Patent ID: 8197446

Claim:
A cannula assembly, which comprises: a housing; and a cannula member having a proximal end secured to the housing, and a distal end, the cannula member defining a longitudinal axis and including an outer wall, wherein a portion of the outer wall spaced from the distal end of the cannula member forms a restrictor hinge extending radially inward towards the longitudinal axis so as to engage a surgical instrument inserted therethrough, the restrictor hinge including hinge segments obliquely arranged with respect to the longitudinal axis and intersecting at an inflection segment, the restrictor hinge being adapted to transition from a first stage, in which the inflection segment of the restrictor hinge defines a first internal dimension, to a second stage, in which the inflection segment of the restrictor hinge defines a second internal dimension, upon engagement of at least the inflection segment with the surgical instrument such that contact between the restrictor hinge and the surgical instrument is minimized, the second internal dimension being greater than the first internal dimension.