Revision Flashcards
Compact bone (cortical)
Long bones 80% of skeleton appendicular skeleton 80-90% calcified mainly mechanical and protective
Trabecular bone (cancellous)
Vertebrae & pelvis 20% of skeleton axial skeleton 15-25% calcified mainly metabolic, large surface
describe the fibre organisation in woven bone (immature)
Randomly oriented collagen fibres, becomes lamellar after remodelling
Lamellar bone (mature)
Collagen fibres in lamellae (sheets), oriented in the same direction in each layer, different directions in different layers ↑ strength
cortical bone lamellae structures
circumferential
concentric
interstitial
trabecular
what are the types of bone biopsy?
- Closed (needle)
: core biopsy (with Jamshidi needle) - Open
: for sclerotic (hardening) / inaccessible lesions
what is metabolic bone disease?
reduced bone mass
reduced bone strength
due to imbalance of vitamins, hormones, minerals
what effect does metabolic bone disease have on bones?
- altered bone cell activity
- rate of mineralisation
- changes in bone structure
what are the most common metabolic bone disease?
Osteoporosis Osteomalacia/Rickets Primary hyperparathyroidism Renal osteodystrophy Paget’s disease
which enzyme converts vitamin D into 25 dihydroxy Vit D? where is this enzyme produced?
25 hydroxylase
produced in the liver
which enzyme converts 25 dihydroxy Vit D to 1,25 dihydroxy Vit D? where is this enzyme produced?
1 alpha hydroxylase
produced in the kidney
describe osteoporosis in two phrases
reduced bone mass
normal bone chemistry
define rickets/osteomalacia simply
Defective mineralisation of normally synthesized bone matrix
what are the causes of rickets/osteomalacia?
- Deficiency of vitamin D, Calcium, Phosphate
- High alkaline phosphatase
- anticonvulsants
- phytic acid chelates Vit D
- lack of sun
what is sequelae?
bone pain/tenderness, fracture, proximal weakness, bone deformity
what are the causes of osteoporosis?
- hyperthyroidism
- Cushing’s syndrome
- lack of exercise and disuse
- lack of oestrogen
describe Paget’s disease simply
Disorder of bone remodelling of unknown cause where there is increased bone resorption followed by increased compensatory bone formation
features of primary hyperparathyroidism?
hypercalcaemia:
Stones (Calcium oxalate renal stones)
Bones (osteitis fibrosa cystica, bone resorption)
Abdominal groans (acute pancreatitis)
Psychic Moans (psychosis & depression)
radiology of osteoporosis
- Loss of cortical bone/thinning of the cortex
- Loss of trabeculae
- Insufficiency fractures
normal bone chemistry
reduce bone mass
what are the radiological signs of osteomalacia?
- Looser’s zones (translucencies in X-ray)
- Codfish Vertebrae (biconcave deformity)
- Osteopenia
- Bending deformities
demineralisation of normal bone matrix
radiology of rickets
- Indistinct metaphyseal margin
- Widened growth plate without calcification
- Cupping metaphases due to weight bearing
- Enlargement of anterior ribs
- Osteopenia
immature bone in the young with demineralisation
radiology of hyperparathyroidism
- Bone resorption (subperiosteal, subchondral, intracortical)
- Brown tumuors
high Calcium due to increased bone resorption
what is a brown tumour?
lesion caused by excessive osteoclast activity (bone resorption due to high PTH)
radiology of Paget’s
- Cortical thickening
- Bone expansion
- Coarsening of the trabeculae
- Osteolytic, osteosclerotic and mixed lesions
- Osteoporosis circumscripta
bone remodelling disorder
more resorption and more formation
radiology of renal osteodystrophy
- Subperiosteal erosions
- Brown tumours (more osteoclast activity)
- Soft tissue calcification (vessels, cartilages)
