Musc 10 - Fractures through the ages Flashcards Preview

Year 2 Collin > Musc 10 - Fractures through the ages > Flashcards

Flashcards in Musc 10 - Fractures through the ages Deck (12)
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1
Q

What is the ratio of matrix to cells in bone

A

90% matrix, 10% cells

2
Q

Which part of the osteoclast secretes enzymes which dissolves bone?

A

Ruffled border

3
Q

Explain normal bone turnover

In young healthy adult, more bone formation than resorption

A
  1. Signal arrives (e.g. bone damage, hormones, etc)
  2. Osteoclasts resorb bone
  3. Osteoblasts lay down osteoid (inorganic matrix)
  4. Osteoid mineralised by hydroxyapatite
  5. Normal bone achieved and cells return to resting state
4
Q

What are bisphosphonates and what do they do

A

Class of drugs that prevent osteoclasts from resorbing bone

Osteoclasts absorb bisphosphonates and their cell cytoskeleton is damaged (particularly ruffled border)

Used to treat osteoporosis

5
Q

How can long term use of bisphosphonates cause femoral fractures

A

Osteoclastic activity suppressed - which also suppresses osteoblastic activity. Bone remodelling hindered

6
Q

How does denosumab work

A

Mimics molecule (osteoprotegerin) that interferes with RANKL pathway - prevents osteoclast precursors from becoming osteoclasts

May also lead to stress fractures

Denosumab has only a half life of 6 months compared to 10 years for bisphosphonates

7
Q

What is the precursor OG of osteoclasts

A

Macrophages

8
Q

Name 3 functions of calcium in the blood

A

Nerve function
Muscle function
Clotting

9
Q

What are the requirements for bone healing

A
  1. Vascularity
  2. Adequate mechanical stability of fracture

Also bone requires some load

10
Q

Explain callus healing (this is the form of healing if someones in a cast)

FRACTURE IS THE SAME AS A BREAK

A

Week 1 - haematoma / inflammation. Macrophages, etc. Granulation tissue forms. Progenitor cells invade.

Week 2-3 - Soft callus. Chondroblasts and fibroblasts differentiate - form collagen (2) and fibrous tissue. Proteoglycans produced –> prevent mineralisation. Chondrocytes release Ca into ECM and degradation enzymes to break down proteoglycans - allows mineralisation

Week 4-16 - Hard callus. Soft callus invaded by blood vessels. Chondroblasts breakdown calcified callus. Replaced by osteoid (Type 1 collagen) from osteoblasts. osteoid calcifies –> woven bone

Weeks 17+ - remodelling. Woven becomes lamellar bone. Shape relative to stresses - Wolffs law. Medullary canal forms.

11
Q

Rates of remodelling are highest in?

A

Children and adults

12
Q

Describe fracture patterns

A
  1. Spiral fracture = twisting
  2. Oblique fracture = direct result of compression
  3. Butterfly fragment - from a bending force (very high energy)
  4. Transverse fracture = tension. e.g. patella, olecranon

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