bone tumours

Question 1

what is the composition of bone?

Answer 1

INORGANIC - 65%
calcium hydroxyapatite (10Ca 6PO4 OH2)
is storehouse for 99% of Ca in the body
85% of the phosphorous, 65% Na & Mg

ORGANIC - 35%
– bone cells and protein matrix
– made of the likes of collagen, carbs, water, etc

Question 2

what are the types of bones? differences?

Answer 2

Cortical / Compact

• long bones
• appendicular skeleton
• 80-90% calcified

Cancellous / Trabecular

• axial skeleton
• 15% calcified
• Cancellous bone is metabolically more active than cortical.

Question 3

what are osteocytes?

Answer 3

osteoblast like cells which sit in the lacunae in bone

Question 4

whats the structure of cortical bone?

Answer 4

circumferential lamellae outside

concentric
interstitial
trabecular lamellae

in decreaseing order

Haversian canal - up and down - contains blood vesse;s, nerves, lymph
volkmann canal - side to side

Question 5

osteobalsts come from?

Answer 5

osteoprogenitor cells

Question 6

what increases bone resorption?

Answer 6

when RANK-Ligand binds to RANK on the surface of an osteoclast

Question 7

what is a regulator in bone resorption?

Answer 7

Osteoprotegerin:

competes with RANK for RANK-Ligand

meaning less osteoclast activation/osteoclastogenesis

Question 8

what is the effect of tumours on bone and how?

Answer 8

1. Bone resorption:
   production of PTHrp & serum RANKL
   these induce osteoclasts hence resorption
2. Bone formation:
   via TGFB, FGF, ET1

Tumours not only induce bone resorption (osteolysis) but can induce new bone formation. Metastatic prostate carcinoma often causes more bone growth than destruction.

Question 9

What type of bone is found in conditoins eg (Pagets disease of bone, certain stages of flouride treatment, tumours).

how is it different from normal bone?

Answer 9

Woven bone:
lamellar are absent. Collagen fibres are laid down in a disorganized fashion: such as states of high bone turnover

viewed under polarised light

Question 10

what is required for bone histology?

Answer 10

• Histology requires bone biopsy from the iliac crest

* The sample must be processed and un-decalcified for histomorphometry

Question 11

• Bone mineralisation is studied using _____

* Histodynamic parameters are obtained from ______

Answer 11

a. osteoid parameters

b. fluorescent tetracycline labelling

Question 12

for osteoporosis,

what is the aetiology, pathogenesis and which parameters are used to determine osteoporosis

Answer 12

low initial bone mass or accelerated bone loss can reduce bone mass below the fracture threshold

Aetiology – 90% cases due to insufficient Ca intake and post-menopausal oestrogen deficiency

1º - age, post-menopause
2º - drugs, systemic disease

‘High turnover’ OP results from ↑ bone resorption
‘Low turnover’ OP results from ↓ bone formation

Question 13

most common presentation of osteoporosis ?

Answer 13

Patients commonly present with back pain and Fracture

Fractures; wrist (Colles’), hip (Neck of femur and intertrochanteric) & pelvis may be the first sign of disease  

> 60% vertebral # are asymptomatic

Question 14

how would you ivx osteoporosis and what results would you see?

Answer 14

§ Serum calcium, phosphate and ALP (usually NORMAL)
			§ Urinary calcium 
			§ Collagen breakdown products 
○ Imaging 
○ Bone Densitometry 

§ T-Score of -1 to -2.5 = osteopaenia
T score lower than -2.5 = osteoporosis

Question 15

what is osteomalacia? subtypes?

Answer 15

Defective bone mineralisation

2 types effectively:
1. Deficiency of vitamin D
2 Deficiency of PO4

Question 16

looser zone fractures are associated with?

Answer 16

osteomalacia

Question 17

list causes of primary and secondary hyperparathyroidism?

Answer 17

1º -
parathyroid adenoma (85-90%)
chief cell hyperplasia

2º -
chronic renal deficiency
vit D deficiency
malabsorption

Question 18

what does Renal Osteodystrophy entail?

Answer 18

Comprises all the skeletal changes of chronic renal disease

Increased bone resorption (osteitis fibrosa cystica)
Osteomalacia
Osteosclerosis
Growth retardation 
Osteoporosis

Question 19

what does the clinical chemistry look like for Renal Osteodystrophy?

Answer 19

High PO4-
High PTH

Low Ca2+
metabolic acidosis
aluminium deposits.

Question 20

what are the types of pagets?

Answer 20

1. Osteolytic
2. Osteolytic-osteosclerotic
3. Quiescent osteosclerotic

Question 21

which disease is the following implicated:

autosomal pattern of inheritance with incomplete penetrance (mutation 5q35-qter - sequestosome 1 gene)

Answer 21

Pagets

Question 22

Parvomyxovirus type particles have been seen on EM in ___ bone

Answer 22

Pagetic bone

Question 23

when is a bone biopsy warranted?

Answer 23

Suspected osteomalacia
Diagnostic classification of renal osteodystrophy
Osteopaenia in young patients <50y

Osteopaenia associated with abnormal Ca metabolism
Classification of hereditary childhood bone disease

Evaluation of treatment

Question 24

what is the clinical picture in pagets?

Answer 24

pain
microfractures
nerve compression (incl. Spinal N and cord)
skull changes may put medulla at risk
+/- haemodynamic changes, cardiac failure
Development of sarcoma in area of involvement 1%