Orthopaedics - Fractures Flashcards
Fact about osteoporosis and how can it be assessed?
Bone STRUCTURE is MORE IMPORTANT than its composition
Assessed using DEXA scans:
• T score – based off score of a white pre-menopausal woman.
• Z score – age and gender matched score.
Range is -4.0 –> +1.0 (osteoporosis =
4 bone cells to know as part of bone remodelling?
o Osteoclasts – break down bone – big and have a ruffled border
o Osteoblasts – lay down new bone
o Osteocytes – mature osteoblasts – act as mechanoreceptors
o Osteoprogenitors.
Normal bone turnover is CONTINUOUS (5% at any one time)
Explain how the structure of osteoclasts relates to its function
Osteoclast ruffled borders contain the digestive bone enzymes
• Bisphosphonates destroy the osteoclast cytoskeleton which breaks down the ruffled border so they no longer can release digestive enzymes.
What can inhibit the constant bone remodelling?
BISPHOSPHONATE Use
Bisphosphonates inhibit the constant bone remodelling (so limit the bone reabsorption)
• BUT this can lead to a build-up of microfractures which can then spontaneously break over time and use
What can biphosphonate use lead to?
Microfactures!
o Suppressed activity can make bones MORE brittle (the exact thing bisphosphonates try to stop).
o Fractures – atypical fractures – typically sub-trochanteric
What drug can be used to inhibit osteoclast activation?
Denosumab
• OPG analogue/RANK analogue
Denosumab inhibits osteoclast activation – soluble RANKL or OPG analogue
Osteoclasts – exhibit RANK
Osteoblasts – exhibit RANKL
o OPG also acts to supress osteoclast activation.
What does Wolff’s Law describe?
Wolff’s law describes how bone can remodel according to the stresses applied to it – e.g. exercise.
o Internal structures of trabeculae undergo adaptive changes whilst secondary appositional bone growth can occur.
Why is Wolff’s Law important to consider in healing patients then?
o There is a need for exercise and a healthy diet in the younger population so that we can BUILD UP SUFFICIENT “STORES” of bone so that in old age, we have more to lose before clinical symptoms appear
Note that it is not just exercise that influences bone growth but also diet, VitD, PTH, calcitonin, etc
How many stages are there to Fracture Healing?
Stage 1: Haemotoma/Inflammation
• up to 1 week
Stage 2: Soft callous formation
• 1-4 weeks
Stage 3: Hard callus formation
• 1-4 months
Stage 4: Remodelling
• up to several years
Explain Stage 1 of Fracture Healing
Stage 1:
• Haematoma/Inflammation
• up-to 1 week
(a) Macrophages, leucocytes, IL-1-6, BMPs
(b) Granulation tissue formation
(c) Progenitor cell invasion
Explain Stage 2 of Fracture Healing
Stage 2:
• Soft callus formation
• 1-4 weeks
(a) Chondroblasts –> collagen (II)
Fibroblasts –> fibrous tissue
(b) Proteoglycans produced (prevent mineralisation)
(c) Chondrocytes release calcium + enzymes to break down proteoglycans (allows mineralisation)
Explain Stage 3 of Fracture Healing
Stage 3:
• Hard callus formation
• 1-4 months
(a) Blood vessel invasion of soft callus
(b) Chondroclasts break down calcified callus and this is replaced by osteoid (T1 collagen) from osteoblasts
(c) Osteoid calcified into WOVEN bone.
Explain Stage 4 of Fracture Healing
Stage 4
• Remodelling
• up-to several years
(a) Woven –> lamellar bone
(b) Shapes according to Wolff’s law
(c) Medullary canals form
What are some general fractures?
Spiral
• e.g. twisting arm in arm wrestle
Oblique
• e.g. due to blunt trauma
Butterfly fragment/Communitive fracture (multiple bits)
• e.g. due to blunt trauma when in car accident
Transverse
• e.g. hit something with blunt force and then withdraw
What is fractures in children called?
Greenstick fractures
