Screws of cortical bone and method of manufacture thereof

• US 7,063,702 B2
• Filed: 10/02/2001
• Issued: 06/20/2006
• Est. Priority Date: 05/05/1999
• Status: Expired due to Term

• Current Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Original Assignee: SDGI Holdings Incorporated (Medtronic Plc)
• Inventors: Michelson, Gary K.
• Primary Examiner(s): Robert, Eduardo C.
• Assistant Examiner(s): Araj, Michael J.
• Application Number:
  US09/970,294
• Publication Number:
  US 20020016595A1
• Time in Patent Office: 1,722 Days
• Field of Search: 606 69- 73, 623/16.11, 623/17.11, 623/23.51, 623/23.58, 623/23.61, 623/23.63, 411/411, 411/417, 411/423, 411/416, 411/308, 411/904
• US Class Current: 606/307
• CPC Class Codes: A61B 17/7059 Cortical plates A61B17/7007, A61B17/7058 take precedence
• CPC Class Codes: A61B 17/8033 having indirect contact with screw heads, or having contact with screw heads maintained with the aid of additional components, e.g. nuts, wedges or head covers
• CPC Class Codes: A61B 17/8038 the additional component being inserted in the screw head
• CPC Class Codes: A61B 17/8042 the additional component being a cover over the screw head
• CPC Class Codes: A61B 17/8057 the interlocking form comprising a thread
• CPC Class Codes: A61B 17/8605 Heads, i.e. proximal ends projecting from bone
• CPC Class Codes: A61B 17/866 Material or manufacture
• CPC Class Codes: A61B 17/888 the driver bit acting on the central region of the screw head
• CPC Class Codes: A61B 2017/00004 (bio)absorbable, (bio)resorbable, resorptive for implantable prostheses A61F2210/0004
• CPC Class Codes: A61F 2/28 Bones joints A61F2/30
• CPC Class Codes: A61F 2/442 Intervertebral or spinal discs, e.g. resilient non-disc-shaped intervertebral inflatable pockets A61F2/441; non-disc-shaped intervertebral fusion implants A61F2/4455
• CPC Class Codes: A61F 2/4455 for the fusion of spinal bodies, e.g. intervertebral fusion of adjacent spinal bodies, e.g. fusion cages intervertebral discs A61F2/442
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/2839 Bone plugs or bone graft dowels
• CPC Class Codes: A61F 2002/30507 using a threaded locking member, e.g. a locking screw or a set screw
• CPC Class Codes: A61F 2002/30578 having apertures, e.g. for receiving fixation screws
• CPC Class Codes: A61F 2002/30774 internally-threaded
• CPC Class Codes: A61F 2002/30777 Oblong apertures
• CPC Class Codes: A61F 2002/30787 inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/30797 internally-threaded
• CPC Class Codes: A61F 2002/30904 : serrated profile, i.e. saw-toothed
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2310/00359 : Bone or bony tissue
• CPC Class Codes: A61F 2310/00976 : Coating or prosthesis-covering structure made of proteins or of polypeptides, e.g. of bone morphogenic proteins BMP or of transforming growth factors TGF
• CPC Class Codes: Y10S 606/909 : Bone
• CPC Class Codes: Y10T 29/49947 : by applying separate fastener

Abstract

A screw formed of cortical bone for use in the human body with an implant having a screw hole for receiving at least a portion of a screw therethrough, includes a shaft with a thread along at least a portion of its length. The thread has an outer diameter dimensioned to pass through the screw hole in the implant. The trailing end of the screw is configured to cooperatively engage at least a portion of the screw hole of the implant so as to prevent the screw from linear motion along the mid-longitudinal axis of the shaft in a direction opposite to the direction of insertion when the screw is threaded through the screw hole to attach the implant to a bone portion of the human body. The screw is formed substantially of cortical bone of a single cortical thickness.

