A 62-year-old woman with osteoporosis falls on her outstretched hand (FOOSH injury) while gardening. Plain radiographs of the wrist show a fracture of the distal radius with the distal fragment displaced dorsally and radially, creating a characteristic 'dinner fork' deformity. The fracture extends into the radiocarpal joint. Comminution is noted on the volar aspect. Which classification best describes this injury?