> Replace cartilage
- DMB (demineralised bone matrix)
> Jump straight to bone
- Bone graft
- Bone substitutes
What is meant by an allograft?
From someone else (Or cadaver)
What are the risks we think of when using an allograft?
Risk of disease transfer = Think of prions and Mad cows disease
What type of bone formation is there in allograft bone repair?
> Osteoconductive
> Creeping substitution
What is meant by cancellous?
Cancellous = “cut up” into small pieces
What is meant by osteoconductive?
Doesn’t have the cells within it to stimulate osteoinduction (growth)
What is meant by creeping substitution?
Creeping substitution = Removal of dead bone and replaced within living
Occurs within allograft bone repair
What occurs during stage 3 (hard callus) bone repair?
> Conversion of cartilage to woven bone
> Typical long bone fracture
- Endochondral bone formation
- Membranous bone formation
What is the main role of stage 3 bone (Hard callus) repair?
Increasing bone rigidity
What is meant by primary and secondary bone healing in stage 3 (Hard callus) of bone healing?
Secondary = Normal bone healing
Surgery = Primary bone healing
What occurs in stage 4 (Remodelling) of bone healing/
> Conversion of woven bone to lamellar bone
> Medullary canal is reconstituted
> Bone responds to loading characteristics Wolff’s Law
What is critical in progression of fracture repair?
> Mechanical properties of tissue and their environment are critical for the progression of fracture healing described by Wolff’s law
> If strain is too low mechanical induction of tissue differentiation fails
> Too high and healing process does not progress to bone formation
The may delayed union occur in fractures?
> high energy injury distraction (increased osteogenic jumping!) > instability > infection > steroids > immune suppressants > smoking > warfarin > NSAID > Ciprofloxacin
What should you do when there is delayed healing in a fracture?
Consider an alternative management:
> different fixation
> dynamisation
> bone grafting
Non-union?
Failure of fracture to heal
> failure calcification fibrocartilage > instability -excessive osteoclasis > abundant callus formation > pain + tenderness > persistent fracture line sclerosis
