My pre-surgery dexa scan (Apr 26, '07) results are in. My bone density is extremely low - deep in the "osteoporosis" realm. My left hip femoral neck is extreme. T score is -3.7. This may compromise my ability to get the cementless resurfacing I want. This has launched me on a new quest - to understand bone density and its change with age and with physical activity. Here are papers relevant to this issue. I am impressed at the economy and intelligence in how the body allocates bone remodelling energy and resources.
Mechanical stimulation in the form of vibration prevents postmenopausal bone loss in ovariectomized rats. Frequency: 50 Hz, acceleration: 2 g, 30 min/day for 5 days/week), Vibration prevented early bone loss after ovariectomy
Randomized controlled study of effects of sudden impact loading on rat femur (1998) - Rat femurs accomodated to sudden impact loading by improving their mechanical properties without increasing mineral density in this somewhat artificial set up. Point being, that BMD is not perfectly correlated with bone strength. Exercise gains in bone are lost if followed by no exercise. No surprise there. But can re-exercise bring it all back? THAT's the important question.
Effects of remobilization on rat femur are dose-dependent (2001)- For rats the answer seems to be "yes" - remobilizing brings back bone density in dose-dependent way. Free cage activity, to slow running, and finally to fast running. Fast running reversed the bone loss almost back to normal.
Femoral neck response to exercise and subsequent deconditioning in young and adult rats (2003) - Both young and old rats adapt equally to exercise; young rats by making femoral neck diameter thicker, old rats by making bone denser.
Effect of 6-Month Whole Body Vibration Training on Hip Density, Muscle Strength, and Postural Control in Postmenopausal Women - High-frequency, high intensity mechanical strain (2.5g - 5.1g) seems to stimulate bone strength in animals. In this randomized controlled trial, hip BMD was measured in postmenopausal women after a 24-week whole body vibration (WBV) training program. Vibration training significantly increased BMD of the hip by 1%. These findings suggest that WBV training might be useful in the prevention of osteoporosis.
Low-frequency vibratory exercise reduces the risk of bone fracture more than walking: a randomized controlled trial - After 8 months, BMD at the femoral neck in the WBV group was increased by 4.3% (P = 0.011) compared to the Walking group. In contrast, the BMD at the lumbar spine was unaltered in both groups. Balance was improved in the WBV group (29%) but not in the Walking group.
Anabolism: Low mechanical signals strengthen long bones - And here's a better link - Very low amplitude high frequency vibration for 20min/day for 1 year increased sheep trabecular bone density by 34%.....yes, 34%!
Transmissibility of 15hz to 35hz Vibrations to the Human Hip and Lumbar Spine: Determining the Physiologic Feasibility of Delivering Low-Level Anabolic Mechanical Stimuli to Skeletal Regions of Greatest Risk of Fracture Due to Osteoporosis - At ~0.2g accelerations at the hip and spine were 50-85% of platform accelerations, depending on frequency. Resonance was near 20hz for the human subjects, with transmissibility lower at higher frequency.
Here's a re-print of an article in the Los Angeles Times in October '07 on osteopenia in runners versus bicyclists. My own reading, and anecdotal's, is right in line with this conclusion - cycling isn't effective, you need impact to stimulate bone growth and maintenance. We're born to run.
Here's the best starting point for vibration therapy - Dr. Clinton Rubin at SUNY-Stoneybrook is a pioneer in this technology and has a lot of concern about the advertising hype that's accompanied most of the commercial vibration units that have come on line. Strong vibration can cause damage to the nervous system, including the brain. Also, he advocates strictly vertical acceleration at low g's, not the rotationally-induced vibration of e.g. the soloflex and more expensive models using off-center weighted motors. If he's right, and so far I'm in his camp (haven't read everything yet), then it's not going to be so easy to get a proper vibration unit. Even before finding Dr. Rubin's site, it's clear from basic mechanical theory that the acceleration delivered to a person will depend sensitively on the frequency and amplitude, and a plot of the acceleration (g's in the lingo) against either and both of these variables will show big peaks and valleys according to how close one is to a resonance point. It seemed to me the only solution to that would be to have a unit which can continuously tune both the power and frequency delivered and then use an accelerometer while you (who have a unique weight and body geometry) are on the unit, then tune the parameters until you're in the optimum and safe delivered acceleration range.
