A trocar cannula assembly can have a retention mechanism for advanced fixation. The retention mechanism can include a first, or distal balloon, and a second or proximal balloon to retain the position of the trocar cannula assembly with respect to a body wall of a patient. An inlet can be fluidly coupled to the retention mechanism via a fluid conduit so that the balloons can be selectively inflated and deflated. The retention mechanism can be coupled to the cannula, forming an integrated cannula assembly, or the retention mechanism can be removably attached to the cannula. Where the retention mechanism is removably attached to the cannula, it can include a double layer inflatable member with an outer layer including the first and second balloons, and an inner layer for retaining the cannula.