Groove of Abductor digiti I longus [extensor carpi obliquus]

On the dorsal surface, next to the styloid process of the radial distal extremity, the groove of abductor digiti I longus (Sulcus musculi abductor digiti I longus/Musculi extensori carpi obliquus) is weak and oblique.

The two others are vertical and really dorsal: the groove of extensor carpi radialis, in the middle, is the wider and corresponds to the tendos of the radial extensors of the carpus muscles (or of the radial extensor of the carpus that result of their union); the groove of extensor digitali communis is narrower and corresponds to the common extensor of the fingers.