Musculoskeletal Growth/Injury and Repair - bone growth and fracture healing

Question 1

what si the process of bone growth?

Answer 1

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

Question 2

Long Bone Anatomy - what are its different features?

Answer 2

Diaphysis (Shaft)

Metaphysis - Flare at end of shaft

Epiphysis - On Joint side of physis

Physis Growth - Plate

Medullary canal

Femur

Multiple growth plates

Question 3

Cortical vs Cancellous bone

Answer 3

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

Question 4

what is a fracture?

Answer 4

Break in structural continuity of bone

May be a crack, break, split, crumpling, buckle

( # = shorthand sign for a fracture )

Question 5

why do bones fail?

Answer 5

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)

Question 6

what is the biology of a fracture?

Answer 6

Mechanical and structural failure of bone

Disruption of blood supply

Regenerative process - No scar and Four stages

Question 7

What do the 4 stages of fracture repair look like?

Answer 7

Question 8

when does Stage 1 inflammation begin and what is involved?

Answer 8

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

Question 9

stage 1 inflammation - how might we affect?

Answer 9

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

Question 10

what are Platelet Concentrates?

Answer 10

“Buffy coat”

Platelet-derived growth factor (PDGF)

Transforming growth factor-beta (TGF-B)

Insulin like growth factor (IGF)

vascular endothelial growth factor (VEGF)

Question 11

what is involved in Stage 2 soft callus?

Answer 11

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

Question 12

how may we affect Stage 2 soft callus?

Answer 12

Replace cartilage - DMB (demineralised bone matrix) – can put in the fracture

Jump straight to bone - Bone graft, Bone substitutes

Question 13

what is a Autogenous Cancellous Bone graft?

Answer 13

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

Question 14

picture showing osteoconduction

Answer 14

Allows cells to grow in form either end

Question 15

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)

Answer 15

Cortical

Cancellous

Fresh

Prepared

Structural

Question 16

what are the different features of allograft bone?

Answer 16

Osteoconductive

Not osteoinductive

Creeping substitution

Risk of Disease transmission

Question 17

what is involved in Stage 3 hard callus?

Answer 17

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

Question 18

what is inolved in Stage 4 bone remodeling?

Answer 18

Conversion of woven bone to lamellar bone

Medullary canal is reconstituted

Bone responds to loading characteristics Wolff’s Law

Remodels back to normal

Question 19

Fracture Biology - _________ properties of tissue and their environment are critical for the progression of ________ healing

Answer 19

Mechanical

fracture

Question 20

what is strain?

Answer 20

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

Question 21

what is Delayed Union?

Answer 21

• failure to heal in expected time

Question 22

what are reasons for delayed union?

Answer 22

• 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

Question 23

if there is delayed healing you should consider alternative management such as what?

Answer 23

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

Question 24

non union is a failure to heal and what may this be caused by and what are the symptoms

Answer 24

• 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

Question 25

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 ___________

Answer 25

four

histological

environmental

mechanical

non-unions