Intraoperative Simulated Weightbearing Lateral Foot Imaging: The Clinical Utility and Ability to Predict Sagittal Plane Position of the First Ray in Lapidus Fusion

The sagittal plane relationship of the first to second ray is a primary determinant of proper alignment in Lapidus midfoot fusion as assessed both clinically and on postoperative weightbearing lateral radiographs. The traditional approach to intraoperative fluoroscopic imaging allows for accurate assessment of fixation placement and intermetatarsal angle correction but only a crude evaluation of final sagittal plane alignment. Surgeons have used various methods in an attempt to load the foot during lateral imaging. This had led to inconsistent results and the potential for poor outcome. Skepticism exists regarding the ability of simulated weightbearing fluoroscopy to predict the final outcome, and evidence is lacking to support this practice. A prospective investigation was performed to assess the correlation of the first to second ray sagittal plane alignment as demonstrated on intraoperative simulated weightbearing lateral foot imaging studies and the 10-week postoperative lateral weightbearing radiograph. A consistent simulated weightbearing technique was used prospectively with 50 consecutive cases of Lapidus midfoot fusion with the goal of achieving parallel sagittal plane alignment of the first and second metatarsals with no divergence. Although 47 cases had no divergence and 3 had divergence with mild first ray elevatus, all 50 cases demonstrated a direct correlation between the intraoperative simulated and postoperative full weightbearing images. In conclusion, we believe the findings from our intraoperative imaging technique are a reliable predictor of first ray sagittal plane alignment in Lapidus midfoot fusion.