Differences between image-based and imageless robotics for total knee arthroplasty - an overview

Robot-assisted total knee arthroplasty (TKA) has revolutionized implant positioning by enhancing surgical precision. However, significant differences exist between image-based and imageless robotic systems, influencing their accuracy, workflow, and potentially clinical outcomes. As such, this review aims to provide a structured comparison between image-based and imageless systems for TKA relevant to the surgeon. Image-based systems utilize preoperative imaging modalities such as computed tomography (CT) or magnetic resonance imaging (MRI) to construct three-dimensional (3D) anatomical models for surgical planning and intraoperative guidance. In contrast, imageless systems rely on intraoperative anatomical landmark registration, reducing costs and radiation exposure but yielding a potential higher inaccuracy to define the joint-specific coordinate system. This current concepts review examines key differences between these technologies, focusing on coordinate system accuracy, anatomical landmark identification, resection precision, and clinical implications. Image-based systems may demonstrate superior accuracy in defining coordinate systems, particularly for femoral and tibial rotational axes, yet involve higher costs and logistical complexity. Imageless systems offer real-time adaptability and avoid preoperative imaging but may be more susceptible to anatomical registration errors. Comparative clinical studies suggest similar coronal plane alignment error between the two approaches, though image-based systems may offer advantages in tibial slope precision. Radiation exposure is an important consideration, as it varies significantly based on imaging protocols and may warrant greater attention from surgeons, especially for patients who receive frequent CT follow-up. As well, while both system types allow for assessing patellofemoral tracking, in addition patient-specific 3D models allow to restore the native trochlea orientation. Although both systems improve implant positioning compared to conventional techniques, evidence on mid- and long-term improved clinical outcomes compared to the conventional technique is still lacking.