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.[2] 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.[4] 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.[