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Problem: Osteonecrosis

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Problem -- Osteonecrosis

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.

   ---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.

   ---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.

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Definition

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.

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).

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.

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.

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.

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

DYSBARIC OSTEONECROSIS

History
In the late 1800's and early 1900's many people worked building tunnels and bridges using compressed air in caissons to keep the workplace dry. It is from this population that Bassoe(1911) in the United States and Bornstein and Plate (1911) in Germany were the first to report disabling hip and shoulder conditions which were associated with radiological evidence of joint degeneration. The first case in a diver was not reported for another 30 years. (Grutzmacher, 1941). This, too, presented as pain in a joint. Around 10 or more cases were reported in the literature during the next ten years and all were in divers who had sought treatment for persistent joint pain. It is not possible to draw valid conclusions from these cases because the x-rays are not always published and there was no agreed standard for radiological diagnosis. Alnor et al (1964) found 72 cases of necrosis in 131 divers and of the 65 who had been kept under observation for more than 10m years, only twenty-two of them remained free from radiological lesions. Of the 43 with lesions, 17 had symptoms and 7 were "totally unable to work".

• The effect the condition has on organs vital to safe diving (central nervous system, heart, lungs, ears, eyes)
• The limitation of physical ability caused by the condition; alteration of the diver/buddy relationship
• The effect on diving of medications taken for the condition
• Complex interactions between the above that require Solomonic wisdom as to the probity of diving.

In addition, the underwater environment causes a diver to be at a tremendous disadvantage due to:

• the difficulty in propulsion through the surrounding water;
• through rapid heat loss to water generally colder than body temperature;
• breathing gas of compressed density;
• the diver uses an altered cardiorespiratory system from a changed environment;
• in order to prevent damage to air-containing spaces in the body, the diver has to accommodate to changes in gas volume and pressure;
• accommodation to the effects of the partial pressure of gases that can cause toxic, narcotic, stimulatory and gas solubility changes to bodily functions.

Divers have to have a reasonable level of physical and physiological fitness because of the obligatory stresses of the underwater environment. They must also be free of other limitations compromising safety in the underwater milieu. For safe diving, the millions of recreational and sport divers should maintain a reasonable level of fitness, the medical requirements for sport diving not being stringent.

Risk Factors for Arthritis
Age and sex are two of the most important risk factors for the rheumatic diseases. Most of the major joint conditions show a remarkable sex difference in incidence; eg, systemic lupus erythematosus (SLE) occurs primarily in women, whereas ankylosing spondylitis (Spine) is both more frequent and more severe in males. The reasons for this are unclear. Divers of all ages will need to be aware of the few but important relationships to this widespread condition.

The musculoskeletal system does not "wear out"; it thrives on usage and, unlike most mechanical systems, "lasts a lifetime." The underwater 'weightlessness' lends itself nicely toward allowing this great sport of scuba to be enjoyed by many people who would otherwise not be able to participate in athletics. However, like gender, age very strongly affects the incidence, expression, and impact of musculoskeletal diseases. Some conditions only occur in childhood; others, like SLE and ankylosing spondylitis, usually start in young adults, while polymyalgia rheumatica and giant cell arteritis rarely begin in those less than 55 yr. Rheumatoid arthritis (RA), SLE, gout, and other major inflammatory rheumatic diseases are expressed differently if they begin in older patients. With minimal assistance with entrances and exits, the arthritic diver can usually manage a moderately difficult dive with ease.

Diagnosis and Assessment Important to the Diver
Rheumatology is mainly a clinical specialty, still depending more on the skills of history-taking and examination than on special investigations. There are 2 main aspects to diagnosis: (1) differentiating the type of rheumatic disorder present and (2) assessing its impact on daily life. Diagnosis is based largely on pattern recognition --the chronology, distribution, and associated features of the disorder. The assessment of pain, disability, and handicap is often more difficult, involving investigation of patients' functional abilities, as well as their hopes, fears, needs, and aspirations. This assessment requires careful documentation in prospective divers for comparison in the case of a possible bout with decompression sickness. Most musculoskeletal disorders cause chronic pain and disability without having a great effect on life expectancy; the prevalence is therefore highest in older people. Some arthritic divers have described significant relief from pain at depth.

Treatment
A few types of arthritis are treatable with specific therapy (eg, gout can be completely controlled with drugs, or Lyme disease can be treated with antibiotics), but there are no "magic bullets" for most chronic rheumatic disorders. Management principles are often similar, regardless of diagnosis, and may depend more on the patient's age and circumstances, the balance of disease processes (eg, amount of inflammation), and the outcome (severity of pain and handicap) than on the specific disease. Most arthritic divers will want to know about the effect of diving on the drugs they are taking; such as, aspirin, NSAIDs, steroids, and the numerous other medications in use for secondary (fallback) treatment of certain arthritic illnesses (gold, Cyclosporin, Immuran, etc).

