An insertion device includes a first engagement arm having a first body portion and a first proximal extension, a second engagement arm including a second body portion and a second proximal extension, and an adjustment mechanism. The second proximal extension is disposed about the first proximal extension and is slidable therealong to vary a spacing between the first and second engagement arms. The adjustment mechanism includes an adjustment screw rotatably coupled to the first proximal extension and an adjustment cylinder coupled to the second proximal extension. The adjustment cylinder is configured to receive the adjustment screw in threaded engagement therewith such that rotation of the adjustment screw relative to the adjustment cylinder urges the second proximal extension to translate along the first proximal extension to vary the spacing between the first and second engagement arms.
