Pathophysiology

  • Osteoporosis describes a change in bone structure and loss of bone mass occurring due to an imbalance in bone resorption and remodelling, by osteoclasts and osteoblasts respectively. 
    • Bone mineral density of 2.5 SDs < mean peak mass 
      • DEXA value: < -2.5 = osteoporosis
  • Fragility fractures: fractures occurring spontaneously (vertebral), following a fall from standing height or less or during a routine activity. They classically affect the wrist, spine and hip. 

Assessment 

  • Assess:
    • All women aged 65+ or 50-64 with risk factors
    • All men aged 75+ or 50-74 with risk factors
  • Risk factors:
    • Medical history: hx fragility fracture, falls, hypogonadism, premature menopause, endocrine disorders, malabsorptive disorders, rheumatoid, myeloma, COPD/CLD/CKD. 
    • Lifestyle: Smoker, alcohol > 14 units/wk, low BMI
  • NICE also advises assessing people < 50 years with risk factors including current/frequent use of corticosteroids, untreated premature menopause, hx fragility fractures or taking associated medications. 

See:https://cks.nice.org.uk/topics/osteoporosis-prevention-of-fragility-fractures/management/assessment/

Investigations & Diagnosis

Offer a DEXA to measure Bone Mineral Denisty (BMD) 1st line for patients who:

  • > 50 yrs age with a history of fragility fracture
  • < 40 years of age with a major risk factor

For all other patients:

  • Calculate the Qfracture score (preferred) (alt: FRAX score)  - 10 year major OP fracture risk
    • If high risk (10% risk or more) - perform DEXA assessment of BMD

DEXA - T-score:

  • > -1.0 = normal
  • - 1.0 - -2.5 = osteopenia
  • < -2.5 = osteoporosis 

Management 

  • If the T-score if greater than -2.5 modify risk factors and repeat the DEXA when appropriate (e.g. in 2 years)
  • If the T-score (of BMD) is -2.5 or lower offer bone-sparing drug treatment (1st line - bisphosphonates) 
  • NICE: If oral bisphosphonate not tolerated/contraindicated, consider specialist referral.
    • Specialist options include zoledronic acid, strontium ranelate, raloxifene, denosumab, and teriparatide. 

Bone-Sparing Treatments

Bisphosphonates

  • Bisphosphonates are 1st Line: alendronate or risedronate
  • Mechanism: Pyrophosphate analogues - inhibit osteoclastic bone resorption 
  • Adverse effects - gastritis/oesophagitis, osteonecrosis of jaw, atypical fractures 

Calcium

  • If calcium intake is satisfactory - prescribe vitamin D 400 units OD
  • If calcium intake inadequate - prescribe vitamin D with calcium - e.g. adcalD3

If bisphosphonates are not tolerated, consider alternatives including once yearly zoledronic acid, denosumab, strontium, raloxifene, teriparatide or HRT for younger postmenopausal women. 

Denosumab

  • Mechanism - monoclonal antibody which inhibits RANK-ligand - inhibits osteoclast development
  • 60 mg subcutaneous, every 6 months
  • SEs: Dyspnoea, Diarrhoea 


 

References and Further Reading

NICE CKS. Osteoporosis- prevention of fragility fractures [April 2023]. Available at URL: https://cks.nice.org.uk/topics/osteoporosis-prevention-of-fragility-fractures/