Occupational therapists participate early, helping patients adjust to the situation and teaching ways to protect joints from excess stress; later, they assist in managing physical handicap, providing aids, appliances, and further education. Scuba diving can be an important part of the therapists armamentarium. Physical therapy is useful for prevention as well as for treatment, since keeping physically fit and active helps prevent musculoskeletal pain and morbidity; and, in early disease, the maintenance of muscle strength and a full range of joint motion will help prevent subsequent disability. Physiotherapy also plays a central role in rehabilitation and pain management.

Drug therapy

Disease suppression can be achieved with hypouricemic drugs for gout, corticosteroids and immunosuppressive agents for immunologic and inflammatory diseases, and a range of miscellaneous slow-acting antirheumatic drugs for RA and the arthropathies associated with spondylitis. Specific agents are also available for many bone conditions, eg, Paget's disease. The recent development of more effective and sophisticated drug therapy for RA has been significant. Gold injections were first used in the 1930s, but we now have many similar agents, including penicillamine, hydroxychloroquine, and sulfasalazine, some of which are also active in other forms of arthritis. None of these drugs alter consciousness and therefore are not dangerous to the diver. Some blunt the immune response, however, and divers need to be aware of the increased possibility of infection in polluted and sea water.

Surgery

Surgery has become important in rheumatic disease management. Synovectomy, tendon repairs, decompression, and other procedures are sometimes warranted in early inflammatory disease. In late destructive disease of any type, joint replacement, and less commonly an arthrodesis, can be performed. Joint prostheses from metal or silicone pose no problem to the diver in that they are not air containing and thus are not effected by changes in pressure.

Clinical Approach to Arthritis as related to Diving

A complete history and physical examination are important because joint symptoms may be part of a systemic disease. Laboratory and x-ray data are usually of only supplementary help. Even mildly inflammatory or noninflammatory arthritis may be the first indication of SLE, hypertrophic pulmonary osteoarthropathy due to bronchogenic carcinoma, or a metabolic disease such as hemochromatosis. Conditions easily misinterpreted as arthritis by the patient include phlebitis, arteriosclerosis obliterans, cellulitis, edema, neuropathy, vascular compression syndromes, the stiffness of Parkinson's disease, periarticular stress fractures, myositis, and fibromyositis.Add to this the joint pains associated with "bends" or decompression illness, and you have the possibility of confusion in diagnosis. Dysbaric osteonecrosis affecting the joint cartilage can easily be mistaken for an arthritic joint.

Prominent tenderness of bones adjacent to joints and joint effusions occur in sickle cell disease and hypertrophic pulmonary osteo-arthropathy. Both sickle cell disease and pulmonary osteoarthropathy pose dangers to the diver--scuba diving being capable of causing a sickle cell crisis through hypoxia, and pulmonary disease of the extent to cause arthropathy being adverse to diving due to the possibility of barotrauma.

Physical Examination of the Musculoskeletal System
Changes from previously recorded physical findings are important in differentiating pre-existing arthritis from suspected decompression sickness. A sequence of inspection, palpation, and determination of the range of motion of each involved joint area is followed. In most cases, this determines the presence of joint disease and establishes whether the joint, the adjacent structures, or both are involved. Involved joints should be compared with their uninvolved opposites or with those of the examiner. Information is recorded objectively and quantitatively; eg, by using a numbered grading system and by measuring the range of motion in degrees.

Joint motion, generally painful in joint disease, may not be painful in periarticular, bone, or soft tissue disease. Swelling is an important finding. All swollen joints should be palpated. The examiner should then "ballotte" the joint to (1) elicit the presence of fluid; (2) differentiate between simple effusion, synovial thickening, and capsule or bony enlargement; and (3) determine whether the swelling is confined to the joint or is periarticular; (4) apply pressure to check for the relief seen in DCS.

The foot and ankle: The prospective diver should test his weightbearing ability with full equipment and weight belt. Inability to handle the weight should not preclude diving, however, since suiting up can be done while sitting on the dive platform. Since weight-bearing may elucidate certain abnormalities, part of the examination should be performed with the patient standing. Since finning is such a vital part of safe diving, disorders of the foot and ankle might be adverse to diving. 

The knee: Such gross deformities as swelling (eg, popliteal cysts), quadriceps muscle atrophy, and joint instability may be more obvious when the patient stands and walks, particularly with scuba gear. With the patient supine, careful palpation of the knee, especially noting the presence of joint fluid, synovial thickening, and local tenderness, helps detect arthritis.

The hip: A limp is common in patients with significant hip arthritis. It may be due to pain, shortening of the leg, flexion contracture, or muscle weakness. Loss of internal rotation, flexion, extension, or abduction can usually be demonstrated. Aseptic necrosis of the hip from barotrauma is a definite part of the differential diagnosis of hip pain.

The vertebral column: Cervical and lumbar motion should be measured. Inability to reverse the normal lumbar lordosis on flexion occurs in degenerative arthritis. Limited lumbar flexion is characteristic of ankylosing spondylitis. Neck motion can be limited either by degenerative arthritis or by ankylosing spondylitis. This can become a problem in the diver with the tank position abutting the head. The effect of movement on pain should be noted. Localized bone pain suggests such disorders as osteomyelitis, leukemia, primary or metastatic cancer, compression fracture, or herniated disk. Chest expansion should be measured, as it is typically impaired in ankylosing spondylitis. This is often associated with pulmonary emphysema, particularly dangerous to the diver. Disk disease can be aggravated by the extra weight of scuba gear causing nerve root compression and confusion as to the possibility of spinal decompression illness.

