Implant fracture of the Trochanteric Fixation Nail Advanced (TFNA) lag screw through a cement fenestration: a case report

Introduction: Cephalomedullary nails (CMNs) are commonly used to treat proximal femur fractures. The Trochanteric Fixation Nail Advanced (TFNA, DePuy Synthes ) is a CMN system, introduced in 2015, featuring significant design modifications compared to its predecessors. These include a new Ti-15Mo alloy and a fenestrated lag screw that permits cement augmentation of the femoral head. Nevertheless, device-specific failures have emerged. We report a unique mode of failure: breakage of the lag screw through a cement fenestration. Case presentation: An 81-year-old woman with an AO/OTA 31-A2.1 pertrochanteric fracture underwent long TFNA fixation (130°, 10 × 400 mm) with a 90-mm lag screw positioned center–center in dynamic mode. At 7.5 months, she developed severe atraumatic hip pain and imaging demonstrated non-union, autodynamization, and lag screw breakage. Retrieval of the broken implant demonstrated a fracture through the first cement fenestration of the lag screw. She subsequently underwent conversion to total hip arthroplasty. Discussion: There have been several reports of increased implant breakage associated with the TFNA in a distinctive “stepped propagation” pattern of metal cracking. These typically occur at the lag screw aperture. However, fenestrations in the lag screw also appear to act as stress risers when cement is not used. In non-union, stress is concentrated at the first fenestration, initiating crack propagation and implant failure. Conclusion: TFNA lag screws are vulnerable to fatigue fracture in the setting of non-union. Fenestrated head elements should be reserved for cases in which cement augmentation is planned. Patients treated with TFNA implants should be monitored closely for delayed union to mitigate the risk of fatigue failure.