Claims

1. A screw for use in the human body formed of cortical bone from a major long bone having a medullary canal, said screw comprising a leading end, a trailing end opposite said leading end, and a shaft therebetween, said shaft having a mid-longitudinal axis, a length, and a thread extending from said shaft along at least a portion of its length, said shaft having a cross section transverse to said mid-longitudinal axis through said thread having a concavedly arcuate portion and a convexedly arcuate portion opposite said concavedly arcuate portion, said concavedly arcuate portion being formed from at least a portion of the medullary canal and extending along a majority of the length of said screw, said cross section bisecting a rotation of said thread.

2. The screw of claim 1, wherein said cross section has opposite convex portions with approximately the same radius, said concavedly arcuate portion and said convexedly arcuate portion being between said opposite convex portions, said convexedly arcuate portion having a radius greater than the radius of said opposite convex portions, said cross section being through said concavedly arcuate portion of said thread.

3. The screw of claim 1, wherein said trailing end is configured to cooperatively engage at least a portion of the screw hole of an implant so as to prevent said screw from linear motion along the mid-longitudinal axis of said shaft in a direction opposite to the direction of insertion when said screw is threaded through a screw hole to attach the implant to a bone portion of the human body.

4. The screw of claim 1, wherein said screw is formed substantially of cortical bone of a single cortical thickness.

5. The screw of claim 4, wherein said cortical bone is obtained from a human.

6. The screw of claim 4, wherein said cortical bone is obtained from a generally intramembraneously formed cortical bone.

7. The screw of claim 4, wherein said cortical bone is obtained from a large tubular bone of a human.

8. The screw of claim 7, wherein said cortical bone is from the diaphyseal region of said large tubular bone.

9. The screw of claim 7, wherein the tubular bone is a femur.

10. The screw of claim 1, further comprising an enlarged portion proximate said trailing end with a dimension transverse to the mid-longitudinal axis of said shaft greater than said outer diameter of said thread, said enlarged portion configured to prevent said trailing end from passing through the screw hole in the implant.

11. The screw of claim 10, wherein said enlarged portion forms a head.

12. The screw of claim 10, wherein said enlarged portion forms a lip.

13. The screw of claim 1, wherein said trailing end includes a second thread having a different thread pitch than said thread along said shaft.

14. The screw of claim 13, wherein the thread pitch of said second thread is similar to a metal screw pitch.

15. The screw of claim 13, wherein the thread pitch of said thread along said shaft is similar to a wood screw pitch.

16. The screw of claim 1, wherein the thread pitch of said thread along said shaft is similar to a wood screw pitch.

17. The screw of claim 1, wherein at least a portion of said trailing end is expandable.

18. The screw of claim 17, wherein at least a portion of said trailing end is divided into at least two members with an opening therebetween.

19. The screw of claim 18, further comprising an insert configured to fit into said opening of said trailing end and to move said at least two members apart when inserted into said opening.

20. The screw of claim 19, wherein said insert is configured to be inserted by linear advancement into said opening.

21. The screw of claim 20, wherein said insert has a cruciate shape and said opening has a corresponding cruciate shape.

22. The screw of claim 19, wherein said insert is configured to be inserted by rotational movement into said opening.

23. The screw of claim 22, wherein said insert is threaded.

24. The screw of claim 1, wherein at least a portion of said trailing end is configured to cooperatively engage a driving instrument for insertion of said screw.

25. The screw of claim 24, wherein said trailing end includes a recess to cooperatively engage a driving instrument.

26. The screw of claim 25, wherein said recess is one of cruciate-shape and hex-shaped.

27. The screw of claim 24, wherein said trailing end includes a protrusion to cooperatively engage a driving instrument.

28. The screw of claim 27, wherein said protrusion has a hex-shaped perimeter.

29. The screw of claim 1, wherein said thread is sharper proximate said leading end than proximate said trailing end.

30. The screw of claim 1, wherein said thread has a V-shaped cross section with an apex and a base adjacent to said shaft, said base being substantially wider than said apex.

31. The screw of claim 1, wherein said thread has a peak as measured from said shaft, the peak being greater proximate said leading end than said trailing end.

32. The screw of claim 1, wherein said shaft has a root diameter that increases in the direction from said leading end to said trailing end.

