Osteoporosis

Osteoporosis is a condition where there is a reduction in the density of the bones. Osteopenia refers to a less severe reduction in bone density than osteoporosis. Reduced bone density makes bone less strong and more prone to fractures.

Risk Factors for Osteoporosis

  • Older age
  • Female
  • Reduced mobility and activity
  • Low BMI (<18.5 kg/m2)
  • Rheumatoid arthritis
  • Alcohol and smoking
  • Long term corticosteroids. NICE suggest the risk increases significantly with the equivalent of more than 7.5mg of prednisolone per day for more than 3 months)
  • Other medications such as SSRIs, PPIs, anti-epileptics and anti-oestrogens

 

Post-menopausal women are a key group where osteoporosis should be considered. Oestrogen is protective against osteoporosis. Unless they are on HRT postmenopausal women have less oestrogen. They also tend to be are older and often have other risk factors for osteoporosis.

 

FRAX Tool

The FRAX tool gives a prediction of the risk of a fragility fracture over the next 10 years. This is usually the first step in assessing someone’s risk of osteoporosis.

It involves inputting information such as their age, BMI, co-morbidities, smoking, alcohol and family history. You can enter a result for bone mineral density (from a DEXA scan) for a more accurate result but it can also be performed without the bone mineral density.

It gives results as a percentage 10-year probability of a:

  • Major osteoporotic fracture
  • Hip fracture

 

Bone Mineral Density

Bone mineral density (BMD) is measured using a DEXA scan, which stands for dual-energy xray absorptiometry. DEXA scans are brief xray scans that measure how much radiation is absorbed by the bones, indicating how dense the bone is. The bone mineral density (BMD) can be measured at any location on the skeleton, but the reading at the hip is key for the classification and management of osteoporosis.

Bone density can be represented as a Z score or T score. Z scores represent the number of standard deviations the patients bone density falls below the mean for their age. T scores represent the number of standard deviations below the mean for a healthy young adult their bone density is.

The most clinically important outcome is the T score at the persons hip. This forms the basis for the WHO classification of their level of osteoporosis. DEXA scans can be used to confirm osteoporosis and monitor treatment.

 

WHO Classification

T Score at the Hip

Bone Mineral Density

More than -1

Normal

-1 to -2.5

Osteopenia

Less than -2.5

Osteoporosis

Less than -2.5 plus a fracture

Severe Osteoporosis

 

Assessing For Osteoporosis

The first step is to perform a FRAX assessment on patients at risk of osteoporosis:

  • Women aged > 65
  • Men > 75
  • Younger patients with risk factors such as a previous fragility fracture, history of falls, low BMI, long term steroids, endocrine disorders and rheumatoid arthritis.

 

The NOGG Guidelines from 2017 suggest the next step in management based on the probability of a major osteoporotic fracture from the FRAX score:

FRAX outcome without a BMD result will suggest one of three outcomes:

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

 

FRAX outcome with a BMD result will suggest one of two outcomes:

  • Treat
  • Lifestyle advice and reassure

 

Management

Lifestyle Changes:

  • Activity and exercise
  • Maintain a healthy weight
  • Adequate calcium intake
  • Adequate vitamin D
  • Avoiding falls
  • Stop smoking
  • Reduce alcohol consumption

 

Vitamin D and Calcium:

NICE recommend calcium supplementation with vitamin D in patients at risk of fragility fractures with an inadequate intake of calcium. An example of this would be Calcichew-D3, which contains 1000mg of calcium and 800 units of vitamin D (colecalciferol).

Patients with an adequate calcium intake but lacking sun exposure should have vitamin D supplementation.

 

Bisphosphonates:

Bisphosphonates are the first-line treatment for osteoporosis. They work by interfering with osteoclasts and reducing their activity, preventing the reabsorption of bone. There are a few key side effects to remember:

  • 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

 

Examples of bisphosphonates are:

  • Alendronate 70mg once weekly (oral)
  • Risedronate 35 mg once weekly (oral)
  • Zoledronic acid 5 mg once yearly (intravenous)

 

Other Medical Options:

Other options if bisphosphonates are contraindicated, not tolerated or not effective:

  • Denosumab is a monoclonal antibody that works by blocking the activity of osteoclasts.
  • Strontium ranelate is a similar element to calcium that stimulates osteoblasts and blocks osteoclasts but increases the risk of DVT, PE and myocardial infarction.
  • Raloxifene is used as secondary prevention only. It is a selective oestrogen receptor modulator that stimulates oestrogen receptors on bone but blocks them in the breasts and uterus.
  • Hormone replacement therapy should be considered in women that go through menopause early.

 

Follow Up

Low-risk patients not being put on treatment should be given lifestyle advice and followed up within 5 years for a repeat assessment. 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.

 

Last updated April 2019
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