Device for securing spinal rods

A method of securing a spinal rod to a spine comprising:

• providing a head portion having a channel extending therethrough for receiving a spinal rod, the channel in the head portion being bounded by opposed side walls each having an engagement slot formed therein;
• providing a bone fastener depending from the head portion;
• arranging the spinal rod in the channel of the head portion;
• providing a locking cap having an upper portion and a lower portion that are mechanically joined together for rotation relative to one another, the upper portion of the locking cap having opposed engagement flanges receivable in the engagement slots of the head portion, the lower portion of the locking cap having an elongated recess engageable with an exterior surface of the spinal rod;
• assembling the locking cap with the head portion so that the recess is in contact with the spinal rod and the flanges are at least partially aligned with the channel;
• while maintaining the recess of the lower portion of the locking cap in contact with the spinal rod, rotating the upper portion of the locking cap so that the opposed flanges of the upper portion engage the respective slots of the side walls of the head portion, such rotation translating into a locking force applied by the lower portion of the locking cap onto the spinal rod.

A method of securing a spinal rod to a spine comprising:

• providing a spinal rod having a longitudinal axis and a cylindrical exterior surface;
• providing a head portion having a channel extending therethrough for receiving the spinal rod, the channel in the head portion being bounded by a first side wall having a first slot and a second side wall having a second slot, the head portion defining a central axis perpendicular to the channel, an aperture at a lower end of the head portion and a seat surrounding the aperture at the lower end of the head portion;
• providing a bone fastener including a fastener head and a threaded body depending from the fastener head and assembling the bone fastener with the head portion so that the fastener head is in contact with the seat of the head portion and the threaded body extends through the aperture at the lower end of the head portion;
• arranging the spinal rod in the channel of the head portion so that the longitudinal axis of the spinal rod extends between the first and second side walls of the head portion;
• providing a locking cap having an upper portion and a lower portion that are rotatable relative to one another, the upper portion of the locking cap having diametrically opposed flanges that are spaced from one another, the lower portion of the locking cap having an underside with a recess having a cylindrical surface that conforms to the cylindrical exterior surface of the spinal rod;
• assembling the locking cap with the head portion so that the recess of the lower portion of the locking cap is in contact with the exterior surface of the spinal rod and so that the diametrically opposed flanges extend away from one another along a first axis that is substantially parallel to the longitudinal axis of the spinal rod;
• after the assembling step, rotating the upper portion of the locking cap about ¼ turn so that each of the diametrically opposed flanges engage one of the first and second side walls and so that the diametrically opposed flanges extend away from one another along a second axis that traverses the longitudinal axis of the spinal rod.