Osteoporosis is defined as an increased bone fragility that results in an increased risk of fractures. Typical fractures are of the wrist, vertebra, upper arms, ankles and hips. There are important risk fractures that predispose to thinner bones and to fracture, including:
- Low body mass index (BMI)
- Low oestrogen or testosterone status
- Family history of fractured hip
- Previous history of a fracture
- High alcohol consumption and smoking
- Use of certain medications, especially steroids
The biggest risk factor of all is age - it's much more common to sustain an osteoporotic fracture in later life rather than in your 40's or 50's, irrespective of the patient's bone mass. It's more sensible to take medications to protect against fracture at an age when at greater risk, rather than committing a patient to long-term drugs from the age of 50.
A bone density scan (DEXA) is a useful measurement that helps to predict future risk of fracture, in the same way that cholesterol levels can help predict the risk of heart disease. But the DEXA scan result must be put in context and interpreted together with the individual's other risk factors and not treated in isolation. There are a lot of individuals who have been diagnosed with osteopenia (mild bone thinning), rather than osteoporosis, following a bone density scan and who are prescribed drugs unnecessarily.
The FRAX calculation tool, available on www.shef.ac.uk/FRAX, is a simple way of assessing future fracture risk using clinical risk factors together with the bone density result. If a patient is at increased risk of future fracture, there are various treatments that can reduce the chance of fracture, usually by the order of 50%. These include oral bisphosphonates, such as alendronic acid, strontium (Protelos) and hormonal treatments. Intravenous bisphosphonates are a useful recent addition and include an annual infusion of Zoledronate (Aclasta) or 3 monthly injections of Ibandronate (Bonviva). Denosumab (Prolia) inhibits bone loss and is given as a simple subcutaneous injection twice yearly. Teriparetide (Forsteo) is perhaps the most effective at building new bone and is usually used for more advanced cases. It is given as a daily injection for up to 2 years. Most of these medications are well tolerated and the risks reported by the media, such as osteonecrosis of the jaw (ONJ), tend to be exaggerated occurring in 1:50,000 patients treated. Patients should be monitored to ensure that they are tolerating and responding to treatment, with a view to withdrawing drugs following 5-10 years of continuous use.
Recommended website www.nos.org.uk