Abstract: A device for assisting surgery includes means for offsetting a rotation of a first type and a second type, a mechanism for transmitting a rotation of a third type, and a mechanism for transforming the rotation of a third type into a translation. An elastic element is connected at one end to the mechanism for transmitting the rotation of a third type. The mechanism for transmitting the rotation of a third type is connected to a rotary motor, the rotation of the motor in a first direction causing the lowering of a tool and an elongation of the elastic element, the rotation of the motor in a second direction causing the raising of the tool and a contraction of the elastic element, and, when the tool is lowered and the rotary motor is not exerting any torque, the elastic element returns to an initial shape causing the raising of the tool.