A fixture for performing percutaneous surgery under direct visualization and through a single cannula includes a housing/body attachable to the proximal end of the cannula by a ring. The ring encircles the cannula and is provided with a pair of opposing arms defining a slot therebetween. A mechanism connected to the arms is operable to compress and release the arms such that the fixture can grip the cannula at a plurality of locations along the cannula. The housing/body includes a support column extending between the housing/body and the ring and an optics bore for supporting a portion of a viewing element.