The invention relates to modular joint prostheses, comprising a curved head part to the conical pins of which a slip-on joint ball is attached, and comprising a nail which can be inserted into the bone marrow canal of the long bone and has a nail neck, wherein a connecting means is provided between the head part and the nail neck which holds the head part in a non-rotatable manner. The connecting means comprises at least one collar-like module which is located in the axial direction of the nail and has at least two semi-shells, which are divided in the axial direction of the module, are detachably connected to each other, form an axially extending passage for inserting the nail head into the passage and have recesses for receiving a tensioning means, which in the tensioned state fixes the nail head in the passage exclusively by way of factional engagement.
