Osteoporosis

Question 1

Definition

Answer 1

Osteoporosis implies reduced bone mass

Reduced bone density

(Defined as <2.5 standard deviations below peak bone mass achieved by healthy adults, i.e. T-score

Resulting in bone fragility and increased fracture risk.

Question 2

Causes

Answer 2

Primary → idiopathic (<50 years), post-menopausal

Secondary

↘ Malignancy: myeloma, metastatic carcinoma

↘ Endocrine: Cushing’s disease, thyrotoxicosis, 1O

hyperparathyroidism, hypogonadism

↘ Drugs: corticosteroids, heparin

↘ Rheumatological: RhA, ankylosing spondylitis

↘ GI: malabsorption syndromes, liver disease, anorexia

Question 3

Risk factors

Answer 3

age, FHx, low BMI, low Ca2+ intake, smoking, lack of exercise, lack of sunlight exposure, alcohol, late menarch, early menopause

Steroid use
Hyperthyroidism, hyperparathyroidism, hypercalciuria Alcohol and tobacco use
Thin (BMI <22)
Testosterone↓
Early menopause
Renal or liver failure
Erosive/inflammatory bone disease (e.g. myeloma or RhA) Dietary Ca2+↓/malabsorption; T1DM

Question 4

Epidemiology

Answer 4

In those >50yrs): men 6%, women 18%
Women lose trabeculae with age
In men, (although there is reduced bone formation) numbers of trabeculae are stable and their lifetime risk of fracture is less

Question 5

Symptoms

Answer 5

Often asymptomatic until characteristic fractures occur Femoral neck fractures after minimal trauma may be seen Colles’ fracture of distal radius after fall onto outstretched hand

If trabecular bone is affected → crush fractures of vertebrae are common (hence the ‘littleness’ of little old ladies and their dowager’s hump, loss of height or stooped posture)

If cortical bone is affected → long bone fractures are more likely, e.g. femoral neck

Question 6

Signs

Answer 6

Tenderness on percussion (over vertebral fractures) Thoracic kyphosis (if multiple vertebral fractures)
Severe pain with leg shortened and externally rotated (in a femoral neck fracture).

Question 7

Investigations

Answer 7

Bloods

• Calcium
• Phosphate
• ALP
• IMPORTANT: these are NORMAL in PRIMARY osteoporosis

X-Ray

• Used to diagnose fractures
• Often normal because it takes > 30% loss of bone density before showing any changes in radiolucency or cortical thinning
• May show biconcave vertebrae and crush fractures

Isotope Bone Scans

• Highlights areas of stress and microfractures

DEXA (Dual-Energy X-Ray Absorptiometry) Scan

• T-score: the number of standards deviations the bone mineral density measurement is above or below the young normal mean bone mineral density
• Z-score: the number of standard deviations the measurement is above or below the age-matched mean bone mineral density. Z-score may be helpful in identifying patients who may need a work-up for secondary causes of osteoporosis