Catastrophic Failure After Open Reduction Internal Fixation of Femoral Neck Fractures With a Novel Locking Plate Implant

Objectives: To determine if the use of a novel proximal femoral locking plate could reduce the incidence of femoral neck shortening and improve clinical outcomes after open reduction internal fixation (ORIF) for femoral neck fractures as compared with historical controls. Design: Single surgeon, retrospective case-control study. Setting: Academic level I trauma center. Patients/Participants: Twenty-one femoral neck fractures treated with the posterolateral femoral locking plate (Synthes, Inc, Paoli, PA) were eligible for inclusion. Eighteen met inclusion/exclusion criteria with a mean follow-up of 16 months. Intervention: ORIF of femoral neck fracture with the posterolateral femoral locking plate. This consists of a side plate with multiple locking screws directed into the femoral head at converging/diverging angles and a single shaft screw. Intraoperative compression was achieved with partially threaded screws before locking screw insertion. Main Outcome Measurements: Maintenance of reduction was assessed by comparing immediate postoperative and final follow-up radiographs. Clinical outcome was assessed with Harris Hip Scores after 1 year. Complications and secondary operations were noted. Results: Seven (36.8%) of 18 patients experienced catastrophic failure. Five of these patients required total hip replacement, whereas the remaining 2 died before further treatment. The remaining 11 patients (61.1%) achieved bony union; the average displacement of the center of the head did not differ when compared with historical controls (0.78 mm inferiorly, 1.62 mm medially, and 2.4 degrees of increased varus vs. 0.86 mm, 1.23 mm, and 0.6 degree). Complications in this group include 1 instance of screw fracture, 2 total hip replacements, and a peri-implant subtrochanteric femur fracture. The average patient age and proportion of displaced fractures did not differ between the historical control and experimental groups. Fracture displacement was strongly associated with catastrophic failure in the experimental group only. Average Harris Hip Scores was significantly worse compared with that of historical controls (67.9 vs. 84.7, P = 0.05). Conclusions: ORIF of femoral neck fractures using a locking plate construct yielded unacceptably poor outcomes in this patient population. We hypothesize that the stiffness of this construct prevents any fracture site micromotion, placing the mechanical burden on the implant, which can result in failure at the bone-screw interface or fatigue failure of the implant itself.