We present an interactive and multimodal-based augmented reality system for computer-assisted surgery in the context of ear, nose and throat (ENT) treatment. The proposed processing pipeline uses fully digital stereoscopic imaging devices, which support multispectral and white light imaging to generate high resolution image data, and consists of five modules. Input/output data handling, a hybrid multimodal image analysis and a bi-directional interactive augmented reality (AR) and mixed reality (MR) interface for local and remote surgical assistance are of high relevance for the complete framework. The hybrid multimodal 3D scene analysis module uses different wavelengths to classify tissue structures and combines this spectral data with metric 3D information. Additionally, we propose a zoom-independent intraoperative tool for virtual ossicular prosthesis insertion (e.g. stapedectomy) guaranteeing very high metric accuracy in sub-millimeter range (1/10 mm). A bi-directional interactive AR/MR communication module guarantees low latency, while consisting surgical information and avoiding informational overload. Display agnostic AR/MR visualization can show our analyzed data synchronized inside the digital binocular, the 3D display or any connected head-mounted-display (HMD). In addition, the analyzed data can be enriched with annotations by involving external clinical experts using AR/MR and furthermore an accurate registration of preoperative data. The benefits of such a collaborative surgical system are manifold and will lead to a highly improved patient outcome through an easier tissue classification and reduced surgery risk.