Osteoporosis

Question 1

What is osteoporosis?

Answer 1

complex skeletal disease characterised by low bone density and micro-architectural defects in bone tissue, resulting in increased bone fragility and susceptibility to fracture.

Question 2

What is osteopenia

Answer 2

Osteopenia refers to a less severe reduction in bone density than osteoporosis.

Question 3

Epidemiology of osteoporosis

Answer 3

• Osteoporosis affects over 3.2 million people in the UK.
• Prevalence is higher in women and increases following menopause as oestrogen levels fall. Women also lose trabeculae with age.
• An ageing population is contributing to a rise in fragility fractures
• Caucasians and asians more at risk
• 1/2 women and 1/5 men over 50
• NHS cost £2.3 billion

Question 4

Aetiology of osteoporosis

Answer 4

Primary disease (e.g. with older age)
Secondary disease, may be due to: malignancy, diabetes, Cushing, IBD, CKD, COPD, SSRis, PPIs

Question 5

Pneumonic for RFs for osteoporosis

Answer 5

SHATTERED

Question 6

SHATTERED

Answer 6

• Steroid use (long term corticosteroids)
• Hyperthyroidism, hyperparathyroidism, hypercalciuria
• Alcohol and tobacco use
• Thin - Low BMI (<18.5 kg/m2)
• Testosterone decrease
• Early menopause
• Renal or liver failure
• Erosive/ inflammatory bone disease e.g. myeloma or RA
• Dietary (reduced Ca2+, malabsorption, diabetes)

Question 7

Other RFs for osteoporosis

Answer 7

• Older age
• Female (especially post-menopausal, as oestrogen is protective)
• Caucasian/ asian
• Family history
• Previous fragility fracture
• Reduced mobility and activity

Question 8

Which genes are involved in getting to your peak bone mass?

Answer 8

Multiple genes are involved, including

• collagen type 1A1,
• vitamin D receptor
• oestrogen receptor genes.

Question 9

What other factors are involved in peak bone mass?

Answer 9

• Nutritional factors
• sex hormone status
• physical activity

also affect peak bone mass.

Question 10

Oestrogen

Answer 10

Oestrogen deficiency leads to an increased rate of bone loss. Oestrogen is key to the activity of bone cells with receptors found on osteoblasts, osteocytes, and osteoclasts.

osteoclasts survive longer in the absence of oestrogen, and there is arrest of osteoblastic synthetic architecture.

Question 11

What do Glucocorticoids cause

Answer 11

increased turnover of bone and osteoporosis. Prolonged use can result in reduced turnover state - though even here synthesis is affected more leading to a loss of bone mass.

Question 12

Basic pathophysiology

Answer 12

Osteoclast are primarily responsible for bone breakdown whilst osteoblasts are responsible for bone formation. As we age, the activity of osteoclasts increases and is not matched by osteoblasts.As such bone mass decreases.

Question 13

Clinical manifestation for osteoporosis

Answer 13

Asymptomatic condition with the exception of fractures

Common fragility fractures include vertebral crush fracture and those of the distal wrist (Colles’ fracture) and proximal femur.

Question 14

Investigations

Answer 14

FRAX Tool
DEXA Scan
Vertebral fracture assessment

Question 15

FRAX tool

Answer 15

• Predicts the risk of a fragility fracture over the next 10 years. Usually the first step of assessment and is done on patients at risk of osteoporosis
  
  • Women >65 years, men >75 years, younger patients with risk factors
    involves inputting information such as their age, BMI, co-morbidities, smoking, alcohol and family history +/- bone mineral density

Question 16

What does the DEXA scan do

Answer 16

Measures bone mineral density by measuring how much radiation is absorbed by the bones.

Question 17

DEXA scan (dual-energy xray absorptiometry) method

Answer 17

• Can be measured anywhere on the skeleton but reading at the hip is KEY.
• 2 scores are obtained:
  
  • Z score - represent the number of standard deviations the patients bone density falls below the mean for their age.
  • T score - represent the number of standard deviations below the mean for a healthy young adult their bone density is.

Question 18

What is management based on?

Answer 18

Management based on NOGG guidelines, using the FRAX score

Question 19

FRAX without bone mineral density

Answer 19

• Low risk – reassure
• **Intermediate risk – offer DEXA scan and recalculate the risk with the results
• High risk – offer treatment*

Question 20

FRAX with bone mineral density

Answer 20

• Treat
• Lifestyle advice and reassure*

Question 21

1st line treatment

Answer 21

Bisphosphonates

• Interfere with osteoclasts and reducing their activity, preventing the reabsorption of bone.
• Examples of bisphosphonates are:
  
  • Alendronate 70mg once weekly (oral)
  • Risedronate35mg once weekly (oral)
  • Zolendronic acid 5 mg once yearly (intravenous)

Question 22

Other management

Answer 22

• Lifestyle changes -
  exercise, weight, vit D, smoking, alcohol
• NICE - recommend calcium + vit D supplementation
• Denosumab: monoclonal antibody that blocks the activity of osteoclasts.
• HRT- for early menopause
• Raloxifeneis used as secondary prevention only.

Question 23

What does raloxifene do

Answer 23

It is a selective oestrogen receptor modulator that stimulates oestrogen receptors on bone but blocks them in the breasts and uterus.

Question 24

Monitoring

Answer 24

Patients on bisphosphonates should have a repeat FRAX and DEXA scan after 3-5 years and a treatment holiday should be considered if their BMD has improved and they have not suffered any fragility fractures. This involves a break from treatment of 18 months to 3 years before repeating the assessment.

Question 25

Complications

Answer 25

• Fractures
• Side effects of bisphosphonates:
  
  • Reflux and oesophageal erosions. Oral bisphosphonates are taken on an empty stomach sitting upright for 30 minutes before moving or eating to prevent this.
  • Atypical fractures (e.g. atypical femoral fractures)
  • Osteonecrosis of the jaw
  • Osteonecrosis of the external auditory canal

Question 26

What is Bone strength determined by?

Answer 26

• BMD:
  
  • How much mineral in bone
  • Determine by the amount gained during growth and amount lost during ageing
• Bone size:
  
  • Short and fat is stronger than long and thin
  • Distribution of cortical bone
• Bone quality:
  
  • Bone turnover, the architecture of it and the mineralisation (if there is not enough mineralisation then bone break, if too much then bones are stiff and shatter)

Question 27

Morbidity in the first year post hip fracture

Answer 27

Death within one year - 20%
Permanent disability - 30%