Turns out, after more reading, that things are much easier than that. After initially bad-mouthing the Soloflex WBV platform as being over-hyped and under-powered, I've now come completely 180 degrees. It actually appears to be nearly ideal. First, the resonances are so far apart that the transmission of the vibrations into the skeleton is nearly constant in the 30-50hz sweet spot range. The Soloflex unit vibrates at 0.3g at 30hz on up to 1.1g at 55 hz. According to the transmissibility study of Dr. Rubin etal, in this range, the transmissibility for an erect person is 75%, so that corresonds to 0.2g (30hz) up to 0.9g (55hz). And for bent knees posture, 0.09g (30hz) to 0.33g (55hz) at the hip, and about 25% higher in the lumbar spine. These accelerations and frequencies are right in the range studied with sheep to produce impressive (~30%) trabecular bone density increases. This unit is also inexpensive, only $300 or so. As I write this, I'm still on my post-surgery crutches, but I intend to buy one and use it when I've recovered enough, about 4-6 months after surgery is my guess. Reading all this, it was a very big surprise that such low impact vibration can be so osteogenic, while at the extremely low frequencies associated with walking or running (~1hz), it takes much higher impacts - 2-4g's typical for running - for significant osteogenesis.
Juvent makes a unit which delivers only vertical vibration, and is tunable. But it costs $2,000 (!!). I think someone with a tad of mechanical smarts could make their own, by shopping for a solenoid and a power supply with variable voltage/current/frequency, for a lot less than $2,000. An accelerometer can be bought from a science supply house, like Fisher or Edmund's. But one thing I'm puzzled by is that the Juvent unit only sees 2%/year bone density increases for osteoporotic women, yet Dr. Rubin's experiments with normal healthy sheep on vibration show 10-30% bone improvement (by various measures) increases. There's more to learn here. Here's a 2010 article on vibration and bone density.
Here's an interesting website from a professor of medicine at Washington University on osteoporosis and treatments. Note the February '07 section on vibration and bone.
For post-surgical healing of bone, here's an informed message from a radiologist who posted on Surfacehippy July 14, '07...
"Healing of bone may take much longer than 6 months depending upon
a lot of factors. these include the underlying bone quality, presence
of cysts, age of patient, metabolic factors & others. As a radiologist,
I have followed patients for a variety of reasons, with sequential nuclear medicine
bone scans. These are dependent upon underlying active bone metabolism. Healing
fractures can still be visible at 1 year, especially when orthopedic hardware
is
present. Any blood clot present must go through a process with de-differentiation,
fibrous tissue production, and slow conversion to bone. The final remodeling
of the underlying bone trabecula (Struts) can take as long as 2 years. I have
seen many cases of micro-fracturing through healing bone. This can lead to "Non-union"
of bone which is resistant to treatment without re-section of the area. I have
seen chronic non-union even with repeated surgery. Over the last few years there
have been a number of people on this site reporting failures. A good number
of these were clearly related to returning to activities which cause repeated
impact on the devices. I was careful not to return to snow skiing until 11 months
post op. It is not worth the risk. Best wishes, Michael (MD in NC), (L) C+,
3/31/03 Dr. Vail"
And here's an encouraging post from Chris S. on SurfaceHippy regarding bone density post-surgery... mess#114203
Chris: He was certainly correct in my case. I have improved a little over 11%
since the surgery.
> De Smet RBHR June 23,2004
> Antoniou LASR May 27, 2005
Ann: Was it all thru exercise and nutrition? What kind of exercising are you doing? Dr. De Smet thinks that through proper nutrition and exercise I can regain bone density in the hip, however I need to monitor it.
Chris: Just walking - I had not been walking more than 100 yards a day for about two years before the operation.
My Conversation with Dr. Gross at 6 week Post Surgery
My First Appointment with an Endocrinologist
At week 11 I had an appointment with Dr. Levine. He was not convinced my free testosterone was low, and we're re-doing the test. There was nothing yet in my history or existing tests which shed light on my osteoporosis. We're doing more tests, including parathyroid. His tentative suggestion is to try the new drug Forteo, which is a formulation of parathyroid hormone. This builds bone instead of merely inhibiting resorption as biphosphonates do. The effects are strong, but it is expensive and not always covered by insurance. We'll see what my tests show. Here's a page on Forteo. May '09: My insurance changed, and I haven't been able to get the doctors interested in pursuing my bone issue now.
April '09
Got a dexascan at the end of April. I don't have the actual output, but I did
get a summary in the mail. Bone mineral density in the right hip and lower spine
is up 3% over the previous reading in April '07 just before my surgery. (left
hip no data due to the metal) That's w/o drugs, using only Ca/Mg/Vit D supplements
and my resumption of running (for just a few months prior to the bone scan).
Hopefully by now - Sept '09, it's gone up further. But my lousy medical insurance
won't pay for another dexascan for another 2 years, till April '11.