Comparison of Custom 3D Printed Spherical Implants vs Femoral Head Allografts for Tibiotalocalcaneal Arthrodeses

CATEGORY: Ankle Arthritis, Hindfoot INTRODUCTION/PURPOSE: Tibiotalocalcaneal (TTC) arthrodesis is a common treatment option for hindfoot arthritis, deformity correction and salvage of failed total ankle replacement. However, union can be difficult to achieve in patients with bulk bone defects. Femoral head allograft is commonly used in the setting of TTC fusion with severe bone loss, but recent studies have reported concerns of arthrodesis rates of 50% or worse and graft collapse in these patients. Retrograde intramedullary nail placement through custom 3D spherical implants is a novel option for these patients. The purpose of this study was to compare fusion rates, graft resorption and complication rates between patients undergoing TTC fusion with 3D sphere implants versus femoral head allografts. METHODS: All patients who underwent TTC arthrodesis with an intramedullary nail along with a 3D spherical implant or femoral head allograft by the senior author at a single institution from 2013 to 2017 and who had at least one year of follow-up were included in this study. There were 7 patients who received a femoral head allograft and 8 patients who received a 3D printed sphere. Baseline patient and operative characteristics were collected and compared between the 3D sphere and femoral head allograft groups. The rate of successful fusion of the tibia, calcaneus and talar neck to the 3D sphere or femoral head allograft, as determined by radiographs and CT scan, as well as graft resorption and complications were compared between the groups. RESULTS: The rates of union of the tibia (87.5% vs 71.4%), calcaneus (87.5% vs 71.4%), and talar neck (100% vs 42.9%) were higher in the 3D sphere group than in the femoral head allograft group. The rate of union of the talar neck was significantly higher to the 3D sphere implant than to the femoral head allograft (p=0.016). The number of patients achieving successful fusion of all three articulations was higher in the 3D sphere group (75%) than the femoral head allograft group (42.9%), although not statistically significant (p=0.22). The rate of graft resorption was significantly higher in the femoral head allograft group (57.1%) than the 3D sphere group (0%, p=0.016).There were no differences between the groups in terms of complications. CONCLUSION: These data demonstrate that the use of a custom 3D-printed sphere implant is safe in patients with severe bone loss undergoing TTC arthrodesis with a retrograde intramedullary nail. The rate of successful fusion of all three tibial, calcaneal and talar neck articulations was higher to the 3D sphere than to the femoral head allograft, although not statistically significant. Union of the talar neck was significantly higher to the 3D sphere implants than it was to the femoral head allograft. Subsidence was significantly higher with the femoral head allograft than the 3D sphere.