The Rise of AI Companions: From Prediction to Surgery in the Digital Twin Era.

Artificial intelligence (AI) is rapidly reshaping orthopaedic surgery, supported by advances in data science, computational power, and perioperative digitalization. Within this evolving landscape, five "AI companions" structure the surgeon's workflow. The "AI Scribe" maximizes administrative efficiency while preserving the surgeon-patient relationship. The "Strategic Assistant" supports the continuum from diagnosis to decision-making and personalized care. The "Surgical Co-pilot" integrates real-time data, digital twins, and vision-language-action synergy to enhance intraoperative guidance. The "Learning Sentinel" leverages collective experience to inform practice, education, and continuous improvement. The "Agile Trauma Vanguard" secures emergency decision-making while contributing to the decentralization of expertise. These systems rely on digital twins, task-specific, data-driven models continuously refined through patient outcomes via automated or semi-automated feedback loops. While early applications have demonstrated feasibility, their clinical value remains insufficiently established, highlighting the need for robust evaluation frameworks focused on patient-centered outcomes and real-world effectiveness. In parallel, economic models remain uncertain for technologies generating largely intangible returns. Their integration into practice will require surgeons to develop strong oversight capabilities and a clear understanding of model performance, scope, and limitations. Open science, data sharing, and digital sovereignty will be critical to ensure transparency, reproducibility, and equitable access. AI companions may ultimately redefine orthopaedic care, provided that their deployment is guided by rigorous validation and appropriate governance. LEVEL OF EVIDENCE: V; Expert opinion, Narrative review.