A surgical instrument arrangement has a modular motor drive unit which has a drive arrangement having at least one output element, an instrument shaft that can be detachably connected to the drive unit, and a drive arrangement having at least one input drive element. The output drive arrangement and the input drive arrangement can be coupled to each other by a mechanical interface that has at least one single-sided linkage, a pin, and a cut-out, wherein the pin can be radially expanded in the cut-out. Alternatively, a gap may be formed between the pin and the cut-out, which gap is wavy in the radial direction, and in which a radially displaceable, axially fixed intermediate element arrangement is arranged. The surgical instrument arrangement may also include a sterile barrier, which is provided to envelop the drive unit and to be arranged between the drive unit and the instrument shaft.