Retrieval and analysis of intramedullary rods.

UNLABELLED: We examined ten intramedullary rods of similar design after routine retrieval from patients. Of these ten rods, four were found to exhibit cracking around their proximal third. This behavior could not be attributed to the surgical techniques employed or to the length of time in vivo of these rods. Rather, the cracking was a function of both the metal alloy used and the method of manufacture, which occasionally allowed a weld zone to be located at the point of maximum stress with the result that cracking occurred. A change in alloy composition to a low-carbon form of 316 stainless steel probably would reduce the risk of cracking. CLINICAL RELEVANCE: In the treatment of orthopaedic disorders, it is important for the operating physician to appreciate the problems that may be encountered in using implants. One of the most important of these problems is the possibility of implant failure. The present report illustrates how a combination of both metallurgical and fabrication factors may cause such an event to occur.