Explanation:
In the Palmer classification for traumatic TFCC tears: 1A is a central perforation, 1B is an ulnar avulsion (with or without ulnar styloid fracture), 1C is a distal carpal attachment tear, and 1D is a radial avulsion. Reference: Palmer AK, 'Triangular fibrocartilage complex lesions: a classification', J Hand Surg Am (1989).