The basics - Osteoporosis

Dr Harry Brown highlights some of the diagnostic features and management options for this common disease.

Kyphosis after a series of vertebral fractures
Kyphosis after a series of vertebral fractures

Osteoporosis is the most common metabolic bone disease in developed countries and represents reduced bone mass with a weakening in the micro-architecture of bone tissue.

In turn, this makes the bone more fragile, increasing the risk of fracture.

The economic considerations resulting from the clinical consequences of osteoporosis - a fracture - are enormous. The total cost to the healthcare budget in the UK is in the region of £2 billion every year. This gives osteoporosis a high clinical and political profile.

Definition
Osteoporosis is quantified by bone mineral density (BMD), which in turn can reflect fracture risk. BMD is often reported as a T score, where T score <-2.5 indicates osteoporosis, >-2.5 to <-1 osteopenia and >-1 normal.

A fragility fracture is defined as bone that breaks after a force that ordinarily would not result in a fracture.

Typically, osteoporosis is associated with fractures of the wrist, hip and spine but other bones can be affected. Osteoporosis is usually silent and asymptomatic until a fracture occurs.

Pathophysiology
Poor creation of bone mass in the younger years (bone mass peaks around the mid-20 age group) and increasing bone loss after the peak has been achieved are some of the risk factors for the development of osteoporosis. Men attain a higher peak bone mass than women, while estrogen deficiency plays an important role in both sexes in the development of osteoporosis.

Generating a peak bone mass is associated with the sex hormones of puberty, genetics and lifestyle factors, such as exercise. Increasing age, smoking and alcohol intake and reduced physical activity may affect the incidence and development of osteoporosis.

The risk of an osteoporotic fracture is closely related to the risk of a fall. There are a large number of clinical, lifestyle and environmental factors related to falls and the risk of a fall must be taken into account when assessing the risk of osteoporosis.

Clinical features


A Colles' fracture may be the first indication of osteoporosis

The clinical features of a fracture, particularly of a long bone such as a Colles' fracture, are well known. These include pain, swelling, haematoma formation, loss of function and local tenderness.

A vertebral fracture is a common manifestation of osteo-porosis and yet many events are asymptomatic and may only be found on X-ray examination. Vertebral fractures may lead to loss of height and a deformity in the upper spine, called a Dowager's hump.

Hip fractures are associated with significant morbidity and increased mortality rates. They can have a dramatic onset and usually render the patient acutely immobile, often requiring acute and urgent surgical intervention.

A hip fracture can result in considerable subsequent physical disability and increased mortality.

Osteoporotic fractures can result in a loss of quality of life.

An evaluation tool for frac-ture risk can be found at www.shef.ac.uk/FRAX/.

Diagnosis
While fractures may be easily detected on X-ray, asymptomatic osteoporosis may be more difficult to detect. A dual energy X-ray absorptiometry (DEXA) scan measures BMD and is the gold standard.

It is also important to identify patients at higher risk of developing osteoporosis, such as those taking steroids long term, women who have untreated premature menopause or patients who have a condition that can predispose to osteoporosis, such as coeliac disease.

Hyperthyroidism and excessive alcohol intake can also be associated with osteoporosis.

Treatment
Lifestyle changes include exercise and encouraging an appropriate intake of calcium and vitamin D, especially in older people. Smoking cessation and reduction of alcohol intake are also appropriate lifestyle interventions.

It is important to assess the patient's risk of falls, particularly in the frail, elderly patient. Good nutrition and physical activity should also be encouraged.

Bisphosphonates inhibit bone resorption. Strontium ranelate and raloxifene are used in postmenopausal women in specific circumstances. It is usually advisable to prescribe vitamin D and calcium supplementation, if indicated.

Bisphosphonates reduce the process of bone turnover. Risedronate and alendronate can both be given as a once-a-day preparation but a weekly preparation is also available. Zoledronate can be given as an infusion every year.

Bisphosphonates taken orally must be consumed with a reasonable volume of water, either standing or sitting in the upright position on an empty stomach. Taking it first thing in the morning is one possible strategy. The patient must then remain upright and fasting for another 30 minutes after taking the tablet. Generally this type of medication is well tolerated but the exact duration of therapy remains unclear.

Bisphosphonates are used in both the treatment and prevention of osteoporosis; alendronate is the recommended first choice. If this is unsuitable or not tolerated, other bisphosphonates may be used.

Alternatives include strontium ranelate, which can be helpful for patients who cannot cope with the administration routine of bisphosphonates. The mechanism of action of strontium ranelate is not well defined. Raloxifene may reduce the risk of vertebral fracture in some women.

Bisphosphonates can also be used for the prophylaxis and treatment of steroid-induced osteoporosis. A daily dose of either alendronate or risedronate can be used in the treatment of osteoporosis in men.

Patient education is vital to understanding the condition, appreciating the importance of lifestyle and pharmacological management and maintaining compliance with therapy. Sometimes the provision of written information may be a useful adjunct (see www.mims.co.uk/PatientResources).

- Dr Brown is a GP in Leeds

Useful websites
- www.nos.org.uk/
- www.arc.org.uk/arthinfo/patpubs/6028/6028.asp
- http://guidance.nice.org.uk/TA160
- www.osteoporosisinscotland.org/
- www.brsoc.org.uk/
- www.iofbonehealth.org/health-professionals.html
- www.shef.ac.uk/NOGG/NOGG_Pocket_Guide_for_Healthcare_Professionals.pdf
- www.shef.ac.uk/FRAX/
- www.mims.co.uk/PatientResources

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