Research progress on the application of mixed reality technology in femoral tunnel positioning during anterior cruciate ligament reconstruction

Femoral tunnel malposition remains a leading technical contributor to graft failure and revision after anterior cruciate ligament reconstruction (ACLR), particularly in revision surgery, remnant-preserving reconstruction, and multiligament knee reconstruction where arthroscopic landmarks are distorted and tunnel collision must be avoided. Conventional positioning strategies (e.g., clock-face orientation, bony landmarks, and radiographic quadrant methods) provide incomplete three-dimensional control and are susceptible to surgeon dependency and anatomical variability. Mixed reality (MR), distinct from virtual reality (VR) and conventional augmented reality (AR), enables depth-aware holographic visualization, spatial anchoring of patient-specific anatomy, and hands-free interaction, offering a potentially intuitive platform to enhance intraoperative guidance. This narrative review synthesizes evidence on (i) persistent limitations of existing femoral tunnel positioning methods and technology-assisted navigation, (ii) current MR-assisted workflows and intraoperative constraints (registration accuracy and drift, occlusion, sterility and ergonomics), and (iii) transferable lessons from orthopedic MR applications beyond ACLR. Available clinical evidence in ACLR remains limited, but early studies suggest improved tunnel localization consistency without clear short-term functional superiority. Future research should prioritize robust registration/tracking solutions, standardized accuracy endpoints, and well-designed comparative trials to determine whether MR meaningfully improves long-term stability, revision risk, and patient outcomes.