Method and apparatus for minimally invasive insertion of intervertebral implants

An access device for accessing an intervertebral disc, the access device comprising:

• a) an outer cannula having a first substantially tubular portion that is elongate along a longitudinal direction, a first proximal end portion, a first distal end portion opposite the first proximal end portion along the longitudinal direction, a first outer surface that extends between the first proximal end portion and the first distal end portion along the longitudinal direction, and a first longitudinal throughbore defining a first inner surface, wherein the outer cannula has a length along the longitudinal direction configured to extend from an incision to a vertebra that partially defines a Kambin's Triangle,
• b) an inner cannula having a second substantially tubular portion that is elongate along a central axis that is oriented along the longitudinal direction, and a flange that extends out from the second substantially tubular portion along a radial direction that is perpendicular to the longitudinal direction, the flange extending along the longitudinal direction along greater than half a length of the inner cannula, the length of the inner cannula defined along the longitudinal direction, the second substantially tubular portion further having a second proximal end portion, a second distal end portion opposite the second proximal end portion along the longitudinal direction, and a second longitudinal throughbore defining a second inner surface, wherein the inner cannula defines a second outer surface that extends about the second substantially tubular portion and the flange, the central axis is disposed between the second outer surface at the flange and the second outer surface at the tubular portion with respect to the radial direction, and the central axis is spaced further from the second outer surface at the flange than it is from the second outer surface at the tubular portion along the radial direction,
• wherein the second outer surface of the inner cannula is configured to substantially nest within the first inner surface of the outer cannula, such that the outer cannula surrounds an entirety of the inner cannula in a plane that is oriented perpendicular to the central axis,
• wherein the outer cannula defines a flange that extends radially out from only a single side of the first outer surface at the first substantially tubular portion, and the flange of the outer cannula receives the flange of the inner cannula, and
• wherein the outer cannula is radially aligned with the first substantially tubular portion.