Which two sites describe the insertions of the common/long extensor tendon?

• A. Extensor Process Of Coffin Bone; Front Of Middle And Proximal Phalanx
• B. Front Of Middle And Proximal Phalanx; Extensor Process Of Coffin Bone
• C. Extensor Process Of Coffin Bone; Navicular Bone
• D. Proximal Phalanx; Short Pastern Bone

Answer: (A)

The main idea here is where the common/long extensor tendon attaches in the digit. It has two key insertion points: first, on the extensor process of the coffin bone (the distal phalanx), and second, on the dorsal (front) surfaces of the proximal and middle phalanges. So the two sites described are the extensor process of the coffin bone and the front of the middle and proximal phalanges. Other options mention bones that aren’t insertion sites for this tendon, like the navicular bone or the short pastern bone, so they don’t fit the tendon’s actual attachments.