Osteo- articular Pathology

Question 1

Name 3 osteo articular developmental disorders?

Answer 1

osteogenesis imperfecta, achondroplasia, osteopetrosis

Question 2

Name 5 osteo articular systemic disorders?

Answer 2

osteomyelitis, osteoporosis, osteomalacia / rickets, pagets, skeletal effects of hyperparathyroidism

Question 3

Name 3 osteo articular neoplastic diseases?

Answer 3

Bone forming tumours, cartilage tumours, fibrous tumours

Question 4

Name 2 osteo arthritis joint diseases?

Answer 4

osteoarthritis, rheumatoid arthritis

Question 5

Describe the structure of bone?

Answer 5

Bone is made of :
outer dense cortex (compact lamella bone)
inner medulla (sponge like tissue of trabecula/cancellous bone) - weight bearing and hosts marrow

Question 6

What is in bone marrow?

Answer 6

adipose tissue

Amaemopoetic tissue

Question 7

How is bone made?

Answer 7

Mesenchymal cells - cartilage - bone

Question 8

What are the two types of bone ossification?

Answer 8

Intra-membranous and Endochondral

Question 9

Which bones are made via intra-membranous ossification?

Answer 9

Makes up the flat bones of the skull, part of mandible, maxilla and clavicles
For development and repair

Question 10

Describe the process of intra-membranous ossification?

Answer 10

1) Mesenchymal cells are centrally located and differentiate into osteoblasts, forming an ossification centre
2) Osteoblasts secrete osteoid (withing fibrous membrane) which is mineralised in a few days
3) Trapped osteoblasts become osteocytes
4) Vascularised mesenchyme condenses and become periostium - osteoid laid down between embryonic blood vessels - network of trabecules
5) Trabecular thicken and form woven bone
6) Spongey bone internal and vascular tissue becomes marrow

Question 11

What bones are made using endochondral ossification?

Answer 11

Long tubular bones

Lengthening

Question 12

Describe the process of endochondral ossification?

Answer 12

1) Bone collar around hyaline cartilage
2) Cavitation of hyaline
3) Invasion of internal cavities by periosteal bud
4) Medullary cavity forms, appearance of secondary ossification centres in epiphyses
5) Ossification of epiphyses - hyaline cartilage in epiphyseal plates
(In the growth plate, as the cells hypertrophy they become calcified and turn to bone. Failure to calcify leads to failure of bone growth)

Question 13

What is achondroplasia?

Answer 13

A developmental disorder of osteo-articular pathology
Endochondral affected, not intramembranous -
Restriction of growth in the length of long bones
Point mutation in R of FGF3 - active which inhibits growth
Normally the growth plate in well ordered columns of chondrocytes which enlarge as they approach the end of bone that is growing, then calcify and ossify
In achondroplasia, the chondrocyte columns are disrupted and dont calcify and ossify
75% sporadic, 25% genetic

Question 14

How does someone with achondroplasia present?

Answer 14

Short limb, normal trunk length, contracted base of skull

Question 15

What is osteogenesis imperfecta (OI)?

Answer 15

A developmental disorder of osteo-articular pathology
Abnormality in the synthesis of type 1 collagen
Bones are thin and lack cortex of compact bone
Numerous point mutations in the collagen 1 genes - most caused by COL1A1 and COL1A2 genes
Can be mild, mod (onset early osteoporosis)or severe (lethal perinatally, if survive then extreme fragility)

Question 16

How does someone with osteogenesis imperfecta present?

Answer 16

Sclera of eye is blue
Dentinogenesis imperfecta seen in OI type 3 and 4
Loose joints, poor muscle tone, early hearing loss, eyes protrude

Question 17

What is osteoporosis?

Answer 17

An osteo articular systemic disorder
Rare inherited disorder
Defect in osteoclasts to break down bone
Bone gets dense and marrow cavity disappears so they have compromised haemopoiesis

Question 18

What is osteoporosis?

Answer 18

An osteo articular systemic disorder
Very common F>M
Loss of bone mass because of disuse, diet, drugs or endocrine so bones get weak
Bone has thinner trabeculae
Three main sites for fracture - vertebra, femur, forarm

Question 19

What is osteomalacia /rickets?

Answer 19

An osteo articular systemic disorder.
Metabolic bone disease cause by inadequate mineralisation of existing organic bone matrix - lack of activated vitamin D
In growing bones = rickets. Mechanical weakness in long lower bones and so they deform under weight
In mature bones = osteomalacia. Occurs at sites of active turnover

Question 20

What are the causes of osteomalacia / rickets?

Answer 20

Intrinsic Vit D disturbance
Kidney disease
Inborn error

Question 21

What is the pathway of Vit D in the body?

Answer 21

Vit D - liver (1st hydorxylation) - kidney (2nd hydroxylation) - promote calcium resorption from gut and kidney
Therefore any disease of kidney or liver causes a problem

Question 22

What is osteoarthritis?

Answer 22

An osteo arthritis joint disease
Disorder of the synovial joints characterised by cartilage degeneration with secondary changes in adjacent bone
Pain, stiffness, imobility

Question 23

What is Hyperparathyroidism?

Answer 23

An osteo articular systemic disorder
Causes osteitis fibrosa cystica or Recklinghausens disease
Overactivity of parathyroid gland - excess of TH that regulates calcium and phosphate ions
Primary = hyperfunction of parathyroid glands
Secondary = response to hypocaloemia (Vit D deficiency and chronic renal failure)
Bone pain, high calcium levels in plasma

Question 24

What is the normal process when low calcium?

Answer 24

Low calcium - more PTH - more calcium released - low PTH

Question 25

What happens when there is low calcium with a hyperfunctioning parathyroid?

Answer 25

Low calcium - more PTH - more calcium released - more PTH - more calcium etc so increased bone resorption

Question 26

What is Pagets?

Answer 26

An osteo articular systemic disorder
Excessive breakdown and formation of bone, followed by disorganised bone remodelling (llamellae not in same direction)
Associated with previous infection
Chronic condition, localised, asymptomatic, hearing loss when it affects the skull

Question 27

What is fibrous dysplasia?

Answer 27

Intramedullary fibro - osseous lesion
Affects children and adults
M = ribs and skull
F = long bones
Bone is expanded by a lytic lesion that could be solid or cystic
No extension into soft tissue - usuallly asymptomatic

Question 28

What is osteosarcoma?

Answer 28

Rare bone tumours (wont save rest)
Common in femur or tibia
Tumour in medullary cavity of bone so bone has an uneven appearance
Tumour made of disorganised sheets of malignant osteoblasts
The prescence of tumour osteoid is crucial to diagnosis