33. The screw of claim 1, wherein said leading end forms a tip and said tip is fluted.

34. The screw of claim 1, further comprising a bioresorbable material other than cortical bone.

35. The screw of claim 34, wherein said material includes bioresorbable plastics.

36. The screw of claim 34, wherein said material includes at least one of glycolide polymers, lactide, capralactone, trimethylene carbonate, and dioxanone.

37. The screw of claim 1, wherein said screw comprises bone growth promoting material.

38. The screw of claim 37, wherein said bone growth promoting material is selected from one of bone morphogenetic protein, hydroxyapatite, and genes coding for the production of bone.

39. The screw of claim 1, wherein said screw is treated with a bone growth promoting substance.

40. The screw of claim 1, in combination with a bone growth promoting material.

41. The screw of claim 40, wherein said bone growth promoting material includes at least one of bone morphogenetic protein, mineralizing proteins, hydroxyapatite, and genetic material coding for the production of bone.

42. The screw of claim 1, in combination with an instrument for inserting said screw.

43. The screw of claim 1, wherein said thread has a plurality of turns, a majority of said turns including said concavedly arcuate portion.

44. The screw of claim 43, wherein all of said turns include said concavedly arcuate portion.

45. The screw of claim 43, wherein the radii of at least two of said concavedly arcuate portions vary along the length of said shaft.

46. The screw of claim 1, wherein said thread has an outer diameter that is generally constant along the length of said shaft.

47. A screw formed from a major long bone having a medullary canal, said screw comprising a leading end, a trailing end opposite said leading end, and a shaft therebetween, said shaft having a mid-longitudinal axis, a length, and a thread extending from said shaft along at least a portion of its length, said shaft having a cross section transverse to said mid-longitudinal axis through said thread having a concavedly arcuate portion and a convexedly arcuate portion opposite said concavedly arcuate portion, said concavedly arcuate portion being formed from at least a portion of the medullary canal and extending along a majority of the length of said screw, said cross section bisecting a rotation of said thread, said screw being formed by the process of cutting a strip of cortical bone having a single cortical thickness from the long bone in the direction of the longitudinal axis of the long bone and machining said strip to form a thread.

48. The screw of claim 47, wherein said strip of cortical bone is cut with a trephine having a diameter greater than the cortical thickness of the long bone.

49. The screw of claim 48, wherein said cross section has opposite convex portions with approximately the same radius, said concavedly arcuate portion and said convexedly arcuate portion being between said opposite convex portions, said convexedly arcuate portion having a radius greater than the radius of said opposite convex portions, said cross section being through said concavedly arcuate portion of said thread.

50. The screw of claim 47, in combination with a bone growth promoting material.

51. The screw of claim 50, wherein said bone growth promoting material includes at least one of bone morphogenetic protein, mineralizing proteins, hydroxyapatite, and genetic material coding for the production of bone.

52. The screw of claim 47, in combination with an instrument for inserting said screw.

53. The screw of claim 47, wherein said thread has a plurality of turns, a majority of said turns including said concavedly arcuate portion.

54. The screw of claim 53, wherein all of said turns include said concavedly arcuate portion.

55. The screw of claim 53, wherein the radii of at least two of said concavedly arcuate portions vary along the length of said shaft.

56. The screw of claim 47, wherein said thread has an outer diameter that is generally constant along the length of said shaft.

57. A method for forming a screw made of cortical bone, comprising the steps of:

cutting a strip of cortical bone having a single cortical thickness from a long bone in the direction of the longitudinal axis of the long bone; and

machining said strip to form a screw having a shaft with a mid-longitudinal axis, a length, and a thread extending from said shaft along at least a portion of its length, said shaft having a cross section transverse to said mid-longitudinal axis through said thread having a concavedly arcuate portion and a covexedly arcuate portion opposite said concavedly arcuate portion, said cross section bisecting a rotation of said thread.

58. The method of claim 57, wherein the cutting step includes the sub-step of using a trephine having a diameter greater than the cortical thickness of the long bone.

59. The method of claim 58, wherein the machining step includes the sub-steps of forming said cross section with opposite convex portions having approximately the same radius, said concavedly arcuate portion and said convexedly arcuate portion being between said opposite convex portions, said convexedly arcuate portion having a radius greater than the radius of said opposite convex portions, said cross section being through said concavedly arcuate portion of said thread.

