Musculoskeletal Growth/Injury and Repair - bone growth and fracture healing Flashcards
what si the process of bone growth?
Long bones
Secondary ossification centre at each end
Epiphyseal plate at each end of the long bone to allow it to grow over time and closes at end of growth at skeletal maturity
Long Bone Anatomy - what are its different features?
Diaphysis (Shaft)
Metaphysis - Flare at end of shaft
Epiphysis - On Joint side of physis
Physis Growth - Plate
Medullary canal
Femur
Multiple growth plates
Cortical vs Cancellous bone
Cortical:
- Diaphysis
- Resists - Bending and Torsion
- Laid down circumferentially
- Less biologically active
Cancellous:
- Metaphysis
- Resists/absorbs - compression
- Site of longitudinal growth (physis)
- Very biologically active
Cancellous is spongy and designed to take load, in-between layers of compact bone on the outsid
what is a fracture?
Break in structural continuity of bone
May be a crack, break, split, crumpling, buckle
( # = shorthand sign for a fracture )
why do bones fail?
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
(osteomalacia - a disease characterized by the softening of the bones caused by impaired bone metabolism primarily due to inadequate levels of available phosphate, calcium, and vitamin D, or because of resorption of calcium. The impairment of bone metabolism causes inadequate bone mineralization)
what is the biology of a fracture?
Mechanical and structural failure of bone
Disruption of blood supply
Regenerative process - No scar and Four stages
What do the 4 stages of fracture repair look like?
when does Stage 1 inflammation begin and what is involved?
Begins immediately after fracture
Hematoma and fibrin clot
Platelets, PMN’s, Neutrophils, Monocytes, Macrophages (all released)
By products of cell death – lysosomal enzymes
Fibroblasts
Mesenchymal & Osteoprogenitor cells - Transformed endothelial cells from medullary canal and/or periosteum, Osteogenic induction of cells from muscle and soft tissues
Angiogenesis - Oxygen gradient required (low), Macrophages – produce angiogenic factors under hypoxic conditions
stage 1 inflammation - how might we affect?
NSAID’s – reduced inflammation and may slow repair
Loss haematoma – reduce biological driver to bring in repair cells - Open fractures and Surgery
Extensive tissue damage - Poor blood supply
what are Platelet Concentrates?
“Buffy coat”
Platelet-derived growth factor (PDGF)
Transforming growth factor-beta (TGF-B)
Insulin like growth factor (IGF)
vascular endothelial growth factor (VEGF)
what is involved in Stage 2 soft callus?
Begins when pain and swelling subside
Lasts until bony fragments are united by cartilage or fibrous tissue
Some stability of fracture
Angulation can still occur
Continued increase in vascularity
how may we affect Stage 2 soft callus?
Replace cartilage - DMB (demineralised bone matrix) – can put in the fracture
Jump straight to bone - Bone graft, Bone substitutes
what is a Autogenous Cancellous Bone graft?
Gold standard
Osteoconductive - allows cells to grow through it to create bone
Osteoinductive - contains many factors to stimulate bone formation and has a high concentration of cells which will create bone
Best choice for the majority of bone graft needs
picture showing osteoconduction
Allows cells to grow in form either end
what are the different types of allograft bone?
(Allograft bone transplant involves bone that has no living cells so that the risk of rejection is minimal as opposed to organ transplants, in which living cells are present)
Cortical
Cancellous
Fresh
Prepared
Structural
what are the different features of allograft bone?
Osteoconductive
Not osteoinductive
Creeping substitution
Risk of Disease transmission
what is involved in Stage 3 hard callus?
Conversion of cartilage to woven bone (not really any structure, Can respond to load from any direction)
Typical long bone fracture - Endochondral bone formation, Membranous bone formation
Increasing rigidity - “Secondary” bone healing, Obvious callus
what is inolved in Stage 4 bone remodeling?
Conversion of woven bone to lamellar bone
Medullary canal is reconstituted
Bone responds to loading characteristics Wolff’s Law
Remodels back to normal
Fracture Biology - _________ properties of tissue and their environment are critical for the progression of ________ healing
Mechanical
fracture
what is strain?
Degree of instability is best expressed as magnitude of strain (% change of initital dimension)
If strain is too low mechanical induction of tissue differentiation fails
Too high and healing process does not progress to bone formation
what is Delayed Union?
• failure to heal in expected time
what are reasons for delayed union?
• high energy injury
• distraction – fracture ends not close together
(increased osteogenic jumping!)
- instability – to much movement
- infection
- steroids – immunosuppressant supress the bone formation
- immune suppressants
- smoking
- warfarin
- NSAID
- Ciprofloxacin
if there is delayed healing you should consider alternative management such as what?
different fixation - change way fracture if fixed
dynamisation - make the fracture ends closer together or make them move slightly more
bone grafting - add a bone graft
non union is a failure to heal and what may this be caused by and what are the symptoms
- failure calcification fibrocartilage
- instability - excessive osteoclasis - Instability means too much movement so fibrocartilage is kept and any bone formed is taken away by osteoclasis almost immediately
- abundant callus formation
- pain + tenderness
- persistent fracture line
- sclerosis
Summary:
Logical progression of ____ stages
Based on _________ and ___________ factors
Changes in chemical, cellular, or __________ properties affect process
Knowledge of the process gives insight into optimum treatment of fractures and ___________
four
histological
environmental
mechanical
non-unions
