Shoulder complications in sickle cell disease: Challenges, management strategies, and future directions

Table 1 Cruess classification of shoulder avascular necrosis

Stage	Radiographic features	Additional features/details
Stage 1	Radiographs appear normal	Magnetic resonance imaging detects early changes in the bone marrow signal, indicating the onset of the disease without structural alterations
Stage 2	Reparative process with sclerotic or mottled osteopenia	The sphericity of the humeral head is preserved
Stage 3	Appearance of the "crescent sign"	Subchondral radiolucent line signifies a subchondral fracture, with minor joint surface depressions due to localized subchondral collapse
Stage 4	Complete collapse of the articular surface	Destruction of the trabecular pattern and compromise of joint structural integrity
Stage 5	Articular changes in the glenoid	Joint incongruity with osteo-cartilaginous flaps detaching and becoming loose bodies within the joint