Patent ID: 8777954

Claim:
An anchor extension for releasably coupling to a spinal bone anchor, comprising: an elongate hollow outer sleeve having a distal end and a proximal end; an elongate hollow inner sleeve disposed within said outer sleeve and having a distal end and a proximal end and an inner surface and an outer surface, said outer sleeve and said inner sleeve being movable relative to each other; an anchor engaging member projecting radially outwardly from the outer surface of the distal end of said inner sleeve for releasably engaging the bone anchor; a securement member including cooperative interlocking engagement surfaces defined on and adjacent to the distal end of said inner sleeve and said outer sleeve operable upon relative movement of said inner sleeve and said outer sleeve to directly interlock with each other and radially secure said inner sleeve and said outer sleeve together against radial movement for minimization of splaying and to maintain the engagement of said anchor engaging member and said bone anchor; and a lock between said inner sleeve and said outer sleeve separate and apart from said securement member and spaced proximally of said anchor engaging member operable in a first position to allow said relative movement between said outer sleeve and said inner sleeve and in a second position to prevent such relative movement.