Extension ready spinal support systems
An “extension ready” spinal support system that enables the extension to be accomplished with minimal disturbance to an existing spinal support structure to which the extension system is coupled. In some embodiments, the existing spinal support rod and pedicle screws can remain intact while extension subassemblies are mounted directly to the existing base rod receptacles. The extension subassemblies include a skirt portion that surrounds and engages the existing base receptacle to prevent splaying of the base receptacle. Additional resistance to splaying may be provided by a canted thread arrangement between the skirt and the base receptacle. In some embodiments, the extension receptacle is provided with a low profile (i.e., shortened axial length from the base rod receptacle) by providing a monoaxial rotation structure that rotates about but does not pitch relative to the extension axis and is shorter relative to polyaxial rotation structures.
1. A spinal support system, comprising:
a first rod receptacle for mounting to a pedicle screw, said first rod receptacle having a first side wall that includes a first interior surface and a first exterior surface, said first side wall defining a first pair of diametrically opposed slots that extend axially along said first side wall and are open at a proximal end of said first rod receptacle, said first interior surface defining first interior threads, said first exterior surface defining first exterior threads; and
an extension assembly including a second rod receptacle mounted to a base portion, said second rod receptacle including an internal flange having an interior face and defining an axial thickness, said base portion including a mounting platform and a skirt portion that extends from said mounting platform, said skirt portion including interior threads for mating with said first exterior threads of said first rod receptacle, said second rod receptacle having a second side wall that includes a second interior surface and a second exterior surface, said second side wall defining a second pair of diametrically opposed slots that extend axially along said second side wall and are open at a proximal end of said second rod receptacle, said second interior surface defining second interior threads,
wherein said extension assembly includes a pivot member that attaches said second rod receptacle to said base portion, said pivot member including a head portion and a shaft portion, said shaft portion including a stop that cooperates with said base portion to define a predetermined axial gap dimension between said head portion and said mounting platform of said base portion, said shaft portion being in fixed relationship with said mounting platform, said head portion of said pivot member being dimensioned to extend over said interior face of said internal flange to couple said second rod receptacle and said base portion, said axial gap being greater than said axial thickness of said internal flange to enable monoaxial rotation of said extension rod receptacle about said pivot head portion.
2. The spinal support system of claim 1 , wherein:
said second rod receptacle defines an opening at a distal end thereof, said opening sized to accommodate passage of said shaft portion of said pivot member; and
said mounting platform of said base portion defines a center hole for receiving said pivot member.
3. The spinal support system of claim 2 , wherein said shaft portion includes external shaft threads formed on an exterior surface thereof, and said center hole includes interior threads for mating with said external shaft threads.
4. The spinal support system of claim 2 , wherein said shaft portion is right cylindrical and includes a smooth exterior surface, and said center hole is right cylindrical and dimensioned for a sliding fit with said shaft portion.
5. The spinal support system of claim 2 , wherein said shaft portion is welded to said base portion.
6. The spinal support system of claim 2 , wherein said shaft portion is swaged to said base portion.
7. The spinal support system of claim 1 , wherein:
said head portion of said pivot member is one of a flat head and a countersink head; and
said interior face of said internal flange of said second rod receptacle is machined to conform to said head portion to enable selective monoaxial rotation about said head portion.
8. The spinal support system of claim 1 , wherein a set screw portion is integral with and extends from a distal face of said mounting platform, said set screw portion including threads configured to mate with said first interior threads of said first rod receptacle.
9. The spinal support system of claim 8 , wherein said threads of said set screw portion and said first interior threads of said first rod receptacle define canted cantilever profiles configured to threadably engage each other.
10. The spinal support system of claim 1 , wherein said second exterior surface of said second rod receptacle includes second exterior threads.
11. The spinal support system of claim 10 , comprising a cap including a skirt portion having interior threads for mating with said second exterior threads of said second rod receptacle.
12. The spinal support system of claim 1 , wherein said first exterior threads and said interior threads of said skirt portion define canted cantilever profiles configured to threadably engage each other.
13. A spinal rod support system, comprising:
an extension rod receptacle including an internal flange at a distal end, said internal flange defining an axial thickness;
a base portion including a mounting platform that defines a center hole accessible from a proximal face of said mounting platform;
a pivot member including a head portion and a stop, said stop registering against said proximal face of said platform to define a predetermined axial gap dimension between said head portion and said mounting platform that is greater than said axial thickness of said internal flange of said extension rod receptacle; and
means for coupling said pivot member to said base portion,
wherein said internal flange of said extension rod receptacle is captured between said head of said pivot member and said proximal face of said mounting platform, said extension rod receptacle being monoaxially rotatable about said head portion.
14. The spinal support system of claim 13 , wherein said means for coupling said extension rod receptacle to said base portion includes said pivot member threadably engaged with said center hole.
15. The spinal support system of claim 13 , wherein said means for coupling said extension rod receptacle to said base portion includes said pivot member swaged to said center hole.
16. The spinal support system of claim 13 , wherein said means for coupling said extension rod receptacle to said base portion includes said pivot member fused to said center hole.
17. The spinal support system of claim 16 , wherein said pivot member is welded to a periphery of said center hole at a distal face of said base portion.
18. The spinal support system of claim 13 , comprising:
a base rod receptacle; and
means for coupling said base portion to said base rod receptacle.
19. The spinal support system of claim 18 , wherein:
said base portion includes a skirt portion; and
said means for coupling said base portion to said base rod receptacle includes threaded engagement of said skirt portion to said base rod receptacle.
20. The spinal support system of claim 19 , wherein:
said base portion includes a set screw portion that is unitary with and extends from a distal face of said mounting platform; and
said means for coupling said base portion to said base rod receptacle includes threaded engagement of said set screw portion to said base rod receptacle.