Boomerang screw trajectory: A recognizable pattern of screw malposition in arthroscopic subtalar arthrodesis

Background and Aims: Arthroscopic subtalar arthrodesis requires precise screw placement within a constrained medial calcaneal corridor, where malposition may compromise fixation and risk cortical violation. While conventional screw misplacements are recognized, atypical patterns remain underreported. This study aimed to describe a distinctive medial screw deviation pattern, termed the Boomerang Screw Trajectory, and to highlight its anatomical pathway, clinical implications, and intraoperative recognition. Materials and Methods: A case of posterior arthroscopic subtalar arthrodesis performed for isolated subtalar arthritis was evaluated. Clinical findings, radiographic and computed tomography imaging, surgical technique, and postoperative outcomes were analyzed. Intraoperative fluoroscopic views included lateral, oblique, and anteroposterior projections, while postoperative assessment incorporated axial (Harris) view imaging to evaluate screw trajectory. Results: Postoperative imaging demonstrated an unrecognized medial screw deviation following an in–out–in trajectory. The screw engaged the calcaneal tuberosity, exited the medial cortex inferior to the sustentaculum tali, and re-entered the calcaneal body before achieving talar purchase, forming a curved “boomerang-like” configuration. Despite early union and absence of symptoms, the screw was electively removed. At one-year follow-up, successful fusion and satisfactory clinical outcomes were observed. Conclusion: The Boomerang Screw Trajectory represents a distinct pattern of screw malposition characterized by medial cortical exit and re-entry. Recognition of this configuration underscores the limitations of standard fluoroscopic views and highlights the importance of axial or projected calcaneal imaging during guidewire placement. Awareness of this pattern may improve intraoperative vigilance, optimize screw positioning, and reduce hardware-related complications in subtalar arthrodesis.