Osteoporosis

 

• Background

  Pathophysiology

  • Reduced mass of structurally normal bone.
  • Involves trabecular bone loss and cortical thinning.
  • Primary (age-related) or secondary to disease or drugs.
  • Actually reduces the risk of osteoarthritis.
  • Osteopenia is a milder form.

  Epidemiology

  Lifetime risk of osteoporotic fracture:

  • 1 in 3 women.
  • 1 in 5 men.

• Signs and symptoms

  Fragility fractures:

  • Fractures resulting from a low energy mechanism of injury that should not have cause a fracture in a healthy bone.
  • In addition to osteoporosis, they may suggest underlying tumour (mets or a primary), or Paget's disease.
  • Common sites: spine (vertebrae), hip (proximal femur), and wrist (distal radius). May also occur in arm (humerus), pelvis, or ribs.

  Vertebral fractures:

  • Aka vertebral collapse, compression fracture.
  • Often affects multiple vertebrae.
  • Leads to back pain and height reduction.
  • Causes thoracic kyphosis, leading to SOB, abdominal bulging due to loss of space under ribs, and neck pain.
  • Neurological complications: radiculopathy, cauda equina syndrome.

• Risk factors

  Primary osteoporosis:

  • Commonest in postmenopausal women.

  Secondary osteoporosis, SHATTERED:

  • Steroids
  • Hyperthyroidism
  • Alcohol and smoking.
  • Thin (BMI<22).
  • Testosterone deficient.
  • Early menopause.
  • Renal or liver failure.
  • Erosive or inflammatory bone disease e.g. RA, ank spond.
  • Dietary Ca2+ deficient. May occur in coeliac disease.

• Investigations

  Dual energy X-ray absorptiometry (DEXA) at vertebra and femoral neck:

  • Osteoporosis is ≤-2.5 standard deviations (SD) from mean. T-score used for most, which are SDs from a 30 year old sex-matched mean. Z-score used if pre-menopausal, which is an age-matched SD.
  • A fragility fracture makes the diagnosis 'established' or 'severe'.
  • Osteopenia is a T-score of -1 to -2.5.
  • Indications to perform scan: patients with risk factors or patients with fragility fracture. However, in postmenopausal women with a fragility fracture (especially if age >75), diagnosis can be made and treatment started without DEXA.

  X-ray:

  • ↓Density, cortical thinning.
  • Low sensitivity and specificity, but often where the disease is first detected after a fracture.

  Bloods to assess for underlying causes:

  • FBC and ESR/CRP for inflammatory disease.
  • Bone profile: Ca2+, alk phos, PO43-, albumin.
  • U+E, LFT.
  • Metabolic: TFT, PTH, vitamin D.
  • Others: anti-tTG IgA (coeliac), paraproteins (myeloma), testosterone.

  Risk stratification:

  • FRAX score: gives 10 year fracture risk in patients age 40-90 years.
  • QFracture is an alternative.
  • Treat if above thresholds.

• Management

  Lifestyle and nutritional:

  • Stop smoking.
  • Reduce alcohol.
  • Weight-bearing and balance exercises.
  • Ca2+ + vitamin D supplement.
  • Home adjustment to reduce fall risk.

  Medical:

  • 1st and 2nd line: bisphosphonates.
  • 3rd line: strontium, denosumab, raloxifene, HRT.

  Surgical:

  • Screws or hemiarthroplasty for proximal femoral fracture.

  Steroid patients:

  • All patients aged >70 who are on regular steroids should receive bisphosphonates.
  • If younger, do DEXA every few years.

• Bisphosphonates

  Drugs

  • Alendronate is 1st line.
  • Risedronate
  • Zoledronate

  Mechanism

  • ↑Osteoclast apoptosis, thus reducing bone breakdown.

  Side effects

  • GI inflammation causing pain, dyspepsia, and/or ulceration.
  • Photosensitivity
  • Osteonecrosis of the jaw.
  • Teratogenicity

  Management

  • Most are taken weekly. Zoledronate can also be given as an annual IM injection.
  • Take on an empty stomach with a lot of water. Stay upright for 30 mins after ingestion.
  • Take vitamin D + Ca2+ 2 hours before or 4 hours after.