Polyaxial bone screw

A receiving assembly for a bone screw comprising:

• a receiver configured to be movably mounted on a head of the bone screw, the receiver defining a channel for receiving a rod member therein;
• a retaining ring disposed within the receiver for holding the head of the bone screw in the receiver;
• an insert disposed in the receiver above the retaining ring;
• and
• a saddle disposed in the receiver above the insert, the saddle defining a cradle for seating the rod member in the receiver;
• wherein the retaining ring comprises a discontinuous ring member, and wherein the insert comprises a discontinuous ring member such that no portion of the insert extends continuously around an entire circumference of the insert.

A receiving assembly for a bone screw comprising:

• a receiver configured to be movably mounted on a head of the bone screw, the receiver defining a channel for receiving a rod member therein;
• and
• a continuous retaining ring disposed within the receiver for holding the head of the bone screw in the receiver, the continuous retaining ring being configured to expand a receiving area of the retaining ring to permit at least a portion of the head of the bone screw to be inserted through the retaining ring;
• wherein the retaining ring defines a plurality of channels, the receiving assembly further comprising a plurality of balls received in respective channels, the balls being moveable in the channels to expand the receiving area of the retaining ring.