The invention relates to an augment device, in particular a tibial augment for a knee joint endoprosthesis, comprising a hollow sleeve (10) surrounding a channel (11) extending through the hollow sleeve (10) from a top (12) to a bottom (14) of the hollow sleeve (10), the hollow sleeve (10) comprising a wall (17) having an inner face (14) and an outer face (15). According to the invention the hollow sleeve (10) comprises at least one bending joint (3´), the bending joint (3, 3´) being configured for compressing the channel (10). Thereby the hollow sleeve (10) may be compressed under an external force, leading to a decreased circumference and width of the hollow sleeve (10). This leads to a gap between the perimeter of the augment device (1) and surrounding bone material, breaking any connections. By virtue of this, a much facilitated removal of the augment device (1) can be achieved. Further, the invention provides an extraction tool (5) having grippers (6) for engaging and compressing the augment device (1), and further instruments, particularly a jig (8), for achieving an effective removal. The invention further relates to a corresponding method of handling the augment device (1).La invención se refiere a un dispositivo de aumento, en particular un aumento tibial para una endoprótesis articular de rodilla, comprendiendo una funda hueca (10) que rodea un canal (11) que se extiende a través de la funda hueca (10) desde una parte superior (12) a una parte inferior (14) de la funda hueca (10), la funda hueca (10) comprendiendo una pared (17) que tiene un lado interior (14) y un lado exterior (15). De acuerdo con la invención la funda hueca (10) comprende al menos una junta de flexión (3´), la junta de flexión (3, 3´) configurándose para comprimir el canal (10). Así la funda hueca (10) puede comprimirse bajo una fuerza externa, conduciendo a un ancho y circunferencia disminuidos de la funda hueca (10). Esto conduce a un espacio entre el perímetro del dispositivo de au
