A trocar comprising: a retention cannula comprising: a proximal end, a distal end, and a longitudinal axis; a cannula body between the proximal end of the cannula and the distal end, the cannula body comprising a cannula wall defining a lumen extending between the proximal end and the distal end; and the cannula body comprises a threaded portion; characterized in that the threaded portion comprises: a first plurality of thread roots extending into the cannula wall, the first plurality of thread roots comprising a first plurality of flat cuts extending circumferentially about the wall of the cannula in a direction generally perpendicularly to the longitudinal axis of the cannula; and a second plurality of thread roots extending into the cannula wall, the second plurality of thread roots defining a continuous channel extending along the threaded portion, the second plurality of thread roots comprising a plurality of second flat cuts each extending circumferentially about the cannula wall perpendicularly to the longitudinal axis of the cannula and a plurality of angled cuts each extending circumferentially about the cannula wall oblique to the longitudinal axis, and wherein each second flat cut of the plurality of second flat cuts are joined to an adjacent angled cut of the plurality of angled cuts to define the continuous channel; wherein the cannula body comprises a retention region over the threaded portion having an outer diameter and a remainder region having an outer diameter, wherein the outer diameter of the retention region is relatively high compared to the outer diameter of the remainder region, and wherein the first plurality of thread roots and the second plurality of thread roots define an inverted pattern extending into the cannula wall at the retention region. a retention cannula comprising: a proximal end, a distal end, and a longitudinal axis; a cannula body between the proximal end of the cannula and the distal end, the cannula body comprising a cannula wall defining a lumen extending between the proximal end and the distal end; and the cannula body comprises a threaded portion; a proximal end, a distal end, and a longitudinal axis; a cannula body between the proximal end of the cannula and the distal end, the cannula body comprising a cannula wall defining a lumen extending between the proximal end and the distal end; and the cannula body comprises a threaded portion; characterized in that the threaded portion comprises: a first plurality of thread roots extending into the cannula wall, the first plurality of thread roots comprising a first plurality of flat cuts extending circumferentially about the wall of the cannula in a direction generally perpendicularly to the longitudinal axis of the cannula; and a second plurality of thread roots extending into the cannula wall, the second plurality of thread roots defining a continuous channel extending along the threaded portion, the second plurality of thread roots comprising a plurality of second flat cuts each extending circumferentially about the cannula wall perpendicularly to the longitudinal axis of the cannula and a plurality of angled cuts each extending circumferentially about the cannula wall oblique to the longitudinal axis, and wherein each second flat cut of the plurality of second flat cuts are joined to an adjacent angled cut of the plurality of angled cuts to define the continuous channel; a first plurality of thread roots extending into the cannula wall, the first plurality of thread roots comprising a first plurality of flat cuts extending circumferentially about the wall of the cannula in a direction generally perpendicularly to the longitudinal axis of the cannula; and a second plurality of thread roots extending into the cannula wall, the second plurality of thread roots defining a continuous channel extending along the threaded portion, the second plurality of thread roots comprising a plurality of second flat cuts each extending circumferentially about the cannula wall perpendicularly to the longitudinal axis of the cannula and a plurality of angled cuts each extending circumferentially about the cannula wall oblique to the longitudinal axis, and wherein each second flat cut of the plurality of second flat cuts are joined to an adjacent angled cut of the plurality of angled cuts to define the continuous channel; wherein the cannula body comprises a retention region over the threaded portion having an outer diameter and a remainder region having an outer diameter, wherein the outer diameter of the retention region is relatively high compared to the outer diameter of the remainder region, and wherein the first plurality of thread roots and the second plurality of thread roots define an inverted pattern extending into the cannula wall at the retention region.