Pedicle screw extension for use in percutaneous spinal fixation

摘要

A bone screw extension assembly for use in placing a connecting rod percutaneously into tissue of a patient comprises a multi-axial bone screw and a screw extension releasably coupled to yoke of the bone screw. The screw extension includes coaxially disposed outer sleeve and inner sleeves that are rotatable relative to each other. A screw engaging member projects radially from the distal end of the inner sleeve and is configured to engage an extension coupling surface on the outer sleeve upon relative rotation of the inner and outer sleeves. A securement member including cooperative surfaces is defined adjacent the distal end of the inner and outer sleeves that is operable upon relative rotation of the inner sleeve and outer sleeve to radially secure the sleeves together to thereby maintain the engagement of the screw engaging member and the bone screw.

主权项

1. An anchor extension for releasably coupling to a spinal bone anchor comprising:
an elongate hollow outer sleeve having a distal end, a proximal end, and a perimetric sidewall defining a bore through said distal and proximal ends, an interlocking engagement surface defined adjacent the distal end of said outer sleeve, and a pair of opposing slots formed through said sidewall, each slot opening through the distalmost edge of said outer sleeve and extending for a length proximally of said interlocking engagement surface; an elongate hollow inner sleeve disposed within the bore of said outer sleeve and having a distal end, a proximal end, and a perimetric sidewall defining a bore through said distal and proximal ends, a cooperative interlocking engagement surface defined adjacent the distal end of said inner sleeve, and a pair of opposing slots formed through said sidewall, each slot opening through the distalmost end of said inner sleeve and extending for a length proximally of said cooperative interlocking engagement surface, said outer sleeve and said inner sleeve being movable rotationally relative to each other such that the slots of said inner sleeve are aligned with the slots of said outer sleeve without the perimetric sidewall of the distal end of said outer sleeve extending across the slots of said inner sleeve; and an anchor engaging member projecting radially from the distal end of one of said outer sleeve and said inner sleeve for engaging the bone anchor upon relative rotation of said inner sleeve and said outer sleeve, said anchor engaging member being separate from and more distally of each of said interlocking engagement surface and said cooperative interlocking engagement surface, wherein said interlocking engagement surface and said cooperative interlocking engagement surface are operable upon relative rotation of said inner sleeve and said outer sleeve to directly interlock cooperatively with each other and thereby radially secure said inner sleeve and said outer sleeve together against radial movement for maintaining the engagement of said screw engaging member and said bone screw with said slots of said inner sleeve and said outer sleeve being in alignment.