Heatmaps on Radiological Safety in Minimally Invasive Midfoot Fusion: A Cadaver Study

Category: Midfoot/Forefoot Introduction/Purpose: The popularity of minimally invasive (MIS) techniques in foot and ankle surgery continues to grow exponentially. However, it comes with certain limitations that present notable challenges. One significant hurdle is the absence of direct visualization of neurovascular structures and tendons. This study aims to present fluoroscopic heatmaps that illustrate the trajectories of major structures encountered during MIS midfoot procedures. Methods: Sequential dissection was performed on nine below-knee specimens identifying the following anatomy structures: anterior tibialis tendon (ATT), extensor hallucis tendon (EHL), extensor digitorum longus tendon (EDL), superficial peroneal nerve (SPN) and dorsal neurovascular bundle (DNVB). Subsequently, flexible wires were positioned and securely placed adjacent to the medial and/or lateral borders of these structures to visualize their trajectories on X-ray imaging. Anteroposterior (AP) and oblique fluoroscopy images of the foot, featuring a calibration marker of a known diameter, were taken, alongside macroscopic photos. All fluoroscopy images were adjusted to a uniform scale and standardized to a single foot fluoroscopy. The coordinates of the structures were marked on these standardized foot AP and oblique fluoroscopy views. These coordinates were then inputted into a custom-made Python script to generate heatmaps. Results: Successfully generated heatmaps encompassed the DNVB, ATT, EDL, EHL, and SPN, on AP and oblique fluoroscopy images of the foot. The color gradient used visually represents varying magnitudes, with red indicating the most frequent locations of the structures and blue signifying lower occurrences. These heatmaps also illustrate the highest-risk areas for iatrogenic injury to the structures during MIS procedures. Conclusion: This study can empower surgical navigation and improve safety in MIS midfoot procedures by providing surgeons with a fluoroscopic heatmap detailing the trajectories of major anatomical structures.