Implant, arrangement comprising an implant, and method for inserting said implant in bone tissue

• US 20040006346A1
• Filed: 04/14/2003
• Published: 01/08/2004
• Est. Priority Date: 08/15/2001
• Status: Active Grant

• Current Assignee: Astra Tech AB
• Original Assignee: Astra Tech AB
• Inventors: Wendel, Mats, Holmen, Anders, Rasmusson, Lars
• Granted Patent: US 8,029,285 B2
• Time in Patent Office: Days
• US Class Current: 606/73
• CPC Class Codes: A61C 8/0022 Self-screwing A61C8/0028 takes precedence
• CPC Class Codes: A61C 8/0025 with multiple threads

Abstract

The present invention relates to a screw implant (1) for insertion into a bore hole (50) arranged in bone tissue, said implant having a cancellous portion (3), and a cortical portion (2) having an axial length such that, when installed in the bore hole (50), the engagement of said cortical portion (2) with the bone tissue will generally be confined to the cortical bone tissue layer (52). Said cortical portion (2) presents an outer surface which is threaded for accomplishing said engagement, and has an outer design such that, when being screwed into said bore hole under action of a screwing torque, said cortical portion (2) acts so as to increase the compression of the cortical bone tissue only, in essentially radial directions of the implant, resulting in a distinct increase of the screwing torque needed for screwing the implant (1). Said increase is usable as an indication that the implant (1) is in place or nearly in place in the bore hole.

The invention also relates to an arrangement comprising an implant and a bore hole, and a method for insertion of an implant into a bore hole.

Claims

1. A screw implant (1) for insertion into a bore hole (50) arranged in bone tissue, said implant having a cancellous portion (3), and a cortical portion (2) having an axial length such that, when installed in the bore hole (50), the engagement of said cortical portion (2) with the bone tissue will generally be confined to the cortical bone tissue layer (52), said cortical portion (2) presenting an outer surface which is threaded for accomplishing said engagement, and having an outer design such that, when being screwed into said bore hole under action of a screwing torque, said cortical portion (2) acts so as to increase the compression of the cortical bone tissue only, in essentially radial directions of the implant, resulting in a distinct increase of the screwing torque needed for screwing the implant (1), which increase is usable as an indication that the implant (1) is in place or nearly in place in the bore hole.

5. A screw implant (1) according to any of the preceding claims, wherein a maximum diameter of the implant (1) is located in the cortical portion (2).

6. A screw implant (1) according to any of the preceding claims, wherein the cortical portion (2) has the shape of a truncated regular cone.

7. A screw implant (1) according to any of the preceding claims, wherein said angle (α

) is in the range 0.5 to 5°

.

8. A screw implant (1) according to any of the preceding claims, wherein said angle (α

) is less than less than 3°

.

9. A screw implant (1) according to any of the preceding claims, wherein said angle (α

) is in the range 0.5 to 3°

.

10. A screw implant (1) according to any of the preceding claims, wherein said angle (α

) is in the range 1 to 2°

.

11. A screw implant (1) according to any of the preceding claims, wherein the axial length of the cortical portion (2) is equal to 3 mm.

12. A screw implant (1) according to any of claims 1 to 10, wherein the axial length of the cortical portion (2) is less than 3 mm.

13. A screw implant according to any of the claims 1 to 10, wherein the axial length of the cortical portion (2) is in the range 0.5 to 1.5 mm.

14. A screw implant (1) according to any of the preceding claims, wherein said cancellous portion (3) is provided with a threaded outer surface that merges with said threaded outer surface of the cortical portion (2), such that both threaded outer surfaces are engagable in a common inner threaded surface of the bore hole.

15. A screw implant (1) according to claim 14, wherein both threaded outer surfaces present the same lead.

16. A screw implant (1) according to any of the preceding claims, wherein the implant (1) is provided with at least a first threading (11).

17. A screw implant (1) according to claim 16 in combination with claim 15 or 14, wherein both threaded surfaces are provided with said first threading (11).

18. A screw implant (1) according to claim 16 or 17, wherein the full axial length of the cortical portion (2) is provided with said first threading (11).

