Osteo- articular Pathology Flashcards
Name 3 osteo articular developmental disorders?
osteogenesis imperfecta, achondroplasia, osteopetrosis
Name 5 osteo articular systemic disorders?
osteomyelitis, osteoporosis, osteomalacia / rickets, pagets, skeletal effects of hyperparathyroidism
Name 3 osteo articular neoplastic diseases?
Bone forming tumours, cartilage tumours, fibrous tumours
Name 2 osteo arthritis joint diseases?
osteoarthritis, rheumatoid arthritis
Describe the structure of bone?
Bone is made of :
outer dense cortex (compact lamella bone)
inner medulla (sponge like tissue of trabecula/cancellous bone) - weight bearing and hosts marrow
What is in bone marrow?
adipose tissue
Amaemopoetic tissue
How is bone made?
Mesenchymal cells - cartilage - bone
What are the two types of bone ossification?
Intra-membranous and Endochondral
Which bones are made via intra-membranous ossification?
Makes up the flat bones of the skull, part of mandible, maxilla and clavicles
For development and repair
Describe the process of intra-membranous ossification?
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
What bones are made using endochondral ossification?
Long tubular bones
Lengthening
Describe the process of endochondral ossification?
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)
What is achondroplasia?
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
How does someone with achondroplasia present?
Short limb, normal trunk length, contracted base of skull
What is osteogenesis imperfecta (OI)?
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)
How does someone with osteogenesis imperfecta present?
Sclera of eye is blue
Dentinogenesis imperfecta seen in OI type 3 and 4
Loose joints, poor muscle tone, early hearing loss, eyes protrude
What is osteoporosis?
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
What is osteoporosis?
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
What is osteomalacia /rickets?
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
What are the causes of osteomalacia / rickets?
Intrinsic Vit D disturbance
Kidney disease
Inborn error
What is the pathway of Vit D in the body?
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
What is osteoarthritis?
An osteo arthritis joint disease
Disorder of the synovial joints characterised by cartilage degeneration with secondary changes in adjacent bone
Pain, stiffness, imobility
What is Hyperparathyroidism?
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
What is the normal process when low calcium?
Low calcium - more PTH - more calcium released - low PTH
What happens when there is low calcium with a hyperfunctioning parathyroid?
Low calcium - more PTH - more calcium released - more PTH - more calcium etc so increased bone resorption
What is Pagets?
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
What is fibrous dysplasia?
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
What is osteosarcoma?
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
