Codman Triangle (Codman Angle)

Reactive triangles of periosteal new bone formation (Figure 1) were pointed out by Hugo Ribbert ¹ (Bonn University) in 1914. In bone tumors of central origin, he said that the elevation of the periosteum represented ‘an area of newly formed non-tumor bone … due to … the adjacent expanding tumor mass.’ ² Figure 2 ‘Registry #513. One sees not only the tumor developing radiating spicules outside of the cortex but an area of loss of density within the bone itself.’<xref ref-type="bibr" rid="ref19_1"> ¹ </xref> A Codman triangle is evident at the proximal margin of the tumor along the anterior surface of the femur. Reprinted from Codman<xref ref-type="bibr" rid="ref19_5"> ⁵ </xref> The nomenclature used by the Registry of Bone Sarcoma. <italic>Am. J. Roentgenol.,</italic> 13, <bold>10</bold>5–126, with permission of the ARRS https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003076568/34c29fd5-5662-4e8f-b58c-badd7fa5d724/content/fig19_2_B.jpg"/>