A device for sterile coupling of a percutaneous surgical instrument to a rotary drive tool (5). The device has a flexible envelope (1) intended to confine the drive tool (5), a connector piece (3) for 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), and also a tubular ring (2) positioned on the inner surface of the envelope (1) in the area of the opening (12) and configured to rigidly connect the envelope (1) to the body of the drive tool (5). The connector piece (3) is configured to be able to pass through the ring and turn freely inside the ring when driven by the rotary drive tool (5). The connector piece (3), the ring and the envelope have means (22, 34, 14) which 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).
