Patent ID: 8221471

Claim:
A locking mechanism for locking a rod in a screw and rod fixation assembly, the locking mechanism comprising: a generally cylindrical cap, configured to apply a downward axial force on a rod, the cap having an external sidewall and an annular recess formed in the sidewall, the recess extending radially inwardly into the cap; and a locking element movably disposed in the recess and circumscribing at least a portion of the cap, the locking element retained in a captive condition in the recess such that the cap encloses the locking element on two sides so the locking element cannot be removed from the recess, the locking element being radially deformable between a compressed condition, in which the locking element assumes a first cross-sectional dimension, and a relaxed condition, in which the locking element assumes a second cross-sectional dimension, the second cross-sectional dimension being larger than the first cross-sectional dimension.