MODULAR PEDICLE SCREW ASSEMBLY

摘要

A modular head pedicle screw assembly has a bone screw, a tulip and a saddle. The saddle is positioned in a recess inside of the tulip. The saddle has a proximal end for engaging a rod and a distal end for receiving a hemispherical or at least partial hemispherical head of the bone screw. The saddle is sized to move axially inside the tulip. The saddle has a plurality of fingers separated by slots extending from near the proximal end through the distal end in an initial un-loaded position and upon insertion of the tulip over the head of the bone screw, the saddle moves proximally over the head simultaneously causing the fingers to move past a maximum diameter of the hemispherical head and upon tightening the rod by a set screw, the fingers locking the bone screw into the tulip.

主权项

1. A modular head pedicle screw assembly comprising:
a bone screw, the bone screw having at least a partially hemispherical head of a maximum diameter; a tulip; a saddle being internal of the tulip positioned in a recess inside the tulip, the saddle having a proximal end for engaging a rod and a distal end for receiving the bone screw, the saddle having an exterior surface positioned between the ends, the exterior surface being sized to move axially inside the tulip, the saddle having a plurality of fingers separated by slots extending from near the proximal end through the distal end in an initial pre-loaded position; and wherein upon insertion of the tulip over the head of the bone screw, the saddle moves proximally over the head simultaneously causing the fingers to move past a maximum diameter of the hemispherical head and upon tightening the rod by a set screw, the fingers locking the bone screw into the tulip.