A surgical instrument comprising: - an elongated arm extending along a longitudinal axis and having a distal member mounted at a distal end of the elongated arm with means forming a pivot joint around a pivot axis orthogonal to the longitudinal axis; - a rotation shaft coaxial with the elongated arm comprising means forming a universal joint facing the pivot joint; - a distal tool securely fastened at a distal end of the rotation shaft and rotatably mounted on and in the extension of the distal member of the elongated arm, such that the distal tool has two rotational degrees of freedom, distinct and independent of each other, one degree of freedom being around the pivot axis and the other degree of freedom being around an axis collinear to an own axis of the distal tool; - an actuation unit mounted on and in the extension of a proximal end of the elongated arm, said actuation unit comprising motorized means for actuating the motion of the distal tool through at least one of the two rotational degrees of freedom and further comprising controlling means for a user to control the motorized means; - a handle extending from the actuation unit and comprising a lever mechanically coupled to the distal tool for actuation of said distal tool via an actuation cable extending coaxially within said elongated arm and rotation shaft; wherein the handle has a non-axially-symmetric shape and is mounted on and in the extension of the actuation unit with coupling means (12,22) enabling rotation of the handle relative to the actuation unit around the longitudinal axis, and the actuation unit comprises a casing for receiving the motorized means, and wherein the controlling means are adapted to be operated by the user whatever the rotational position of the handle relative to the actuation unit, characterized in that the casing further receives the controlling means, said casing comprising prehensile means for holding the surgical instrument while rotating the handle and the actuation unit relative to one another. - an elongated arm extending along a longitudinal axis and having a distal member mounted at a distal end of the elongated arm with means forming a pivot joint around a pivot axis orthogonal to the longitudinal axis; - a rotation shaft coaxial with the elongated arm comprising means forming a universal joint facing the pivot joint; - a distal tool securely fastened at a distal end of the rotation shaft and rotatably mounted on and in the extension of the distal member of the elongated arm, such that the distal tool has two rotational degrees of freedom, distinct and independent of each other, one degree of freedom being around the pivot axis and the other degree of freedom being around an axis collinear to an own axis of the distal tool; - an actuation unit mounted on and in the extension of a proximal end of the elongated arm, said actuation unit comprising motorized means for actuating the motion of the distal tool through at least one of the two rotational degrees of freedom and further comprising controlling means for a user to control the motorized means; - a handle extending from the actuation unit and comprising a lever mechanically coupled to the distal tool for actuation of said distal tool via an actuation cable extending coaxially within said elongated arm and rotation shaft; wherein the handle has a non-axially-symmetric shape and is mounted on and in the extension of the actuation unit with coupling means (12,22) enabling rotation of the handle relative to the actuation unit around the longitudinal axis, and the actuation unit comprises a casing for receiving the motorized means, and wherein the controlling means are adapted to be operated by the user whatever the rotational position of the handle relative to the actuation unit, characterized in that the casing further receives the controlling means, said casing comprising prehensile means for holding the surgical instrument while rotating the handle and the actuation unit relative to one another.