What is the 'working part' of the nail in an IM nail?

What is the 'working part' of the nail in an IM nail?

• A. The threaded distal tip
• B. The region near the entry point
• C. Area between the most distal and most proximal screws
• D. The segment with the largest diameter

Answer: (C)

In an intramedullary (IM) nail, the part that actually carries bending load during weight bearing is the segment between the locking screws that hold the nail in place at each end of the fracture. This is the area between the most proximal screw and the most distal screw—the working length. The stiffness and stability of the construct are determined by how long or short that segment is: a longer working length makes the construct more flexible, while a shorter one makes it stiffer. The other features described (such as the threaded distal tip, the region near the entry point, or the diameter of a particular segment) do not define the load-bearing portion of the nail. They relate to fixation, placement, or geometry but not to which portion actually transmits bending stress between locking screws.

In an intramedullary (IM) nail, the part that actually carries bending load during weight bearing is the segment between the locking screws that hold the nail in place at each end of the fracture. This is the area between the most proximal screw and the most distal screw—the working length. The stiffness and stability of the construct are determined by how long or short that segment is: a longer working length makes the construct more flexible, while a shorter one makes it stiffer.

The other features described (such as the threaded distal tip, the region near the entry point, or the diameter of a particular segment) do not define the load-bearing portion of the nail. They relate to fixation, placement, or geometry but not to which portion actually transmits bending stress between locking screws.