Patent ID: 9655656
Date: 2017-05-23
CPC Classifications: A61B

Claim:
1. A modular head polyaxial pedicle screw assembly comprising: a bone screw, the bone screw having a polyaxial at least partially spherical head with a driving feature at a proximal end to tighten the screw into bone and a threaded shank; a tulip assembly configured to be pushed onto the head of the bone screw, the tulip assembly comprising: a tulip configured to have parallel walls that are opposing defining a slotted opening configured for receiving a spinal rod, opening walls of the tulip having a thread configured to receive a set screw, the tulip having a recess on an inner surface of the tulip configured to receive a locking split ring, the recess having an upper surface; a locking split ring internal of the tulip positioned in the recess of the inner surface of the tulip, the locking split ring having a relaxed inner diameter and a relaxed outer diameter in an unexpanded position or condition; a saddle having a proximal end with a concavity for engaging the spinal rod and a distal end for receiving the bone screw, the saddle having an opening through which the driving feature of the bone screw can be accessed, the saddle having an exterior surface positioned between the ends and an exterior recess or groove to which the locking split ring can be affixed when expanded, the exterior surface being sized to be inserted through a distal opening of the tulip and positioned below the thread of the opening walls of the tulip to move axially inside the tulip; and wherein the saddle holds the locking split ring in an initial pre-loaded expanded position at the exterior recess or groove and, upon insertion of the tulip assembly over the bone screw, the saddle moves proximally, which causes the locking split ring to abut the upper surface of the recess of the tulip, this abutting disengages the locking split ring from the exterior recess or groove of the saddle, thereby releasing the locking split ring from the saddle and causing the inner diameter to reduce to the relaxed unexpanded condition upon release of energy which causes the locking split ring to snap against and simultaneously slide along an exterior surface of a lower portion of the polyaxial at least partially spherical head of the bone screw between a maximum diameter of said polyaxial at least partially spherical head and the shank of the bone screw, wherein the snap provides a tactile feedback to a surgeon and further provides a locking of the locking split ring in the unexpanded position or condition against the lower portion of the exterior surface of the head of the bone screw inside the tulip, wherein the relaxed outer diameter of the locking split ring is larger than the distal opening of the tulip allowing the locking split ring to affix the tulip to the bone screw in a locked and loaded position while providing a polyaxially movable condition of the bone screw relative to the tulip and, upon engaging the rod into the concavity of the saddle and inserting and tightening the set screw, the bone screw movement relative to the tulip is locked in position as the head is fixed between the saddle and the disengaged lock ring at the distal opening of the tulip.