Abstract: A pelvis part prosthesis comprises an essentially hemispherically-shaped shell portion provided with two formed appendices, each of which has a positioning aperture and two connection elements connected to the appendices, and each being provided with a pin inserted with a self-locking tight fit in the positioning apertures. The connection elements are preferably designed as curved plates. The material layer, adjacent to the residual bone material of the pelvis, of the aforementioned parts of the prosthesis, may be in the shape of an open-cell structure to allow the bone material to grow into said structure.