Laboratory Studies
Laboratory studies are typically not indicated in the diagnosis of osteonecrosis. Tests can be utilized to identify inciting factors, such as the following:
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Sickle cell disease in African Americans
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Lipid profile to reveal if there is underlying hyperlipidemia
Imaging Studies
Radiographs help establish the diagnosis in most cases. Essential radiographic views include anteroposterior (AP), true AP, and axillary. See the images below.
Magnetic resonance imaging (MRI) is the diagnostic modality of choice for cases in which there is clinical suspicion of shoulder osteonecrosis but radiographs are normal; MRI has sensitivity and specificity greater than 98% for shoulder osteonecrosis. [8] The extent of humeral head necrosis on MRI is a good predictor of future collapse. [9]
Other imaging modalities include the following:
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Bone scan [8] – Can be helpful when disease is suggested clinically but is not apparent on radiographs; not commonly used because of the high success rates of MRI
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Tomography – Helpful in stage II disease to further define the lesion
Other Tests
Additional studies may include the following:
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Biopsy – Can be performed at the time of surgery (eg, core decompression), but the diagnosis usually is based on clinical and radiographic findings.
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Venography
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Intraosseous pressure measurements
Histologic Findings
The first phases involve cell and marrow necrosis. The reparative phase occurs as the dead bone is removed and replaced by healthy bone. During this period, the bone is weak and subject to subchondral collapse. Following collapse of the subchondral plate, damage to the articular cartilage occurs with resultant arthritic changes to the joint.
Staging
Osteonecrosis of the humeral head has been staged by Ficat and Arlet (modified for the shoulder) [10] :
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Stage I - Normal
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Stage II - Cystic and/or osteosclerotic lesions; humeral head contour is normal; see the image below
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Stage III - Subchondral collapse or crescent sign
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Stage IV - Narrowing of joint space; secondary osteoarthritic changes of the glenoid fossa and the glenohumeral head, such as cysts, marginal osteophytes, and destruction of cartilage, as seen in the image below
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Shoulder osteonecrosis stage II disease.
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Shoulder osteonecrosis stage IV disease.
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Shoulder hemiarthroplasty in a patient with shoulder osteonecrosis.
