Dysbaric Osteonecrosis and Diving

Osteonecrosis – definition

Dysbaric osteonecrosis is the death of a portion of the bone that is thought to be caused by nitrogen embolization “blockage” of the blood vessels in divers. Although the definitive pathologic process is poorly understood, there are several hypotheses:

  • Intra- or extravascular nitrogen in bones, “nitrogen embolization”.
  • Osmotic gas effects due to intramedullary pressure effects.
  • Fat embolization
  • Hemoconcentration and increased coagulability.

The lesion begins as a random finding on x-ray without symptoms. Symptomatic lesions usually involve joint surfaces and fracture with attempted healing occurs. This process takes place over months to years and eventually causes disabling arthritis, particularly of the femoral head (hip). In a study of bone lesions in 281 compressed air workers done by Walder in 1969, 29% of the lesions were in the humeral head (shoulder), 16% in the femoral head (hip), 40% in the lower end of the femur(lower thigh at the knee) and 15% in the upper tibia (knee below the knee cap).

Diving Concerns – Condition Related

Worsening of the condition from continued decompression in an asymptomatic x-ray finding may occur.

Diving Concerns – Treatment Related

The treatment is less than successful, often requiring a joint replacement. Spontaneous improvement occasionally happens and some juxta-articular lesions don’t progress to collapse. Other treatments include immobilization and osteotomy of the femur. Diving would be precluded during active treatment and rehabilitation.
The best treatment is prevention by using the safest decompression table possible. Because of the high relationship with DCS, all DCS symptoms should be treated with Recompression and HBO.

Diving Concerns – Diver Related

If the diver has not been exposed to excessive depth and decompression and presents as DON, there may be a predisposition for the condition. Diving should be restricted to shallow depths.

Diving Risk Assessment

  • Risk from the Condition
  • Fracture of a juxta-articular lesion during a dive.
  • Risks from the Treatment
  • Failure of various modalities
  • Unknown long term outlook for joint replacements in the younger population usually affected by DON
  • Risks to the Diver
  • Worsening of the condition by continued diving

Advising the Diver

  • Potential for injury from future diving

There is the potential for worsening of dysbaric osteonecrosis for any diving where there might be a need for decompression, experimental or helium diving.

  • Modifiers
  • Degree of disability [Staging]
  • Type of lesion; juxtaarticular or shaft
  • Findings on studies and degree of benefit from treatment as determined by studies.
  • Need to dive; recreational, work related.

Dive or not dive
Physically stressful diving should probably be restricted, both in sport diving and work diving due to the possibility of unnecessary stress to the joint. Any diving should be less than 40 feet/12 meters.

Process
The lesion begins as a random finding on x-ray without symptoms. Symptomatic lesions usually involve joint surfaces and fracture with attempted healing occurs. This process takes place over months to years and eventually causes disabling arthritis, particularly of the femoral head (hip).

Where it Occurs
In a study of bone lesions in 281 compressed air workers done by Walder in 1969, 29% of the lesions were in the humeral head (shoulder), 16% in the femoral head (hip), 40% in the lower end of the femur(lower thigh at the knee) and 15% in the upper tibia (knee below the knee cap).

Why It’s Important
It is a significant occupational hazard, occurring in 50% of commercial Japanese divers, 65% of Hawaiian fishermen and 16% of commercial and caisson divers in the U.K. It’s relationship to compressed air is strong in that it may follow a single exposure to compressed air, may occur with no history of DCS but is usually associated with significant compressed air exposure. The distribution of lesions differs with the type of exposure-the juxta-articular lesions being more common in caisson workers than in divers. There is a definite relationship between length of time exposed to extreme depths and the percentage of divers with bone lesions.

Diagnosis
The diagnosis is made by x-ray/MRI appearance and has five juxta-articular classifications and four head, neck and shaft classifications indicating early radiological signs.

MRI of Dysbaric Osteonecrosis

Pathology
Early on there is flattening of articular surfaces, thinning of cartilage with osteophyte (spur) formation. In juxta-articular lesions without symptoms, there is dead bone and marrow separated from living bone by a line of dense collagen. Microscopic cysts form, fill with necrotic material and there is massive necrosis with replacement by cancellous bone with collapse of the lesions.

Treatment
The treatment is less than successful, often requiring a joint replacement. Spontaneous improvement occasionally happens and some juxta-articular lesions don’t progress to collapse. Other treatments include immobilization and osteotomy of the femur. Cancellous bone grafts are of little help.

The best treatment is prevention by using the safest decompression table possible. Because of the high relationship with DCS, all DCS symptoms should be treated with Recompression and HBO.

