Bone Disease

Question 1

What is Osteoporosis?

Answer 1

Disease characterised by reduced bone mineral density & microarchitectural deterioration of bone tissue
-leads to inc bone fragility/inc risk fractureq

Question 2

How does bone mass change over a normal lifetime?

Answer 2

Bone mass peaks at 20-30yrs
Falls in post menopausal women
-due to oestrogen deficiency

Question 3

What are the risk factors for Osteoporosis?

Answer 3

Age
Female sex
Genetics
Low peak bone mass
Disuse
Smoking

Question 4

What are the secondary causes of Osteoporosis?

Answer 4

Primary hyperparathyroidism
Thyrotoxicosis
Steroid-induced
Cushing's disease
Anorexia nervosa
Malabsorptive conditions
Chronic inflammatory/neoplastic disease

Question 5

How does Primary Hyperparathyroidism cause Osteoporosis?

Answer 5

High PTH increases bone turnover

Question 6

How does Thyrotoxicosis cause Osteoporosis?

Answer 6

Increases bone turnover

Question 7

How do Steroids cause Osteoporosis?

Answer 7

Dec intestinal Ca absorption & inc renal Ca excretion
-leads to 2o hyperparathyroidism
Direct inhibition of osteoblast activity & stimulation of osteoblast apoptosis

Question 8

How does Cushing’s Disease cause Osteoporosis?

Answer 8

As per steroids

Question 9

How does Anorexia Nervosa cause Osteoporosis?

Answer 9

Ca deficiency
Wt loss
Hypogonadism

Question 10

How do Malabsorptive conditions cause Osteoporosis?

Answer 10

Ca deficiency

2o hyperPTH

Question 11

How does chronic inflammatory/neoplastic disease cause Osteoporosis?

Answer 11

Increase bone resorption

Suppress bone formation

Question 12

How does Osteoporosis present?

Answer 12

Mainly asymptomatic
Fragility fractures
Back pain
Height loss
Kyphosis

Question 13

What are the most common sites for osteoporotic fractures?

Answer 13

Wrist (Colles)
Neck of Femur
Spine (vertebral crush/wedge fracture)

Question 14

What investigations may be appropriate in suspected Osteoporosis?

Answer 14

BMD measurements using DEXA
   -measured at lumbar spine/iliac crest
   -gives T-score
Serum Ca/phosphate
TFTs
ESR
Sex hormone panel
Vit D/PTH

Question 15

What T-scores reflect Osteopenia?

Answer 15

-1 to -2.5

Question 16

What T-scores reflect Osteoporosis?

Question 17

What is a FRAX score?

Answer 17

Screening tool used in GP for pts >50yrs

-estimates risk of fragility fracture

Question 18

What lifestyle advice should pts w/ osteopenia be given?

Answer 18

Stop smoking
Limit alcohol intake to <20 units/week
Increase exercise
Increase dietary Ca intake

Question 19

What management is available for pts w/ osteoporosis?

Answer 19

Weekly bisphosphonates (aldendronic acid) 1st line
Vit D
HRT
Testosterone replacement therapy
Calcitonin
Recombinant PTH

Question 20

How do bisphosphonates work?

Answer 20

Decrease bone resorption

Allow mineralisation of existing bone

Question 21

What are the main s/e of bisphosphonates?

Answer 21

GI s/e

Osteonecrosis of jaw

Question 22

What is Osteomalacia?

Answer 22

Inadequate bone mineralisation

-usually caused by Vit D defiency

Question 23

How does Osteomalacia present?

Answer 23

Bone pain
Bone fragility/fractures
Malaise/weakness (can be insidious onset)

Question 24

What is Rickets?

Answer 24

Syndrome resulting from osteomalacia in growing skeleton

-bone deformity and sx of osteomalacia

Question 25

How is Vit D synthesised?

Answer 25

7-dehydrocholesterole in skin + UV light = cholecalciferol

Question 26

How is Vit D metabolised?

Answer 26

Cholecalciferol metabolised in liver/kidneys - produces 1,25-dihydroxycholecalciferol (calcitriol) - inc ca uptake, dec ca excretion

Question 27

What is the underlying pathophysiology of Osteomalacia?