60. The method of claim 57, further comprising the step of coating the screw with at least one of bone morphogenetic protein, mineralizing proteins, hydroxyapatite, and genetic material coding for the production of bone.

61. A screw for use in the human body formed of cortical bone from a major long bone having a medullary canal, said screw comprising:

a leading end and a trailing end opposite said leading end;

a shaft between said leading and trailing ends, said shaft having a mid-longitudinal axis, a length, and a thread extending from said shaft along at least a portion of its length, said thread having an outer diameter, said shaft having a cross section transverse to the mid-longitudinal axis through said thread having a concavedly arcuate portion and a convexedly arcuate portion opposite said concavedly arcuate portion, said concavedly arcuate portion being formed from at least a portion of the medullary canal and extending along a majority of the length of said screw, said cross section bisecting a rotation of said thread; and

an enlarged portion proximate said trailing end with a dimension transverse to the mid-longitudinal axis of said shaft greater than the outer diameter of said thread, said enlarged portion configured to prevent said trailing end from passing through a screw hole in an implant, said enlarged portion including a concavedly arcuate portion formed from at least a portion of the medullary canal.

62. The screw of claim 61, wherein said cross section has opposite convex portions with approximately the same radius, said concavedly arcuate portion and said convexedly arcuate portion being between said opposite convex portions, said convexedly arcuate portion having a radius greater than the radius of said opposite convex portions, said cross section being through said concavedly arcuate portion of said thread.

63. The screw of claim 61, wherein said trailing end is configured to cooperatively engage at least a portion of the screw hole of the implant so as to prevent said screw from linear motion along the mid-longitudinal axis of said shaft in a direction opposite to the direction of insertion when said screw is threaded through the screw hole to attach the implant to a bone portion of the human body.

64. The screw of claim 61, wherein said screw is formed substantially of cortical bone of a single cortical thickness.

65. The screw of claim 64, wherein said cortical bone is obtained from a human.

66. The screw of claim 64, wherein said cortical bone is obtained from a generally intramembraneously formed cortical bone.

67. The screw of claim 64, wherein said cortical bone is obtained from a large tubular bone of a human.

68. The screw of claim 67, wherein said cortical bone is from the diaphyseal region of said large tubular bone.

69. The screw of claim 67, wherein the tubular bone is a femur.

70. The screw of claim 61, wherein said enlarged portion forms a head.

71. The screw of claim 61, wherein said enlarged portion forms a lip.

72. The screw of claim 61, wherein the thread pitch of said thread along said shaft is similar to a wood screw pitch.

73. The screw of claim 61, wherein at least a portion of said trailing end is configured to cooperatively engage a driving instrument for insertion of said screw.

74. The screw of claim 73, wherein said trailing end includes a recess to cooperatively engage a driving instrument.

75. The screw of claim 61, wherein said thread is sharper proximate said leading end than proximate said trailing end.

76. The screw of claim 61, wherein said thread has a V-shaped cross section with an apex and a base adjacent to said shaft, said base being substantially wider than said apex.

77. The screw of claim 61, wherein said thread has a peak as measured from said shaft, the peak being greater proximate said leading end than said trailing end.

78. The screw of claim 61, wherein said shaft has a root diameter that increases in the direction from said leading end to said trailing end.

79. The screw of claim 61, wherein said leading end forms a tip and said tip is fluted.

80. The screw of claim 61, further comprising a bioresorbable material other than cortical bone.

81. The screw of claim 80, wherein said material includes bioresorbable plastics.

82. The screw of claim 80, wherein said material includes at least one of glycolide polymers, lactide, capralactone, trimethylene carbonate, and dioxanone.

83. The screw of claim 61, wherein said screw is treated with a bone growth promoting substance.

84. The screw of claim 61, in combination with a bone growth promoting material.

85. The screw of claim 84, wherein said bone growth promoting material includes at least one of bone morphogenetic protein, mineralizing proteins, hydroxyapatite, and genetic material coding for the production of bone.

