Dem Bones….Understanding your DEXA scan results. Part 1

Frequently patients present to me with their DEXA scan asking me what they can do to prevent osteoporosis.  Recently I had one such patient who presented with a peculiar situation.  For several years she had been attending a local health fair that included a ‘wellness’ blood testing screen as well as a cursory DEXA scanning to determine her bone density.  She was concerned because her most recent bone scan (DEXA) showed that she was modestly osteopenic in her wrist and osteoporotic in her hip.  This isn’t unusual, but in her case it was.  You see she was only 40 years old!  She had had a major joint replacement surgery within the last year and was just beginning to deal with a thyroid problem.  Now, this news of osteoporosis had her scared and confused.  Was she really aging that rapidly?  Would she be dealing with the debility and pain of broken bones and compressed vertebra  before her kids finished high school?  She needed information, so we talked.  Here’s what we talked about.

DEXA scans have two numbers that they give you.  A Z-score and a T-score.  A T-score is where they compare your bone density against the bone density of a sex and ethnicity matched (in this case white female)30 year olds (someone at their highest bone density potential).  Or to restate, they compare it against a baseline perfect score.  The T-score is given as a numeral that compares you to that given optimal score (which is given as Zero).  So in this case her hips T-score was -2.6 (that’s negative 2.6).  So what that means is that her bone density is a little over two and one half points deviated from the norm.  If your T-score is more than 2.5 points under the norm of 0 (zero), then you will be officially designated as osteoporotic.  If you have a history of recent bone fracture(and a T-score below -2.5) or are more than 3 points below the norm of zero you are officially SEVERELY osteoporotic.

Now, she also had a T-score of -2.0 in her wrist.  A T-score between -1.0 and -2.5 is what is medically termed osteopenic.  Osteopenia means hungry for bone or wanting for more bone.  So parts of her skeleton were officially problem areas and others were awfully close.  That was concerning for her to say the least, and me because I’m the doctor that takes care of those bones and nerves manually.  You certainly don’t want overly aggressive chiropractic technic on brittle bones….OUCH!

But before we get too far we should discuss the z-score.  Z-score compares you against people your age (and sex and ethnicity).   So as expected her numbers were again below zero.  What does this mean?  Well, loss of bone density is something that occurs naturally over the course of time, just like wrinkles and well you get the picture.   So its pretty much expected that by the time you reach ninety years of age that your T-score would be under -2.  But if you compared a 90 year old against average 90 year olds they should be pretty similar right?  Exactly!  So if your t-score is below normal (lets just say -2 or under) your bones are aged compared to a 30 year olds.  But if your Z-score is below -2 then you have a problem that is more than just normal aging! 

What would happen if you went to space for 3 months?  Well, you would do TONS OF EXERCISE! Why?  Because if you didn’t put you skeleton under some stress it would deteriorate!   Remember, there’s less gravity in space!  Therefore there’s less stressing your bones.  Bones under less stress do not remodel and remain strong!  Most long mission astronauts become osteopenic or porotic in a matter of weeks simply from the reduction of gravitational stress.  Have you ever wondered why they show images of astronauts being helped out of their space capsule upon their return?  They’ve lost bone density and muscle strength while they were gone.   So, if you’ve ever wondered why astronauts are always riding a stationary bicycle in space, its to prevent sarcopenia (muscle wasting) and osteopenia (bone wasting). 

Anyway, back to the story…

I spoke with my patient about her treatment options and some inconsistencies that I had seen in her scans.  Her previous years scan had scanned her left wrist and then the following year her right wrist and then the next year back to her left.   I found that quite confusing?   You see, bone scans should ALWAYS be consistent.  Measure the same thing the same way EVERY time.  In fact, use the exact same machine as you used previously if you can.

Not all DEXA scanning machines are equal, just like some camera’s are inherently better than another some scanners are too.  Good quality bone scans will measure the hip and spine primarily.  Other machines will only test the wrist or heel and make educated assumptions from that.   I was beginning to think that the machine being used for this health fair (or the technician running it) wasn’t that great.  So I suggested she receive another scan from a reliable machine at a consistent location that she could follow up with in the future as needed.  We decided on the local hospital’s machine and her results were interesting.   END PART 1!

