Composite material spinal implant

1. A collar sized and shaped for coupling between a rod and a pedicle screw or one or more adapters of the screw, comprising:

a distal end comprising a geometry shaped to (a) engage a head of said pedicle screw or (b) contact one or more adapters, if any, mounted on said head of said pedicle screw;

a proximal end; wherein a long axis of said collar extends between said distal end and said proximal end;

a portion adjacent said proximal end, said portion defining a cavity shaped and sized to receive at least a portion of a rod, wherein at least 60% of a top semicircular arc of said rod positioned within said cavity and facing away from said screw head or adapters is in contact with a top solid un-interrupted collar wall portion of said cavity, said top collar wall portion formed as a single unit; and wherein an external profile of said least one of said screw head and said rod, such that the ring axis extends axially along at least a portion of said long axis of said collar.

2. The collar according to claim 1 , wherein walls of said cavity encircle at least 70% of a circumference of said rod received within said cavity.

3. The collar according to claim 1 , wherein said geometry of said distal end of said collar defines a second cavity, said second cavity shaped and sized to receive at least a portion of said pedicle screw.

4. The collar according to claim 3 , wherein said second cavity is shaped and sized to maintain hold of a head of said pedicle screw.

5. The collar according to claim 3 , wherein an opening of said second cavity is co-axial with said long axis of said collar.

6. The collar according to claim 1 , wherein said collar comprises a slot separating a distal portion of said collar into at least two sub portions.

7. The collar according to claim 6 , wherein said slot extends from said distal end of said collar up to said cavity in which at least a portion of said rod is received.

8. The collar according to claim 6 , wherein said top collar wall portion extending over said top semicircular arc of the rod is arc shaped, and acts as a bridging load transferring element between said first and second sub portions of said collar separated from each other by said slot.

9. The collar according to claim 1 , wherein a distal portion of said collar comprises one or more slots extending from said distal end of said collar in the proximal direction to allow the collar to compressively fit over a head of a screw.

10. The collar according to claim 1 , wherein said collar comprises reinforcing filaments embedded in a polymer matrix.

11. The collar according to claim 10 , wherein said reinforcing filaments comprise carbon fibers and wherein said polymer matrix comprises PEEK.

12. The collar according to claim 10 , wherein said collar comprises reinforcing filaments arranged around said cavity and extending at least along said top collar wall portion.

13. The collar according to claim 12 , wherein said reinforcing filaments are U-shaped.

14. The collar according to claim 1 , wherein said external profile comprises a step.

15. The collar according to claim 1 , wherein said collar comprises one or more radiopaque markers.

16. The collar according to claim 15 , wherein said marker is in the form of a tantalum pin positioned in a proximal portion of said collar.

17. The collar according to claim 15 , wherein said radiopaque marker is in the form of powder, said powder comprising gold.

18. The collar according to claim 1 , wherein said cavity defines an elongated tubular profile that snugly engages said rod.

19. The collar according to claim 1 , wherein said top collar wall portion is arc shaped and wherein 100% of said top semicircular arc of said rod is in contact with said portion.

20. The collar according to claim 1 , wherein said top collar wall portion is an integral part of said collar.

21. A pedicle screw implant construct kit comprising:

a collar according to claim 1 ;

at least one pedicle screw comprising a head shaped and sized to be engaged by said collar;

an elongated rod shaped and sized to be engaged by said collar.

22. The kit according to claim 21 , wherein said kit further comprises one or more adapters shaped to embrace said screw head, said one or more adapters defining a cylindrical or conical external profile when placed over said screw head.

23. The kit according to claim 22 , wherein a distal end surface of said collar is configured to be positioned over a proximally facing surface of said one or more adapters.

24. The kit according to claim 22 , further comprising a locking ring shaped and sized to be positioned over at least a part of said collar or over said one or more adapters for fastening said collar to said screw head by exerting radial compression force onto said collar.

25. The kit according to claim 21 , comprising two adapters that complete each other to define a conical external profile, and an internal spherical recess in which said screw head is received.

26. The kit according to claim 21 , wherein a longitudinal axis of said collar is at an angle to a longitudinal axis of said screw when said screw is received within said collar.

27. A method of restraining relative movement of components of a pedicle screw construct comprising a rod, a collar and a pedicle screw, said method comprising:

providing a collar according to claim 1 ;

inserting said rod through said cavity of said collar;

positioning a second cavity of said collar over a head of said pedicle screw; and

radially compressing the collar to restrain movement of said rod relative to said pedicle screw.

28. The method according to claim 27 , wherein said radially compressing the collar comprises pulling a locking ring over at least a portion of said collar.

29. The method according to claim 27 , wherein two collars are provided; wherein said rod is inserted through said two collars; wherein said two collars are then positioned over two pedicle screws, said pedicle screws implanted in adjacent vertebrae.