86. The screw of claim 61, in combination with an instrument for inserting said screw.

87. The screw of claim 61, wherein said thread has a plurality of turns, a majority of said turns including said concavedly arcuate portion.

88. The screw of claim 87, wherein all of said turns include said concavedly arcuate portion.

89. The screw of claim 87, wherein the radii of at least two of said concavedly arcuate portions vary along the length of said shaft.

90. The screw of claim 61, wherein said thread has an outer diameter that is generally constant along the length of said shaft.

91. A screw formed of cortical bone for use in the human body, said screw comprising a leading end, a trailing end opposite said leading end, and a shaft therebetween, said shaft having a mid-longitudinal axis, a length, and a thread extending from said shaft along at least a portion of its length, said shaft having a cross section transverse to said mid-longitudinal axis through said thread having a concavedly arcuate portion and a convexedly arcuate portion opposite said concavedly arcuate portion, said cross section having opposite convex portions with approximately the same radius, said concavedly arcuate portion and said convexedly arcuate portion being between said opposite convex portions, said convexedly arcuate portion having a radius greater than the radius of said opposite convex portions, said cross section bisecting a rotation of said thread and being through said concavedly arcuate portion of said thread.

92. The screw of claim 91, wherein said trailing end is configured to cooperatively engage at least a portion of a screw hole of an implant so as to prevent said screw from linear motion along the mid-longitudinal axis of said shaft in a direction opposite to the direction of insertion when said screw is threaded through a screw hole to attach the implant to a bone portion of the human body.

93. The screw of claim 91, wherein said screw is formed substantially of cortical bone of a single cortical thickness.

94. The screw of claim 91, wherein at least a portion of said trailing end is configured to cooperatively engage a driving instrument for insertion of said screw.

95. The screw of claim 91, further comprising a bioresorbable material other than cortical bone.

96. The screw of claim 95, wherein said material includes bioresorbable plastics.

97. The screw of claim 95, wherein said material includes at least one of glycolide polymers, lactide, capralactone, trimethylene carbonate, and dioxanone.

98. The screw of claim 91, wherein said screw comprises bone growth promoting material.

99. The screw of claim 98, wherein said bone growth promoting material is selected from one of bone morphogenetic protein, hydroxyapatite, and genes coding for the production of bone.

100. The screw of claim 91, wherein said screw is treated with a bone growth promoting substance.

101. A screw comprising a leading end, a trailing end opposite said leading end, and a shaft therebetween, said shaft having a mid-longitudinal axis, a length, and a thread extending from said shaft along at least a portion of its length, said shaft having a cross section transverse to said mid-longitudinal axis through said thread having a concavedly arcuate portion and a convexedly arcuate portion opposite said concavedly arcuate portion, said cross section having opposite convex portions with approximately the same radius, said concavedly arcuate portion and said convexedly arcuate portion being between said opposite convex portions, said convexedly arcuate portion having a radius greater than the radius of said opposite convex portions, said cross section bisecting a rotation of said thread and being through said concavedly arcuate portion of said thread, said screw being formed by the process of cutting a strip of cortical bone having a single cortical thickness from a long bone in the direction of the longitudinal axis of the long bone and machining said strip to form a thread.

102. The screw of claim 101, wherein said strip of cortical bone is cut with a trephine having a diameter greater than the cortical thickness of the long bone.

103. The screw of claim 101, in combination with a bone growth promoting material.

104. The screw of claim 103, wherein said bone growth promoting material includes at least one of bone morphogenetic protein, mineralizing proteins, hydroxyapatite, and genetic material coding for the production of bone.

105. The screw of claim 101, in combination with an instrument for inserting said screw.

106. The screw of claim 101, wherein said thread has a plurality of turns, a majority of said turns including said concavedly arcuate portion.

107. The screw of claim 106, wherein all of said turns include said concavedly arcuate portion.

108. The screw of claim 106, wherein the radii of at least two of said concavedly arcuate portions vary along the length of said shaft.

109. The screw of claim 101, wherein said thread has an outer diameter that is generally constant along the length of said shaft.