Failure of medullary tubes. A materials analysis

The objective of this study is to determine the effects of autoclaving on the stress, strain, ultimate tensile strength (UTS), fracture strain, modulus, and yield stress of nylon medullary tubes. There are three reports describing nylon medullary tube failure in the literature. All cases involved the use of nylon medullary tubes during open reduction internal fixation of fractured long bones. We demonstrated increased brittleness and decreased strength with increased exposure of medullary tubes to autoclaving, most dramatically after 100 autoclave cycles. Visual inspection of tubes is a clear indication of material degradation after repeated autoclaving. Furthermore, there is a significant difference in ultimate tensile strength (P < 0.0001) between tubes exposed to less than 100 sterilization cycles compared to tubes exposed to greater than 100 cycles. Likewise, there is a significant decrease in yield stress (P < 0.0004) between the same groups. We recommend disposal and replacement of nylon medullary tubes before they are exposed to 100 autoclaving cycles in order to avoid failure of the device.