| 主权项 |
1. A sequential dilation system, comprising:
a first cannula having a first wall, a second wall, and opposing sidewalls each extending from a proximal end to a distal end and together having an oblong cross-section the first cannula further having a first lumen extending from sidewall to sidewall and from the proximal end to the distal end, wherein the distal end of the cannula includes a wedge, the distal end of the wedge comprising extensions of the first and second walls such that the first cannula has a first length dimension at a center that is greater than a second length dimension adjacent the sidewalls, the proximal end of the wedge having a pair of convergent tapered surfaces extending proximally into the first lumen and intersecting at an edge, thereby bifurcating the first lumen at the distal end; and a second cannula having a first wall, a second wall, and opposing sidewalls each extending from a proximal end to a distal end and a lumen extending from sidewall to sidewall and from the proximal end to the distal end, the second lumen having a length dimension, a width dimension, and an oblong cross-section taken across the width dimension, the second lumen dimensioned to slideably receive the first cannula therein. |
