The evolving nature of surgical treatments creates gaps between evidence-based guidelines and actual clinical practice.This article addresses the emerging clinical practice of the EndoVascular Aneurysm Repair (EVAR), a surgical treatment of patients with Abdominal Aortic Aneurysm (AAA). Drawing on a qualitative study across three hospitals, we identified three interplaying expertise traits: the collective, the interpersonal and the technical, each being present to promote surgical work. The evolvement of EVAR is contextualized within technical artefacts and patient characteristics, along with a joint decision approach. The intertwinement between various expertise traits and contextual factors forms a 'community of guidance', nourishing further EVAR innovation without formalized institutions, evidence, training or guidelines. However, the lack of a shared context limits the transfer of evolving knowledge across hospital boundaries.