D
ysbaric osteonecrosis (DON) is the destruction
of bone tissue in the long bones, hips
and shoulders associated with diving and
compressed-air work. Generally considered to
be the result of circulation disruption, osteonecrosis can
occur without exposure to pressure changes; indeed, cases
of osteonecrosis that are unrelated to diving far outnumber
cases of DON. Recognized risk factors for osteonecrosis
include chronic steroid use, coagulopathies, alcoholism,
smoking, antiretroviral drugs and many other conditions.
The annual prevalence of symptomatic osteonecrosis in
the general population is estimated at 0.2 to 0.5 percent. In
at-risk populations, such as people with HIV, a prevalence of
5.6
percent was reported.
The association between decompression and
osteonecrosis was initially suspected because of an
unexpectedly high incidence of osteonecrosis among divers
and compressed-air workers. In the 1970s, the estimated
prevalence was 2 to 5 percent in Navy divers, 25 to 35
percent in tunnel workers, 16 to 55 percent in commercial
divers in the U.K. and 50 to 65 percent in fishermen divers.
In comparison to the risk of osteonecrosis in the general
population, the risk of DON was 10 times greater in Navy
divers and 100 times greater in fishermen. The risk increased
with greater deviations from safe decompression procedures.
DON does not seem to be a problem for recreational
divers. There are very few reported cases, and some of
these may have resulted from causes other than diving.
Divers risk DON with significant inert gas loading followed
by inadequate decompression. Recognized recreational
depth and time limits minimize the risk of DON. However,
some recreational divers exceed these limits by engaging in
harvesting or other commercial activities or by practicing
extreme exposures as in technical diving. Turkish scuba
divers have been found to be at increased risk of DON,
but they seem to disregard safe decompression practices.
Technical divers, on the other hand, make deep and long
dives, but so far there is no indication DON affects them
more than recreational divers. This may be due to safe
decompression protocols or the use of more oxygen, or it
may be underdiagnosed.
Occurrence of DON is not necessarily associated with
a history of decompression sickness (DCS). Most cases of
DON are asymptomatic at the time of onset and remain so
for life. However, if damage occurs near a joint, over the
years that joint may collapse and cause significant pain and
disability. Such patients usually require joint replacement,
which involves major and expensive surgery. Thus, DON
represents a major hazard in diving with a minimal risk in
recreational diving and an unknown risk in technical diving.
What are the risk factors for DON?
Emmanuel Gempp, M.D.:
There is extensive medical
literature dealing with this topic that goes back to the
1970
s, but it deals primarily with professional divers and
compressed-air workers. Although gas-bubble formation
during decompression is the primary cause of DON,
it alone may not be sufficient to cause ischemic bone
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FALL 2012
Dysbaric
Osteonecrosis
in Recreational
Diving
RESEARCH, EDUCATION & MEDICINE
//
E X P E R T O P I N I O N S
B y P e t a r D e n o b l e , M . D . , D . S c .
STEPHEN FRINK
Historically, the incidence of
osteonecrosis has been higher
among working divers than in
the general public.