Today, collaboration is no more limited to the designers' sphere. Especially the design of products or systems dedicated to expert users requires the active participation of the users themselves. The aim of this paper is to explore the design collaboration process between designers and expert users in the specific case of new surgical instruments. Two design meetings have been studied; one technical design review without the user, and one design validation meeting with the expert user. Designers were using an annotation tool as a communication support during the design process, before and during the first meeting. Our observations showed that the designers were not able to make decisions about the technical solutions that contained user related issues. Moreover, the expert user's comments during the validation meeting altered the proposed solution. In conclusion, it seemed that the actual design organization should be changed in order to integrate the expert user more actively. Annotation as a communication tool proved to be useful for technical exchanges, but we found important limitations for non technical users, we then propose solutions for further improvement of the tool.