ORTHO 119 Shoulder Trauma

Question 1

What is bone?

Answer 1

A specialised form of connective tissue

Question 2

What are the two types of bone?

Answer 2

Trabecullar (cancellous) and cortical (compact) bone

Question 3

Describe trabecular bone

Answer 3

Spongy bone with high turnover axially. Site of bone remodelling and mineral homeostasis

Question 4

Describe cortical bone

Answer 4

Compact bone with low turnover, found peripherally. Has trabecullar shell and has mainly mechanical and protective functions. Contain lacunae, haversian canals, osteons and canniliculi

Question 5

Describe lacunae and where are they found?

Answer 5

Concentric layers of dense connective tissue in cortical bone

Question 6

What type of collage comprises most of organic bone?

Answer 6

Type 1 from osteoblasts

Question 7

What is inorganic bone?

Answer 7

Bone with high mineral content of calcium hydroxyapetitie crystals

Question 8

What is an osteoid?

Answer 8

It is an area of newly formed unmineralised bone

Question 9

What are the 4 types of bone cells?

Answer 9

Osteoprojenitor, Osteoblasts, osteocytes and osteoclasts

Question 10

What are osteoprojenitor cells?

Answer 10

Self replicating precursor cells that differentiate into bone forming cells

Question 11

What are osteoblasts?

Answer 11

Bone forming cells that deposit osteoid and control mineralisation

Question 12

What are osteocytes?

Answer 12

Modified osteoblasts which have become surrounded by newly formed bone

Question 13

What are osteoclasts?

Answer 13

Macrophage like cells that resorb bone

Question 14

What is the role of canniliculi?

Answer 14

They permeate through the new bone and link lacunae between adjacent osteocyte processes
Act as mechanotransducting cells

Question 15

What controls bone resorption and remodelling?

Answer 15

The RANK/OPG system

Question 16

What causes increased OPG and therefore decreased bone resorption?

Answer 16

Oestrogen, IL1 and TNF alpha

Question 17

What causes increased RANK and therefore increased resorption?

Answer 17

PTH, Vit D3 and PgE2

Question 18

How does cartilage work as a shock absorber?

Answer 18

Collagen forms a meshwork holding in the proteoglycans. Proteoglycans have a high osmotic potential drawing water into the joint

Question 19

What is the dry weight of cartilage?

Answer 19

3/4 collagen and 1/4 proteoglycans

Question 20

What is the wet weight of cartilage?

Answer 20

70% water, 20% collagen, 7% PG’s, 2% cells and 1% of other proteins

Question 21

What is the major proteoglycan in cartilage?

Answer 21

Aggrecan

Question 22

What is the structure of aggrecan?

Answer 22

Protein core surrounded by covalently attached glycosaminoglycans. Contains hydroxyl and sulfate groups as well as chondroitin, keratin sulfate and hyaluronan groups

Question 23

What enables the strong binding of water to aggrecan?

Answer 23

Its negatively charged hydroxyl and sulfate groups

Question 24

What is the difference between adult and young cartilage?

Answer 24

Adult: hypocellular, aneural, avascular, extensive matrix, zonal morphology and tidemark
Young: hypercellular, little organisational matrix, no zonal morphology or tidemark

Question 25

What is the function of the tidemark?

Answer 25

Prevents cartilage from utilitsing blood supply and therefore nutrients from subchondral bone

Question 26

What are the two main classes of proteolytic enxymes involved in the degradation of cartilage?

Answer 26

ADAMTS and MMP's

Question 27

Name the 3 matrix metalloproteinases and what they degrade

Answer 27

Collagenases- triple helix collagens, gelatinases - denatured collagens and stromelysins - non-collagenous matrix proteins (not aggrecan though)

Question 28

Where is the specific activity of ADAMTs

Answer 28

Between the glutamate and alanine in aggrecans interglobular domain

Question 29

What occurs to cartilage in ageing?

Answer 29

``` Slowed cell metabolism Increased collagen and matrix protein cross linking Decreased collagen IX synthesis Changes in aggrecan Accumulation of degradation products ```

Question 30

What is arthritis?

Answer 30

Joint space narrowing can cause pain, swelling, loss of function

Question 31

What is RA due to?

Answer 31

Deposition of immune complexes in joint space, therefore influx of inflammatory cells and secretion of cytokine which degrade cartilage

Question 32

What is OA usually as a result of?

Answer 32

Increased mechanical stresses on the joint, often after injury or trauma

Question 33

What is the commonest cause of shoulder pain?

Answer 33

Rotator cuff tendonosis - often following trauma worse on arm abduction and elevation = painful arc

Question 34

What is dupytrens contracture?

Answer 34

Painless palpable fibrosis of the palmar aponeurosis with fibroblasts invading the dermis.