DEXA scanner (the person is not me!) Photo by By Nick Smith photography – ALSPAC web site, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=26389366

Dear Readers, yesterday I had a break from the Whittington Hospital and went instead to the Royal Free for a bone scan. It’s a bit more of a pain to get to (there’s Hampstead Heath between us and the hospital, so there are a lot of single lane, narrow roads to navigate) and the hospital itself is a bit busier and more rambunctious, but it was also lovely to drive past all that greenery, and to note that the horse chestnuts look even more raggedy than usual this year.

Anyhow, I have never had a bone density scan before, and so I was intrigued. What the hell is going on? I knew it was some kind of X-ray, but noticed that the technician didn’t hide herself away behind a screen while it was all going on. When I was told that it was finished, she showed me that scans of my spine and pelvis that had been done, and kindly let me know that my scores were all normal. So I don’t have osteoporosis! Yay! My orthopaedic surgeon was right when he said that I had a ‘high energy fracture’, i.e. one that was caused by sufficient force to give anybody a broken bone.

Did someone say ‘Hi-NRG?’

‘Smalltown Boy’ by Bronski Beat

‘You Spin Me Round (Like a Record) by Dead or Alive

Never Can Say Goodbye by the Communards

And if you’re dancing in the kitchen, please be aware of trip hazards :-).

On returning home, I did a bit of research, and here’s what I found out. A DEXA or DXA scan (Dual-energy X-ray Absorptiometry) is performed by using two different X-rays with different energy levels which are aimed at the patient’s bones. Soft tissue and bone reduce the amount of the X-ray passing through the body, but at different amounts – when you get a normal X-ray, the soft tissue is filtered out, leaving only the bones. You could compare it to the way that sunglasses filter out most of the sunlight entering your eyes, or the way that earphones filter out sound. This is known as ‘attenuation’.

However, to look at the actual density of your bones, you need the two different X-rays – with one X-ray you won’t be able to tell how much was filtered out by your soft tissue, and how much by the bone. The two X-rays enable you to calculate and subtract how much of the attenuation was due to flesh and internal organs, so that what remains indicates how much of the X-rays was absorbed by the bone. This relates directly to your bone density.

At the end of the process, you get two scores. The T score compares your bone mineral density score with that of a young adult of the same gender at peak bone density. -1.0 is normal, anything over -2.5 indicates osteoporosis. The Z score compares your bone mineral density with that of a person of the same gender of a similar age and weight. Both of mine were in the normal range, which is a great relief, particularly as I have lower back problems which I was worried were getting worse with age. As it is, I think it’s probably just because of my limp and the reduction in my core muscle strength, both of which I can do something about.

So, if you’re scheduled for a DEXA scan, I would definitely go for it – it’s non-invasive, takes about ten minutes, and if there are problems you’re better off knowing about them now. It’s true that the DEXA scans don’t necessarily correct for some variables (such as the size of the bone that they’re looking at) but they are widely considered to be a pretty accurate measure of bone mineral content, so worth doing for sure.

Incidentally, the technician was very keen on Vitamin D as a supplement, as was the orthopaedic surgeon – he was suggesting 2000 μg per day. Anything above 4000 μg per day is considered to be problematic, so this is well within the safe limits. It’s supposedly especially important for calcium metabolism and bone healing.