In one embodiment, the invention includes a medical instrument for insertion into a subject including an elongate body which includes a proximal end and a distal end, a broad face, a narrow face, a lateral side and a counter-lateral side, said faces and sides defining a trapezoid shape along the length of the elongate body. The broad and narrow faces are generally parallel to one another and the lateral and counter-lateral sides each connect between the broad and narrow faces. The distal end of the instrument includes a cutting edge and is provided for insertion into the subject, wherein an incision made in a target area of the subject results in a linear penetration in the target area. An aperture may be disposed at or near the distal end of the medical instrument.
