Author Topic: Dysbaric Osteonecrosis  (Read 6677 times)

movsrus

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Dysbaric Osteonecrosis
« on: September 08, 2008, 09:53:53 UTC »
I wonder if any divers on this forum can provide some information on dysbaric osternecrosis.  It is a form of avascular necrosis and is associated with DCS.  How "hard" does one have to get bent in order for this to be a problem.  If a diver gets a mild DCS hit- some discomfort in the hip or shoulder that passes within a couple hours and for which no intervention is done (use of O2 or a chamber ride- is there a significant chance that there will be physiological damage?

I have done some research on the internet in which there are reported cases of dysbaric osternecrosis in recreational divers who have done deep dives, done the required deco stops but who also report some symptoms that are indicative of mild DCS.

Understanding that recreational diving is by definition is NDL, is this a problem for the general recreational dive community?

DocV

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Re: Dysbaric Osteonecrosis
« Reply #1 on: September 08, 2008, 11:52:36 UTC »
Hi movsrus,

Before getting underway, let's clarify some terminology lest it confuse the issue. Specifically, you state that: "I have done some research on the internet in which there are reported cases of dysbaric osteonecrosis in recreational divers who have done deep dives, done the required deco stops but who also report some symptoms that are indicative of mild DCS."

Deep dives that generate deco obligations are not recreational dives; they are technical dives that involve large nitrogen loadings. This is an important distinction for several reasons.

Dysbaric osteonecrosis (DON) has a strong association with large numbers of dives involving large nitrogen loadings over extensive periods of time. Not surprisingly, it is primarily a disorder of commercial divers, distantly followed by technical divers. It is extremely unusual in true recreational divers.

Yes, there have been a very, very few cases of DON reported in recreational divers.  Even at that, I'd point out that in several of these cases DON was only a best guess diagnosis after other reasonable explanations had apparently been ruled out.

You ask several specific questions:

Q1. "If a diver gets a mild DCS hit-some discomfort in the hip or shoulder that passes within a couple hours and for which no intervention is done (use of O2 or a chamber ride- is there a significant chance that there will be physiological damage?"

A1. As a point of terminological correctness, DON is caused by a physiological  process, but the actual damage is anatomical. Specifically, areas of bone die because blood vessels serving that bone are occluded by nitrogen bubbles coming out of solution.

No.  In the otherwise normal and healthy recreational diver the chances of DON are extraordinarily small.

Q2. "Understanding that recreational diving is by definition NDL, is this a problem for the general recreational dive community?"

A2. Based on the overall literature and thinking of most diving medicine and physiology experts, in the true recreational diver who remains within NDL and does conservative ascents, safety stops and surface intervals, it is not.

Helpful?

Regards,

DocVikingo

This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual, and should not be construed as such."



movsrus

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Re: Dysbaric Osteonecrosis
« Reply #2 on: September 08, 2008, 23:27:35 UTC »
Dear DocVikingo,

Thanks for the reply. 

DocV

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Re: Dysbaric Osteonecrosis
« Reply #3 on: September 09, 2008, 11:30:16 UTC »
My pleasure, movsrus.

Just realized I probably could have been more responsive to one of the central questions you posed, to wit:  "How 'hard' does one have to get bent in order for this to be a problem.  If a diver gets a mild DCS hit- some discomfort in the hip or shoulder that passes within a couple hours and for which no intervention is done (use of O2 or a chamber ride- is there a significant chance that there will be physiological damage?"

DON typically is the cumulative result of the death of tiny areas of bone due to a long history of repeated exposure to high nitrogen loadings. A "hard" hit is not necessary. In fact, it is at least theoretically possible for DON to develop in the absence of any history of diagnosed or treated DCS. 

However, a single or even a handful of minor incidents of joint-pain only DCS would not be expected to lead to any measurable DON. Mild post-dive discomfort in a hip or shoulder that spontaneously passes within a couple hours almost certainly will not be accompanied any detectible avascular necrosis of the affected joint.

Helpful?

Regards,

DocVikingo

This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual, and should not be construed as such.

movsrus

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Re: Dysbaric Osteonecrosis
« Reply #4 on: September 09, 2008, 22:28:50 UTC »
Doc,

Thanks again.  You have answered my question.  I was diagnosed with DON and the physician (who is not a diver) told me it was probably due to DCS.  I was diving in the Philippines off and on for several years and on two occasions I had moderate to severe shoulder pain following several days of deep diving off the coast of Mindanao.  Both times the pain passed after a couple hours and while the thought did cross my mind that it might be a DCS hit I decided I must have pulled a muscle or something and let it go.

The deep dives ended up being deco dives but nothing really significant.  Most times the deco obligations would clear up as I did my ascent or within a few minutes at 5 meters and I never violated a deco stop.  I had other occasions where I had a deep shoulder pain that was more of an ache than anything else and again they were associated with several days of multiple dives to the 35-45 meter range.

I have changed my profile and now do a 3 minute deep stop on the ascent and will generally hang out for 5 to 10 minutes at 5 meters or until I either get bored or get low on air.  I have decided that as I am getting older it is wiser to spend the time off-gassing at 5 meters than run the risk of additional injury.

Thanks for the info.

Regards,

movsrus


 

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