Distal loading receiver for a polyaxial bone screw and method for implantation thereof
View Patent ↗A distal loading receiver for a polyaxial bone screw includes a body member having a circumferential wall defining a bore disposed longitudinally through the body member. A skirt depends from a distal end of the body member. The skirt defines one or more distally opening slots and an abluminal surface of the skirt includes one or more transverse ribs proximate to a distal end of the skirt. A retaining ring includes a luminal surface having one or more transverse recesses proximate to a distal end of the luminal surface and one or more walls extending inwardly from the luminal surface. The slots accommodate the walls and the recesses accommodate the ribs to attach the body member to the retaining ring when the distal end of the skirt is inserted into a proximal end of the retaining ring.
1. A distal loading receiver for a polyaxial bone screw, comprising:
a body member having a circumferential wall defining a bore disposed longitudinally through the body member;
a skirt depending from a distal end of the body member, wherein the skirt defines one or more distally opening slots and an abluminal surface of the skirt includes one or more transverse ribs proximate to a distal end of the skirt; and
a retaining ring including a luminal surface having one or more transverse recesses proximate to a distal end of the luminal surface and one or more walls extending inwardly from the luminal surface;
wherein distal open ends of the slots receive the walls such that the walls fit within the slots and the recesses accommodate the ribs to attach the body member to the retaining ring when the distal end of the skirt is inserted into a proximal end of the retaining ring.
2. The distal loading receiver of claim 1 , wherein the skirt is adapted to expand from a rest state to receive a bone screw having a proximal head that is larger in diameter than the bore at the distal end of the skirt in the rest state.
3. The distal loading receiver of claim 2 , wherein the circumferential wall includes a pair of oppositely disposed proximally opening slots that each includes a rounded distal end.
4. The distal loading receiver of claim 3 , further comprising a bushing disposed within the bore and including a second pair of oppositely disposed proximally opening slots and a second distally depending skirt, wherein the second pair of oppositely disposed proximally opening slots is adapted to accommodate a fixation rod, and the second distally depending skirt is adapted to abut a periphery of the proximal head.
5. The distal loading receiver of claim 4 , further including the bone screw having a proximal head that is larger in diameter than the bore at the distal end of the skirt in the rest state.
6. The distal loading receiver of claim 1 , wherein an abluminal surface of the skirt depending from the distal end of the body member is diametrically constricted relative to the body member.
7. The distal loading receiver of claim 1 , wherein the retaining ring includes an annular wall extending inwardly from the luminal surface distal to the transverse recesses.
8. A polyaxial screw assembly, comprising:
a polyaxial screw having a proximal head and a threaded shaft;
a body member having a circumferential wall defining a bore for receiving the polyaxial screw, wherein the circumferential wall includes a first pair of oppositely disposed proximally opening slots that each includes a rounded distal end;
a first skirt depending from a distal end of the body member, wherein the first skirt defines one or more distally opening slots and an abluminal surface of the first skirt includes one or more transverse ribs proximate to a distal end of the first skirt; and
a retaining ring including a luminal surface having one or more transverse recesses proximate to a distal end of the luminal surface and one or more walls extending radially inward from the luminal surface;
wherein distal open ends of the slots receive the walls such that the walls fit within slots and the recesses accommodate the ribs to attach the body member to the retaining ring when the distal end of the first skirt is inserted into a proximal end of the retaining ring.
9. The polyaxial screw assembly of claim 8 , further comprising a bushing disposed within the bore and including a second pair of oppositely disposed proximally opening slots and a second distally depending skirt, wherein the second pair of oppositely disposed proximally opening slots is adapted to accommodate a fixation rod, and the second distally depending skirt is adapted to abut a periphery of a proximal head of a bone screw.
10. The polyaxial screw assembly of claim 8 , wherein the first skirt is adapted to expand from a rest state to receive the polyaxial screw, wherein the proximal head is larger in diameter than the bore at the distal end of the skirt in the rest state.
11. The polyaxial screw assembly of claim 8 , wherein an abluminal surface of the first skirt is diametrically constricted relative to the body member.
12. The polyaxial screw assembly of claim 8 , wherein the retaining ring includes an annular wall extending inwardly from the luminal surface distal to the transverse recesses.
13. A method for assembling a polyaxial screw assembly that includes a polyaxial screw, a body member, and a retaining ring, comprising the steps of:
placing the retaining ring over a proximal head of the polyaxial screw, the retaining ring including a luminal surface having one or more recesses proximate to a distal end of the luminal surface and one or more walls extending inwardly from the luminal surface;
aligning a bore of the body member with the proximal head of the polyaxial screw, the body member having a circumferential wall defining the bore disposed longitudinally through the body member;
forcing a distal end of a skirt depending from a distal end of the body member into a proximal end of the retaining ring, the skirt defining one or more distally opening slots and an abluminal surface of the skirt including one or more transverse ribs proximate to a distal end of the skirt; and
inserting the polyaxial screw into a vertebra prior to placing the ring over the proximal head, aligning the bore of the body member with the proximal head, and forcing the distal end of the skirt into the ring,
wherein the slots of the skirt accommodate the walls of the retaining ring and recesses of the retaining ring accommodate the ribs of the skirt to attach the body member to the retaining ring.
14. The method of claim 13 , further comprising the step of inserting a bushing into the distal end of the body member, the bushing including a second pair of oppositely disposed proximally opening slots and a second distally depending skirt, wherein the second pair of oppositely disposed proximally opening slots is adapted to accommodate a fixation rod.