Ulnar Claw Hand (Claw Hand): this is due to a lesion in the ulnar nerve. The MCP joints are hyperextended for that ring and very little fingers because of the loss of the 3rd and fourth lumbrical muscles on account of a lesion of your deep branch in the ulnar nerve. https://www.theorthopaedicandpainpractice.com/what-are-the-different-bones-found-in-my-hand/