Midterm results of porous tantalum femoral cones in revision total knee arthroplasty

Background: Severe bone loss during a revision total knee arthroplasty (TKA) remains a challenging problem. The purpose of this study was to determine the midterm clinical outcomes, fixation as evaluated radiographically, and survivorship of tantalum femoral cones used during revision TKAs in patients with severe femoral bone loss. Methods: From 2003 to 2011, 159 tantalum metaphyseal femoral cones were implanted in 157 patients at a single institution. Knee Society scores, radiographic results, and implant survivorship were analyzed. Two patients were lost to follow-up. Nineteen died of causes unrelated to the surgery but had been followed for >2 years and thus were included in the study. The mean age at the time of the index surgery was 64 years, and 82 patients were male. The mean duration of follow-up was 5 years (range, 2 to 10 years). Results: The mean Knee Society score increased from 47 preoperatively to 65 at the most recent follow-up evaluation (p = 0.1). Radiographically, all 134 unrevised femoral cones were seen to be well fixed without any evidence of loosening. At 5 years, 23 cones had been revised: 14 because of infection, 6 because of aseptic loosening of the cone (all in hinged TKAs in patients with a Type-3 defect), and 3 because of ligamentous instability. The 5-year survivorship was 96% when the end point was revision of the cone due to aseptic loosening, 84% when it was revision of the cone for any reason, and 70% when it was any reoperation. Conclusions: In what we believe to be the largest series of such implants, femoral cones provided a durable and reliable option for metaphyseal fixation during revision TKA with severe femoral bone loss. Aseptic failure of the femoral cone was associated with use of a hinged TKA in a patient with a Type-3 bone defect. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.