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The area of interest was just under the surface of the humerus (the upper arm bone). We both looked at the MRI scan, at the area the radiologist said was a typical lesion of osteonecrosis. The patient was a 39 year old sport diver who had been diving for more than 15 years. In the past five years, he did decompression dives as deep as 180 feet on air. About four months previous, he felt painin his left shoulder, which never disappeared. He was even treated in a chamber once when it seemed to get worse after a dive. During a period of four months, the pain increased and, although it responded to anti-inflammatory drugs for a while, it was always present. He finally sought medical consultation.
The first X-rays were not revealing, but the physicians persisted. The MRI definitely showed the bone necrosis lesion in the head of the left humerus and some collapse of the joint surface had already begun. He had pain when straining the shoulder joint with even moderate lifting. The question being posed was whether the osteonecrosis was caused by diving or whether other factors may have been the cause.
Bone necrosis (dysbaric osteonecrosis) is a well known long term consequence of diving. There are several theories on why. The common problem is the occlusion of small blood vessels that supply the bone. These apparently become occluded by either bubbles, small blood clots or small globules of fat that break loose from the bone marrow.
The incidence of osteonecrosis in divers is related to depth and time of exposure. Up to now, the bone injury has been found in commercial air, hardhat divers who spent long bottom times at 150 to 200 feet, in saturation divers and in compressed air workers doing tunnel and caisson work. Of interest is the different location of the bone lesions: shoulders in divers, hips in compressed air workers. There are other sites, but lesions in the shaft of long bones and the less common elbow lesions are usually not disabling. Lesions in the hip and shoulder can cause severe arthritis of the joint and, ultimately, may require joint replacement.
Other causes of osteonecrosis include congenital abnormalities that compromise the blood supply to the bone, long term use of cortisone-like (steroid) medications, chronic kidney failure, alcoholism and inflammation of blood vessels (vasculitis). My patient had no history of any of those disorders and the only risk factor seemed to be diving. I have reviewed other cases of osteonecrosis in sport divers, but they were always associated with other medical disorders. For example, one diver had lupus (a chronic immune disease), was on prednisone (a cortisone analog) and did dives of 60 to 90 feet, well within the no decompression limits. He had osteonecrosis of both shoulders, probably owing to the prednisone, and vasculitis associated with lupus. Diving, in this case, is the least likely contributor. Another dive guide who spent many years guiding tours underwater needed both hips replaced because of osteonecrosis.
Commercial divers have an increasing incidence of osteonecrosis as they increase their years of exposure. A Japanese study indicated that about 70 percent of divers with 25 years of experience have some bone lesions. Sport divers who limit diving to 130 feet or shallower have not developed osteonecrosis and, for many years, we have been able to state that sport diving was not a risk factor for osteonecrosis. With some sport divers extending their depth limits to 170 to 200 feet, it is likely that more osteonecrosis will appear among noncommercial divers.
Treatment of osteonecrosis involving the shoulder or hip usually requires joint replacement. There are other techniques to graft healthy bone chips into the injured area and to drill through the injured area to stimulate growth of new blood vessels. Following joint replacement, it is possible to return to diving. There is little risk of osteonecrosis in a titanium replacement joint. Commercial divers are usually not permitted to dive if they demonstrate osteonecrosis near a joint surface. Shallow diving, which is not likely to produce bubbles, is probably safe. But, commercial diving usually demands deeper diving, so diving is prohibited if a joint lesion is found. Many commercial diving companies require bone X-rays as a condition of employment.
My patient asked if he could continue diving. My response was that deep decompression diving was likely to make the osteonecrosis worse and might cause lesions in other joints. Shallow, no decompression diving is not likely to aggravate the damage already present.
Sport divers have been able to avoid many of the long term effects of diving by minimizing bubble formation and the platelet activation and clotting caused by bubbles in the bloodstream. As divers move into deep decompression diving, they acquire the long term problems already known to occur in commercial divers. For commercial divers, the compensation may be worth the risk; the same cannot be said for sport divers.
You can read more about bone necrosis in our textbook, Diving Medicine, published by W.B. Saunders Co, 1997. Many of the previous diving medicine articles and other commentary on diving medicine can be found at our Web site, www.scubamed.com.
Tuna Fishing Nations Agree on Dolphin Protection Pact: The Center for Marine Conservation (CMC) commended 12 tuna fishing nations for successfully negotiating an historic agreement to protect dolphins and other marine life in the Eastern Tropical Pacific (ETP). The agreement was reached at the meeting of the Inter American Tropical Tuna Commission (IATTC) in La Jolla, California, on February 8, 1998.
It contains many provisions the CMC strongly supports, including establishing measures to avoid, reduce and minimize bycatch; conserving tuna stocks and the tuna fishery; effectively tracking tuna to differentiate between dolphin-safe and unsafe tuna; providing incentives to improve skipper performance; enhancing and strengthening compliance and enforcement; and providing greater protection and promoting the recovery of individual dolphin stocks, especially those that are depleted.
The adoption of this agreement is the culmination of a process begun in 1995, when CMC called on the United States and other tuna fishing nations to develop a cooperative, international management regime for the ETP tuna fishery that would enhance protections for dolphins and other marine species, such as sharks, endangered sea turtles and billfish. The Center for Marine Conservation worked closely with the U.S. and other governments of the tuna fishing nations, as well as conservation organizations, to develop the Panama Declaration, as well as U.S. legislation adopted by Congress in 1997.
Under the Panama Declaration, Belize, Colombia, Costa Rica, Ecuador, France, Honduras, Mexico, Panama, Spain, the U.S., Vanuatu and Venezuela agreed to work together to strengthen dolphin protections. Dolphin deaths in the ETP tuna fishery declined sharply from 100,000 animals in 1989 to fewer than 2,600 in 1996.
“Our analysis of the best available scientific data indicated that, while the U.S. ban on the use of purse seine, or circle nets, to catch tuna in the ETP resulted in fewer dolphin deaths, it was also resulting in too many endangered sea turtle, sharks, billfish and juvenile tuna being killed,” said CMC Marine Mammalogist Nina Young. “We realized that the best way to protect both dolphins and other marine life was to shift from simply banning purse seine fishing to requiring the presence of independent observers on all tuna vessels operating in the ETP and the use of proven dolphin-saving measures. Under this agreement, fishers who fail to do so risk being closed out of major tuna markets worldwide, including the United States.
“We are totally committed to enforcing the provisions of the agreement,” emphasized Ms. Young who is on the review committee for monitoring the agreement.”
“Once [it] is implemented, the ‘dolphin safe’ label will be a true guarantee to consumers that no dolphins died or were seriously injured in catching tuna that bears the ‘dolphin safe’ label…” said CMC President Roger E. McManus.
The Center for Marine Conservation is the leading nonprofit organization dedicated to the protection, research, advocacy and public education of marine conservation issues in the U.S. and world-wide. It seeks to protect ocean environments and conserve the global diversity of marine life. Established in 1972, CMC has 120,000 members. Headquartered in Washington, D.C., the Center for Marine Conservation has regional offices in California, Florida and Virginia.For more information, write to the Center for Marine Conservation at Washington, D.C. 20036; call (202) 429-5609 or fax (202) 872-0619. You can find its Web site at www.cmc-ocean.org.