A non-rotationally symmetrical, conical body with a self-locking seat connects the prosthesis to a shaft (5). The periphery of the conical body is formed and matched to a mating shape (15) in the shaft rotationally fixed relative to a longitudinal axis (9) and keyed by the amount of taper so that connection is releasable and repeatedly fixable in the same angular position. <；??>；Two bearing bodies, which slide one another, are respectively connected to an upper arm (3) by the shaft and to a shoulder bone by a platform.
