Adjustable cannula and methods of use

A surgical instrument, comprising:

• a ring comprising inner surfaces defining a pair of spaced apart circular grooves each having a different radius of curvature, the grooves each being defined by a pair of projections, the projections each extending at an acute angle relative to a planar bottom surface of the ring, the ring comprising an inner wall defining a pathway;
• a positioning member comprising a first portion including an inner surface defining an aperture and a second portion extending from the first portion and including a plurality of spaced apart teeth configured to slidably engage at least one of the grooves to couple the positioning member with the ring, the teeth each extending at an acute angle relative to a planar upper surface of the positioning member, the inner surface of the first portion being concavely curved between opposite first and second ends of the aperture;
• a holding member positioned in the aperture to couple the holding member with the positioning member, the holding member comprising an inner surface defining a passageway, the holding member comprising an annular flange that extends from the inner surface and into the passageway, the passageway defining a first longitudinal axis and including an internal thread form, the flange extending perpendicular to the first longitudinal axis, the holding member comprising an outer surface that is convexly curved between opposite first and second ends of the holding member, the outer surface of the holding member engaging the inner surface of the first portion such that the holding member is rotatable relative to the positioning member;
• three blades positioned in the passageway and each defining a second longitudinal axis, the blades each comprising a lip extending at an acute angle relative to a respective second longitudinal axis, the blades each comprising an arcuate inner surface including an LED light source;
• and
• a locking member rotatably disposed in the passageway such that an external thread form of the locking member engages the internal thread form, a first end surface of the locking member engaging second end surfaces of each of the blades defined by the lips,
• wherein the first portion, the holding member and the blades are positioned within the pathway,
• wherein the blades are movable between a first configuration in which the first and second end surfaces are spaced apart and a portion of each of the blades is substantially aligned with the first longitudinal axis and a second configuration in which the first end surface engages the second end surfaces and the portions of the blades each extend at an acute angle to the first longitudinal axis, and
• the surgical instrument is made entirely from molded plastic.