Falls, fractures & fragility: Your risk factors - and why youth might not prevent a bad break
‘I never thought of myself as fragile,” says Vanessa McKee. Now 46, McKee had always believed she was physically strong. As a child, her family joked she was “big boned”. So, when she tripped over a tennis ball on a Wellington court 10 years ago, rolling her ankle and, it turned out, breaking a metatarsal in her foot and the ulnar and radius bones in her arm, McKee was shocked. Even more so when osteopenia, a loss of bone density, was found via a DXA – a dual-energy X-ray absorptiometry scan, the standard test for bone mineral density.
“I thought, ‘Geez, I haven’t even gone through menopause yet, and that’s meant to be a real time of bone depletion. This is not looking good.’”
Breaks like McKee’s are known as fragility factures, the result of falls you wouldn’t expect to break a bone, such as a fall from standing height. Thanks partly to our ageing population, it’s increasingly common: Osteoporosis New Zealand estimates 22,300 fragility fractures happen each year in those aged 50-plus. One in three women and one in five men over 50 will suffer a fragility fracture, with hip breaks the most serious and life-threatening.
But often a break is the first indication people have that their bones have weakened, possibly to the point of osteoporosis or, as in McKee’s case, its precursor, osteopenia. Bone-health screening is not recommended until after age 65 for women or 70 for men.
Osteopenia means the density in the bones has lowered. A healthy bone, looked at on a scan, appears as a well-connected, dense honeycomb structure. In osteopenia, that structure still looks connected, but the honeycomb is thinner. If not addressed, it can turn into osteoporosis, where the connections are breaking down, and the honeycomb looks more sparse, with bigger holes.
Dynamic bones
Christchurch endocrinologist Dr Anna Fenton’s career has been heavily focused on bone health. She was one of the founders of Auckland Bone Density, the first physician-owned bone-screening clinic in the country. She explains the idea that bone is inert is incorrect: bone is highly dynamic tissue.
“Bone sounds awfully boring – we might think it just kind of sits there and does nothing. But no, you turn over about 10% of your skeleton every year.”
There are two groups of cells involved in the process. “There are the osteoclasts, which are mobile cells,” says Fenton. “They crawl over the bone surface and dig little holes in the bone to renew that area or repair a damaged bone. And once they’ve dug that hole, they get up and wander off somewhere else. Then you get the osteoblasts coming in, which sit there and produce the new bone.”
In an ideal situation, exactly the right amount of bone is being made to replace what has been lost. The osteoclast and osteoblast activity is in balance. This happens for a chunk of our adult life, when bone is stable. We build up strength and density to reach peak bone mass – usually in our late teens or early 20s. After that, it starts slowly breaking down. And at a certain point the loss happens more quickly than the rebuilding.
Risk factors
Certain factors influence how this plays out and how osteopenia can emerge. Age – loss of bone is expected as we get older and it’s not something we can do much about.