13 thoughts on “Dem Bones….Understanding your DEXA scan results. Part 1

  1. J. Persico

    The first time I had a bone scan my OBG was able to relate my density as a % of the average 30-year old. To be precise, my hip scan was 98% of that of a 30-year old and my spine 95%. The last two scans have only given me a T Score and standard deviation does not mean anything to me. How can I convert the T Score to a % as compared to a 30-year old? My current PCP and OBG think I’m being too analytical. Meanwhile we are told to take control of our medical situation. Unfortunately I don’t think doctors understand anything much more than the guidelines for normal vs. abnormal. I would like a more detailed understanding. Can you assist me with this?

  2. DrSteve

    As far as I’m aware you cannot precisely determine your percent of average from a T-Score alone, but you can come close. If your dexa scan relates your findings in (x=your value in)g/cm2. Then you could divide that number by the 30 year olds average in g/cm2 and get your percentage. This is what your initial OBG was relating. The medical powers that be devised the T-score standard deviation for reasons i cannot explain. However, a rule of thumb is that one standard deviation in T-score is approximately 10-15% bone density difference. Thus, if my t-score is -1.0 and yours is -2.0 you are approximately 10-15% less bone mass than me, and another 10-15% less bone mass that 30 year old average (for a total of 20-30%). This is why I said a T-score alone cannot PRECISELY determine your percentage. But lets say you T-score is -.3, that suggests that you are 3 to 4.5% below normal or 96.5 to 97% bone dense. If this isn’t analytical enough, you need a statistician, not a physician. So without a g/cm2 measurement on your current DEXA take the t-score times 10 (i.e. t-score is -.5) {10 x -.5 = -5%} and subtract that percent from 100. Wallah, 95% bone density if your an optimist. now take the t-score times 15 if your a pessimist. (15 x -.5 = -7.5) or 92.5% bone density. Or you could be pragmatic and take the difference at 93.75% bone density. Hope that answers your question. Dr. Steve

  3. Marybeth

    I have two dents in the top of my head close to my forehead…interventional radiologist says it is one dent with a ridge in the middle.I am a breast cancer survivor(stage three, bilateral mastectomy,6 months chemo,7 weeks of daily radiation)recent pet scan and cat scan of head say nothing unusual…all is well.
    Dents were not there a month ago…do you have an idea what they could be?Thank you for your help.

  4. DrSteve

    Marybeth, It’s difficult to formulate a hypothesis without examining the area. However, it sounds as though it has been pretty well investigated with imaging. Good luck on your healing journey. Dr. Steve

  5. Doris

    I enjoyed your information. I am 67 yrs. old and had a -3.7 spine reading and a -2.7 hip reading. I’ve had blood work done, everything was good. I’m very active, have been taking calcium for over 20 yrs. I eat a good diet and am of normal weight. I don’t know what to do to exersise my spine. I do use a chiropractor for back and neck problems. Is this a bad idea? Thank You

  6. DrSteve

    Doris, The best things you can do to improve the health of you spine is this. First, start some form of weight bearing exercise (virtually anything besides swimming). Walking is a great start, adding weights, within reason, is also a good addition. I have some concern as your numbers (-3.7 and -2.7) show very poor bone density and do in fact confirm osteoporosis. I can only assume these are your T-scores. However, if I was your doctor I would be interested in your z-scores too, as it could be that your osteoporosis my be secondary to some other underlying cause (parathyroid disease, glucocorticoid therapies, etc). If your osteoporosis is secondary, that secondary cause will need to be addressed to better influence your outcomes. Taking calcium, 1200 to 1500 mg/day, is good, but other things may need to be addressed like vitamin D and K, as well as addressing your ability to assimilate those nutrients. It’s for these reasons that you should be working with a professional to guide you through these things. It’s foolhardy to go rafting down a river if you don’t know the terrain, so too is trying to navigate health issues as serious as osteoporosis without a knowledgeable guide. So my advice would be to discuss all your findings (t and z-Scores, and potential secondary concerns) with your chiropractor. He or she can then take that information and change your treatment plan accordingly. This is important because an osteoporotic body needs just as much chiropractic care, and likely more, that one that is not. So often Chiropractors are seen as bone doctors because that’s what the majority of our manipulations are performed upon, but we are in fact doctors that concern ourselves with the care and maintenance of the nervous system AS WELL AS each patient’s overall physiology. This includes carefully adjusting fragile osteoporotic bones, diabetic bones, high end athletes bones, baby’s bones, you name it. Thanks for you comment! Dr. Steve

