Lesson plan
Codman triangle
The Codman triangle (previously referred to as Codman's triangle) is the triangular area of new subperiosteal bone that is created when a lesion, often a tumor, raises the periosteum away from the bone. A Codman triangle is not actually a full triangle. Instead, it is often a pseudotriangle on radiographic findings, with ossification on the original bone and one additional side of the triangle, which forms a two sided triangle with one open side. This two sided appearance is generated due to a tumor (or growth) that is growing at a rate which is faster than the periosteum can grow or expand, so instead of dimpling, the periosteum tears away and provides ossification on the second edge of the triangle. The advancing tumour displaces the periosteum away from the bone medulla. The displaced and now lateral periosteum attempts to regenerate underlying bone. This describes a periosteal reaction. The main causes for this sign are osteosarcoma, Ewing's sarcoma, eumycetoma, and a subperiosteal abscess.
Article summary
The Codman triangle (previously referred to as Codman's triangle) is the triangular area of new subperiosteal bone that is created when a lesion, often a tumor, raises the periosteum away from the bone. A Codman triangle is not actually a full triangle. Instead, it is often a pseudotriangle on radiographic findings, with ossification on the original bone and one additional side of the triangle, which forms a two sided triangle with one open side. This two sided appearance is generated due to a tumor (or growth) that is growing at a rate which is faster than the periosteum can grow or expand, so instead of dimpling, the periosteum tears away and provides ossification on the second edge of the triangle. The advancing tumour displaces the periosteum away from the bone medulla. The displaced and now lateral periosteum attempts to regenerate underlying bone. This describes a periosteal reaction. The main causes for this sign are osteosarcoma, Ewing's sarcoma, eumycetoma, and a subperiosteal abscess.
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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Key claims and bibliography are generated from the same tracked claims and sources as the article page.