Biomechanical considerations in intramedullary fixation of lower-extremity fracture.

Since Gerhard Kuntscher's first cloverleaf design was introduced in the early 1940s, intramedullary nail geometry has become increasingly complex. Many design changes have been introduced, and these have had profound effects upon the mechanical performance of intramedullary devices, making them more versatile. The subset of long-bone fractures amenable to intramedullary fixation is expanding, largely because of these advancements in nail design. Selection of the appropriate nail and bone-nail construct for each fracture configuration requires a knowledge of basic biomechanical principles behind nail design and the implant-host interface. Appropriate clinical application of this knowledge not only ensures the best possible intramedullary fixation of long-bone fractures, but it also aids in avoiding some of the complications that may occur.