  7. ChrisKeys

    Hi Dr. Steve, I’m a male, 23 y/o weightlifter. I’ve been lifting weights since I was 16, and have developed some pretty high strength. I’m in a study at my college that lasts two months, you get 3 DEXA scans for free in total. 1 at the start, 1 after 1 month, and 1 more after the 2nd month. 1 month ago my tscore was 3.8, zscore 3.1, yesterday – tscore is 4.4, zscore is 3.6. The weird thing is, I haven’t done much differently in my training besides work more hypertrophy in vs. strength training (well, I added heavy deadlifts in). Is hypertrophic training going to produce more bone density than strength training? Also, what’s the highest t/zscore you’ve seen? The tech told me mine was the highest he’d seen in his 26 years of doing them! Thanks – Chris

  8. DrSteve

    Well Chris, you broach some interesting questions. In my clinical experience overall, bone density (as measured by DEXA) does not change very quickly. This is why when dealing with osteoporotic patients you typically will only retest a patients DEXA scan every year. This is because the scan isn’t terribly good at determining minute changes in bone density. I’m not sure what the point of this study you’re undergoing is trying to achieve, but it sounds interesting. I find it unusual that you would have that much bone density change in 1 months time, perhaps its due to your age and exercise quantity and quality. As for different types of training affecting bone density this would be something worthy of further study but far from my field of specialty. Lastly, the highest T-score I’ve seen?…Honestly, I tend to ignore and forget high t and z scores as they aren’t attributed to disease states like low ones are. Nobody ever comes in and says, hey doc I think I have great bone density, lets spend money to see just how good it is! That being said I would suspect yours are the highest I’ve encountered. Thanks for discussion

  9. ChrisKeys

    The main goal is to determine visceral fat %, and to see if 2 months of ab work (spot training) will decrease it. First month is conventional ab workouts, such as crunches and planks, second month is using an electric shock belt. The tech said each scan would normally go for $300 a pop, so I think this is pretty cool.

    Thanks very much for replying, I appreciate it!

  10. Jules

    My guess, this patient has undiagnosed Celiac Disease. CD and osteoporosis go hand in hand. If she get’s the correct diagnosis via a scope and biopsy and finds the CD, goes on a gluten free diet and works hard at weight bearing exercises, she can turn this around.

  11. DrSteve

    I agree, there is a strong correlation between gluten sensitivity and osteoporosis. It is something I consider in all cases of osteopenia/osteoporosis, particularly if the patient is under 60 years of age. Thanks for the input. Dr. Steve

  12. Marlene

    I received a call from my doctor’s office with the following results of my Dexa scan done this morning. They said my T-score is -2.1, right hip is -2.1 and femoral neck bone is -2.6. Should I be concerned? The doctor wants me to take Fosomax and I refuse due to negative reports. Please advise. Thank you.

  13. DrSteve

    Marlene, It looks by your scan that you are osteopenic in your hips and osteoporotic in your femur heads. Without your age and z-score its hard to determine if this is primary or secondary osteoporosis. It can only be assumed that your doctor has made those determinations appropriately and has set about a proper treatment plan. I would be glad to discuss alternatives to your doctors advice either in person or by phone. Just contact Kathi (406)222-9373 and set up an appointment time. Dr. Steve

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