Introduction: Metaphyseal bone defects seen at revision total knee replacement (TKA) have traditionally been treated with bone graft or cement. Recently, metal augments have surfaced as viable alternatives to conventional methods previously used in these patients. Newer 3D-printed metal cones offer better biological fixation as a means of improving construct stability. This study aimed to determine clinical and radiographic outcomes of the novel 3D-printed titanium cone augments for femoral and tibial metaphyseal bone defects.
Materials and methods: A retrospective review was undertaken of 72 patients who underwent revision TKA with metaphyseal cones (Stryker) and stemmed implants from 2015-2017. Knee Injury and Osteoarthritis Outcome Scores (KOOS Jr) and VR/SF-12 scores were recorded. Knee Society radiographic scores were calculated at latest follow up to evaluate for radiolucency and biological fixation. Loosening noted on radiographs and reoperation for any reason were the endpoints to determine survivorship.
Results: A total of 68 patients with 78 cones (58 tibial, 20 femoral) met inclusion criteria. Mean follow up was 3.4 years (range 2-5.4 years). The average KOOS Jr score increased from 38 preoperatively to 66 at two years. The average VR/SF-12 PH score increased from 33 preoperatively to 37 at two years. The average VR/SF-12 MH score increased from 46 preoperatively to 54 at two years. Twelve percent of tibial implants and 10% of femoral implants with cones were found to have lucency in at least one radiographic zone. Overall survivorship at latest follow up was 93% with two patients requiring revision for infection, two revised following mechanical complications, and one patient who underwent polyethylene exchange after experiencing mechanical complications. When considering only aseptic loosening, survivorship was 100%.
Conclusion: This 3D-printed titanium femoral and tibial cone augment system showed excellent survivorship, biological fixation, clinical outcomes, and radiographic outcomes in the setting of TKA. Further studies are needed for assessment of long-term survivorship.