Diagnostic Studies

X-rays are most important in the initial evaluation of relatively localized unexplained complaints to detect possible primary or metastatic tumors, osteomyelitis, bone infarctions, periarticular calcifications, or other changes in deep structures that may escape physical examination. Erosions, cysts, and joint space narrowing can be seen in more chronic RA, gout, and osteoarthritis (OA). X-rays also are especially useful in examination of the spine. CT scans, MRI, and tomograms can help define puzzling lesions. These offer excellent baselines for future reference to the diving physician.

Other studies useful in selected patients include needle or surgical synovial biopsy, ultrasound, arthroscopy, arthrography, bone and marrow scans, electromyography, nerve conduction times, thermography, and muscle or bone biopsy.

The importance of a good physical examination of the arthritic diver has been spot-lighted as vital for differentiation of the many signs and symptoms of decompression sickness that can mimic arthritis and nerve compression. Weight-bearing has been discussed, as well as the difficulties specific to such illnesses as sickle cell disease and pulmonary osteoarthropathy. 

A chronic, systemic inflammatory disorder of unknown etiology, characterized by dryness of the mouth, eyes, and other mucous membranes and often associated with rheumatic disorders sharing certain autoimmune features (eg, RA, scleroderma, and SLE) and in which lymphocyte infiltration into affected tissues is seen.  The syndrome is more common than SLE (systemic lupus erythematosus) but less common than RA (rheumatoid arthritis). The effects of pressure are unknown. The condition causes keratoconjunctivitis and dry mouth, both conditions possibly inimical to the diver.

 The diver with Sjogren's Syndrome should be in good physical conditioning, be in remission from the acute processes of the disease, be capable of physically managing his/her entry, exit, scuba gear and be capable of assisting a buddy with a diving problem. They should be taking no medication that would alter their ability to function or make decisions.

Pathophysiology, Symptoms, and Signs
In some, SS affects only the eyes or mouth (primary SS; sicca complex; sicca syndrome); in others, there is an associated generalized collagen-vascular disease (secondary SS).
Ocular symptoms occur when atrophy of the secretory epithelium of the lacrimal glands causes desiccation of the cornea and conjunctiva (keratoconjunctivitis sicca.  In advanced cases, the cornea is severely damaged and epithelial strands hang from the corneal surface (keratitis filiformis). This would be adverse to diving.

One third of SS patients develop enlarged parotid glands that are usually firm, smooth, fluctuating in size, and mildly tender. Chronic salivary gland enlargement is rarely painful. When salivary glands atrophy, saliva diminishes, and the resulting extreme dryness of the mouth and lips (xerostomia) inhibits chewing and swallowing and promotes tooth decay and calculi formation in the salivary ducts. Taste and smell faculties may be lost. This may reduce the diver's ability to manage the mouthpiece of the regulator or snorkel.

Drying out may also develop in the skin and in mucous membranes of the nose, throat, larynx, bronchi, vulva, and vagina. Alopecia may occur. Dryness of the respiratory tract often leads to lung infections and sometimes to fatal pneumonia. Associated mucous membrane problems could lead to difficulties equalizing the middle ears or pulmonary barotrauma.

Knee or Hip Replacement

There should be no diving limitations or restrictions placed on diving with a knee or hip replacement, or any other metallic inserts or implants. The effects of pressure are not any specific danger for implants which do not contain compressible gases. Gas laws (Boyle's and Henry's) don't effect an implanted solid; the supposition that there is an increased chance of gas bubble formation in scar tissue or areas of deranged blood supply has no firm basis in man or animal studies.

Main limitations would be purely those imposed by rehabilitation from surgery, i.e., ability to walk around with heavy gear prior to entry and climb ladders (or shore) for exits. All wounds should be completely healed and the diver should have been released by the surgeon for full weight-bearing activities. Physical conditioning should have been accomplished.

One should be able to dive the usual limits of sport diving without any restrictions.

Diving After Knee or Hip Reconstruction

Much  depends on the original cause of disability. Generally, the guidelines for the new diver are much more stringent than for an experienced diver who is returning from an injury. The sport diver should have no problem as long as there is good range of motion and the diver is able to bear weight.

To become a commercial diver, the candidate must have excellent mobility and dexterity and must be in a robust physical condition in order to meet the demands of the proposed work. For personal safety and that of others, all joints must have a normal full range of mobility.

The knee and hip are especially susceptible to dysbaric osteonecrosis and this must be kept in mind with the injury. Differentiating between residual x-ray findings and osteonecrosis may be difficult.

As far as commercial diving is concerned, it all depends on the examiner and the medical guidelines of the company and the type of work. Baseline radiologic studies are required and clearance by the orthopedic surgeon, that will go a long way to persuading the company doctors to allow return to work.