A device is provided for sterile coupling of a percutaneous surgical instrument to a rotary drive tool (5). The device has a flexible envelope (1) confining the drive tool (5), a connector piece (3) coupling to the percutaneous surgical instrument via one end, and to the drive tool (5) via its other end, by passing through the envelope via an opening (12) A tubular ring (2) is positioned on the inner surface of the envelope (1) in the area of the opening (12) and is configured to rigidly connect the envelope (1) to the body of the drive tool (5). The connector piece (3) passes through the ring and turns freely inside the ring when driven by the rotary drive tool (5). The connector piece (3), the ring, and the envelope interact in order to form a leaktight barrier between the inside and the outside of the envelope (1) in the area of the opening (12).