Osteoporosis

Question 1

Defintion

Answer 1

Reduced bone density (defined as > 2.5 standard deviations below peak bone mass achieved by healthy adults (i.e. T-score > 2.5)) resulting bone fragility and increased fracture risk

Question 2

Aetiology (primary)

Answer 2

o Idiopathic (if < 50 yrs)

o Post-menopausal

Question 3

Aetiology (secondary)

Answer 3

o Malignancy - myeloma, metastatic carcinoma

o Endocrine:
· Cushing's disease
· Thyrotoxicosis
· Primary hyperparathyroidism
· Hypogonadism

o Drugs - corticosteroids, heparin

o Rheumatological - rheumatoid arthritis, ankylosing spondylitis

o Gastrointestinal:
· Malabsorption (e.g. coeliac disease, partial gastrectomy)
· Liver disease (e.g. primary biliary cirrhosis)
· Anorexia

Question 4

Risk factors

Answer 4

o Age
o Family history
o Low BMI
o Low calcium intake
o Smoking
o Lack of physical exercise
o Low exposure to sunlight
o Alcohol abuse
o Late menarche
o Early menopause
o Hypogonadism

Question 5

Epidemiology

Answer 5

· COMMON

· In > 50 yrs
o Females: 1/3
o Males: 1/12

· More common in CAUCASIANS than Afro-Caribbeans

Question 6

Presenting symptoms

Answer 6

· Often ASYMPTOMATIC until fractures occur

· Characteristic fractures:
o Neck of femur (after minimal trauma)
o Vertebral fractures (leading to loss of height, stooped posture and acute back pain on lifting)
o Colles’ fracture (of the distal radius after falling on an outstretched hand)

Question 7

Signs on physical examination

Answer 7

· Often NO SIGNS until complications develop:

o Tenderness on percussion (over vertebral fractures)

o Thoracic kyphosis (due to multiple vertebral fractures)

o Severe pain when hip flexed and externally rotated (suggests NOF fracture)

Question 8

Investigations (DEXA)

Answer 8

· DEXA (Dual-Energy X-Ray Absorptiometry) Scan

o T-score: the number of standards deviations the bone mineral density measurement is above or below the young normal mean bone mineral density

o 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

Question 9

Investigations (other scans)

Answer 9

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

· Isotope Bone Scans
o Highlights areas of stress and microfractures

Question 10

Investigations (bloods)

Answer 10

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