Intramedullary rod

The oldest intramedullary nail was found in the left knee of a mummy named Usermontu, the remains of an Egyptian man from more than 3,500 years ago. Researchers believe the pin was inserted after the man's death, but before his burial.

Design

The earliest IM nails were triangular or V-shaped in cross-section. Later they were modified to their present and more rotationally stable clover-leaf shape. Several modifications and shapes were introduced subsequently for various bones such as V-nails for tibia, radius and ulna nails, Rusch nails etc.

Although stainless steel was used for older IM nails, titanium has several advantages, including lower mechanical failure rates and improved biocompatibility. A more significant problem with earlier designs was their failure to prevent collapse or rotation in inherently unstable fractures. This was addressed by the introduction of the concept of 'locking' the nails, where bolts on each end of the nail fix it to the bony cortex, preventing rotation among the fragments. This led to the emergence of locked IM nailing, which is the standard today.

The extension mechanism of intramedullary can be of two types: ratcheting, such as in the Bliskunov, Albizzia, and the Internal Skeletal Kinetic Distractor (ISKD, removed from market in 2015) nails; and rotating spindle, as in the Fitbone, Phenix, PRECICE, and PRECICE 2 nails.