19. A screw implant (1) according to any of the claims 16 to 18, wherein said threading (11) is a single threading.

20. A screw implant (1) according to any of the claims 16 to 18, wherein said threading (11) is a multiple threading.

21. A screw implant (1) according to any of the claims 16 to 20, wherein said threading (11) comprises a screw thread.

22. A screw implant (1) according to any of the claims 16 to 21, wherein said threading (11) is defining a thread height being no greater than 0.20 mm.

23. A screw implant (1) according to any of the claims 16 to 22, wherein said threading (11) is defining a thread height in the range 0.02 to 0.15 mm.

24. A screw implant (1) according to any of the claims 16 to 23, wherein said threading (11) has a rounded outer design.

25. A screw implant (1) according to any of the claims 16 to 24, wherein said threading (11) is symmetrical.

26. A screw implant (1) according to any of the claims 16 to 25, further being provided with a second threading (12).

27. A screw implant (1) according to claim 26, wherein the first threading (11) and the second threading (12) merge with each other such that both threadings (11, 12) are engagable in a common inner thread.

28. A screw implant (1) according to claim 26 or 27, wherein said first and second threading (11, 12) are providing the same lead.

29. A screw implant (1) according to any of the claims 26 to 28, wherein a transversal border plane (P2) between the first and second threadings (11, 12) is provided below a transversal border plane (P1) between the cortical portion (2) and the cancellous portion (3).

30. A screw implant (1) according to any of the claims 26 to 28, wherein a transversal border plane (P2) between the first and second threadings (11, 12) is coinciding with transversal border plane (P1) between the cortical portion (2) and the cancellous portion (3).

31. A screw implant (1) according to any of the preceding claims, wherein the cortical portion (2) is adapted to hold a superstructure (20).

32. A screw implant (1) according to claim 31, wherein a blind bore (7) extends into the implant (1) from the uppermost end of the cortical portion (2) for holding a superstructure (20).

33. A screw implant (1) according to claim 32, said blind bore (7) being internally threaded.

34. A screw implant (1) according to any of the claims 1 to 30, wherein the implant (1) is formed integrally with a superstructure provided coronally of said cortical portion (2), said superstructure protruding from the bone tissue when the implant is in its implanted state.

35. A screw implant (1) according to any of the preceding claims, wherein the implant (1) is a dental implant.

36. A screw implant (1) according to any of the preceding claims, wherein said axial length of the cortical portion (2) is relatively short in relation to the axial length of said cancellous portion (3).

37. A screw implant (1) according to any of the preceding claims, wherein said cortical portion (2), when being screwed into said bore hole (50), acts so as to slightly compress cortical bone tissue in essentially radial directions of the cortical portion (2).

38. A method of installing an implant (1) according to any of the preceding claims in a bone, comprising the following steps:

forming in said bone a bore hole (50) having a shape being adapted to the general shape of the implant (1) but being smaller in diameter,

screwing said implant (1) into the bore hole (50) by applying an insertion torque to the implant (1) until the cortical portion (2) of said implant (1) meets said bore hole resulting in a distinct rise in the screwing torque needed to turn the implant (1), which is an indication that the implant (1) is or is soon to be in place.

39. A method according to claim 38, wherein an outer part of said bore hole (50) is formed so as to correspond to the cancellous portion (3) of the implant (1).

40. A method according to any of the claims 38 and 39, wherein said bore hole (50) is cylindrical.

41. A method according to any of the claims 38 to 40, wherein said bore hole (50) is slightly smaller in diameter than the implant (1).

2. A screw implant (1) for insertion into a bore hole (50) arranged in bone tissue, said implant having a cancellous portion (3) presenting an outer surface, and a cortical portion (2) having an axial length, such that, when installed in the bore hole (50), the engagement of said cortical portion (2) with the bone tissue will generally be confined to the cortical bone tissue layer (52), said cortical portion (2) presenting a conical outer surface being threaded for accomplishing said engagement and which has a conical taper such that said conical outer surface forms a non-zero angle (α

) of less than 5°

in relation to the outer surface of the cancellous portion (3).

3. A generally cylindrical screw implant (1) for insertion into a cylindrical bore hole (50) arranged in bone tissue, said implant (1) having a cancellous portion (3) presenting a cylindrical outer surface, and a cortical portion (2), having an axial length such that, when installed in the bore hole (50), the engagement of said cortical portion (2) with the bone tissue will generally be confined to the cortical bone tissue layer (52), said cortical portion (2) presenting a conical outer surface being threaded for accomplishing said engagement and which has a conical taper such that said conical outer surface forms a non-zero angle (a) of less than 5°

in relation to the cylindrical outer surface of the cancellous portion (3).

