What causes Snow-capping in the epiphysis (often femoral or humeral head) on plain radiography?
Let me know in the comments.
Click to reveal the answer
Dense sclerosis of the epiphysis representing the healing phase of avascular necrosis (osteonecrosis), a condition caused by interruption of blood supply leading to bone cell death, revascularization, and repair; associated with risk factors including trauma, glucocorticoid use, sickle cell disease, alcohol abuse, and systemic lupus erythematosus.
Why is it called so?
The sign is named for the appearance of dense sclerosis capping the superior aspect of the femoral or humeral head on plain radiographs, resembling a snow-capped mountain peak.
Pathophysiology
Interruption of vascular supply causes ischemic necrosis of osteocytes within the epiphysis; during the reparative healing phase, reactive bone formation at the necrotic interface produces dense sclerosis visible as a radiopaque cap prior to potential subchondral collapse.
Alternative names: Snowcap sign, snowcapping
Other associated named signs: Crescent sign, double-line sign
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
Improve Content And Help Your Colleagues!
Found an error in the post? Please let us know using our contact page and we will update it with due credits!
If you wish to contribute radiological images for this case (or any other article on the website), you can submit them here and you will be duly credited: Submit radiology case