Bones, Fractures and healing Flashcards
Function of the bones
Framework for organs -Supports lungs, heart
Protective function- Ribcage-Lungs,heart Skull-brain Vertebrae- spinal cord
Mobilise
Production of blood cells
Regulation of calcium homeostasis
What are the two main categories of bones and what do they consist of?
Axial- central, skull and spine encasing central nervous system
Appendicular- role of ambulation and movement. bones of the limn
What type of growth do irregular bones grow?
By both intramembranous and endochondral ossification
What are the different parts of the long bone?
Epiphysis- rounded end of a long bone covered in articular cartilage - terminal portion
Metaphysis- Where it starts to flare out on either end
Diaphysis- Long shaft of the bone
What proportion of skeletal mass is corticial bone
~80%
Why is the femur clinically important?
Mostly likely place for elderly people to get a hip fracture
What are Osteoprogenitor Cells
Multipotent
Differentiated from mesenchymal stem cells which are pluripotent and they differentiate into osteoblasts
What is one of the main transcription factors involved in coordinating mesenchymal stem cells into osteoprogenitor cells into
RUNX2
What is RUNX2
one of the main transcription factors involved in coordinating mesenchymal stem cells into osteoprogenitor cells into
What do osteoblasts produce?
Type I collagen
ALP — initiates calcification
Calcium phosphate
Depositing calcium and phosphate crystals in the form of calcium phosphate and calcium and calcium hydroxyapatite
What is the half-life of osteocytes?
t1/2 —25 years
What is the osteocytes roles?
mechanosensory role and important in bone remodelin
How do osteoclasts do their function
Bind to the surface of variable with protein osteopontin
acidified the extracellular fluid between ruffled border between the bone
aids in breaking down the matrix and mineralised portion of bone
What is osteopontin?
Proteins that help osteoclasts to bind to variable
What is the structure of osteoclasts? Importance
Ruffled border increases surface area to secrete proteins active transport process Secretes: TRAP osteopotin Cathepsin K
What is the function of TRAP?
involved in producing reactive oxygen species that breaks down bone matrix
What is Cathepsin K ?
protease that breaks down the type one collagen bone matrix
What are the percentages of the composition of the bone matrix?
Organic ‘osteoid’ - 25%
Inorganic- 50%
Water - 25%
What is remodelling key for?
Adapting to new physical activity (Putting under new stress)
After trauma and after bone heals in re-establishing the normal architecture
What happens when osteoclastic activity predominates over osteoblastic activity
Osteoporosis- weak bones prone to fractures
How is osteoporosis caused?
osteoclastic activity predominates over osteoblastic activity
What happens when osteoblastic activity predominates over osteoclastic activity
osteopetrosis bones like marble
also known as bone marble diesease
What is disuse osteopenia
where low bone density because not using those bones ( not enough stress) because of injury
How does bone break?
Hooks law
- Strain on bone ‘elastic material’ back to its original shape
too much strain elastic limit will break bone
apply a force to one side of a bone
nearest side is going to be compressed and bone is strong in compression. heals very well in compression
tension because bone is being pulled apart-
Bone hates tension and cant heal tension
Increase in force tension increases tension
tensile stresses increase, and the bone will break
Types of bone healing? differences?
Primary- (NO CALLOUS)
Secondary - (CALLOUS FORMATION)
What environment provides primary bone healing
absolute stability and compression
What environment provides secondary bone healing
Relative stability
What is better callous bone healing or no callous?
NO CALLOUS
What is better primary or secondary bone healing
Primary
When is callous reasonable for bone healing?
Where there is no joints fractured
What strain causes primary bone healing?
Less than 2% strain
What strain causes secondary bone healing?
2%-10% strain
How is absolute stability achieved in bone healing?
Bolts and crews to keep fractured bone in place
Which is natural primary or secondary bone healing
Secondary
What strain causes no bone healing?
More than 10%
If strain is less than 2% what type of healing would it be?
Primary
If strain is 2%-10% what type of healing would it be?
Secondary
If strain is more than 10% what type of healing would it be?
No healing
What are the stages of secondary bone healing
Inflammatory/ Reactive Phase
Soft callous -Reparative Phase
Hard callous - Reparative Phase
Remodelling phase
stages of secondary bone healing- Inflammatory/ Reactive Phase
Haematoma formation and bruising
platelet aggregation
initiation of the clotting cascade
blood clot forms template for the ongoing formation of the callous
cytokines, mesenchymal stem cells to lay osteoblasts Immune cells
key transcription factors
stages of secondary bone healing- Reperative Phase
First stage - soft callous
Fibroblasts- make fibrous tissue and they produce a lot of type two collagen
et new blood vessels growing through that hematoma as well
connective tissue in them give an element of stability
Fibreblasts mature and differnetiate into chondroblasts that make cartiladge and lay down cartilage framework within this soft callus.
Stage 2- hard callous
Rigidity bone can actually go from a position of being in a high strain environment to higher than 10%
it stabilizes itself and creates the environment for bone healing
Osteoblasts come laying down type 1 colagen and mineralising bone
Remodelling stage
Cutting cone formation for osteoclasts cut through irregular woven bone
reforming this normal lamella constructs
Factors influencing healing
Fracture variables:
- Blood supply (most important)
- Complexity
- Immobilisation/Biomechanical environment
Patient variables:
- Nicotine
- Diabetes mellitus
- Diet, nutritional deficiencies, malabsorption (Ca2+ & Vit D)
- COX-2 inhibitors / NSAIDSHIV
What are the main examples of non- union?
hypertrophic
atrophic
What is hypertrophic non- union?
Prolific callous formation causes gap in diaphysis
What causes hypertrophic non- union?
Too much movement or strain
Where is the most likely place to get hypertrophic non- union? Why?
Humerus- because hard to stabilise bone and if unstable then more callous formation
What is the consequence of too much movement or strain
hypertrophic non-union
Where is the most likely place to get atrophic non- union? Why?
tibia because it has a poor blood supply
What is atrophic non-union
No callous formation but gap in diaphysis