Answer 27

Vit D deficiency --> low plasma Ca --> 2o hyperPTH -stimulates osetoclastic bone resorption -decreases ca excretion -increases phosphate excretion Progressive loss of Ca/PO4- from bone --> defective mineralisation

Question 28

What are the common causes of Vit D deficiency?

Answer 28

Inadequate dietary intake (vegans, malabsorption) Inadequate synthesis (housebound pts, muslim women) Renal disease (CKD) Liver disease Drugs

Question 29

What are the features of Vit D deficiency?

Answer 29

Insidious onset - bone pain - pathological fractures - general malaise - proximal muscle weakness, waddling gait

Question 30

What blood tests should be done in a pt presenting w/ Osteomalacia?

Answer 30

``` U&Es ALP (high) Plasma Ca (normal/low) Serum PO4 (low) Serum PTH (high) Serum Vit D (low) ```

Question 31

What are the X-ray signs of Osteomalacia?

Answer 31

``` Normal Looser zones of defective mineralisation -long bone -pelvis -ribs Widening of epiphyseal plate (children) ```

Question 32

What is the management of Osteomalacia?

Answer 32

Oral Vit D replacements | -high dose for 4 weeks, then maintenance

Question 33

What are the rare causes of Osteomalacia?

Answer 33

Hypophosphataemia Bisphosphonates Fluoride/Aluminium intoxication

Question 34

What is Paget's Disease of Bone?

Answer 34

Common disease of unknown origin affecting bones in elderly

Question 35

How common is PDB?

Answer 35

10% at 85yrs

Question 36

What is the underlying pathophysiology of PDB?

Answer 36

Excessive uncontrolled resorption of bone by large, abnormal multinucleated osteoclasts Destruction of cortical/trabecular bone in waves New bone is women, non-lamellar w/ fibrosis of marrow spaces

Question 37

What are the clinical features of PDB?

Answer 37

``` 80% asymptomatic Waxing/waning bone pain Bone deformities (bowed tibia/skull changes) Cranial nerve palsies (CN VIII) Cardiac failure ```

Question 38

What is the classical presentation of PDB?

Answer 38

Bone pain Pathological fractures Deafness

Question 39

What is the main complication of PDB?

Answer 39

30x inc risk of developing osteogenic sarcoma

Question 40

What investigations may be appropriate in suspected PDB?

Answer 40

Bloods - ALP, Ca, PO4 (normal) Urine - raised hydroxyproline XR - variable presentation, sclerotic & lytic lesions Bone scans

Question 41

What use are bone scans in PDB?

Answer 41

Show extent of bone involvement | Cannot differentiate b/w Paget's & Sclerotic Mets

Question 42

What is the management of PDB?

Answer 42

Analgesics Bisphosphonates Monitor serum ALP Surgery for 2o joint disease/neurological complications

Question 43

What is Osteonecrosis?

Answer 43

General term for ischaemic bone necrosis

Question 44

How long does Ischaemia take to cause Osteonecrosis?

Answer 44

W/ ischaemia bone marrow dies w/i 12hrs, bone cells die b/w 12-24hrs

Question 45

Describe osteonecrosis in the shaft of a long bone

Answer 45

Bone infarction | Involves trabecular bone & bone marrow in medulla

Question 46

Describe osteonecrosis in the epiphysis of a long bone

Answer 46

Avascular necrosis | Involves trabecular bone, bone marrow & cortical bone

Question 47

What are the common causes of osteonecrosis?

Answer 47

Interrupted arterial supply (fractures) Interrupted venous drainage Retrograde arterial stoppage

Question 48

What are the risk factors for osteonecrosis?

Answer 48

Fracture (subcapital NOF, scaphoid fracture) Idiopathic (Perthe's, AVN of fem head) Bone marrow infiltration (malig) Alcohol abuse Cushing's/exogenous corticosteroids/chemo Infection (SA)

Question 49

Which bones are most susceptible to osteonecrosis?

Answer 49

Head of femur Proximal scaphoid Lunate Body of talus

Question 50

How does osteonecrosis present?

Answer 50

Pain Stiffness Swelling in local joint/over bone

Question 51

What are the XR signs of osteonecrosis?

Answer 51

Distinctive segment of inc bone density | -present after 6mo

Question 52

What is the management of osteonecrosis?

Answer 52

``` Eliminate cause Prevent complications (potential surgical intervention) ```