Interlocking screw backout from a preassembled polymer inlay in a retrograde femoral nail system: A retrospective review.

Interlocking screw backout is a significant complication of femoral nailing that may lead to pain, fixation failure, and need for reoperation. The risk for this is increased in osteoporotic bone or in cases of so-called "extreme nailing" when the articular segment is short, and fixation is limited. A newly developed retrograde femoral nailing system (DePuy Synthes RFN-Advanced™ Retrograde Femoral Nailing System (DePuy Synthes, Monument, CO)) was designed specifically to prevent this known failure mode and was recently approved for use within the United States. A preassembled polymer inlay at the distal portion of the nail (through which the distal interlocking screws are placed) is marketed as eliminating interfragmentary motion and screw toggle which can ultimately lead to screw backout. Despite this purposeful design, multiple surgeons at our Level I trauma center in the southeastern US have noted a relatively high occurrence of distal interlocking screw backout when compared to other nail designs used in the same time. We present a single institution retrospective review of placed retrograde femoral nails and their complications, particular loss of interlock bolt fixation and revision surgery in the DePuy Synthes RFN-A group (21.43 %), compared to other implant designs (5.41 %) during the initial implementation period at our institution.