*Reference: David Elliott, Medical Seminars, 1996

References for Dysbaric Osteonecrosis

Ronson. C.T.LI, Oxygen Decompression may prevent dysbaric osteonecrosis in compressed air tunneling, The 3rd Conference U.S. – Japan Panel on Aerospace
Chryssanthou CP, 1978 Dysbaric osteonecrosis. Etiological and pathogenetic concepts. Clin Orthop 130, 94-106 (1978)
Jones JP Jr, 1978 Prevention of dysbaric osteonecrosis in compressed-air workers. Clin Orthop 130, 118-128 (1978)
Lauritzen JB, 1987 Dysbaric osteonecrosis. Ugeskr Laeger 149(12), 771-773 (1987)
Chryssanthou CP, 1976 Dysbaric osteonecrosis in mice. Undersea Biomed Res 3(2), 67-83 (1976)
Kawashima M, 1978 Pathological review of osteonecrosis in divers. Clin Orthop 130, 107-117 (1978)
Wade CE, 1978 Incidence of dysbaric osteonecrosis in Hawaii’s diving fishermen. Undersea Biomed Res 5(2), 137-147 (1978)
Jones JP Jr, 1993 The pathophysiologic role of fat in dysbaric osteonecrosis. Clin Orthop 296, 256-264 (1993)
Jones JP Jr, 1978 Osteonecrosis. Clin Orthop 130, 2-4 (1978)
Slichter SJ, 1981 Dysbaric osteonecrosis: a consequence of intravascular bubble formation, endothelial damage, and platelet thrombosis. J Lab Clin Med 98(4), 568-590 (1981)
Goupille P, 1991 Dysbaric osteonecrosis. AJR Am J Roentgenol 156(6), 1327-1328 (1991)
Chryssanthou C, 1981 Animal model of human disease: dysbaric osteonecrosis. Am J Pathol 103(2), 334-336 (1981)
Gorman DF, 1989 Decompression sickness and arterial gas embolism in sports scuba divers. Sports Med 8(1), 32-42 (1989)
Xue HL, 1983 Dysbaric osteonecrosis–a radiological study and classification of 106 cases .Chung Hua Fang She Hsueh Tsa Chih 17(3), 191-195 (1983)
Chang CC, 1993 Osteonecrosis: current perspectives on pathogenesis and treatment. Semin Arthritis Rheum 23(1), 47-69 (1993)
Kang JF, 1992 Delayed occurrence of dysbaric osteonecrosis: 17 cases. Undersea Biomed Res 19(2), 143-145 (1992)
Davidson JK, 1989 Dysbaric disorders: aseptic bone necrosis in tunnel workers and divers. Baillieres Clin Rheumatol 3(1), 1-23 (1989)
Gregg PJ, 1977 Serum ferritin and dysbaric osteonecrosis. Undersea Biomed Res 4(1), 75-79 (1977)
Schrantz WF, 1993 Dysbaric osteonecrosis of the femoral diametaphysis. Mil Med 158(5), 352-355 (1993)
Lin E, 1983 Avascular necrosis of bone in decompression sickness
Harefuah 105(7), 162-163 (1983)
Xue HL, 1988 Dysbaric osteonecrosis and its radiographic classification in China. Undersea Biomed Res 15(5), 389-395 (1988)
Hungerford DS, 1981 Pathogenetic considerations in ischemic necrosis of bone.Can J Surg 24(6), 583-587 (1981)
Cruess RL, 1986 Osteonecrosis of bone. Current concepts as to etiology and pathogenesis. Clin Orthop 208, 30-39 (1986)
Uhthoff HK, 1981 Avascular osteonecrosis. Can J Surg 24(6), 553 (1981)
Jones JP Jr, 1985 Fat embolism and osteonecrosis.
Orthop Clin North Am 16(4), 595-633 (1985)
James PB, 1993 Dysbarism: the medical problems from high and low atmospheric pressure J R Coll Physicians Lond 27(4), 367-374 (1993)
Pearson RR, 1982 Bone scintigraphy as an investigative aid for dysbaric osteonecrosis in divers. J R Nav Med Serv 68(2), 61-68 (1982)
Heard JL, 1978 Radiographic findings in commercial divers. Clin Orthop 130, 129-138 (1978)
Daniels S, 1984 Ultrasonic monitoring of decompression procedures.
Philos Trans R Soc Lond B Biol Sci 304(1118), 153-175 (1984)
Elinskii MP, 1969 “Mute” gas bubbles and their role in decompression sickness Voen Med Zh 9, 56-59 (1969)

AUTHOR

Ernest S. Campbell, M.D., FACS

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