Bone Growth and Fracture Healing Flashcards
What are the differences between Cortical and Cancellous bone?
Cortical
- Diaphysis
- Resists - bending and torsion.
- laid down circumferentially
- less biologically active.
Cancellous
- metaphysis
- Resists and absorbs - compression
- Site of longitudinal growth (physis)
- very biologically active
What is a fracture?
Break in structural continuity of bone. May be a crack, break, split, crumpling or buckle.
What is the biology of a fracture?
Mechanical and structural failure of bone.
Disruption of blood supply.
Regenerative 4 stage process with no scarring.
What is stage 1 of fracture healing?
Inflammation
Begins immediately after fracture. Haematoma and fibrin clot are formed. Platelets, PMNs (polymorphonuclear neutrophils), Neurtrophils, monocytes and macrophages are all involved. By products of cell death are also broken down by lysosomal enzymes.
Fibroblasts are then signalled as well as mesenchymal and osteoprogenitor cells. Angiogenesis occurs, requiring a low oxygen gradient and macrophages aid this by producing angiogenic factors under hypoxic conditions.
What are Mesenchymal and osteoprogenitor cells?
Transformed endothelial cells from medullary canal of bone and/or periosteum. Osteogenitor cells then induce cells from muscle and soft tissues.
What is stage 2 of fracture healing?
Soft callus
Begins when pain and swelling subside.
Lasts until bony fragments are united by cartilage or fibrous tissue. Provides some stability to the fracture. Continued increase in vasculature.
What is an autogenous cancellous bone graft?
Utilises bone obtained from the same individual receiving the graft. It is osteoconductive and osteoinductive.
Gold standard treatment.
What is meant when it is said a graft is osteoconductive?
The bone graft material serves as a scaffold for new bone growth that is perpetuated by the native bone.
What is meant when it is said a bone graft is osteoinductive?
Involves the stimulation of osteoprogenitor cells to differentiate into osteoblasts that then begin new bone formation.
What is allograft bone?
Bone derived from humans but not from the individual receiving the graft. Can be taken from cadavers or live donors.
What is stage 3 of fracture healing?
Hard callus
Conversion of cartilage to woven bone.
Typical long bone fracture - endochondral and
membranous bone formation.
Increases rigidity.
What is stage 4 of fracture healing?
Bone remodelling
Conversion of woven bone to lamellar bone. Medullary canal is reconstituted. Bone responds to loading characteristics.
What is Wolff’s law?
Bone in a healthy person or animal will adapt to the loads under which it is placed.
How does strain affect fracture healing?
If strain is too low then mechanical induction of tissue differentiation fails.
If strain is too high then healing process does not progress to bone formation.
What is delayed union?
Failure to heal in expected time.
What are some causes of delayed union?
High energy injury Instability Infection Steroids Immune suppressants Smoking Warfarin NSAID Ciprofloxacin Distraction - increased osteogenic jumping.
What is non union?
Failure to heal
What are some causes of non union?
Failure to calcify fibrocartilage Instability - excessive osteoclasis Abundant callus formation Pain + tenderness Persistant fracture line Sclerosis
What are some management option for delayed healing?
Different fixation
Dynamisation - promotes bone healing through movements and some compressive loading.
Bone grafting
What is the Gustilo classification of open fractures?
Type 1 - Wound <1cm, clean, simple fracture pattern.
Type 2- Wound >1cm, moderate soft tissue damage, adequate skin coverage, simple fracture pattern.
Type 3 - Extensive soft tissue damage, complex fracture pattern.
3A- adequate periosteal coverage.
3B - tissue loss requiring soft tissue coverage procedure.
3C - vascular injury requiring repair.
What is the management of fractures?
Full MDT assessment
Tetanus and antibiotic prophylaxis.
Cefuroxime/Augmentin/Clindamycin at time of fixation.
Repeated examination of neuromuscular status.
No provisional irrigation/exploration
Radiographs of joint and above and below.
What are the indications for emergency fracture surgery?
Polytraumatised patient Marine or farmyard environment Gross contamination Neurovascular compromise Compartment syndrome.
What criterion must be met before amputation?
Dual consultant decision Insensate limb/foot Irretrievable soft tissue or bony damage Other life threatening injuries Guillotine type and refashion at later stage.