4. A screw implant (1) for insertion into a bore hole (50) arranged in bone tissue, comprising a cancellous portion (3) having a lower cylindrical cancellous portion (3′

) and an upper conical cancellous portion (3″

) presenting a conical outer surface, wherein said implant (1) is provided with a cortical portion (2), having an axial length such that, when installed in the bore hole (50), the engagement of said cortical portion (2) with the bone tissue will generally be confined to the cortical bone tissue layer (52), said cortical portion (2) presenting a conical outer surface being threaded for accomplishing said engagement and which has a conical taper such that said conical outer surface forms a non-zero angle (α

) of less than 5°

in relation to the outer surface of the upper, conical cancellous portion (3″

).

42. An arrangement for facilitating the insertion of a screw implant (1) in a bore hole (50) arranged in bone tissue, comprising a screw implant (1), having a cancellous portion (3), and a bore hole (50) having a shape generally corresponding to the outer shape of the implant (1), wherein said implant (1) is provided with a cortical portion (2) having an axial length such that, when installed in the bore hole (50), the engagement of said cortical portion (2) with the bone tissue will generally be confined to the cortical bone tissue layer (52), said cortical portion (2) presenting an outer surface, being threaded for accomplishing said engagement, and having an outer design such that when being screwed into said bore hole (50) under action of a screwing torque, said cortical portion (2) acts so as to increase the compression of cortical bone tissue in essentially radial directions of the implant (1), resulting in a distinct increase of the screwing torque needed for screwing the implant (1), which increase is usable as an indication that the implant (1) is in place or nearly in place in the bore hole (50).

46. An arrangement according to any of the claims 42 to 45, wherein said axial length of said cortical portion (2) is relatively short in relation to the axial length of said cancellous portion (3).

47. A arrangement according to any of the claims 42 to 46, wherein said cortical portion (2), when being screwed into said bore hole (50), acts so as to slightly compress cortical bone tissue in essentially radial directions of the cortical portion (2).

43. An arrangement for facilitating the insertion of a screw implant (1) in a bore hole (50) arranged in bone tissue, comprising a screw implant (1), having a cancellous portion (3), and a bore hole (50) having a shape generally corresponding to a shape of the implant (1), wherein said implant (1) is provided with a cortical portion (2) having an axial length, such that, when installed in the bore hole (50), the engagement of said cortical portion (2) with the bone tissue will generally be confined to the cortical bone tissue layer (52), said cortical portion (2) presenting a conical outer surface being threaded for accomplishing said engagement and which has a conical taper such that said conical outer surface forms a non-zero angle (α

) of less than 5°

in relation to the outer surface of the cancellous portion (3).

44. An arrangement for facilitating the insertion of a screw implant (1) in a bore hole (50) arranged in bone tissue, comprising a screw implant having a cancellous portion (3) presenting a cylindrical outer surface, and a bore hole (50) having a shape generally corresponding to a shape of the implant, wherein said implant (1) is provided with a cortical portion (2), having an axial length such that, when installed in the bore hole (50), the engagement of said cortical portion (2) with the bone tissue will generally be confined to the cortical bone tissue layer (52), said cortical portion (2) presenting a conical outer surface being threaded for accomplishing said engagement and which has a slight conical taper such that said conical outer surface forms an angle (α

) of less than 5°

in relation to the cylindrical outer surface of the cancellous portion (3).

45. An arrangement for facilitating the insertion of a screw implant (1) in a bore hole arranged in bone tissue, comprising a screw implant (1) having a lower cylindrical cancellous portion (3′

) and an upper conical cancellous portion (3) presenting a conical outer surface and a bore hole (50) having a shape generally corresponding to a shape of the implant, wherein said implant (1) is provided with a cortical portion (2), having an axial length such that, when installed in the bore hole (50), the engagement of said cortical portion (2) with the bone tissue will generally be confined to the cortical bone tissue layer (52), said cortical portion (2) presenting a conical outer surface being threaded for accomplishing said engagement and which has a conical taper such that said conical outer surface forms an non-zero angle (α

) of less than 5°

in relation to the outer surface of the conical part of the cancellous portion (3).