Intramedullary rod

An intramedullary rod, also known as an intramedullary nail (IM nail) or inter-locking nail or Küntscher nail (without proximal or distal fixation), is a metal rod forced into the medullary cavity of a bone. IM nails have long been used to treat fractures of long bones of the body. Gerhard Küntscher is credited with the first use of this device in 1939, during World War II, for soldiers with fractures of the femur. Prior to that, treatment of such fractures was limited to traction or plaster, both of which required long periods of inactivity. IM nails resulted in earlier return to activity for the soldiers, sometimes even within a span of a few weeks, since they share the load with the bone, rather than entirely supporting the bone.

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. However the biggest problem with the earlier designs was the failure to prevent collapse or rotation in inherently unstable fractures. This was addressed by the introduction of the concept of 'locking' of the nails using bolts on each end of the nail (thus fixing the nail to the bony cortex and preventing rotation among the fragments), leading to emergence of locked IM nailing, which is the standard today.

At a median 14 years after tibial nailing of isolated tibial fractures, patients' function is comparable to population norms, but objective and subjective evaluation shows persistent sequelae which are not insignificant.

...
Wikipedia