Top-entry rod retainer

An apparatus for use in retaining a longitudinally extending member in position relative to a spinal column, said apparatus comprising a body having an open ended recess which extends through the body and is open along one side to enable the longitudinally extending member to be moved into the recess, said recess having a side opening, a first end opening formed in a first side of the body and intersecting the side opening, and a second end opening formed in a second side of the body opposite from the first side and intersecting the side opening to enable the longitudinally extending member to be moved into the recess through the side opening and to extend from the first and second sides of said body through the first and second end openings, said body including first and second flanges disposed on opposite sides of said side opening, a connector element extending from a side of said body opposite from the side opening and connectable with the spinal column to connect said body with the spinal column, an end cap movable between a disengaged position spaced from said body and an engaged position extending across the side opening in said body, said end cap including a base, a is an inner thread convolution which is disposed in said end cap. first retainer surface connected with and disposed adjacent a first side of said base, and a second retainer surface connected with and disposed adjacent a second side of said base, said first flange being engageable with said first retainer surface and said second flange being engageable with said second retainer surface upon rotation of said end cap through less than one half of a revolution relative to said body from a disengaged position to an engaged position to releasably interconnect said end cap and said body, and a clamp-member mounted on said end cap, said clamp member being movable relative to said end cap when said end cap is in the engaged position to clamp a longitudinally extending member disposed in the recess against said body and to press said first and second retainer surfaces against said first and second flanges to hold said end cap against movement from the engaged position to a disengaged position.