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Osteoporosis

A condition of reduced bone mass and strength resulting in fractures. The most important consideration is an individual's absolute risk of fracture. This can be estimated using the FRAX or Garvan calculation tools. These calculations can be made without BMD to get an estimate of fracture risk.

These tools are guides to fracture risk. FRAX takes into account a number of important risk factors for fracture but does not include the severity of these risk factors. For instance it does not adjust the risk according to steroid dose or cigarette pack year history. The Garvan tool takes into account the number of fractures and fall history. If these factors are present, the Garvan tool can more than double the fracture risk as assessed by FRAX. These tools are mainly geared to "normal people" not those who might be in hospital clinics or beds. They use femoral neck or total hip BMD and ignore spinal BMD.

• Major risk factors for osteoporosis:
  • Prior fracture. Vertebral fracture is associated with 5-10 times the risk of future fracture. 10- 20% will refracture over the next year. Peripheral fractures double the risk of future fracture.
  • Age - 4% of 50 yr olds have osteoporosis compared to 33% of 70 yr olds.
  • Steroid usage - the higher the cumulative dose, the greater the risk of fracture. Over 7.5 mg prednisone /day is associated with 5 times the risk of fracture.
• Other risk factors:
  • Maternal hip fracture, weight less than 57 kg, smoking, proximal muscle weakness.
• Conditions commonly associated with osteoporosis:
  • Hypogonadism (e.g., premature menopause, anorexia, prostate cancer survivors, prolonged Depo-Provera™), coeliac disease, anticonvulsant use, COPD, alcoholism, hyperthyroidism, hyperparathyroidism.

Consider BMD scan, to assess risk of fracture and need for treatment. Results reported as T score (standard deviation score (sds) compared to normal young adult) and Z score (sds compared to age matched normal control). The World Health Organization defines osteoporosis as T score < -2.5 and low bone mass as T score -1 to -2.5. Degenerative bone disease can give falsely reassuring bone mineral density scores at hip and spine.

Note: Patients over 75 with a significant osteoporotic fracture demonstrated radiologically do not necessarily require a BMD before treatment for PHARMAC medication access.

Guidelines for treatment based on BMD results:

• T score < -2.5: treat.
• T score -1 to -2.5: treat if fragility fracture or 10 year fracture risk calculation is ≥20% for overall fracture risk or ≥3% for hip fracture risk. Otherwise correct risk factors and consider calcium and vitamin D.
• T score > -1: don't treat.
• If on supra-physiological steroid therapy, treat if T score < -1.5.

Investigations

All patients should have Ca, PO₄, alb, ALP, creatinine, and CBC + diff. If BMD for age is low (i.e., Z < -2), consider secondary causes of osteoporosis. Possible tests include: vitamin D, PTH, testosterone & SHBG (in males), LH, FSH, coeliac antibodies, TFTs, SPE and serum free light chains, fasting urine calcium/creatinine ratio.

Treatment

Treatment, as well as addressing any underlying cause, involves:

Calcium

• By diet or supplement to approximately 1000 mg per day. Calcium carbonate 1.25 g (500 mg Ca per tablet) one BD with food or calcium carbonate effervescent 1.75 g (1000 mg Ca) one nocte.

  It remains controversial whether calcium supplements increase the risk of vascular complications, particularly in women over 70. Calcium by diet is preferred or alternatively take smaller doses with food to diminish peak calcium levels. A number of large controlled trials have failed to show any increased cardiovascular risk if using both calcium and vitamin D supplements together.

Vitamin D

• Consider loading dose, i.e., cholecalciferol 1.25 mg (50,000 units) one daily for 3 days if likely to be low, for example older post hip fracture patients, institutional care, anticonvulsant medication. Maintenance dose is recommended for most patients on bisphosphonates: cholecalciferol 1.25 mg (50,000 units) monthly. If taken daily, a dose of at least 800 units is required.

  Calcium and vitamin D reduce fractures and falls in frail older persons but usually osteoporosis requires additional treatment.

Bisphosphonates

• Alendronate: 70 mg once a week 30 mins before breakfast with water, remain upright after taking tablet for at least 30 minutes and until after breakfast. Alendronate leads to a 50% reduction in all fractures, but special authority is required. Fosamax Plus™ contains 800 units per day of vitamin D. Initial loading with cholecalciferol however is still required in those likely to have significant vitamin D deficiency (see above). Some patients may require a higher maintenance dose of vitamin D than that provided by Fosamax Plus™.

  Consider a period off treatment after 5 years of alendronate if bone density has improved out of the osteoporotic range, particularly at the femoral neck, and there have been no further fractures, particularly vertebral, for 2 years. This could be most relevant in younger patients with potential long term exposure to bisphosphonates.

• IV zoledronic acid (IV pamidronate is now rarely used for osteoporosis):
  • Zoledronic acid has the same indications as alendronate and requires special authority.
  • It has similar efficacy to alendronate on fracture risk.
  • It is the first choice agent for patients who have GI intolerance to oral bisphosphonates or a high likelihood of this, or potential compliance issues.

  To avoid possible hypocalcaemia it is important to ensure that patients are vitamin D replete before administering an IV bisphosphonate. If in doubt give 2 cholecalciferol tablets (2.5 mg 100,000 units) in the week before the infusion. Information packs for patients are available through the Bone Clinic.

  • Give zoledronic acid 5 mg IV every 1-3 years. The funded preparation is Aclasta™ and this contains zoledronic acid 5 mg in 100 mL for infusion over 15-30 minutes.
  • If calculated creatinine clearance is <35 mL/min zoledronic acid is contraindicated.
  • Side effects of oral bisphosphonates include nausea, indigestion, abdominal pain, diarrhoea. All bisphosphonates may cause transient mild bone pain, also hypocalcaemia if vitamin D deficient.
  • IV bisphosphonates cause transient fever and flu-like symptoms following the first dose in up to 20% of patients. This can be reduced by taking paracetamol 1 g QID for 48 hours and ensuring good hydration. GI side effects are not seen.
  • Osteonecrosis of the jaw is extremely rare in patients treated with bisphosphonates for osteoporosis and probably no more common than in the normal population. We do not recommend a change from standard dental treatment for these patients.
  • Bisphosphonates are not licensed for use in premenopausal women and their use requires careful assessment of risk versus benefit.

Hormone Replacement Therapy (HRT)

• It is important in young hypogonadal females, for example premature menopause, to preserve bone mass. HRT is likely to be beneficial. In postmenopausal women, HRT may be safe and effective in patients under 60 years or within 10 years of menopause and has similar fracture efficacy to bisphosphonates. In older individuals, risks of vascular disease and breast cancer need to be considered and therefore HRT is not commonly recommended. Testosterone replacement should be considered in all hypogonadal males.
• Teriparatide (PTH) and raloxifene are approved for funding

  and require special authority

  :
  • Raloxifene 60 mg tablet daily is an option for women who cannot take bisphosphonates.
  • Teriparatide 20 microgram subcut daily is a potent stimulator of bone formation and is funded as a rescue option for those who have a fracture after at least 1 year of bisphosphonate treatment.
  • Additional criteria include:
    • T score is ≤ -3.
    • Must have at least 2 fractures.

Consider Falls Risk

• Review medications (anti-hypertensives, hypnotics), safe environment, physiotherapy, hip protectors. See Falls section in Older Persons Health.

Topic Code: 3748