主权项 |
1. A surgical instrument for use with a surgical portal apparatus, which comprises:
an elongate shaft defining a longitudinal axis; and a dilating member supported at a distal end of the elongate shaft and having a continuous closed outer end, the dilating member having a first longitudinal arc segment and a second longitudinal arc segment in diametrical relation and intersecting along a median plane of intersection, the first and second longitudinal arc segments each having a semi-circular cross-section orthogonal to the median plane of intersection and defining respective first and second radii of curvature, the first radius of curvature being different from the second radius of curvature at predetermined longitudinal positions along the dilating member, the first longitudinal arc segment defining a peripheral surface circumscribing an outer periphery of the second longitudinal arc segment, the peripheral surface coplanar with the median plane of intersection. |