Osteoporosis

Question 1

What is the epidemiology of osteoporosis?

Answer 1

Most common bone disorder
F>M
More common in Caucasians
Affects 35% of people 50yrs in the UK; 25% of those over 80yrs

1/3 and 1/5 men will have an osteoporotic fracture in their life

Question 2

What is the aetiology of osteoporosis?

Answer 2

Genetics:

• High MZ concordance rates
• Parental Hx hip fracture
• Osteogenesis imperfecta = a rare type of monogenic osteoporosis

Risk factors:

• Post-menopausal bone loss secondary to oestrogen deficiency
• Hyperparathyroidism
• Malabsorption e.g. coeliac
• Anorexia nervosa
• RA
• Cushing’s syndrome
• Alcohol excess
• Smoking
• Hypopituitarism
• Myeloma
• Vit D deficiency
• Lack of weight bearing exercise
• Drugs: corticosteroids, anticonvulsants, heparin, thyroxine

Question 3

What is the mnemonic used to remember the risk factors for osteoporosis?

Answer 3

SHATTERED:
Steroid use 
Hyperthyroid/parathyroid/calcaemia 
Alcohol + tobacco 
Thin (low BMI, <19kg/m2)
Testosterone (low)
Early menopause 
Renal/liver failure 
Erosive/inflammatory bone disease (RA + myeloma)
Dietary calcium (low)

Question 4

What is the pathophysiology of osteoporosis?

Answer 4

Imbalance of bone reabsorption and formation:
- Osteoclast breakdown > osteoblast formation
- Mineralisation is normal
(opposed to osteomalacia where bone isn’t properly mineralised despite the normal production of
bone matrix)
- Affects trabecular i.e. long bones and cortical i.e. spine

Question 5

How does osteoporosis present?

Answer 5

Largely asymptomatic in of itself, but will present:

Small physical changes ee.g. reduced height, stooping posture/kyphosis

Incidentally e.g. on scans

Following complications:

• Fractures e.g. vertebrae, forearm (distal radius, humerus), hip/proximal femur, shoulder are common
• Compression syndrome e.g. nerve root compression
• Pain

Question 6

What characterises osteoporotic fractures?

Answer 6

Aka fragility fractures

Result from mechanical forces that would not ordinarily result in fracture

Associated with low bone mineral density

Question 7

How do you investigate osteoporosis?

Answer 7

Duel energy X-ray absorbtiometry (DEXA) scan = gold standard for Dx

• Low dose X ray of the femoral neck
• An assessment of bone mineral density

Other tests: (to exclude secondary causes)

• FBC, ESR, CRP
• U+E, LFT, TFT, Ca
• Testosterone/gonadotrophins in men
• Serum IgGs and paraproteins, urinary Bence-Jones’ proteins

Question 8

How do you interpret a DEXA scan?

Answer 8

Bone density values expressed as a standard deviation (SD) in relation to a reference population

• T score = difference between your measurement and that of a healthy young adult (30yrs)
• Z score = difference between your measurement and that of someone the same age

T scores:

• Above -1 SD = normal
• Between -1 and -2.5 SD = osteopaenia
• At or below -2.5 SD = osteoporosis; lower = more severe

Z scores:
- Below -2 = bone density is lower than it should be for someone of a given age

Question 9

What is a FRAX score?

Answer 9

Score predicting the 10-year risk of fracture, either hip or a major osteoporotic fracture of the spine, forearm, hip or shoulder; in people aged 40-99

Takes into account:

• Age
• BMI
• Hx fracture
• Parental Hx hip fracture
• Current smoking status
• Alcohol units >3/day
• RA
• Glucocorticoid status
• Conditions causing secondary osteoporosis (early menopause, renal or liver disease, Cushing’s, coeliac etc.)
• Femoral neck BMD (g/cm2)

Question 10

What lifestyle advice do you give to someone with osteoporosis (or osteopaenia)?

Answer 10

High Ca + vit D diet +/- supplementation

• E.g. AdCal
• Tools for assessing Ca intake exist online
• Prescribe different ratios for different existing dietary intakes and sunlight exposures
• Combined vit D AND Ca = more effective at preventing fractures

Increase weight bearing exercise

Stop smoking, reduce alcohol intake

Falls risk management: 
Falls prevention service 
Home modification 
Pendant alarms 
Managing medical conditions and polypharmacy

Question 11

What drugs are used to manage osteoporosis?How do you council them? What are the important side effects? How do they work?

Answer 11

Bisphosphonates:

• Alendronic acid 70mg PO weekly
• Used for primary prevention in postmenopausal women who have never had a fragility fracture
• Specifics of guidelines depend on age of woman, DEXA score and other risk factors for fragility fractures

Administration:

• Should be taken sitting upright with a glass of water (++), first thing in the morning before food/on an empty stomach, should remain sat up for 30 mins after to prevent damage to the stomach
• If experience heartburn, should seek medical advice as they may have injured lower oesophagus and need discontinuation
• Is likely to reduce the incidence of further vertebral and non-vertebral fractures

SEs:

• GI adverse effects
• Osteonecrosis of the jaw
• Atypical femoral fractures

Mechanism:
- Inhibit osteoclasts

Question 12

What other drug can be used to treat osteoporosis?

Answer 12

Denosumab:

• Monoclonal antibody reducing osteoclast activity (and hence bone breakdown)
• Given SC every 6/12
• As an alternative to those intolerant to bisphosphonates

Question 13

How does osteoporosis appear on X-ray?

Answer 13

Loss of trabecular bone

• E.g. ‘ghost vertebrae’
• Lower density/blacker than normal

Joint space thinning

Evidence of (compression) fractures) e.g. wedge fracture of vertebrae