Locking device introducer instrument

A fixation assembly for an elongated spinal fixation member, the fixation assembly comprising:

• A. a receiver component comprising:
• a receiver body comprising an outermost circumferential surface and a pair of arms, the pair of arms defining an annular groove on an inner surface of the body;
• and
• two rounded ledges projecting radially outwardly from the outermost circumferential surface of the receiver body,
• each rounded ledge including two arcuate perimetric regions defining rounded portions facing radially outwardly and a flat perimetric region defining a flat portion facing radially outwardly and extending between the rounded portions,
• the flat portions of the rounded ledges being diametrically opposed to one another with each flat portion projecting in a radially outward direction beyond the outermost circumferential surface of the receiver body,
• the rounded ledges being separated from one another by a pair of slots defined between the ledges,
• each arm extending away from an upper surface of a corresponding ledge and in a direction along the length of the receiver body, wherein an outermost circumference of the pair of arms is less than an outermost circumference of the two ledges, and
• B. a locking mechanism comprising:
• a generally cylindrical cap comprising an outer wall which defines an annular recess;
• a locking ring formed of a resilient flexible material, the locking ring positioned in the annular recess and around a circumference of the cap, the locking ring including an inner face that opposes and is separated from an end wall of the annular recess by a radial clearance when the locking ring is in a relaxed condition,
• the locking ring being deformable between a radially compressed condition, in which the locking ring is pressed inwardly into the annular recess, and a radially expanded condition, in which an outer portion of the locking ring extends outwardly from the recess,
• the annular groove of the receiver body being sized to receive the outer portion of the locking ring when the annular groove of the locking ring is axially aligned with the annular groove of the receiver body.

A fixation assembly for an elongated spinal fixation member, the fixation assembly comprising:

• A. a receiver component comprising:
• a generally cylindrical receiver body having a socket therein, the receiver body having an outermost circumferential surface and a pair of arms, the pair of arms defining an annular groove on an inner surface of the receiver body;
• and
• two ledges projecting radially outwardly from the outermost circumferential surface of the receiver body,
• each ledge including two arcuate perimetric regions defining rounded portions facing radially outwardly and a flat perimetric region defining a flat portion facing radially outwardly and extending between the rounded portions,
• the flat portions of the ledges being diametrically opposed to one another, with each flat portion projecting in a radially outward direction beyond the outermost circumferential surface of the receiver body,
• the ledges being separated from one another by a pair of slots extending longitudinally along the receiver body between the ledges, the slots being diametrically opposed to one another and defining a channel for receiving a rod which extends through the socket and between the ledges in a direction generally perpendicular to a longitudinal axis of the body,
• each arm extending away from an upper surface of a corresponding ledge and in a direction along the length of the receiver body, wherein an outermost circumference of the pair of arms is less than an outermost circumference of the two ledges, and
• B. a locking mechanism comprising:
• a generally cylindrical cap comprising an outer wall which defines an annular recess, the annular recess extending radially inward toward a longitudinal axis of the cap and terminating at an end wall;
• a locking ring formed of a resilient flexible material, the locking ring positioned in the annular recess and around a circumference of the cap, the locking ring including an inner face that is separated from the end wall of the annular recess by a radial clearance when the locking ring is in a relaxed condition,
• the locking ring being deformable between a radially compressed condition, in which the locking ring is pressed inwardly into the annular recess, and a radially expanded condition, in which an outer portion of the locking ring extends outwardly from the recess,
• the annular groove inside the receiver component being sized to receive the outer portion of the locking ring when the locking ring is axially aligned with the annular groove.