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Osteoporosis

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Osteoporosis

Written by Dr Dan Rutherford, GP

Osteoporosis is where the amount of bone tissue in the body is below what is normal for a person, taking into account their sex and age.

Put simply, osteoporosis causes weaker bones, increasing the likelihood of a fracture. Osteoporosis on its own does not cause symptoms. Unless it's caused a bone fracture, it's not a painful condition, nor is it a type of arthritis.

Understanding bone structure

Bone has a complex structure that achieves the maximum amount of strength for the least amount of weight.

It can increase its thickness in areas subjected to repeated heavy loads, repair itself when broken and is the site of manufacture of most of the components of blood (the bone marrow).

If you take a typical bone such as the femur (upper leg bone) and cut it across, you will see there is an outer shell of very hard bone. In the middle space it has a honeycomb structure, through which is mingled the bone marrow.

Bone is made up mostly of collagen fibres, upon which are laid down crystals made from calcium and phosphate that give bone its ability to withstand compression and bending forces.

Cells that repair and dissolve bone If you looked at bone under a microscope, you'd see two types of specialised cells scattered throughout:

cells that continually make new bone, called osteoblasts.

cells that continuously dissolve bone into its component materials, called osteoclasts.

Bone is therefore not a static tissue, but is always on the go. The actions of bone manufacture and disassembly are usually exactly balanced.

How bone repairs itself

When increased loads are repeatedly put upon a bone, the osteoblasts become more active, laying down more bone and increasing the strength of the region.

When a bone fractures, osteoblasts go into overdrive around the fracture site, laying down more collagen fibres and minerals on top to strengthen them.

How does osteoporosis affect bone?

In osteoporosis, the osteoclasts - usually over years - dissolve a bit more bone than is replaced, resulting in weaker bones.

Fractures in bone affected by osteoporosis are most likely in areas where there is a greater percentage of the honeycomb type of bone, which is less able to take the shock of a fall:

in the wrist

in the femur close to the hip joint (called the 'neck' of the femur)

in the vertebrae of the lower spine.

Hip and wrist fractures usually result from falls, whereas fractures of the spine tend to occur spontaneously when a weakened vertebra eventually crumples under the stress of supporting the body's weight.

The scale of the problem

One in three women and 1 in 12 men over the age of 50 will suffer a fracture of the hip, wrist or spine as a result of osteoporosis.

In total, osteoporosis causes 310,000 fractures in the UK every year. The estimated cost of treating these fractures is an enormous Â£1.7 billion each year.

But the cost to the individual can be higher:

bone fractures can cause considerable pain and disability.

50 per cent of people who suffer a fractured hip lose the ability to live independently.

around 20 per cent of people who fracture a hip die within a year, as a result of their fracture.

Detecting osteoporosis

The majority of people who suffer a fracture from osteoporosis are not known to have the condition prior to breaking their bone.

Osteoporosis is an under-recognised condition, which is partly because an organised approach to detecting it has not yet been developed in the UK. As a result, people at high risk of getting a fracture are not offered appropriate advice or treatment to reduce their risk.

Many people who have had a fracture due to osteoporosis do not receive follow-up treatment that helps reduce the chance of their getting another one.

There are wide variations throughout the UK in the quality and quantity of effort put into detecting and treating osteoporosis.

There are further divisions in the quality of care delivered to people from different social groups. In a recent study in Glasgow, people from the most deprived areas were eight times less likely to be referred for tests to detect osteoporosis than those from affluent areas.

The government has recognised the deficiencies that exist in osteoporosis management nationally. More funding is slowly coming through to expand the services, to be used for bone scanning machines to help diagnosis as well as specialists in osteoporosis.

What's classified as 'abnormally weak'?

It is normal for bone to get a bit weaker each year after the age of about 30, when our bones are at their maximum strength. Men tend to have greater bone mass than women of the same age.

For a few years after the menopause, women experience an increased rate of bone loss. This is secondary to the drop in oestrogen that is part of the hormone change of menopause - oestrogen has a protective effect upon bone strength.

Defining when bones are abnormally weak has to take account of what is normal for the two sexes and the different age groups.

Modern bone scanning devices can measure the density of bones and have allowed doctors to set a range for normal bone strength. Osteoporosis can therefore be diagnosed if a person's bone density measurement is significantly low compared to these standards.

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