Polyaxial bone anchors with pop-on shank, fully constrained friction fit retainer and lock and release insert

Abstract

A polyaxial bone screw assembly includes a threaded shank body having an integral upper portion receivable in an integral receiver, the receiver having an upper channel for receiving a longitudinal connecting member and a lower cavity cooperating with a lower opening. The receiver can have crimp tabs, but is devoid of spring tabs and collet-like flexible structures. A down-loadable compression insert (some with lock and release feature), a down-loadable friction fit split retaining ring having super structure for temporary friction fit with an up-loadable shank upper portion cooperate to provide for pop- or snap-on assembly of the shank with the receiver either prior to or after implantation of the shank into a vertebra. The shank and receiver once assembled cannot be disassembled.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of U.S. patent application Ser. No. 13 / 317,387, filed Oct. 19, 2011, now U.S. Pat. No. ______, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61 / 455,482 filed Oct. 21, 2010 that are each incorporated by reference herein. This application is also a continuation-in-part of U.S. patent application Ser. No. 12 / 924,802 filed Oct. 5, 2010 that claims the benefit of the following U.S. Provisional Patent Application Ser. Nos. 61 / 278,240, filed Oct. 5, 2009; 61 / 336,911, filed Jan. 28, 2010; 61 / 343,737 filed May 3, 2010; 61 / 395,564 filed May 14, 2010; 61 / 395,752 filed May 17, 2010; 61 / 396,390 filed May 26, 2010; 61 / 398,807 filed Jul. 1, 2010; 61 / 400,504 filed Jul. 29, 2010; 61 / 402,959 filed Sep. 8, 2010; 61 / 403,696 filed Sep. 20, 2010; and 61 / 403,915 filed Sep. 23, 2010, all of which are incorporated by reference herein. This application is also a continuation-in-part of U.S. patent appli...

AI Technical Summary

Benefits of technology

The present invention is a polyaxial screw used in spine surgery that has an improved design for resisting pull out forces and is secured in place after implantation. The screw includes a retainer ring base that is positioned below the shank head and can resist larger pull out forces. The retainer ring base is better supported on a horizontal loading surface and cannot be disassembled. The screw also includes a pre-assembled receiver, compression insert, and friction fit split retainer that can be easily attached to the shank head and securely locked in place. The final locking occurs through an expansion-type of contact between the shank head and the lower portion of the retainer and an expansion-type of non-tapered locking engagement between the lower portion of the retainer ring and the locking chamber in the lower portion of the receiver cavity. The retainer spring tabs are deployed outwardly stabilizing the retainer and creating good rotational stability between the retainer and receiver and an additional rotational friction fit between the shank head and the receiver.

Problems solved by technology

Collect-like structures extending downwardly from lower pressure inserts, when used in modular polyaxial screw designs, as shown in the prior art, have been found to be somewhat weak with respect to pull-out forces encountered during some spinal reduction procedures.

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