AI-Driven CT-MRI Image Fusion and Segmentation for Automatic Preoperative Planning of ACL Reconstruction

BACKGROUND: The goals of this study were to develop an artificial intelligence (AI)-driven automated preoperative planning system for anterior cruciate ligament (ACL) reconstruction by integrating deep learning with computed tomography (CT)-magnetic resonance imaging (MRI) image fusion and segmentation, and to evaluate its accuracy. METHODS: Structures on CT and MRI scans of 200 knee joints from patients with an intact ACL (aged 18 to 50 years, 81.0% male, all ethnic Chinese) were manually annotated. Fusion of the CT and MRI images was performed using a Dual-UNet registration architecture incorporating multiscale information fusion, enabling dynamic 3D reconstruction of the fused images for ACL insertion site identification and isometry assessment. A deep-learning framework was trained to analyze the fused image to precisely optimize ACL tunnel positioning, including identifying the entrances and exits of the femoral and tibial tunnels. Criteria in the automated planning included proximity to the ideal point, coverage of the anatomical footprint area, and isometric length variation of <2 mm. The accuracy of the AI system was then validated in 36 ACL reconstructions performed in bone models by comparing the drilled femoral and tibial tunnel lengths and graft length between the tunnels with the planned values. Finally, clinical feasibility was tested in 36 patients undergoing ACL reconstruction surgery using 3D-printed patient-specific guides derived from the AI planning, with 36 conventional surgeries as controls. Deviation of tunnel positions from the planned positions was compared between the 2 groups. RESULTS: CT-MRI image fusion was able to generate an individualized 3D model with high segmentation accuracy (Dice coefficient = 0.864). The AI planning required 192 ± 90.2 seconds per case. In the bone model validation, the mean deviation between the planned and executed values was <1 mm for the femoral and tibial tunnel lengths and graft length between the tunnels (all p > 0.05). In the clinical testing, the AI-guided group demonstrated significantly smaller deviations from the ideal point compared with the conventional group in the deep-to-shallow (D-S), high-to-low (H-L), medial-to-lateral (M-L), and anterior-to-posterior (A-P) directions (all p < 0.05). CONCLUSIONS: The AI-driven segmentation of CT-MRI fusion images and automatic preoperative ACL reconstruction planning demonstrated the capability to automatically, precisely, and reproducibly generate plans for nearly ideal tunnel entry and exit points with isometric, anatomical, and individualization characteristics. This technology is expected to hold clinical potential for ACL reconstruction, including reduced complication and revision rates and enhanced postoperative function.