Bone Healing/Fx Decision Making Flashcards
4 fundamental questions of fx decision making
- Is it anatomically reconstructible or not?
- Where is the fx?
- What are the fx biomechanics? (How strong does it need to be to heal?)
- What is the fx biology? (How long will it take to heal?)
anatomically reconstructible achieves
absolute stability w/ no fx gap and interfragmentary compression
> 3 pieces =
not anatomically reconstructible
load sharing is achieved if…
a fx is anatomically reconstructible (2 (maybe 3) piece fx)
stability of a fx = 5 key considerations
- Type of fx
- Whether anatomically reconstructed
- Method of repair
- Single or multi-limb injury
- Patient size + activity levels
list the biological factors of fx assessment
- Age of animal
- Blood supply
- Location of fx/type of bone
- Infection
- Concurrent disease/injuryes
how does bone type influence fx healing?
Metaphyseal fxs heal faster than diaphyseal dt higher cancellous to cortical bone ratio
- pelvis and scapula also have high cancellous bone = heal faster
4 stages of indirect bone healing
- Inflammation - fx haematoma + GFs
- Soft callus –> fibroblasts form fibrous tissue
- Hard callus –> cartilage tissue undergoes endochondral ossification
- Remodelling: via osteoclasts + osteons (Haversian remodelling) - months to years
when does indirect bone healing occur
if >2% strain
3 requirements of direct bone healing
- Perfect anatomic reduction (gap <1mm)
- Absolute stability (<2% strain)
- Good blood supply
describe process of direct bone healing
bone healing proceeds directly to the harversian remodelling stage where bone formation by osteons across fx line
a simple, uncomplicated fx in a young animal – you would expect to see a mineralised callus in how many wks?
as fast as 2-3wks post op
radiographic findings of an xs large callus w/ no bridging mineralisation indicates
viable non-union
rad finding /w absence of callus in fx where indirect healing expected indicates
non-viable non-union
which stage of indirect bone healing is radiographically apparent?
the hard callus
the size of the callus (given a good blood supply exists) is proportional to…
the degree of instability
no radiographic callus is expected in what type of healing?
direct
direct healing usually results in absence of fx lines on rads in how many weeks?
8-12wks
why may fracture lines appear larger 2-3wks post op in direct healing?
dt some bone resorption – widening the gap to reduce strain (as small gaps magnify strain)
how does strain act on comminuted fxs?
comminuted fxs dissipate strain –> callus/indirect healing
what type of bone is used in bone grafts?
cancellous –> highly trabecular/spongey bone
why are autogenous bone grafts used?
histocomptability/ no problem with rejection or inflammation of the graft is cancellous bone is translocated w/in the body from the same individual
what do bone grafts provide?
1 Osteogenesis: viable translocated bone cells produce new bone
- Osteoinduction: GFs induce surrounding pluri-potent cells to transform into fibroblasts + osteoblasts to produce new bone
- Osteoconduction: encourages revascularisation via provides trellis/framework for new blood vessels to bridge gap
Do cancellous bone grafts provide structural support?
no
